CA2909003A1

CA2909003A1 - Dispersion of responsive particles with switchable surface charge for use in membrane processes

Info

Publication number: CA2909003A1
Application number: CA2909003A
Authority: CA
Inventors: Chenguang Liang
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-10-19
Filing date: 2015-10-19
Publication date: 2017-04-19

Abstract

Transport phenomena occur across gradients until an equilibrium is reached.
For example, diffusion is a process wherein a substance moves from a region of high concentration to a region of low concentration; along the concentration gradient. By further including a membrane, certain substances are selectively restricted to one side of the membrane; depending on its properties. Both the electrolytic conductivity and the ionic strength of a solution can be modulated using particles with switchable surface charge upon application or removal of an ionization trigger. The concentration of dissolved salts or dispersed solids in a solution may be controlled by modulating the electrochemical gradient or the osmotic gradient across a membrane using a dispersion of particles with switchable surface charge.

Description

2 The compositions, systems, and methods of the present invention have broad applicability

3 in separation of materials from solutions using a membrane process based on modulation of

4 an electrochemical gradient and/or an osmotic gradient.
BACKGROUND OF THE INVENTION
6 Diffusion is a process wherein a substance moves from a region of high concentration to low 7 concentration along the concentration gradient. Osmosis is a diffusive process wherein 8 solvent molecules moves across a semi-permeable membrane from a region of low solute 9 concentration to a region of high solute concentration, until the solute concentrations on both sides equalize. Osmotic pressure is defined to be the minimum pressure required to maintain 11 equilibrium, with no net movement of solvent. Osmotic pressure is a colligative property and 12 depends on the molar concentration of the solute but not on its identity. The osmotic gradient 13 is the difference in concentration between two solutions on either side of a semi-permeable 14 membrane. Both forward osmosis and reverse osmosis have been used to treat water in order to remove specific contaminants. Diffusion across a membrane may also occur 16 according to an electrochemical gradient where imbalance in ion concentration contributes 17 to the difference in electrochemical potential.
18 Surfactant-Free Switchable Emulsions Using CO2-Responsive Particles C.
Liang, Q.
19 Liu, and Z. Xu [DOI: 1 0.1021/am5007113] describes surfactant-free emulsions are prepared using bi-wetting particles which occupy the oil¨water interface to effectively reduce the oil-21 water interfacial area. The equilibrium position of the particle at the interface is determined 22 by its wettability. 002-reponsive chemical functional groups are grafted onto the surface of 23 silica particles. Particles with only 002-switchable functional groups are capable of stabilizing 24 oil-in-water emulsions. Particles prepared with both 002-responsive and hydrophobic chemical functional groups on its surface are capable of stabilizing water-in-oil emulsions.
26 Emulsion stability is disturbed when the wettability of the stabilizing particle is altered by 27 introducing CO2 gas to the biphasic mixture, leading to phase separation of emulsions 28 prepared using the functionalized particles. The emulsion stability can be re-established by 29 the removal of CO2 through air sparging. The presence of CO2 imposes positive surface 30 charge to the responsive particles, increasing wettability and, consequently, the ability of the 31 particles to destabilize emulsions.
32 Emulsion Polymerization of Styrene and Methyl Methacrylate Using Cationic 33 Switchable Surfactants C. Fowler, C. Muchemu, R. Miller, L. Phan, C.
O'Neill, P.
34 Jessop, and M Cunningham C. Fowler, C. Muchemu, R. Miller, L. Phan, C. O'Neill, P.
35 Jessop, and M. Cunningham [DOI: 10.1021 /ma102936a] describes colloidal latexes of 36 polystyrene and poly(methyl methacrylate) prepared by emulsion polymerization using 37 cationic amidine-based switchable surfactants. Particles with sizes ranging from 50 to 350 38 nm were obtained and the effect of initiator type, initiator amount, surfactant amount, and 39 solid content on the particle size and -potential of the resulting latexes was examined.
40 Destabilization of the latexes requires only air and heat which destabilize the latex by 41 removing CO2 from the system and switching the active annidinium bicarbonate surfactant to 42 a surface inactive amidine compound. The resulting micrometer-sized particles can be easily 43 filtered to yield a dry polymer powder and a clear aqueous phase.
44 Red ispersible Polymer Colloids Using Carbon Dioxide as an External Trigger M.
45 Mihara, P. Jessop, and M. Cunningham [DOI: 10.1021/ma200249q] describes polystyrene 46 latexes prepared using a carbon dioxide switchable amidine surfactant and a switchable free 47 radical initiator can be aggregated using only nitrogen and gentle heat and redispersed using 48 carbon dioxide and sonication. The long-term colloidal stability of the redispersed latexes is 49 excellent provided they are maintained under a carbon dioxide atmosphere. Redispersion of 50 the particles is most effective when both the surfactant and the initiator contain switchable 51 amidine moieties. The zeta potential of the original particles (with the switchable 52 surfactant/initiator in their active form) decreases when the surfactant and initiator are 53 converted to their inactive form upon addition of nitrogen and heat.
Zeta potential is restored 54 to its original value upon conversion of the surfactant and initiator to their active forms with 55 carbon dioxide addition. This is the first report of red ispersible polymer colloids that can be 56 aggregated by reduction of surface charge, without requiring added acid or base solution.
57 These switchable latexes demonstrate the future potential for switchable polymer colloids, 58 capable of undergoing multiple reversible aggregation-redispersion cycles.

59 Reversibly Coagulateable and Redispersible Polystyrene Latex Prepared by Emulsion 60 Polymerization of Styrene Containing Switchable Amidine Q. Zhang, W.
Wang, Y. Lu, 61 B. Li, and S. Zhu [DOI: 10.1021/ma201056g] describes An easily coagulatable/redispersible 62 polystyrene latex system was developed in this work. The coagulatability and redispersibility 63 of the latexes were achieved by incorporating 1.6 ¨ 5.3 wt % of newly synthesized amidine-64 containing styrene derivative in a soap free emulsion polymerization of styrene. The resulted 65 latex particles were coagulated by adding a small amount of caustic soda and redispersed 66 by CO2 bubbling, which switched amidine moieties between neutral and ionic states. The 67 coagulation/redispersion processes were repeatable, even with washed and dried latexes.
68 The styrene butyl acrylate, styrene methyl methacrylate, and styrene acrylonitrile copolymer 69 latexes produced with the same approach were also reversibly coagulatable and 70 redispersible.
71 Surfactant-Free Polymerization Forming Switchable Latexes That Can Be Aggregated 72 and Redispersed by CO2 Removal and Then Readdition X. Su, P. G. Jessop, and M. F.
73 Cunningham [DO!: 10.1021 /ma202547c] describes polystyrene latexes prepared using the 74 bicarbonate salt of initiator 2,2'-azobis[2-(2-imidazolin-2-yl)propane]
via surfactant-free 75 emulsion polymerization can be aggregated using only argon and gentle heat and 76 redispersed using carbon dioxide and sonication. The bicarbonate and hydrochloride salts 77 of the initiator have similar thermal decomposition behavior, but only the bicarbonate salt of 78 2,2'-azobis[2-(2-imidazolin-2-y0propane] can be switchable between ionic and non-ionic 79 forms by addition and removal of 002. Measurements of partiae size and zeta potential were 80 used to study the aggregation and red ispersion of the latexes. The latex is aggregated by 81 heating and bubbling with argon to remove CO2 and convert the active cyclic amidinium 82 groups to their neutral form. When treated with sonication and bubbling with 002, the 83 aggregated polystyrene latex can be redispersed successfully, as evidenced by restoration 84 of the original latex particle size and zeta potential from the large aggregated polymer 85 particles. This is the simplest method to date to prepare a redispersible latex stabilized by 86 002.
87 Aryl Amidine and Tertiary Amine Switchable Surfactants and Their Application in the 88 Emulsion Polymerization of Methyl Methacrylate C. Fowler, P. Jessop, and M.
89 Cunningham [D01:10.1021/ma2027484] describes the switchability and bicarbonate 90 formation of CO2 triggered aryl amidine and tertiary amine switchable surfactants have been 91 investigated. Despite the lower basicity of these compounds compared to alkylacetamidine 92 switchable surfactants, it was found that amidinium and ammonium bicarbonates could be 93 formed in sufficiently high enough concentrations to perform emulsion polymerization of 94 methyl methacrylate and stabilize the resulting colloidal latexes.
Particle sizes ranging from 95 80 to 470 nm were obtained, and the effects of surfactant concentration, surfactant basicity, 96 initiator type, initiator concentration, and CO2 pressure on particle size and -potential have 97 been examined. Destabilization of latexes is traditionally achieved by addition of salts, strong 98 acids for anionically stabilized latexes, or alkalis for cationically stabilized latexes. However, 99 with 002-triggered switchable surfactants, only air and heat are required to destabilize the 100 latex by removing 002 from the system and switching the active amidinium or ammonium 101 bicarbonate surfactant to a surface inactive neutral compound. This process occurs much 102 more rapidly in the case of these less basic aryl amidine and tertiary amine based surfactants 103 compared to previously reported alkyl amidine surfactants.
104 2-(Diethyl)aminoethyl Methacrylate as a CO2-Switchable Comonomer for the 105 Preparation of Readily Coagulated and Redispersed Polymer Latexes J.
Pinaud, E.
106 Kowal, M. Cunningham, and P. Jessop [DOI: 10.1021 /mz3003215] describes 002 stimuli-107 responsive polystyrene latexes having a solids content of 27% were prepared in a surfactant-108 free emulsion polymerization (SFEP) under a CO2 atmosphere, employing only commercially 109 available chemical compounds: styrene, the initiator VA-061, and 0.54 mol % of the 002-110 switchable co-monomer DEAEMA. The resulting polymer particles are 230-300 nm in diameter and are monodisperse (PDI 0.054), as confirmed by DLS, TEM, and SEM.
112 Although they are stable under a CO2 atmosphere, the latexes can be easily destabilized by 113 the bubbling of air through the sample at 40 C, allowing for recovery of the particles by 114 filtration. Recovered polymer particles can be dried to powder and readily redispersed in 115 carbonated water, yielding latexes with very similar zeta-potential and particle size as the 116 original latexes. In addition, the bicarbonate salt of poly(DEAEMA) formed during the 117 polymerization has been found to act as a 002-switchable flocculant, thus, facilitating the 118 coagulation of the latex without altering the properties of the latex after redispersion.
119 One-Pot Synthesis of Pol y((diethylamino)ethyl methacrylate-co-120 styrene)-b-poly(methyl methacrylate-co-styrene) Nanoparticles via N
itroxide-121 Mediated Polymerization A. Darabi, P. G. Jessop, and M. F. Cunningham [DOI:
122 10.1 021/acs.macromo1.5b00258] describes poly((diethylamino)ethyl methacrylate-co-123 styrene)-b-poly(methyl methacrylate-co-styrene) nanoparticles were prepared by one-pot 124 process via nitroxide-mediated polymerization (NMP). For synthesizing the first block, the 125 SG1-mediated copolymerization of 2-(diethylamino)ethyl methacrylate (DEAEMA), a pH-126 sensitive monomer, and a small percentage of styrene (S) was performed in water at 90 C
127 using 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (VA-044) as a positively 128 charged stabilizer and initiator. The resultant macroalkoxyamine was then employed without 129 any purification in the protonated form as both macroinitiator and stabilizer in the same pot 130 for the surfactant-free emulsion copolymerization of methyl methacrylate (MMA) and styrene 131 at 90 C, which proceeded via polymerization-induced self-assembly (PISA). Latex particles 132 had monomodal size distribution, narrow size polydispersity, and small average size. The 133 polymerization kinetics, the control over molar mass and molar mass distribution, the effect 134 of the charge density on the particles size and latex stability, and the colloidal characteristics 135 of the in situ formed block copolymer micelles were studied in detail.
136 Highly Water-Soluble Magnetic Nanoparticle as Novel Draw Solutes in Forward 137 Osmosis for Water Reuse M. Ling, K. Wang, and T. Chung [DOI:
10.1021/ie100438x]
138 describes molecularly design of highly hydrophilic magnetic nanoparticles. For the first time, 139 the application of highly water-soluble magnetic nanoparticles as novel draw solutes in 140 forward osmosis (FO) was systematically investigated. Magnetic nanoparticles 141 functionalized by various groups were synthesized to explore the correlation between the 142 surface chemistry of magnetic nanoparticles and the achieved osmolality. We verified that 143 magnetic nanoparticles capped with polyacrylic acid can yield the highest driving force and 144 subsequently highest water flux among others. The used magnetic nanoparticles can be 145 captured by the magnetic field and recycled back into the stream as draw solutes in the FO
146 process. In addition, magnetic nanoparticles of different diameters were also synthesized to 147 study the effect of particles size on FO performance. We demonstrate that the engineering 148 of surface hydrophilicity and magnetic nanoparticle size is crucial in the application of 149 nanoparticles as draw solutes in FO. It is believed that magnetic nanoparticles will soon be 150 extensively used in this area.

151 Forward Osmosis as Appropriate Technology with Starch-based Draw Agent H.
152 Yoon, J. Kim, J. Yoon [DOI: 10.1080/19443994.2015.1040268] describes a conceptual 153 small-scale FO system with a starch-based draw agent. This FO system successfully 154 produced about 17.3 L/m2d of drinking water and achieved 95% of the arsenic removal rate 155 using a starch paste combined with amylase as a draw agent. The osmotic pressure, which 156 is necessary for producing permeate water, was generated by small molecules, such as 157 maltose. These molecules were formed from the decomposition of starch by amylase.
158 Because the draw agent used in this study is edible, the permeate water is directly drinkable 159 without any further separation. In addition, diverse starch-containing foods such as flour, raw 160 potatoes, raw sweet potatoes, and bananas were also confirmed as an alternative starch 161 source for draw agent.
162 A study of Poly(sodium 4-styrenesulfonate) as Draw Solute in Forward Osmosis E.
163 Tian, C. Hub, Y. Qin, Y. Ren, X, Wang, X. Wang, P. Xiao, and X. Yang [DOI:
164 10.1016/j.desa1.2015.01.001] describes draw solutions from poly (sodium 4-165 styrenesulfonate) (PSS) polyelectrolytes with different molecular weights (Mws) and different 166 concentrations. The physical properties, such as pH, conductivity and viscosity, have also 167 been investigated. The conductivity increases with the increase of PSS
concentration, which 168 may lead to higher osmotic pressure. Higher viscosity, lower diffusion coefficient and more 169 severe concentration polarization, which is generated by the polyelectrolyte with higher Mw, 170 result in a lower water flux. Among the PSS polyelectrolytes, 0.24 g=mL-1 PSS (70,000) 171 exhibits the best FO flux. Experiment results demonstrate the advantage of using PSS as 172 draw solute to conventional ionic salt of 0.5 mol=L- 1 NaCI. The regeneration of PSS from 173 diluted DSs and the repeatability of the FO performance after recovery have been evaluated.
174 The PSS was easily recycled by a low pressure-driven ultrafiltration (UF) system under 2 bar 175 with low energy consumption. In order to realize a satisfactory regeneration of PSS DS in 176 the FO process, it is necessary to select or prepare an appropriate UF
membrane with 177 accurate MWCO.
178 W02011050469 Al describes a solvent that reversibly converts from a hydrophobic liquid 179 form to hydrophilic liquid form upon contact with water and a selected trigger (e.g. contact 180 with 002). The hydrophilic liquid form is readily converted back to the hydrophobic liquid form 181 and water. The hydrophobic liquid is an amidine or amine. The hydrophilic liquid form 182 comprises an amidinium salt or an ammonium salt.
183 WO 2011097727 Al describes a method and system for reversibly converting water between 184 an initial ionic strength and an increased ionic strength, using a switchable additive, is 185 described. The disclosed method and system can be used, for example, in distillation-free 186 removal of water from solvents, solutes, or solutions. Following extraction of a solute from a 187 medium by dissolving it in water, the solute can then be isolated from the aqueous solution 188 or "salted-out" by converting the water to a solution having an increased ionic strength. The 189 solute then separates from the increased ionic strength solution as a separate phase. Once 190 the solute is, for example, decanted off, the increased ionic strength aqueous solution can 191 be converted back to water having its original ionic strength and reused. Switching from lower 192 to higher ionic strength is readily achieved using low energy methods such as bubbling with 193 002, CS2 or COs. Switching from higher to lower ionic strength is readily achieved using low 194 energy methods such as bubbling with air, heating, agitating, introducing a vacuum or partial 195 vacuum, or any combination or thereof.
196 W02012079175 Al describes methods and systems for use of switchable water, which is 197 capable of reversibly switching between an initial ionic strength and an increased ionic 198 strength. The disclosed methods and systems can be used, for example, in distillation-free 199 removal of water from solvents, solutes, or solutions, desalination, clay settling, viscosity 200 switching, etc. Switching from lower to higher ionic strength is readily achieved using low 201 energy methods such as bubbling with CO2, CS2 or COs or treatment with Bronsted acids.
202 Switching from higher to lower ionic strength is readily achieved using low energy methods 203 such as bubbling with air, inert gas, heating, agitating, introducing a vacuum or partial 204 vacuum, or any combination or thereof.
206 W02014175833 Al describes a draw solute for forward osmosis comprising a carbon 206 dioxide responsive structural unit and a thermally responsive structural unit, wherein the 207 draw solute is capable of reversibly switching between a protonated state and a 208 deprotonated state. The present invention also provides a forward osmosis method utilising 209 the draw solute.

210 US 20090308727 Al describes a method and apparatus for desalinating seawater which 211 uses an ammonia bicarbonate forward osmosis desalination process.
Seawater is pumped 212 through one side of a membrane assembly. A draw solution is pumped through the other 213 side of the membrane assembly. The draw solution withdraws water molecules from the 214 seawater through the membrane into the draw solution. A draw solution separator receives 215 a heated draw solution which then decomposes into ammonia, carbon dioxide and water.
216 Potable water is separated from ammonia has and carbon dioxide gas. The ammonia gas 217 and carbon dioxide gas are recombined with a portion of the potable water stream to reform 218 the ammonium bicarbonate draw solution.
219 US 20120211423 Al describes a draw solute for forward osmosis may include a copolymer 220 including a first structural unit where a temperature-sensitive side chain is graft polymerized, 221 and a second structural unit including a hydrophilic functional group.
The temperature-222 sensitive side chain may include a structural unit for a side chain including a temperature-223 sensitive moiety.

226 Diffusion is a process wherein a substance moves from a region of high concentration to a 227 region of low concentration; along the concentration gradient. Osmosis is a diffusive process 228 wherein solvent molecules moves through a semi-permeable membrane from a region of 229 low solute concentration to a region of high solute concentration;
along the osmotic gradient 230 until the solute concentrations on both sides equalize. The ionic strength of a solution can 231 be modulated using particles with switchable surface charge upon application or removal of 232 an ionization trigger. The concentration of a solution with dissolved salts or dispersed solids 233 may be controlled by modulating the ionic strength of a solution on one side of a semi-234 permeable membrane using a dispersion of particles with switchable surface charge. The 235 present invention provides a dispersion comprising responsive particles with switchable 236 surface charge for use in membrane processes. The present invention provides systems 237 wherein the electrochemical or the osmotic gradient is modulated across a membrane.
238 Compositions for Use Claims 239 The present invention relates to a dispersion for use in a membrane process comprising 240 responsive particles with switchable surface charge. The responsive particles of the present 241 invention comprise an insoluble particle and a surface functionality wherein the surface 242 functionality reversibly converts between an ionic state and a non-ionic state. In certain 243 embodiments of the present invention, the insoluble particle and surface functionality are 244 linked through chemical bonding, physical entanglement, chemisorption, physisorption, or 245 combinations thereof. The properties of the dispersion of the present invention, comprising 246 responsive particles with switchable surface charge, are responsive and depend on the state 247 of the surface functionality. In one aspect of the present invention, the ionic strength of the 248 dispersion increases when the surface functionality is converted to its ionic state. In another 249 aspect of the present invention, the ionic strength of the dispersion decreases when the 250 surface functionality is converted to its non-ionic state. In one aspect of the present invention, 251 the conductivity of the dispersion increases when the surface functionality is converted to its 252 ionic state. In another aspect of the present invention, the conductivity of the dispersion 253 decreases when the surface functionality is converted to its non-ionic state.

254 In certain embodiments of the present invention, the responsive particles are suspended in 255 solution by mechanical agitation, gas flotation, or pumping. In some embodiments of the 256 present invention, the insoluble particle comprises an inorganic solid, a synthetic polymer, a 257 natural polymer, or a natural polymer derivative. In certain embodiments of the present 258 invention, the inorganic solid comprises silica. In specific embodiments of the present 259 invention, the inorganic solid comprises colloidal silica, silica gel, precipitated silica, 260 mesoporous silica, or fumed silica. In certain embodiments of the present invention, the 261 insoluble particle comprises iron oxide coated with silica or iron oxide coated with 262 polystyrene. In another aspect of the present invention, the responsive particles comprising 263 iron oxide are separated under an applied magnetic field generated by a permanent magnet 264 or an electromagnet. In certain embodiments of the present invention, the insoluble particle 265 comprises carbonaceous material. In some embodiments of the present invention, the 266 synthetic polymer comprises poly(acrylonitrile butadiene styrene), cross-linked polyethylene, 267 poly(ethylene vinyl acetate), poly(methyl methacrylate), polyamide, polybutylene, 268 polybutylene terephthalate, polycarbonate, poly(ether ether ketone), polyester, polyethylene, 269 poly(ethylene terephthalate), polyimide, poly(lactic acid), poly(oxymethylene), poly(phenyl 270 ether), polypropylene, polystyrene, polysulfone, poly(tetrafluoroethylene), polyurethane, 271 polyvinyl chloride, poly(vinylidene chloride), poly(styrene maleic anhydride), poly(styrene-272 acrylonitrile), cyanoacrylate resin, epoxy resin, phenol formaldehyde resin, urea 273 formaldehyde resin, or silicone resin. In a specific embodiment of the present invention, the 274 insoluble particle comprises polystyrene. In other embodiments of the present invention, the 275 natural polymer comprises cellulose, cellulose ether, cellulose ester, chitin, poly(lactic acid), 276 poly(3-hydroxybutyrate), or poly(hydroxyalkanoate). In a specific embodiment of the present 277 invention, the insoluble particle comprises cellulose, cellulose ether, or cellulose ester.
278 In another aspect of the present invention, the surface functionality reversibly converts to its 279 ionic state upon contact with a trigger in the presence of water. In specific embodiments of 280 the present invention, the trigger comprises 002, NO2, COS, or CS2. In some embodiments 281 of the present invention, the surface functionality comprises a nitrogen base wherein upon 282 contact with a trigger in the presence of water protonates said nitrogen base. In certain 283 embodiments of the present invention, the surface functionality, in its non-ionic state, 284 comprises: an amidine, a guanidine, or a tertiary amine. In certain embodiments of the 285 present invention, the surface functionality, in its ionic state, comprises: an amidinium, a 286 guanidinium, or a tertiary aminium. In a preferred embodiment of the present invention, the 287 surface functionality has the following structure in its non-ionic state:
RI

I-E N

289 where ¨ is the surface of the insoluble particle; where R1 and R2 are independently: H; a 290 substituted or unsubstituted Ci to 08 aliphatic group that is linear, branched, or cyclic, 291 optionally wherein one or more C of the alkyl group is replaced by {¨Si(R1 )2-0¨} up to 292 and ncluding eight C being replaced by eight {¨Si(R1 )2-0¨}; a substituted or 293 unsubstituted CnSim group where n and m are independently a number from 0 to 8 and n+m 294 is a number from 1 to 8; a substituted or unsubstituted 04 to 08 aryl group wherein aryl is 295 optionally heteroaryl, optionally wherein one or more C is replaced by {¨Si(R10)2¨O--}; a 296 substituted or unsubstituted aryl group having 4 to 8 ring atoms, optionally including one or 297 more {--Si(R1 )2-0¨}, wherein aryl is optionally heteroaryl; a ¨(Si(R1 )2-0)p¨ chain in 298 which p is from 1 to 8 which is terminated by H, or is terminated by a substituted or 299 unsubstituted Ci to Ca aliphatic and/or aryl group; or a substituted or unsubstituted (Ci to 08 300 aliphatic)-(C4 to C8 aryl) group wherein aryl is optionally heteroaryl, optionally wherein one 301 or more C is replaced by a {¨Si(R1 )2-0¨}; wherein R-1 is a substituted or unsubstituted 302 Ci to C8 aliphatic group, a substituted or unsubstituted Ci to 08 alkoxy, a substituted or 303 unsubstituted 04 to 08 aryl wherein aryl is optionally heteroaryl, a substituted or unsubstituted 304 aliphatic-alkoxy, a substituted or unsubstituted aliphatic-aryl, or a substituted or 305 unsubstituted alkoxy-aryl group; where E is: a substituted or unsubstituted Ci to 08 aliphatic 306 group that is linear, branched, or cyclic, optionally wherein one or more C of the alkyl group 307 is replaced by {¨Si(R10)2_0¨} up to and including 8 C being replaced by 8 {¨Si(R1 )2-308 0¨}; a substituted or unsubstituted CnSim group where n and m are independently a number 309 from 0 to 8 and n+m is a number from 1 to 8; a substituted or unsubstituted 04 to C8 aryl 310 group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by 311 f_si (R10)2_0_, =
a substituted or unsubstituted aryl group having 4 to 8 ring atoms, 312 optionally including one or more {¨Si(R92-0¨}, wherein aryl is optionally heteroaryl; a -313 (Si(R92-0)p- chain in which p is from 1 to 8; or a substituted or unsubstituted (Ci to 08 314 aliphatic)-(C4 to 08 aryl) group wherein aryl is optionally heteroaryl, optionally wherein one 315 or more C is replaced by a {_Si(Rio)2_O_}; and wherein Rl is a substituted or 316 unsubstituted Ci to 08 aliphatic group, a substituted or unsubstituted Ci to 08 alkoxy, a 317 substituted or unsubstituted C4 to 08 aryl wherein aryl is optionally heteroaryl, a substituted 318 or unsubstituted aliphatic-alkoxy, a substituted or unsubstituted aliphatic-aryl, or a 319 substituted or unsubstituted alkoxy-aryl group; and wherein a substituent is independently:
320 alkyl; alkenyl; alkynyl; aryl; aryl-halide; heteroaryl; cycloalkyl;
Si(alkyl)3; Si(alkoxy)3; halo;
321 alkoxyl; amino; alkylamino; alkenylamino; amide; hydroxyl; thioether;
alkylcarbonyl;
322 alkylcarbonyloxy; arylcarbonyloxy; alkoxycarbonyloxy; aryloxycarbonyloxy;
carbonate;
323 alkoxycarbonyl; aminocarbonyl; alkylthiocarbonyl; amidine, phosphate;
phosphate ester;
324 phosphonato; phosphinato; cyano; acylamino; imino; sulfhydryl; alkylthio;
arylthio;
325 thiocarboxylate; dithiocarboxylate; sulfate; sulfato; sulfonate;
sulfamoyl; sulfonamide; nitro;
326 nitrile; azido; heterocyclyl; ether; ester; silicon-containing moieties;
thioester; or a 327 combination thereof. In a preferred embodiment of the present invention, the surface 328 functionality has the following structure in its ionic state:

õ, R2 EmAINIMINININVONI N N

330 where ¨ is the surface of the insoluble particle; where R1 and R2 are independently: H; a 331 substituted or unsubstituted Ci to 08 aliphatic group that is linear, branched, or cyclic, 332 optionally wherein one or more C of the alkyl group is replaced by {¨Si(R92-0¨} up to 333 and ncluding eight C being replaced by eight {¨Si(R92-0¨}; a substituted or 334 unsubstituted CnSim group where n and m are independently a number from 0 to 8 and n+m 335 is a number from 1 to 8; a substituted or unsubstituted C4 to C8 aryl group wherein aryl is 336 optionally heteroaryl, optionally wherein one or more C is replaced by {¨Si(R10)2-0¨}; a 337 substituted or unsubstituted aryl group having 4 to 8 ring atoms, optionally including one or 338 more {¨Si(R1 )2-0¨}, wherein aryl is optionally heteroaryl; a ¨(Si(1:110)2-0)p¨ chain in 339 which p is from 1 to 8 which is terminated by H, or is terminated by a substituted or 340 unsubstituted Ci to Cs aliphatic and/or aryl group; or a substituted or unsubstituted (Ci to 08 341 aliphatic)-(C4 to 08 aryl) group wherein aryl is optionally heteroaryl, optionally wherein one 342 or more C is replaced by a {¨Si(R92-0¨}; wherein Rio is a substituted or unsubstituted 343 Ci to 08 aliphatic group, a substituted or unsubstituted Ci to 08 alkoxy, a substituted or 344 unsubstituted C4 to C8 aryl wherein aryl is optionally heteroaryl, a substituted or unsubstituted 345 aliphatic-alkoxy, a substituted or unsubstituted aliphatic-aryl, or a substituted or 346 unsubstituted alkoxy-aryl group; where E is: a substituted or unsubstituted Ci to C8 aliphatic 347 group that is linear, branched, or cyclic, optionally wherein one or more C of the alkyl group 348 is replaced by {¨Si(R92-0¨} up to and including 8 C being replaced by 8 {¨Si(R10)2-349 0¨}; a substituted or unsubstituted CnSim group where n and m are independently a number 350 from 0 to 8 and n+m is a number from 1 to 8; a substituted or unsubstituted 04 to 08 aryl 351 group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by 352 {¨Si(R92-0¨}; a substituted or unsubstituted aryl group having 4 to 8 ring atoms, 353 optionally including one or more f_s Ri0)2_0_,2 wherein aryl is optionally heteroaryl; a ¨
354 (Si(R92-0)p¨ chain in which p is from 1 to 8; or a substituted or unsubstituted (Ci to 08 355 aliphatic)-(C4 to 08 aryl) group wherein aryl is optionally heteroaryl, optionally wherein one 356 or more C is replaced by a {¨Si(R92-0¨}; and wherein Rio is a substituted or 357 unsubstituted Ci to 08 aliphatic group, a substituted or unsubstituted Ci to C8 alkoxy, a 358 substituted or unsubstituted 04 to C8 aryl wherein aryl is optionally heteroaryl, a substituted 359 or unsubstituted aliphatic-alkoxy, a substituted or unsubstituted aliphatic-aryl, or a 360 substituted or unsubstituted alkoxy-aryl group; and wherein a substituent is independently:
361 alkyl; alkenyl; alkynyl; aryl; aryl-halide; heteroaryl; cycloalkyl;
Si(alkyl)3; Si(alkoxy)3; halo;
362 alkoxyl; amino; alkylamino; alkenylamino; amide; hydroxyl; thioether;
alkylcarbonyl;
363 alkylcarbonyloxy; arylcarbonyloxy; alkoxycarbonyloxy; aryloxycarbonyloxy;
carbonate;
364 alkoxycarbonyl; anninocarbonyl; alkylthiocarbonyl; amidine, phosphate;
phosphate ester;
365 phosphonato; phosphinato; cyano; acylannino; imino; sulfhydryl; alkylthio;
arylthio;
366 thiocarboxylate; dithiocarboxylate; sulfate; sulfato; sulfonate;
sulfamoyl; sulfonamide; nitro;

367 nitrite; azido; heterocyclyl; ether; ester; silicon-containing moieties;
thioester; or a 368 combination thereof.
369 In a most preferred embodiment of the present invention, the surface functionality has the 370 following structure, in its non-ionic state:

I¨ E - N

372 where ¨ is the surface of the insoluble particle; where RI and R2 are independently: H; a 373 substituted or unsubstituted Ci to 08 aliphatic group that is linear, branched, or cyclic, 374 optionally wherein one or more C of the alkyl group is replaced by {¨Si(R92-0¨} up to 375 and ncluding eight C being replaced by eight {¨Si(R1 )2-0¨}; a substituted or 376 unsubstituted CnSim group where n and m are independently a number from 0 to 8 and n+m 377 is a number from 1 to 8; a substituted or unsubstituted 04 to 08 aryl group wherein aryl is 378 optionally heteroaryl, optionally wherein one or more C is replaced by {¨Si 92-0¨}; a 379 substituted or unsubstituted aryl group having 4 to 8 ring atoms, optionally including one or 380 more {¨Si(R92-0¨}, wherein aryl is optionally heteroaryl; a si(Ri 0)2_0 \
) chain in 381 which p is from 1 to 8 which is terminated by H, or is terminated by a substituted or 382 unsubstituted Ci to 08 aliphatic and/or aryl group; or a substituted or unsubstituted (C, to 08 383 aliphatic)-(C4 to 08 aryl) group wherein aryl is optionally heteroaryl, optionally wherein one 384 or more C is replaced by a {¨Si(R92-0¨}; wherein Rio is a substituted or unsubstituted 385 Ci to C8 aliphatic group, a substituted or unsubstituted Ci to Ca alkoxy, a substituted or 386 unsubstituted C4 to 08 aryl wherein aryl is optionally heteroaryl, a substituted or unsubstituted 387 aliphatic-alkoxy, a substituted or unsubstituted aliphatic-aryl, or a substituted or 388 unsubstituted alkoxy-aryl group; where E is: a substituted or unsubstituted Ci to 08 aliphatic 389 group that is linear, branched, or cyclic, optionally wherein one or more C of the alkyl group 390 is replaced by {¨Si(R10)2¨O¨} up to and including 8 C being replaced by 8 1¨Si(R92----391 0-1; a substituted or unsubstituted CnSim group where n and m are independently a number 392 from 0 to 8 and n+nn is a number from 1 to 8; a substituted or unsubstituted 04 to 08 aryl 393 group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by 394 {-Si(R1 )2-0-}; a substituted or unsubstituted aryl group having 4 to 8 ring atoms, 395 optionally including one or more {¨Si(R1 )2-0¨}, wherein aryl is optionally heteroaryl; a -396 (Sl(R92-0)p- chain in which p is from 1 to 8; or a substituted or unsubstituted (C-1 to C8 397 aliphatic)-(C4 to 08 aryl) group wherein aryl is optionally heteroaryl, optionally wherein one 398 or more C is replaced by a {¨Si(R92-0¨}; and wherein R1 is a substituted or 399 unsubstituted Ci to 08 aliphatic group, a substituted or unsubstituted Ci to 08 alkoxy, a 400 substituted or unsubstituted 04 to 08 aryl wherein aryl is optionally heteroaryl, a substituted 401 or unsubstituted aliphatic-alkoxy, a substituted or unsubstituted aliphatic-aryl, or a 402 substituted or unsubstituted alkoxy-aryl group; and wherein a substituent is independently:
403 alkyl; alkenyl; alkynyl; aryl; aryl-halide; heteroaryl; cycloalkyl;
Si(alkyl)3; Si(alkoxy)3; halo;
404 alkoxyl; amino; alkylamino; alkenylamino; amide; hydroxyl; thioether;
alkylcarbonyl;
405 alkylcarbonyloxy; arylcarbonyloxy; alkoxycarbonyloxy; aryloxycarbonyloxy;
carbonate;
406 alkoxycarbonyl; aminocarbonyl; alkylthiocarbonyl; annidine, phosphate;
phosphate ester;
407 phosphonato; phosphinato; cyano; acylamino; imino; sulfhydryl; alkylthio;
arylthio;
408 thiocarboxylate; dithiocarboxylate; sulfate; sulfato; sulfonate;
sulfamoyl; sulfonamide; nitro;
409 nitrile; azido; heterocyclyl; ether; ester; silicon-containing moieties;
thioester; or a 410 combination thereof. In a most preferred embodiment of the present invention, the surface 411 functionality has the following structure, in its ionic state:

0 \

413 where is the surface of the insoluble particle; where R1 and R2 are independently: H; a 414 substituted or unsubstituted Ci to 08 aliphatic group that is linear, branched, or cyclic, 415 optionally wherein one or more C of the alkyl group is replaced by {¨Si(R1 )2-0¨} up to 416 and ncluding eight C being replaced by eight {¨Si(R92-0¨}; a substituted or 417 unsubstituted CnSim group where n and m are independently a number from 0 to 8 and n+m 418 is a number from 1 to 8; a substituted or unsubstituted 04 to C8 aryl group wherein aryl is 419 optionally heteroaryl, optionally wherein one or more C is replaced by {¨Si(1=11 )2-0¨}; a 420 substituted or unsubstituted aryl group having 4 to 8 ring atoms, optionally including one or 421 more {¨Si(R92-0¨}, wherein aryl is optionally heteroaryl; a ¨(Si(R10)2-0)p¨ chain in 422 which p is from 1 to 8 which is terminated by H, or is terminated by a substituted or 423 unsubstituted Ci to C8 aliphatic and/or aryl group; or a substituted or unsubstituted (C-1 to C8 424 aliphatic)-(C4 to 08 aryl) group wherein aryl is optionally heteroaryl, optionally wherein one 425 or more C is replaced by a {¨Si(R92-0¨}; wherein Ri is a substituted or unsubstituted 426 Ci to 08 aliphatic group, a substituted or unsubstituted Ci to 08 alkoxy, a substituted or 427 unsubstituted 04 to 08 aryl wherein aryl is optionally heteroaryl, a substituted or unsubstituted 428 aliphatic-alkoxy, a substituted or unsubstituted aliphatic-aryl, or a substituted or 429 unsubstituted alkoxy-aryl group; where E is: a substituted or unsubstituted Ci to 08 aliphatic 430 group that is linear, branched, or cyclic, optionally wherein one or more C of the alkyl group 431 is replaced by {¨Si(R1 )2-0¨} up to and including 8 C being replaced by 8 {¨Si(R92-432 0¨}; a substituted or unsubstituted CnSim group where n and m are independently a number 433 from 0 to 8 and n+m is a number from 1 to 8; a substituted or unsubstituted 04 to 08 aryl 434 group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by 435 {¨Si(R92-0¨}; a substituted or unsubstituted aryl group having 4 to 8 ring atoms, 436 optionally including one or more {¨Si(R92-0--}, wherein aryl is optionally heteroaryl; a ¨
437 (Si(R92-0)p¨ chain in which p is from 1 to 8; or a substituted or unsubstituted (Ci to 08 438 aliphatic)-(04 to Cs aryl) group wherein aryl is optionally heteroaryl, optionally wherein one 439 or more C is replaced by a {_si (R92-0¨}; and wherein Rio is a substituted or 440 unsubstituted Ci to 08 aliphatic group, a substituted or unsubstituted Ci to 08 alkoxy, a 441 substituted or unsubstituted C4 to C8 aryl wherein aryl is optionally heteroaryl, a substituted 442 or unsubstituted aliphatic-alkoxy, a substituted or unsubstituted aliphatic-aryl, or a 443 substituted or unsubstituted alkoxy-aryl group; and wherein a substituent is independently:
444 alkyl; alkenyl; alkynyl; aryl; aryl-halide; heteroaryl; cycloalkyl;
Si(alkyl)3; Si(alkoxy)3; halo;
445 alkoxyl; amino; alkylamino; alkenylamino; amide; hydroxyl; thioether;
alkylcarbonyl;
446 alkylcarbonyloxy; arylcarbonyloxy; alkoxycarbonyloxy; aryloxycarbonyloxy;
carbonate;
447 alkoxycarbonyl; aminocarbonyl; alkylthiocarbonyl; amidine, phosphate;
phosphate ester;
448 phosphonato; phosphinato; cyano; acylamino; imino; sulfhydryl; alkylthio;
arylthio;
449 thiocarboxylate; dithiocarboxylate; sulfate; sulfato; sulfonate;
sulfamoyl; sulfonamide; nitro;

450 nitrile; azido; heterocyclyl; ether; ester; silicon-containing moieties;
thioester; or a 451 combination thereof.
452 In a less preferred embodiment of the present invention, the surface functionality has the 453 following structure in its non-ionic state:
Ri R2 455 where is the surface of the insoluble particle; where R1 and R2 are independently:
H; a 456 substituted or unsubstituted Ci to Cs aliphatic group that is linear, branched, or cyclic, 457 optionally wherein one or more C of the alkyl group is replaced by {¨Si(R1 )2-0¨} up to 458 and ncluding eight C being replaced by eight {¨Si(R1 )2-0¨}; a substituted or 459 unsubstituted CnSim group where n and m are independently a number from 0 to 8 and n+m 460 is a number from 1 to 8; a substituted or unsubstituted 04 to 08 aryl group wherein aryl is 461 optionally heteroaryl, optionally wherein one or more C is replaced by {¨Si(R1 )2-0¨}; a 462 substituted or unsubstituted aryl group having 4 to 8 ring atoms, optionally including one or 463 more {¨Si(R1 )2-0¨}, wherein aryl is optionally heteroaryl; a ¨(Si(R1 )2-0)p¨ chain in 464 which p is from 1 to 8 which is terminated by H, or is terminated by a substituted or 465 unsubstituted Ci to 08 aliphatic and/or aryl group; or a substituted or unsubstituted (Ci to Cs 466 aliphatic)-(C4 to Cs aryl) group wherein aryl is optionally heteroaryl, optionally wherein one 467 or more C is replaced by a {¨Si(R1 )2-0¨}; wherein Rio is a substituted or unsubstituted 468 Ci to Cs aliphatic group, a substituted or unsubstituted Ci to 08 alkoxy, a substituted or 469 unsubstituted 04 to Cs aryl wherein aryl is optionally heteroaryl, a substituted or unsubstituted 470 aliphatic-alkoxy, a substituted or unsubstituted aliphatic-aryl, or a substituted or 471 unsubstituted alkoxy-aryl group; where E is: a substituted or unsubstituted Ci to Cs aliphatic 472 group that is linear, branched, or cyclic, optionally wherein one or more C of the alkyl group 473 is replaced by {¨Si(R1 )2-0¨} up to and including 8 C being replaced by 8 {¨Si(R10)2-474 0¨}; a substituted or unsubstituted CnSim group where n and m are independently a number 475 from 0 to 8 and n+m is a number from 1 to 8; a substituted or unsubstituted 04 to 08 aryl 476 group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by 477 {-Si(R10)2-0-}; a substituted or unsubstituted aryl group having 4 to 8 ring atoms, 478 optionally including one or more {¨Si(R10)2-0¨}, wherein aryl is optionally heteroaryl; a -479 (Si(R1 )2-0)p- chain in which p is from 1 to 8; or a substituted or unsubstituted (Ci to 08 480 aliphatic)-(C4 to 08 aryl) group wherein aryl is optionally heteroaryl, optionally wherein one 481 or more C is replaced by a {¨Si(R10)2-0¨}; and wherein R1 is a substituted or 482 unsubstituted Ci to 08 aliphatic group, a substituted or unsubstituted Ci to 08 alkoxy, a 483 substituted or unsubstituted 04 to 08 aryl wherein aryl is optionally heteroaryl, a substituted 484 or unsubstituted aliphatic-alkoxy, a substituted or unsubstituted aliphatic-aryl, or a 485 substituted or unsubstituted alkoxy-aryl group; and wherein a substituent is independently:
486 alkyl; alkenyl; alkynyl; aryl; aryl-halide; heteroaryl; cycloalkyl;
Si(alkyl)3; Si(alkoxy)3; halo;
487 alkoxyl; amino; alkylamino; alkenylamino; amide; hydroxyl; thioether;
alkylcarbonyl;
488 alkylcarbonyloxy; arylcarbonyloxy; alkoxycarbonyloxy; aryloxycarbonyloxy;
carbonate;
489 alkoxycarbonyl; anninocarbonyl; alkylthiocarbonyl; amidine, phosphate;
phosphate ester;
490 phosphonato; phosphinato; cyano; acylamino; imino; sulfhydryl; alkylthio;
arylthio;
491 thiocarboxylate; dithiocarboxylate; sulfate; sulfato; sulfonate;
sulfamoyl; sulfonamide; nitro;
492 nitrile; azido; heterocyclyl; ether; ester; silicon-containing moieties;
thioester; or a 493 combination thereof. In a less preferred embodiment of the present invention, the surface 494 functionality has the following structure in its ionic state:

496 where is the surface of the insoluble particle; where R1 and R2 are independently: H; a 497 substituted or unsubstituted Ci to C8 aliphatic group that is linear, branched, or cyclic, 498 optionally wherein one or more C of the alkyl group is replaced by {¨Si(R10)2-0¨} up to 499 and ncluding eight C being replaced by eight {¨Si(R10)2-0---}; a substituted or 500 unsubstituted CnSim group where n and m are independently a number from 0 to 8 and n+m 501 is a number from 1 to 8; a substituted or unsubstituted C4 to 08 aryl group wherein aryl is 502 optionally heteroaryl, optionally wherein one or more C is replaced by {¨Si(R92-0¨}; a 503 substituted or unsubstituted aryl group having 4 to 8 ring atoms, optionally including one or 504 more {¨Si(R92-0¨}, wherein aryl is optionally heteroaryl; a ¨(Si(R1 )2-0)p¨ chain in 505 which p is from 1 to 8 which is terminated by H, or is terminated by a substituted or 506 unsubstituted Ci to 08 aliphatic and/or aryl group; or a substituted or unsubstituted (Ci to 08 507 aliphatic)-(C4 to 08 aryl) group wherein aryl is optionally heteroaryl, optionally wherein one 508 or more C is replaced by a {¨Si(R92-0¨}; wherein R1 is a substituted or unsubstituted 509 Ci to 08 aliphatic group, a substituted or unsubstituted Ci to 08 alkoxy, a substituted or 510 unsubstituted 04 to 08 aryl wherein aryl is optionally heteroaryl, a substituted or unsubstituted 511 aliphatic-alkoxy, a substituted or unsubstituted aliphatic-aryl, or a substituted or 512 unsubstituted alkoxy-aryl group; where E is: a substituted or unsubstituted Ci to 08 aliphatic 513 group that is linear, branched, or cyclic, optionally wherein one or more C of the alkyl group 514 is replaced by {¨Si(R10)2-0¨} up to and including 8 C being replaced by 8 {¨Si(R92-515 0¨}; a substituted or unsubstituted CnSim group where n and m are independently a number 516 from 0 to 8 and n+m is a number from 1 to 8; a substituted or unsubstituted C4 to 08 aryl 517 group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by 518 {¨Si(R92-0¨}; a substituted or unsubstituted aryl group having 4 to 8 ring atoms, 519 optionally including one or more {¨Si(R10)2¨O¨}, wherein aryl is optionally heteroaryl; a ¨
520 (Si(R92-0)p¨ chain in which p is from 1 to 8; or a substituted or unsubstituted (Ci to 08 521 aliphatic)-(C4 to 08 aryl) group wherein aryl is optionally heteroaryl, optionally wherein one 522 or more C is replaced by a {¨Si(R92-0¨}; and wherein R1 is a substituted or 523 unsubstituted Ci to 08 aliphatic group, a substituted or unsubstituted Ci to 08 alkoxy, a 524 substituted or unsubstituted C4 to 08 aryl wherein aryl is optionally heteroaryl, a substituted 525 or unsubstituted aliphatic-alkoxy, a substituted or unsubstituted aliphatic-aryl, or a 526 substituted or unsubstituted alkoxy-aryl group; and wherein a substituent is independently:
527 alkyl; alkenyl; alkynyl; aryl; aryl-halide; heteroaryl; cycloalkyl;
Si(alkyl)3; Si(alkoxy)3; halo;

528 alkoxyl; amino; alkylamino; alkenylamino; amide; hydroxyl; thioether;
alkylcarbonyl;
529 alkylcarbonyloxy; arylcarbonyloxy; alkoxycarbonyloxy; aryloxycarbonyloxy;
carbonate;
530 alkoxycarbonyl; aminocarbonyl; alkylthiocarbonyl; amidine, phosphate;
phosphate ester;
531 phosphonato; phosphinato; cyano; acylamino; imino; sulfhydryl; alkylthio;
arylthio;
532 thiocarboxylate; dithiocarboxylate; sulfate; sulfato; sulfonate;
sulfamoyl; sulfonamide; nitro;
533 nitrile; azido; heterocyclyl; ether; ester; silicon-containing moieties;
thioester; or a 534 combination thereof. In specific embodiments of the present invention, the surface 535 functionality, in its non-ionic state, comprises:
h h0_,N y hON
0 N t\il h y x z y x "I
z y x I
hN hO'N k'.ON
537 y x ,or ) 538 where ¨ is the surface of the insoluble particle; where y and z are independently between 539 0 and 12; and x is between 1 and 12. In more specific embodiments of the present invention, 540 the surface functionality, in its non-ionic state, comprises:
....õ--..õ. 7 hN Ny h0^N---1--N hN Ny h0-'N N
541 I y x I Z Y X I X I Y x I
, hNN'' h0-"NN---\ k`O'NN7 N N x z x y x L542 z y x I
NN.v 1_,0---.NN k,.,0.--NN
x y x z y x 543 , ,or =
544 where ¨ is the surface of the insoluble particle; where y and z are independently between 545 0 and 12; and x is between 1 and 12. In further specific embodiments of the present invention, 546 the surface functionality, in its non-ionic state, comprises:

h07-.N
hN N y x y x z y x \/NN/
hNN
z y x y x , or \/N\/

z y x =

550 where ¨ is the surface of the insoluble particle; where y and z are independently between 551 0 and 12; and xis between 1 and 12.
552 In another aspect of the present invention, the surface functionality reversibly converts to its 553 non-ionic state upon contact with a trigger in the presence of water.
In some embodiments 554 of the present invention, the surface functionality is an oxygen acid wherein upon contact 555 with a trigger in the presence of water protonates said oxygen acid. In certain embodiments 556 of the present invention, the surface functionality comprises an oxygen acid wherein upon 557 contact with a trigger in the presence of water protonates the acid. In certain embodiments 558 of the present invention, the surface functionality, in its ionic state, comprises: a 2-nitro 559 phenoxide. In certain embodiments of the present invention, the surface functionality, in its 560 non-ionic state, a 2-nitrophenol.
561 In a preferred embodiment of the present invention, the surface functionality has the following 562 structure in its ionic state:

E = 0 564 where ¨ is the surface of the insoluble particle; where Q is ¨00C¨, ¨0C¨, ¨NOC¨, or ¨
565 NHOC¨, where Ri and R4 are independently: H; nitro; sulfo; ammonio;
cyano; trihalomethyl;
566 carbonyl; haloformyl; a substituted or unsubstituted Ci to 08 alkoxycarbonyl; a substituted or 567 unsubstituted Ci to 08 alkylformyl; formyl; halo; or a substituted or unsubstituted Ci to 08 568 carbamoyl; and where R2 and R3 are independently: H; alkyl; alkenyl;
aryl; amino; hydroxy;
569 a substituted or unsubstituted Ci to 08 alkylhydroxy; a substituted or unsubstituted Ci to C8 570 carboxyamido; or a substituted or unsubstituted Ci to C8 alkanyloxy;
wherein at least one or 571 more of R1, R2, R3, and R4 is not H; and where E is: a substituted or unsubstituted Ci to 08 572 alkoxycarbonyl; or a substituted or unsubstituted Ci to C8 carbamoyl a substituted or 573 unsubstituted Ci to 08 aliphatic group that is linear, branched, or cyclic, optionally wherein 574 one or more C of the alkyl group is replaced by {¨Si(R92-0¨} up to and including 8 C
575 being replaced by 8 {¨Si(R1 )2-0¨}; a substituted or unsubstituted CnSim group where n 576 and m are independently a number from 0 to 8 and n+m is a number from 1 to 8; a substituted 577 or unsubstituted 04 to C8 aryl group wherein aryl is optionally heteroaryl, optionally wherein 578 one or more C is replaced by {¨Si(fllo)2_0_, /,=
a substituted or unsubstituted aryl group 579 having 4 to 8 ring atoms, optionally including one or more {¨Si(R10)2¨O¨}, wherein aryl is 580 optionally heteroaryl; a ¨(Si(R10)2-0)p¨ chain in which p is from 1 to 8; or a substituted or 581 unsubstituted (Ci to 08 aliphatic)-(C4 to 08 aryl) group wherein aryl is optionally heteroaryl, 582 optionally wherein one or more C is replaced by a {¨Si(R92-0--};
wherein R13 is a 583 substituted or unsubstituted Ci to C8 aliphatic group, a substituted or unsubstituted Ci to 08 584 alkoxy, a substituted or unsubstituted 04 to 08 aryl wherein aryl is optionally heteroaryl, a 585 substituted or unsubstituted aliphatic-alkoxy, a substituted or unsubstituted aliphatic-aryl, or 586 a substituted or unsubstituted alkoxy-aryl group; and wherein a substituent is independently:

587 alkyl; alkenyl; alkynyl; aryl; aryl-halide; heteroaryl; cycloalkyl;
Si(alkyl)3; Si(alkoxy)3; halo;
588 alkoxyl; amino; alkylamino; alkenylamino; amide; hydroxyl; thioether;
alkylcarbonyl;
589 alkylcarbonyloxy; arylcarbonyloxy; alkoxycarbonyloxy; aryloxycarbonyloxy;
carbonate;
590 alkoxycarbonyl; aminocarbonyl; alkylthiocarbonyl; amidine, phosphate;
phosphate ester;
591 phosphonato; phosphinato; cyano; acylamino; imino; sulfhydryl; alkylthio;
arylthio;
592 thiocarboxylate; dithiocarboxylate; sulfate; sulfato; sulfonate;
sulfamoyl; sulfonamide; nitro;
593 nitrile; azido; heterocyclyl; ether; ester; silicon-containing moieties;
thioester; or a 594 combination thereof. In a preferred embodiment of the present invention, the surface 595 functionality has the following structure in its ionic state:

E_Q
= OH

597 where is the surface of the insoluble particle; where Q is ¨000¨, ¨0C¨, ¨NOC¨, or -598 NHOC¨, where R1 and R4 are independently: H; nitro; sulfo; ammonio;
cyano; trihalomethyl;
599 carbonyl; haloformyl; a substituted or unsubstituted Ci to 08 alkoxycarbonyl; a substituted or 600 unsubstituted Ci to 08 alkylformyl; formyl; halo; or a substituted or unsubstituted Ci to 08 601 carbamoyl; and where R2 and R3 are independently: H; alkyl; alkenyl;
aryl; amino; hydroxy;
602 a substituted or unsubstituted Ci to 08 alkylhydroxy; a substituted or unsubstituted Ci to C8 603 carboxyamido; or a substituted or unsubstituted Ci to C8 alkanyloxy;
wherein at least one or 604 more of R1, R2, R3, and R4 is not H; and where E is: a substituted or unsubstituted Ci to 08 605 alkoxycarbonyl; or a substituted or unsubstituted Ci to 08 carbamoyl a substituted or 606 unsubstituted Ci to 08 aliphatic group that is linear, branched, or cyclic, optionally wherein 607 one or more C of the alkyl group is replaced by {¨Si(R92-0¨} up to and including 8 C
608 being replaced by 8 {¨Si(R92-0--}; a substituted or unsubstituted CnSim group where n 609 and m are independently a number from 0 to 8 and n+m is a number from 1 to 8; a substituted 610 or unsubstituted 04 to 08 aryl group wherein aryl is optionally heteroaryl, optionally wherein 611 one or more C is replaced by 1¨Si(R92-0-1; a substituted or unsubstituted aryl group 612 having 4 to 8 ring atoms, optionally including one or more {¨Si(R92-0¨}, wherein aryl is 613 optionally heteroaryl; a ¨(Si(R10)2-0)p¨ chain in which p is from 1 to 8; or a substituted or 614 unsubstituted (Ci to Ca aliphatic)-(C4 to C8 aryl) group wherein aryl is optionally heteroaryl, 615 optionally wherein one or more C is replaced by a {¨Si(R92-0¨}; wherein R1 is a 616 substituted or unsubstituted Ci to 08 aliphatic group, a substituted or unsubstituted Ci to C8 617 alkoxy, a substituted or unsubstituted 04 to 08 aryl wherein aryl is optionally heteroaryl, a 618 substituted or unsubstituted aliphatic-alkoxy, a substituted or unsubstituted aliphatic-aryl, or 619 a substituted or unsubstituted alkoxy-aryl group; and wherein a substituent is independently:
620 alkyl; alkenyl; alkynyl; aryl; aryl-halide; heteroaryl; cycloalkyl;
Si(alkyl)3; Si(alkoxy)3; halo;
621 alkoxyl; amino; alkylamino; alkenylamino; amide; hydroxyl; thioether;
alkylcarbonyl;
622 alkylcarbonyloxy; arylcarbonyloxy; alkoxycarbonyloxy; aryloxycarbonyloxy;
carbonate;
623 alkoxycarbonyl; aminocarbonyl; alkylthiocarbonyl; amidine, phosphate;
phosphate ester;
624 phosphonato; phosphinato; cyano; acylamino; innino; sulfhydryl; alkylthio;
arylthio;
625_ thiocarboxylate; dithiocarboxylate; sulfate; sulfato; sulfonate;
sulfamoyl; sulfonamide; nitro;
626 nitrile; azido; heterocyclyl; ether; ester; silicon-containing moieties;
thioester; or a 627 combination thereof.
628 In a preferred embodiment of the present invention, the surface functionality has the following 629 structure in its ionic state:

E -631 where ¨ is the surface of the insoluble particle; where R1 is: H;
nitro; sulfo; ammonio;
632 cyano; trihalomethyl; carbonyl; haloformyl; a substituted or unsubstituted Ci to 08 633 alkoxycarbonyl; a substituted or unsubstituted Ci to 08 alkylformyl;
formyl; halo; or a 634 substituted or unsubstituted C-1 to 08 carbamoyl; and where R2 and R3 are independently: H;

635 alkyl; alkenyl; aryl; amino; hydroxy; a substituted or unsubstituted Ci to Cs alkylhydroxy; a 636 substituted or unsubstituted Ci to 08 carboxyamido; or a substituted or unsubstituted Ci to 637 C8 alkanyloxy; wherein E is: a substituted or unsubstituted Ci to 08 alkoxycarbonyl; or a 638 substituted or unsubstituted Ci to Cs carbamoyl a substituted or unsubstituted C-1 to 08 639 aliphatic group that is linear, branched, or cyclic, optionally wherein one or more C of the 640 alkyl group is replaced by {¨Si(R10)2-0¨} up to and including 8 C being replaced by 8 {-641 Si(R1 )2-0¨}; a substituted or unsubstituted CnSim group where n and m are independently 642 a number from 0 to 8 and n+m is a number from 1 to 8; a substituted or unsubstituted 04 to 643 08 aryl group wherein aryl is optionally heteroaryl, optionally wherein one or more C is 644 replaced by {¨Si(R1 )2-0¨}; a substituted or unsubstituted aryl group having 4 to 8 ring 645 atoms, optionally including one or more {¨Si(R1 )2-0¨}, wherein aryl is optionally 646 heteroaryl; a ¨(Si(R10)2-0)p¨ chain in which p is from 1 to 8; or a substituted or 647 unsubstituted (Ci to 08 aliphatic)-(C4 to 08 aryl) group wherein aryl is optionally heteroaryl, 648 optionally wherein one or more C is replaced by a 1¨Si(R92-0-1; wherein Rio is a 649 substituted or unsubstituted Ci to C8 aliphatic group, a substituted or unsubstituted C-1 to 08 650 alkoxy, a substituted or unsubstituted 04 to 08 aryl wherein aryl is optionally heteroaryl, a 651 substituted or unsubstituted aliphatic-alkoxy, a substituted or unsubstituted aliphatic-aryl, or 652 a substituted or unsubstituted alkoxy-aryl group; and wherein a substituent is independently:
653 alkyl; alkenyl; alkynyl; aryl; aryl-halide; heteroaryl; cycloalkyl;
Si(alkyl)3; Si(alkoxy)3; halo;
654 alkoxyl; amino; alkylannino; alkenylamino; amide; hydroxyl; thioether;
alkylcarbonyl;
655 alkylcarbonyloxy; arylcarbonyloxy; alkoxycarbonyloxy; aryloxycarbonyloxy;
carbonate;
656 alkoxycarbonyl; aminocarbonyl; alkylthiocarbonyl; amidine, phosphate;
phosphate ester;
657 phosphonato; phosphinato; cyano; acylamino; imino; sulfhydryl; alkylthio;
arylthio;
658 thiocarboxylate; dithiocarboxylate; sulfate; sulfato; sulfonate;
sulfamoyl; sulfonamide; nitro;
659 nitrile; azido; heterocyclyl; ether; ester; silicon-containing moieties;
thioester; or a 660 combination thereof. In a preferred embodiment of the present invention, the surface 661 functionality has the following structure in its non-ionic state:

663 where is the surface of the insoluble particle; where R1 is: H;
nitro; sulfa; ammonia;
664 cyano; trihalomethyl; carbonyl; haloformyl; a substituted or unsubstituted C-1 to 08 665 alkoxycarbonyl; a substituted or unsubstituted Ci to Cs alkylformyl;
formyl; halo; or a 666 substituted or unsubstituted Ci to Cs carbamoyl; and where R2 and R3 are independently: H;
667 alkyl; alkenyl; aryl; amino; hydroxy; a substituted or unsubstituted CI
to 08 alkylhydroxy; a 668 substituted or unsubstituted Ci to Cs carboxyamido; or a substituted or unsubstituted Ci to 669 C8 alkanyloxy; where E is: a substituted or unsubstituted Ci to 08 alkoxycarbonyl; or a 670 substituted or unsubstituted Ci to 08 carbamoyl a substituted or unsubstituted Ci to 08 671 aliphatic group that is linear, branched, or cyclic, optionally wherein one or more C of the 672 alkyl group is replaced by {¨Si(R10)2-0¨} up to and including 8 C being replaced by 8 {-673 Si(R10)2-0¨}; a substituted or unsubstituted CnSim group where n and m are independently 674 a number from 0 to 8 and n+m is a number from 1 to 8; a substituted or unsubstituted 04 to 675 08 aryl group wherein aryl is optionally heteroaryl, optionally wherein one or more C is 676 replaced by {¨Si(R10)2-0¨}; a substituted or unsubstituted aryl group having 4 to 8 ring 677 atoms, optionally including one or more i_si(Ri 0) 2-0-1, wherein aryl is optionally 678 heteroaryl; a ¨(Si(R10)2-0)p¨ chain in which p is from 1 to 8; or a substituted or 679 unsubstituted (C, to Cs aliphatic)-(C4 to Cs aryl) group wherein aryl is optionally heteroaryl, 680 optionally wherein one or more C is replaced by a {¨Si(R1 )2-0¨};
wherein R1 is a 681 substituted or unsubstituted Ci to 08 aliphatic group, a substituted or unsubstituted Ci to Cs 682 alkoxy, a substituted or unsubstituted 04 to 08 aryl wherein aryl is optionally heteroaryl, a 683 substituted or unsubstituted aliphatic-alkoxy, a substituted or unsubstituted aliphatic-aryl, or 684 a substituted or unsubstituted alkoxy-aryl group; and wherein a substituent is independently:
685 alkyl; alkenyl; alkynyl; aryl; aryl-halide; heteroaryl; cycloalkyl;
Si(alkyl)3; Si(alkoxy)3; halo;
686 alkoxyl; amino; alkylamino; alkenylamino; amide; hydroxyl; thioether;
alkylcarbonyl;

687 alkylcarbonyloxy; arylcarbonyloxy; alkoxycarbonyloxy; aryloxycarbonyloxy;
carbonate;
688 alkoxycarbonyl; aminocarbonyl; alkylthiocarbonyl; amidine, phosphate;
phosphate ester;
689 phosphonato; phosphinato; cyano; acylamino; imino; sulfhydryl; alkylthio;
arylthio;
690 thiocarboxylate; dithiocarboxylate; sulfate; sulfato; sulfonate;
sulfamoyl; sulfonamide; nitro;
691 nitrile; azido; heterocyclyl; ether; ester; silicon-containing moieties;
thioester; or a 692 combination thereof.
693 In another preferred embodiment of the present invention, the surface functionality has the 694 following structure in its non-ionic state:

OC) E N

696 where wwis the surface of the insoluble particle; where R1 is: H;
nitro; sulfo; ammonio;
697 cyano; trihalomethyl; carbonyl; haloformyl; a substituted or unsubstituted Ci to 08 698 alkoxycarbonyl; a substituted or unsubstituted Ci to 08 alkylformyl;
formyl; halo; or a 699 substituted or unsubstituted Ci to 08 carbamoyl; and where R2 and R3 are independently: H, 700 alkyl; alkenyl; aryl; amino; hydroxy; a substituted or unsubstituted Ci to 08 alkylhydroxy; a 701 substituted or unsubstituted Ci to C8 carboxyamido; or a substituted or unsubstituted Ci to 702 C8 alkanyloxy; where E is: a substituted or unsubstituted Ci to 08 alkoxycarbonyl; or a 703 substituted or unsubstituted Ci to 08 carbamoyl a substituted or unsubstituted Ci to Cs 704 aliphatic group that is linear, branched, or cyclic, optionally wherein one or more C of the 705 alkyl group is replaced by {¨Si(R10)2-0¨} up to and including 8 C being replaced by 8 {-706 Si(R1 )2-0¨}; a substituted or unsubstituted CnSim group where n and m are independently 707 a number from 0 to 8 and n+m is a number from 1 to 8; a substituted or unsubstituted C4 to 708 08 aryl group wherein aryl is optionally heteroaryl, optionally wherein one or more C is 709 replaced by {¨Si(R92-0¨}; a substituted or unsubstituted aryl group having 4 to 8 ring 710 atoms, optionally including one or more 1¨Si(R92-0-1, wherein aryl is optionally 711 heteroaryl; a ¨(Si(R10)2-0)p¨ chain in which p is from 1 to 8; or a substituted or 712 unsubstituted (Ci to 08 aliphatic)-(C4 to 08 aryl) group wherein aryl is optionally heteroaryl, 713 optionally wherein one or more C is replaced by a {¨Si(R10)2-0¨}; wherein R1 is a 714 substituted or unsubstituted Ci to Cs aliphatic group, a substituted or unsubstituted Ci to 08 715 alkoxy, a substituted or unsubstituted C4 to C8 aryl wherein aryl is optionally heteroaryl, a 716 substituted or unsubstituted aliphatic-alkoxy, a substituted or unsubstituted aliphatic-aryl, or 717 a substituted or unsubstituted alkoxy-aryl group; and wherein a substituent is independently:
718 alkyl; alkenyl; alkynyl; aryl; aryl-halide; heteroaryl; cycloalkyl;
Si(alkyl)3; Si(alkoxy)3; halo;
719 alkoxyl; amino; alkylamino; alkenylamino; amide; hydroxyl; thioether;
alkylcarbonyl;
720 alkylcarbonyloxy; arylcarbonyloxy; alkoxycarbonyloxy; aryloxycarbonyloxy;
carbonate;
721 alkoxycarbonyl; aminocarbonyl; alkylthiocarbonyl; amidine, phosphate;
phosphate ester;
722 phosphonato; phosphinato; cyano; acylamino; imino; sulfhydryl; alkylthio;
arylthio;
723 thiocarboxylate; dithiocarboxylate; sulfate; sulfato; sulfonate;
sulfamoyl; sulfonamide; nitro;
724 nitrile; azido; heterocyclyl; ether; ester; silicon-containing moieties;
thioester; or a 725 combination thereof. In another preferred embodiment of the present invention, the surface 726 functionality has the following structure in its non-ionic state:

\
1 =

--N I-728 where ¨ is the surface of the insoluble particle; where R1 is: H;
nitro; sulfo; annmonio;
729 cyano; trihalomethyl; carbonyl; haloformyl; a substituted or unsubstituted Ci to C8 730 alkoxycarbonyl; a substituted or unsubstituted Ci to 08 alkylformyl;
formyl; halo; or a 731 substituted or unsubstituted Ci to 08 carbamoyl; and where R2 and R3 are independently: H, 732 alkyl; alkenyl; aryl; amino; hydroxy; a substituted or unsubstituted Ci to 08 alkylhydroxy; a 733 substituted or unsubstituted Ci to 08 carboxyamido; or a substituted or unsubstituted C-1 to 734 08 alkanyloxy; where E is: a substituted or unsubstituted Ci to 08 alkoxycarbonyl; or a 735 substituted or unsubstituted Ci to C8 carbamoyl a substituted or unsubstituted Ci to 08 736 aliphatic group that is linear, branched, or cyclic, optionally wherein one or more C of the 737 alkyl group is replaced by {¨Si(R1 )2-0¨} up to and including 8 C being replaced by 8 {-738 Si(R10)2-0¨}; a substituted or unsubstituted CnSim group where n and m are independently 739 a number from 0 to 8 and n+m is a number from 1 to 8; a substituted or unsubstituted 04 to 740 C8 aryl group wherein aryl is optionally heteroaryl, optionally wherein one or more C is 741 replaced by {¨Si(R92-0¨}; a substituted or unsubstituted aryl group having 4 to 8 ring 742 atoms, optionally including one or more {¨Si(R92-0-1, wherein aryl is optionally 743 heteroaryl; a ¨(Si(R1 )2-0)p¨ chain in which p is from 1 to 8; or a substituted or 744 unsubstituted (Ci to 08 aliphatic)-(C4 to 08 aryl) group wherein aryl is optionally heteroaryl, 745 optionally wherein one or more C is replaced by a {¨Si(R92-0¨}; wherein Rio is a 746 substituted or unsubstituted Ci to 08 aliphatic group, a substituted or unsubstituted Ci to 08 747 alkoxy, a substituted or unsubstituted C4 to 08 aryl wherein aryl is optionally heteroaryl, a 748 substituted or unsubstituted aliphatic-alkoxy, a substituted or unsubstituted aliphatic-aryl, or 749 a substituted or unsubstituted alkoxy-aryl group; and wherein a substituent is independently:
750 alkyl; alkenyl; alkynyl; aryl; aryl-halide; heteroaryl; cycloalkyl;
Si(alkyl)3; Si(alkoxy)3; halo;
751 alkoxyl; amino; alkylamino; alkenylamino; amide; hydroxyl; thioether;
alkylcarbonyl;
752 alkylcarbonyloxy; arylcarbonyloxy; alkoxycarbonyloxy; aryloxycarbonyloxy;
carbonate;
753 alkoxycarbonyl; aminocarbonyl; alkylthiocarbonyl; amidine, phosphate;
phosphate ester;
754 phosphonato; phosphinato; cyano; acylamino; imino; sulfhydryl; alkylthio;
arylthio;
755 thiocarboxylate; dithiocarboxylate; sulfate; sulfato; sulfonate;
sulfamoyl; sulfonamide; nitro;
756 nitrile; azido; heterocyclyl; ether; ester; silicon-containing moieties;
thioester; or a 757 combination thereof. In specific embodiments of the present invention, the surface 758 functionality, in its ionic state, comprises:

h=
NO2 hoc =

0 N i le e y 401 s e x H
760 where ¨ is the surface of the insoluble particle; where y and z are independently between 761 0 and 12; and x is between 1 and 12.

762 In more specific embodiments of the present invention, the surface functionality, in its ionic 763 state, comprises:

00 NO 10 h2 NO
o 0 No 1 e e hyx z y x 764 0 , 0 , or o =
765 where is the surface of the insoluble particle; where y and z are independently between 766 0 and 12; and xis between 1 and 12.
767 System Claims 768 The present also invention relates to a system comprising: an aqueous dispersion 769 comprising responsive particles with switchable surface charge; means for switching said 770 responsive particles from ionic state to non-ionic state or from non-ionic state to. ionic state;
771 and wherein the aqueous dispersion has high ionic strength when the responsive particles 772 are in ionic state and the aqueous dispersion has low ionic strength when the responsive 773 particles are in non-ionic state.
774 In certain embodiments of the present invention, the responsive particles comprise: an 775 insoluble particle and a surface functionality which is a base wherein addition of the trigger 776 to the aqueous dispersion protonates said base; and the aqueous dispersion has high ionic 777 strength when said trigger is added to the aqueous dispersion and low ionic strength when 778 said trigger is removed from the aqueous dispersion. In certain embodiments of the present 779 invention, means for switching the responsive particles from non-ionic state to ionic state 780 comprises means for adding the trigger to the aqueous dispersion; and means for switching 781 the responsive particles from ionic state to non-ionic state comprises means for removing 782 said trigger from said aqueous dispersion. In a specific embodiment of the present invention, 783 the surface functionality comprises a nitrogen base. In a preferred embodiment of the present 784 invention, in non-ionic state, the surface functionality comprises: an amidine, a guanidine, or 785 a tertiary amine; and in ionic state, the surface functionality respectively comprises: an 786 amidinium, a guanidinium, or a tertiary aminium.
787 In certain embodiments of the present invention, the responsive particles comprise: an 788 insoluble particle and a surface functionality which is an acid wherein addition of the trigger 789 to the aqueous dispersion protonates said acid; and the aqueous dispersion has low ionic 790 strength when a trigger is added to the aqueous dispersion and the aqueous dispersion has 791 low ionic strength when said trigger is removed from the aqueous dispersion. In certain 792 embodiments of the present invention, means for switching the responsive particles from 793 ionic state to non-ionic state comprises addition of a trigger to the aqueous dispersion; and 794 means for switching the responsive particles from non-ionic state to ionic state comprises 795 removal of said trigger to the aqueous dispersion. In a specific embodiment of the present 796 invention, the surface functionality comprises an oxygen acid. In a preferred embodiment of 797 the present invention, in ionic state, the surface functionality comprises 2-nitrophenoxide;
798 and in non-ionic state, the surface functionality comprises 2-nitrophenol.
799 In another aspect of the present invention, the trigger comprises CO2, NO2, COS, or CS2. In 800 certain embodiments of the present invention, means for adding the trigger to the aqueous 801 dispersion comprises: bubbling said trigger into said aqueous dispersion, adding a trigger 802 solution saturated with said trigger, mixing said aqueous dispersion under said trigger, or 803 combinations thereof. In certain embodiments of the present invention, means for removing 804 the trigger from the aqueous dispersion comprises: heating said aqueous dispersion, sparing 805 said aqueous dispersion with a flushing gas, exposing said aqueous dispersion to vacuum 806 or partial vacuum, agitating said aqueous dispersion, sonicating said aqueous dispersion, or 807 combinations thereof. In a preferred embodiment of the present invention, the flushing gas 808 comprises: air, N2, or other gas with low concentration of CO2, NO2, COS, and CS2.
809 In another aspect of the present invention, the system further comprising means for 810 separating the responsive particles with switchable surface charge from the aqueous 811 dispersion. In certain embodiments of the present invention, means for separating the 812 responsive particles with switchable surface charge from the aqueous dispersion comprises:
813 sedimentation, centrifugation, flotation, gravity filtration, vacuum filtration, or combinations 814 thereof. In another embodiment of the present invention, the responsive particles with 815 switchable surface charge are magnetically susceptible and means for separating said 816 responsive particles comprises: a permanent magnet, an electromagnet, or a high-gradient 817 magnetic separator. In another embodiment of the present invention, the responsive particles 818 with switchable surface charge are in ionic state and means for separating said responsive 819 particles comprises an electric field.

820 System for Modulating the Electrochemical Gradient 821 The present invention relates to a system for modulating the electrochemical gradient across 822 a membrane comprising: an aqueous dispersion comprising responsive particles with 823 switchable surface charge; means for contacting a feed solution with said membrane; means 824 for switching the surface charge of said responsive particles from non-ionic state to ionic 825 state; and means for switching the surface charge of said responsive particles from ionic 826 state to non-ionic state. In one aspect of the present invention, the membrane pore size is 827 smaller than the size of the responsive particles. In one embodiment of the present invention, 828 the aqueous dispersion is located on one side of the membrane and the feed solution is on 829 the opposing side of said membrane. In another embodiment of the present invention, the 830 system for modulating the electrochemical gradient further comprises a receiving solution;
831 wherein the aqueous dispersion is located on one side of the membrane and the feed 832 solution is on the same side of said membrane; and said receiving solution is located on the 833 opposing side of said membrane.
834 In certain embodiments of the present invention, the responsive particles comprise an 835 insoluble particle and a surface functionality which is a base and wherein: means for 836 switching the responsive particles from non-ionic state to ionic state comprises addition of a 837 trigger; and means for switching the responsive particles from ionic state to non-ionic state 838 comprises removal of said trigger. In one embodiment of the present invention, the surface 839 functionality comprises a nitrogen base wherein contact with the trigger in the presence of 840 water protonates said nitrogen base. In a preferred embodiment of the present invention, in 841 non-ionic state, the surface functionality comprises: an amidine, a guanidine, or a tertiary 842 amine; and, in ionic state, the surface functionality comprises: an annidinium, a guanidium, 843 or a tertiary aminium. In certain embodiments of the present invention, the responsive 844 particles comprise an insoluble particle and a surface functionality which is an acid and 845 wherein: means for switching the responsive particles from ionic state to non-ionic state 846 comprises addition of a trigger; and means for switching the responsive particles from non-847 ionic state to ionic state comprises removal of said trigger.
848 In certain embodiments of the present invention, the responsive particles comprise an 849 insoluble particle and a surface functionality which is a base and wherein: means for 850 switching the responsive particles from ionic state to non-ionic state comprises addition of a 851 trigger; and means for switching the responsive particles from non-ionic state to ionic state 852 comprises removal of said trigger. In one embodiment of the present invention, the surface 853 functionality comprises an oxygen acid wherein contact with the trigger in the presence of 854 water protonates said oxygen acid. In a preferred embodiment of the present invention the 855 surface functionality, in ionic state, comprises 2-nitrophenoxide; and, in non-ionic state, the 856 surface functionality comprises 2-nitrophenol.
857 In another aspect of the present invention, the trigger comprises CO2, NO2, COS, or CS2. In 858 certain embodiments of the present invention, means for adding the trigger to the aqueous 859 dispersion comprises: bubbling said trigger into said aqueous dispersion, adding a trigger 860 solution saturated with said trigger, mixing said aqueous dispersion under said trigger, or 861 combinations thereof. In certain embodiments of the present invention, means for removing 862 the trigger from the aqueous dispersion comprises: heating said aqueous dispersion, sparing 863 said aqueous dispersion with a flushing gas, exposing said aqueous dispersion to vacuum 864 or partial vacuum, agitating said aqueous dispersion, sonicating said aqueous dispersion, or 865 combinations thereof. In a preferred embodiment of the present invention, the flushing gas 866 comprises: air, N2, or other gas with low concentration of CO2, NO2, COS, and C52.
867 In another aspect of the present invention, the system for modulating the electrochemical 868 gradient across a membrane further comprises means for separating the responsive 869 particles with switchable surface charge from the aqueous dispersion. In certain 870 embodiments of the present invention, means for separating the responsive particles with 871 switchable surface charge from the aqueous dispersion comprises:
sedimentation, 872 centrifugation, flotation, gravity filtration, vacuum filtration, or combinations thereof. In 873 another embodiment of the present invention, the responsive particles with switchable 874 surface charge are magnetically susceptible and means for separating said responsive 875 particles comprises: a permanent magnet, an electromagnet, or a high-gradient magnetic 876 separator. In another embodiment of the present invention, the responsive particles with 877 switchable surface charge are in ionic state and means for separating said responsive 878 particles comprises an electric field.

879 In another aspect of the present invention, the system for modulating the electrochemical 880 gradient across a membrane for use in reducing or increasing the ionic strength of an 881 aqueous solution wherein the feed solution comprises water, dissolved species, and 882 dispersed solids. In one embodiments of the present invention, the system for modulating 883 the electrochemical gradient across a membrane is for use in reducing or increasing the 884 concentration of multivalent ions in an aqueous solution wherein the feed solution comprises 885 water, dissolved species, and dispersed solids. In a preferred embodiment of the present 886 invention, the system for modulating the electrochemical gradient across a membrane is for 887 use in treating industrial process water. In many chemical processes, additives are required 888 which includes mineral salts and other water-soluble compounds; these soluble compounds 889 are difficult to remove and uncontrolled accumulation of ions is often detrimental to the 890 performance of the process. Treated industrial process water contains reduced ionic 891 strength. In one embodiment of the present invention, the system for modulating the 892 electrochemical gradient across a membrane is for treating process water. Bituminous sand 893 extraction tailings contain dispersed clay particles which sediment extremely slowly. Addition 894 of multivalent ions causes rapid aggregations of dispersed clay particles and accelerates 895 settling rate but is detrimental to bitumen extraction and must be removed. In another 896 preferred embodiment of the present invention, the system is for use in treating bituminous 897 sand extraction tailings.
898 System for Modulating Osmotic Gradient 899 The present invention also relates to a system for modulating the osmotic gradient across a 900 membrane, comprising: an aqueous dispersion comprising responsive particles with 901 switchable surface charge; means for contacting a feed solution with said membrane; means 902 for switching the surface charge of said responsive particles from its non-ionic state to its 903 ionic state; and means for switching the surface charge of said responsive particles from its 904 ionic state to its non-ionic state; wherein means for switching the surface charge of said 905 responsive particles with switchable surface charge from non-ionic state to ionic state raises 906 the ionic strength of said aqueous dispersion above the ionic strength of said feed solution.
907 In one aspect of the present invention, the membrane is selectively permeable for water. In 908 one embodiment of the present invention, the aqueous dispersion is located on one side of 909 the membrane and the feed solution is on the opposing side of said membrane; and wherein 910 means for contacting said feed solution with said membrane permits water from said feed 911 solution to permeate through said membrane into said aqueous dispersion comprising 912 responsive particles with switchable surface charge along the osmotic gradient generated 913 by the difference in ionic strength between said feed solution and said aqueous dispersion 914 when said responsive particles with switchable surface charge are in its ionic state.
915 In another embodiment of the present invention, the system for modulating the osmotic 916 gradient across a membrane further comprises an exchange solution; wherein both the 917 aqueous dispersion and the feed solution are on one side of the membrane while said 918 exchange solution is located on the opposing side of said membrane; and wherein means 919 for contacting said feed solution with said membrane permits flow of water from said 920 exchange solution through said membrane into said feed solution and said aqueous 921 dispersion comprising responsive particles with switchable surface charge along the osmotic 922 gradient generated by the difference in ionic strength between said feed solution and said 923 draw medium when said responsive particles with switchable surface charge are in its ionic 924 state.
925 In certain embodiments of the present invention, the responsive particles comprise an 926 insoluble particle and a surface functionality which is a base and wherein: means for 927 switching the responsive particles from non-ionic state to ionic state comprises addition of a 928 trigger; and means for switching the responsive particles from ionic state to non-ionic state 929 comprises removal of said trigger. In one embodiment of the present invention, the surface 930 functionality comprises a nitrogen base wherein contact with the trigger in the presence of 931 water protonates said nitrogen base. In a preferred embodiment of the present invention, in 932 non-ionic state, the surface functionality comprises: an amidine, a guanidine, or a tertiary 933 amine; and, in ionic state, the surface functionality comprises: an amidinium, a guanidium, 934 or a tertiary aminium.
935 In certain embodiments of the present invention, the responsive particles comprise an 936 insoluble particle and a surface functionality which is an acid and wherein: means for 937 switching the responsive particles from ionic state to non-ionic state comprises addition of a 938 trigger; and means for switching the responsive particles from non-ionic state to ionic state 939 comprises removal of said trigger. In one embodiment of the present invention, the surface 940 functionality comprises an oxygen acid wherein contact with the trigger in the presence of 941 water protonates said oxygen acid. In a preferred embodiment of the present invention the 942 surface functionality, in ionic state, comprises 2-nitrophenoxide; and, in non-ionic state, the 943 surface functionality comprises 2-nitrophenol.
944 In another aspect of the present invention, the trigger comprises CO2, NO2, COS, or CS2. In 945 certain embodiments of the present invention, means for adding the trigger to the aqueous 946 dispersion comprises: bubbling said trigger into said aqueous dispersion, adding a trigger 947 solution saturated with said trigger, mixing said aqueous dispersion under said trigger, or 948 combinations thereof. In certain embodiments of the present invention, means for removing 949 the trigger from the aqueous dispersion comprises: heating said aqueous dispersion, sparing 950 said aqueous dispersion with a flushing gas, exposing said aqueous dispersion to vacuum 951 or partial vacuum, agitating said aqueous dispersion, son icating said aqueous dispersion, or 952 combinations thereof. In a preferred embodiment of the present invention, the flushing gas 953 comprises: air, N2, or other gas with low concentration of CO2, NO2, COS, and CS2.
954 In another aspect of the present invention, the system modulating the osmotic gradient 955 across a membrane further comprises means for separating the responsive particles with 956 switchable surface charge from the aqueous dispersion. In certain embodiments of the 957 present invention, means for separating the responsive particles with switchable surface 958 charge from the aqueous dispersion comprises: sedimentation, centrifugation, flotation, 959 gravity filtration, vacuum filtration, or combinations thereof. In another embodiment of the 960 present invention, the responsive particles with switchable surface charge are magnetically 961 susceptible and means for separating said responsive particles comprises: a permanent 962 magnet, an electromagnet, or a high-gradient magnetic separator. In another embodiment 963 of the present invention, the responsive particles with switchable surface charge are in ionic 964 state and means for separating said responsive particles comprises an electric field.
965 The system for modulating the osmotic gradient is capable of selectively separating water 966 from feed solutions which contain dissolved or dispersed contaminants.
In another aspect of 967 the present invention, the system for modulating the osmotic gradient across a membrane is 968 for water treatment. In certain embodiments of the present invention, the feed solution 969 comprises: water, dissolved species, or dispersed solids. In one embodiment of the present 970 invention, the feed solution is brackish water, saline water, or brine water. In another 971 embodiment of the present invention, the feed solution is seawater, industrial wastewater, or 972 runoff water. Water is selectively driven across the membrane while contaminants are 973 rejected by the membrane. In a preferred embodiment of the present invention, the system 974 for modulating the osmotic gradient across a membrane is for desalination.
Water with 975 certain levels of dissolved salts including sodium chloride cannot be used in agricultural 976 processes or for consumption. For example, seawater cannot be used as drinking water 977 source nor for agricultural irrigation. Industrial process water often contains an undesirable 978 surplus of dissolved ion which can lead to poor performance, increased scale build-up, and 979 other problems. Boilers and other industrial equipment are susceptible to accumulation of 980 insoluble salts such as calcium carbonate which reduces the efficiency of the equipment as 981 well as its service life. In another embodiment of the present invention, the system for 982 modulating the osmotic gradient across a membrane is for increasing or decreasing the ionic 983 strength of water. In another embodiment of the present invention, the system for modulating 984 the osmotic gradient across a membrane is for increase or decreasing the concentration of 985 multivalent ions.
986 Method for Modulating Electrochemical or Osmotic Gradient 987 The present invention also relates to a method for modulating an osmotic gradient or an 988 electrochemical gradient across a membrane comprising: providing an aqueous dispersion 989 comprising responsive particles with switchable surface charge on one side of said 990 membrane; providing a solution on the opposing side of said membrane;
and switching the 991 surface charge of said responsive particles from non-ionic state to ionic state or switching 992 the surface charge of said responsive particles from ionic state to non-ionic state.
993 In one aspect of the present invention, the aqueous dispersion has a greater ionic strength 994 than the solution and said aqueous dispersion has a lower ionic strength when said 995 responsive particles are in non-ionic state. In another aspect of the present invention, the 996 aqueous dispersion has a greater osmotic pressure than the solution when said responsive 997 particles are in ionic state and said aqueous dispersion has a lower osmotic pressure when 998 said responsive particles are in non-ionic state. In one embodiment of the present invention, 999 the membrane pore size is smaller than the responsive particles. In another embodiment of 1000 the present invention, the membrane is selectively permeable for water.
1001 In certain embodiments of the present invention, the responsive particles comprise an 1002 insoluble particle and a surface functionality which is a base and wherein: switching the 1003 responsive particles from non-ionic state to ionic state comprises addition of a trigger; and 1004 switching the responsive particles from ionic state to non-ionic state comprises removal of 1005 said trigger. In one embodiment of the present invention, the surface functionality comprises 1006 a nitrogen base wherein contact with the trigger in the presence of water protonates said 1007 nitrogen base. In a preferred embodiment of the present invention, in non-ionic state, the 1008 surface functionality comprises: an amidine, a guanidine, or a tertiary amine; and, in ionic 1009 state, the surface functionality comprises: an amidinium, a guanidium, or a tertiary aminium.
1010 In certain embodiments of the present invention, the responsive particles comprise an 1011 insoluble particle and a surface functionality which is an acid and wherein: switching the 1012 responsive particles from ionic state to non-ionic state comprises addition of a trigger; and 1013 switching the responsive particles from non-ionic state to ionic state comprises removal of 1014 said trigger. In one embodiment of the present invention, the surface functionality comprises 1015 an oxygen acid wherein contact with the trigger in the presence of water protonates said 1016 oxygen acid. In a preferred embodiment of the present invention the surface functionality, in 1017 ionic state, comprises 2-nitrophenoxide; and, in non-ionic state, the surface functionality 1018 comprises 2-nitrophenol.
1019 In another aspect of the present invention, the trigger comprises CO2, NO2, COS, or CS2. In 1020 certain embodiments of the present invention, addition of the trigger to the aqueous 1021 dispersion comprises: bubbling said trigger into said aqueous dispersion, adding a trigger 1022 solution saturated with said trigger, mixing said aqueous dispersion under said trigger, or 1023 combinations thereof. In certain embodiments of the present invention, removal of the trigger 1024 from the aqueous dispersion comprises: heating said aqueous dispersion, sparing said 1025 aqueous dispersion with a flushing gas, exposing said aqueous dispersion to vacuum or 1026 partial vacuum, agitating said aqueous dispersion, sonicating said aqueous dispersion, or 1027 combinations thereof. In a preferred embodiment of the present invention, the flushing gas 1028 comprises: air, N2, or other gas with low concentration of CO2, NO2, COS, and CS2.

1029 In another aspect of the present invention, the method for modulating an osmotic gradient or 1030 an electrochemical gradient across a membrane further comprises separating the 1031 responsive particles with switchable surface charge from the aqueous dispersion. In certain 1032 embodiments of the present invention, separating the responsive particles with switchable 1033 surface charge from the aqueous dispersion comprises: sedimentation, centrifugation, 1034 flotation, gravity filtration, vacuum filtration, or combinations thereof. In another embodiment 1035 of the present invention, the responsive particles with switchable surface charge are 1036 magnetically susceptible and separating said responsive particles comprises: a permanent 1037 magnet, an electromagnet, or a high-gradient magnetic separator. In another embodiment 1038 of the present invention, the responsive particles with switchable surface charge are in ionic 1039 state and separating said responsive particles comprises an electric field.
1040 In another aspect of the present invention, the method for modulating an osmotic gradient or 1041 an electrochemical gradient across a membrane is for concentrating an aqueous solution 1042 wherein the aqueous solution comprises water and dissolved species. In another aspect of 1043 the present invention, the method for modulating an osmotic gradient or an electrochemical 1044 gradient across a membrane is for concentrating an aqueous solution wherein the aqueous 1045 solution comprises water and dispersed species. In yet another aspect of the present 1046 invention, the method for modulating an osmotic gradient or an electrochemical gradient 1047 across a membrane is for separating water from an aqueous solution wherein the aqueous 1048 solution comprises: water, dissolved species, and dispersed species.
In a preferred 1049 embodiment of the present invention the method is for desalination.

1051 FIG. 1 shows transmission electron micrographs of fumed silica particles at different 3.052 magnification;
1053 FIG. 2 shows scanning electron micrographs of silica gel and flash silica;
1054 FIG. 3 shows the zeta-potential range of various responsive particles with switchable surface 1055 charge in both ionic and non-ionic state;
1056 FIG. 4 shows the conductivity of various responsive particles with switchable surface charge 1057 in both ionic and non-ionic state;
1058 FIG. 5 shows sedimentation and flotation of various responsive particles with switchable 1059 surface charge;
1060 FIG. 6 shows separation of magnetic particles with switchable surface charge;
1061 FIG. 7 shows a diagram of an aqueous dispersion comprising responsive particles with 1062 switchable surface charge;
1063 FIG. 8 shows a diagram of a system for modulating the electrochemical gradient;
1064 FIG. 9 shows a diagram of a system for modulating the osmotic gradient;
1065 FIG. 10 shows a diagram of means for separating responsive particles with switchable 1066 surface charge by sedimentation and flotation;
1067 FIG. 11 shows a diagram of means for separating responsive particles with switchable 1068 surface charge by filtration;
1069 FIG. 12 shows a diagram of means for separating responsive particles with switchable 1070 surface charge under an applied magnetic field and means for switching the surface charge 1071 of responsive particles from non-ionic state to ionic state;
1072 FIG. 13 shows a diagram of a system for modulating the electrochemical gradient; and 1073 FIG. 14 shows a diagram of a system for modulating the electrochemical gradient.

1076 1.0 Definitions 1077 Unless defined otherwise, all technical and scientific terms used herein have the same 1078 meaning as commonly understood by one of ordinary skill in the art to which this invention 1079 belongs. As used in the specification and claims, the singular forms "a", "an" and "the"
1080 include plural references unless the context clearly dictates otherwise. The term "comprising"
1081 as used herein will be understood to mean that the list following is non-exhaustive and may 1082 or may not include any other additional suitable items, for example one or more further 1083 feature(s), component(s), step(s), and/or ingredient(s); as appropriate.
1084 "Aliphatic" refers to hydrocarbon moieties that are linear, branched, or cyclic, may be alkyl, 1085 alkenyl or alkynyl, and may be substituted or unsubstituted. "Alkenyl"
means a hydrocarbon 1086 moiety that is linear, branched, or cyclic and contains at least one carbon to carbon double 1087 bond. "Alkynyl" means a hydrocarbon moiety that is linear, branched or cyclic and contains 1088 at least one carbon to carbon triple bond. "Aryl" means a moiety including a substituted or 1089 unsubstituted aromatic ring, including heteroaryl moieties and moieties with more than one 1090 conjugated aromatic ring; optionally it may also include one or more non-aromatic ring. "C5 1091 to C8 Aryl" means a moiety including a substituted or unsubstituted aromatic ring having from 1092 5 to 8 carbon atoms in one or more conjugated aromatic rings. Examples of aryl moieties 1093 include phenyl. "Heteroaryl" means a moiety including a substituted or unsubstituted 1094 aromatic ring having from 4 to 8 carbon atoms and at least one heteroatom in one or more 1095 conjugated aromatic rings. As used herein, "heteroatom" refers to non-carbon and non-1096 hydrogen atoms, such as, for example, 0, S, and N. Examples of heteroaryl moieties include 1097 pyridyl, tetrahydrofuranyl, and thienyl. "Alkylene" means a divalent alkyl radical, e.g., -CfH2f 1098 wherein f is an integer. "Alkenylene" means a divalent alkenyl radical, e.g., -CHCH-.
1099 "Alkynylene" means a divalent alkynyl radical. "Arylene" means a divalent aryl radical, e.g., 1100 -C6H4-. "Heteroarylene" means a divalent heteroaryl radical (e.g. -05H3N-). "Alkylene-aryl"
1101 means a divalent alkylene radical attached at one of its two free valencies to an aryl radical 1102 (e.g. -CH2-C61-15). 11Alkenylene-aryl" means a divalent alkenylene radical attached at one of 1103 its two free valencies to an aryl radical (e.g. - CHCH-C8I-15).
"Alkylene-heteroaryl" means a 1104 divalent alkylene radical attached at one of its two free valencies to a heteroaryl radical (e.g.

1105 -CH2-05H4N). "Alkenylene- heteroaryl" means a divalent alkenylene radical attached at one 1106 of its two free valencies to a heteroaryl radical (e.g. -CHCH-05H4N-).
"Alkylene-arylene"
1107 means a divalent alkylene radical attached at one of its two free valencies to one of the two 1108 free valencies of a divalent arylene radical (e.g. -CH2-C6H4-).
"Alkenylene-arylene" means a 1109 divalent alkenylene radical attached at one of its two free valencies to one of the two free mo valencies of a divalent arylene radical (e.g. -CHCH-C6H4-). "Alkynylene-arylene" means a 1111 divalent alkynylene radical attached at one of its two free valencies to one of the two free 1112 valencies of a divalent arylene radical (e.g. -CHC-C6H4-). "Alkylene-heteroarylene" means a 1113 divalent alkylene radical attached at one of its two free valencies to one of the two free 1114 valencies of a divalent heteroarylene radical (e.g. -CH2-05H3N-).
"Alkenylene-heteroarylene"
1115 means a divalent alkenylene radical attached at one of its two free valencies to one of the 1116 two free valencies of a divalent heterarylene radical (e.g. -CHCH-05H3N-). "Alkynylene-1117 heteroarylene" means a divalent alkynylene radical attached at one of its two free valencies 1118 to one of the two free valencies of a divalent arylene radical (e.g. -CEO- C5H3N-).
1119 "Substituted" means having one or more substituent moieties whose presence does not 1120 interfere with the desired reaction. Examples of substituents include alkyl, alkenyl, alkynyl, 1121 aryl, aryl-halide, heteroaryl, cycloalkyl (non-aromatic ring), Si(alkyl)3, Si(alkoxy)3, halo, 1122 alkoxyl, amino, alkylamino, alkenylamino, amide, amidine, hydroxyl, thioether, alkylcarbonyl, 1123 alkylcarbonyloxy, arylcarbonyloxy, alkoxycarbonyloxy, aryloxycarbonyloxy, carbonate, 1124 alkoxycarbonyl, aminocarbonyl, alkylthiocarbonyl, phosphate, phosphate ester, 1125 phosphonato, phosphinato, cyano, acylamino, imino, sulfhydryl, alkylthio, arylthio, 1126 thiocarboxylate, dithiocarboxylate, sulfate, sulfato, sulfonate, sulfamoyl, sulfonamide, nitro, 1127 nitrile, azido, heterocyclyl, ether, ester, silicon-containing moieties, thioester, or a 1128 combination thereof. Preferable substituents are alkyl, aryl, heteroaryl, and ether. It is noted 1129 that aryl halides are acceptable substituents. Alkyl halides are known to be quite reactive, 1130 and are acceptable so long as they do not interfere with the desired reaction. The 1131 substituents may themselves be substituted. For instance, an amino substituent may itself 1132 be mono or independently disubstitued by further substituents defined above, such as alkyl, 1133 alkenyl, alkynyl, aryl, aryl-halide and heteroaryl cycloalkyl (non-aromatic ring).
1134 "Polymer" refers a molecule of high relative molecular mass, the structure of which 1135 essentially comprises multiple repetition of units derived from molecules of low relative 1136 molecular mass. "Oligomer" refers a molecule of intermediate relative molecular mass, the 1137 structure of which essentially comprises a small plurality of units derived from molecules of 1138 low relative molecular mass. A molecule can be regarded as having a high relative molecular 1139 mass if the addition or removal of one or a few of the units has a negligible effect on the 1140 molecular properties. A molecule can be regarded as having an intermediate relative 1141 molecular mass if it has molecular properties which do vary significantly with the removal of 1142 one or a few of the units.

1144 Water is used in almost all aspect of life and therefore may include numerous contaminants 1145 which affect its quality and impose limits on its utility. For example, seawater contains 1146 dissalved salts and cannot be use as potable water. Water contaminants include physical 1147 contaminants, chemical contaminants, and biological contaminants. A
basic modern 1148 municipal water treatment process includes: intake, screening, mixing, coagulation and 1149 flocculation, sedimentation, filtration, and chlorination. Industrial wastewater usually contains 1150 additional contaminants which must be removed before recycling or discharging.
1151 Physical contaminants include solids which are removed using a varied of methods 1152 depending on size. A strainer is a tool used specifically to separate solids from liquids.
1153 Industrial strainers are available in different styles from simple basket strainer to advanced 1154 self-cleaning systems. Screening is used to remove very large solids.
Typical materials for 1155 screen filters include stainless steel, polypropylene, nylon, and polyester. Screening 1156 equipment includes rakes, traveling screens, drum screens, and bar screens. Smaller 1157 suspended solids are more difficult to remove. Most biological contaminants are microscopic 1158 including proteins (8 ¨ 1 0 0 nm), viruses (8 ¨ 1 0 0 nm), bacteria (0.2 5 ¨ 1 3 pm), yeast cells (2 1159 - 15 pm), and plankton (>2 pm). Inorganic suspended solids include clay, silt, and organic 1160 matter. Small contaminants are typically treated with chemical flocculants or coagulants such 1161 as aluminum sulfate, iron(III) chloride, and poly(diallyl-dimethylammoniunn chloride). These 1162 chemical compounds interact with suspended particles and promote formation of large flocs 1163 which facilitates separation. Flocs along with adsorbed or enmeshed suspended particles 1164 are subsequently separated by sedimentation in a clarifier unit or settle basin. Overflow from 1165 settling basin is directed to filtration units where remaining suspended solids are separated.
1166 Chemical contaminants are usually dissolved and cannot be removed using conventional 1167 filtration processes. Common salt forming cations include ammonium, calcium, iron, 1168 magnesium, potassium, and sodium. Common salt forming anions include acetate, 1169 carbonate, bicarbonate, chloride, citrate, cyanide, fluoride, nitrate, nitrite, phosphate, and 1170 sulfate. Although many salts are soluble in water, certain salts (barium sulfate, calcium 1171 sulfate, and lead(II) sulfate) are only sparingly soluble in water.
Sodium chloride is found in 1172 many natural sources of water including seawater but the salinity limits its use as potable 1173 water. Removing dissolved ions from water is especially difficult.
Desalination of seawater 1174 relies on reverse osmosis to concentrate water. Other methods such as distillation separate 1175 water as vapour but require significant energy due to the high heat capacity and high heat of 1176 vaporization of water. Dissolved salts also impede industrial processes. For example, 1177 multivalent cations such as magnesium, calcium, and aluminium negatively affect bitumen 1178 recovery if present in the extraction water above a certain concentration. Therefore, a low 1179 energy method of providing water with reduced salt concentration is of great benefit.
1180 Filtration is often performed to remove particles from a fluid such as water. In filtration 1181 processes, solid particles are physically constrained by a screen, filter, membrane, or 1182 combination thereof, while the fluid is allowed to pass through freely. Separation of particles 1183 in filtration is based on size exclusion. Oversized material in the fluid are rejected or retained 1184 by the filter media while undersized material including the fluid, known as the filtrate, is 1185 allowed to pass. The performance of the separation process may be tuned by selection of 1186 filter media which may include depth filters and surface filters. A
media filter uses a packed 1187 bed of solids such as sand to remove unwanted particles. Packed sand columns are depth 1188 filters and extensively used in municipal water purification facilities to remove particulates 1189 which remain dispersed after sedimentation and are trapped within the sand matrix. A screen 1190 filter contains openings which allow the liquid through while rejecting any solids greater than 1191 the size of the openings. Mesh screens are available in a variety of materials with 1192 standardized opening sizes. Ceramic materials are porous and may be used a filter but flow 1193 rate is low due to the small pore size. Cake build-up can dramatically impact the throughput 1194 of performance of a filtration process. Blockage can occur due to the reduced porosity of the 1195 filter after retaining undersize particles or by obstruction of surface pores.
1196 Membranes are selective barriers allowing only certain substances to pass; the degree of 1197 selectivity depends on the membrane pore size. Membrane processes include nnicrofiltration, 1198 ultrafiltration, nanofiltration, reverse osmosis, and forward osmosis.
Membrane processes 1199 generate flux across the membrane which restricts the movement of suspended solids and 1200 dissolved solutes but allows movement of solvent molecules across the membrane.
1201 Microfiltration removes particles greater than about 0.08 ¨ 2 pm and operates at low to 1202 moderate pressure (within a range of about 10 ¨400 kPa).
Microfiltration is used to remove 1203 residual suspended solids, to remove bacteria in order to condition the water for effective 1204 disinfection, and as a pre-treatment step for reverse osmosis.
Membranes used in 1205 microfiltration include membranes made from organic materials such as cellulose acetate, 1206 polysulfone, poly(vinylidene difluoride), poly(ethersulfone), and polyamide and membranes 1207 made from inorganic materials such as sintered metal or porous alumina. Organic 1208 membranes are most commonly used due to their flexibility and chemical properties; while 1209 inorganic membranes may be designed in various shapes and are available in a wide range 1210 of average pore sizes and permeability. In microfiltration, increasing pressure accelerates 1211 flow rate but does not affect the quality of the separation.
Ultrafiltration is similar to 1212 microfiltration and removes particles greater than 0.0 0 5 ¨ 2 pm and operates at moderate to 1213 high pressure (within a range of about 100 ¨ 1000 kPa).
Ultrafiltration is used for many of 1214 the same applications as microfiltration, but is further capable in separation of smaller 1215 material including emulsion droplets and dissolved polymers.
Ultrafiltration membranes have 1216 also been used to remove dissolved compounds with high molecular weight, such as 1217 proteins, carbohydrates, and synthetic polymers. Most ultrafiltration membranes are 1218 polymers including polysulfone, polypropylene, cellulose acetate, and polylactic acid; while 1219 ceramic membranes are used in high-temperature applications.
Nanofiltration can reject 1220 particles smaller than 1 nm and operates at similar pressures as ultrafiltation processes.
1221 Nanofiltration is used for the removal of selected dissolved constituents including polyvalent 1222 ions from wastewater. Nanofiltration membranes include thin films made from polymers such 1223 as poly(ethylene terephthalate) wherein tacks of small pores are made by bombardment of 1224 high-energy particles and later chemically developed. Nanofiltration membranes also include 1225 metallic oxides such as alumina films which are grown electrochemically. Nanofiltration 1226 membranes are expensive, fragile, and extremely prone to fouling. In general, for filtration 1227 processes, the smaller the compound or particle to be rejected, the more expensive the 1228 process.
1229 Although typical filtration processes remove particles through size exclusion, removal of 1230 dissolved species is more complex due to additional diffusion effects.
Osmosis is the 1231 spontaneous net movement of solvent molecules through a semi-permeable membrane into 1232 a region of higher solute concentration, in the direction that tends to equalize the solute 1233 concentrations on the two sides. Osmosis may be opposed by increasing the pressure in the 1234 region of high solute concentration with respect to that in the low solute concentration region.
1235 The force per unit area, or pressure, required to prevent the passage of water through a 1236 selectively permeable membrane and into a solution of greater concentration is equivalent 1237 to the osmotic pressure of the solution. Osmotic pressure increases with osmotic 1238 concentration which is a measure of the solute concentration. Non-ionic compounds do not 1239 dissociate and form only a single solute. On the other hand, ionic compounds such as salts 1240 dissociate in solution and contribute more to the osmotic concentration. Polyelectrolytes 1241 have an even greater response as they are capable of fully dissociating into multiple charges.
1242 Reverse osmosis is a separation process that uses pressure (up to around 850 ¨ 7000 kPa) 1243 to force a solvent through a semi-permeable membrane that retains solutes on one side and 1244 allows pure solvent to pass to the other side; forcing the solvent from a region of high solute 1245 concentration through a membrane to a region of low solute concentration by applying a 1246 pressure in excess of the osmotic pressure. If insufficient pressure is provided, the flow 1247 direction may be revered. Unlike filtration, changing the pressure difference across the 1248 membrane affects the quality of the separation. For reverse osmosis to be effective, the 1249 semi-permeable membrane should not allow large molecules or ions through thru but should 1250 allow smaller components of the solution such as solvent molecules to pass freely across 1251 the membrane. Concentration polarization occurs when the local concentration of rejected 1252 material at the membrane surface is increased and eventually reaches saturation. This 1253 increases the osmotic pressure of the feed side of the membrane and decreases the effective 1254 transmennbrane pressure reducing rate of permeation. Membrane performance is also 1255 affected by fouling wherein particulate deposition, scaling, and biofouling lead to blocked 1256 pore reducing rate of permeation.
1257 Forward osmosis is a related process wherein solvent flux occurs across a semi-permeable 1258 membrane from a region of low solute concentration to a region of high solute concentration 1259 to achieve separation of water from a solution containing unwanted solutes. Forward 1260 osmosis is especially useful in high osmotic pressure application where conventional reverse 1261 osmosis processes cannot be used. The draw solution used in a forward osmosis process 1262 must possess greater osmotic concentration than the feed solution to induce a net flow of 1263 water through a semi-permeable membrane, such that the feed solution becomes 1264 concentrated as the draw solution becomes diluted. The diluted draw medium may then be 1265 used directly or sent to a secondary separation process for the removal of the draw solute.
1266 3.0 Particles 1267 Particles are insoluble and more are easily removed compared to dissolved species.
1268 Dispersed particle are removed by solid-liquid separation using a variety of methods with 1269 different efficiency, throughput, and cost. Flotation, gravity sedimentation, and centrifugation, 1270 are methods of solid-liquid separation wherein the liquid is constrained and the particles 1271 move freely within the liquid. The separation is due to mass forces acting on the particles 1272 due to an external or internal field of acceleration that might be the gravity field, centrifugal 1273 field, or magnetic field.
1274 Sedimentation is a process wherein a material will settle out under the influence of gravity 1275 based on a difference in density. Typically, particles greater than 100 pm may be rapidly 1276 separated through settling processes. Smaller particles have slower rate of sedimentation 1277 which may be beyond the practical limits of a process. The sedimentation rate is limited by 1278 the force of gravity but separation may be further accelerated using a centrifuge or cyclone 1279 which applies an additional centripetal force. Alternatively, the rate of sedimentation is 1280 accelerated by increasing the particle size; for example, through flocculation or aggregation.
1281 Large-scale sedimentation processes often require large ponds but process equipment such 1282 as inclined plate settlers offer increased residence time while providing smaller equipment 1283 footprint. Magnetic separation is possible provided the solid particles are susceptible to 1284 manipulation under an applied magnetic field generated by a permanent magnet, an 1285 electromagnet, or a high-efficiency magnetic separator. Solids are also recovered by 1286 flotation, especially in the mining industry. Flotation uses air bubbles or other gas bubbles 1287 which attach to specific materials which together rise to the surface wherein a solid-rich froth 1288 is skimmed off. Attachment of air bubbles is controlled by the wettability and roughness of 1289 the solid surface. Hydrophobic particles preferentially attach to air bubbles. The level of 1290 control is sometimes sufficient for selective flotation where a desirable material is effectively 1291 separated from gangue material.
1292 Particles are discrete insoluble units which are prepared into a range of sizes, shapes, and 1293 structures. Particles are prepared from both organic material such as polymers and resins 1294 as well as inorganic material such as metals and ceramics. In most cases, the outer surface 1295 of a solid particle may be chemically functionalized in order to accommodate desired surface 1296 functionality including chemical functional groups which switch from a non-ionic state to an 1297 ionic state or from an ionic state to a non-ionic state upon exposure or removal to an 1298 appropriate trigger. This type of surface functionality may be installed during particle 1299 formation or attached in a subsequent step. A particle provides a solid surface where various 1300 chemical moieties may be attached in order to impart, suppress, or enhance formation 1301 surface charge.
1302 Particles are made from inorganic materials such as silica, synthetic organic materials such 1303 as polymers, natural organic materials such as cellulose derivatives, and combinations 1304 thereof. Silica is a commonly available material with a wide range of chemical and physical 1305 properties. Silica is available in various shapes and size; in both crystalline and amorphous 1306 forms; with non-porous, microporous, and mesoporous structure; and many other variants.
1307 Synthetic polymers are prepared using a variety of monomers and techniques which 1308 influence the properties of the product. Synthetic polymers are available in a variety of 1309 physical forms and chemical properties depending on its composition, molecular structure, 1310 and method of manufacture. Certain polymers are water-soluble. However, polymers with 1311 very high molecular mass, containing hydrophobic monomers or constituents, or chemically 1312 cross-linked are insoluble in water. A dispersion of colloidal polymer particles is known as 1313 latex.
1314 Cellulose is the most abundant natural polymer. Cellulose is also available in a variety of 1315 molecular mass and structure due to the biological nature of the source material. The most 1316 common sources for cellulose are wood pulp and cotton linters.
Cellulose derivatives are 1317 chemically treated in order to install, modify, or remove specific chemical functionalities.
1318 Cellulose is unique among biopolymers in that when it is charred below 400 C and above 1319 its decomposition temperature of 280 C it produces an aromatic structure in which domains 1320 of polycyclic aromatic hydrocarbon anneal into larger ensembles containing five- and six-1321 membered aromatic rings. The amorphous carbon produced on charring cellulose becomes 1322 graphitic above 2000 C.
1323 Silica is a versatile material which can be produced in a variety of forms including porous 1324 and non-porous with different physical and chemical properties such as specific surface area 1325 by changing the chemical precursors and the reaction conditions.
Commercially available 1326 silica has a range of properties (Table 2). Solid silica particles are prepared through 1327 hydrolysis of precursors, through precipitation of sodium silicate, or through high-1328 temperature methods. Fumed silica or pyrogenic silica is prepared using flame pyrolysis of 1329 silicon tetrachloride or from vaporized quartz sand. Silica particles with properties outside 1330 the ranges given in Table 2 are readily made using the one or more of the techniques listed.
1331 By controlling synthetic method, silica is prepared with different specific surface area, shape, 1332 particle size distribution, pore size, pore structure, apparent density, surface charge etc.
1333 Table 2 ¨ Typical range of properties for commercial silica particles which may be used to 1334 prepare responsive particles with switch able surface charge.
Property Colloidal Silica Silica Gel Precipitated Silica Fumed Silica Si02 % 15 ¨ 50 97 ¨ 99 85 ¨ 95 98 ¨ 99 Surface Area (m2/g) 50 - 750 200 - 800 25 ¨ 700 35 - 410 Density (g/cm3) 2.2 ¨ 2.3 2.2 1.9 ¨ 2.1 2.2 Bulk Density (g/cm3) 1.2 ¨ 1.4 0.1 ¨ 0.9 0.03 ¨3.0 0.03 ¨0.1 Primary Particle Size 4 ¨ 60 nnn 1 ¨ 100 nm 5 ¨ 50 nm 5 ¨ 50 nm Aggregate Size n/a n/a 100 ¨ 500 nm 100 ¨ 1000 nm Agglomerate Size n/a 2 ¨ 25 pm 1 ¨ 50 pm 1 ¨ 3 pm 1336 Fumed silica particles are spherical particles (5 ¨ 50 nm) which form larger aggregates (100 1337 ¨ 1000 nm) and agglomerates (1 ¨ 3 pm). Fumed silica is non-porous and has high specific 1338 surface area (35 ¨ 410 m2/g). Silanol density in fumed silica ranges from 2 ¨4 groups/nm2.
1339 Colloidal silica particles are non-porous spherical particles (1 ¨ 100 nm) which form larger 1340 agglomerates (3 ¨ 25 pm). Colloidal silica is often available as a stable dispersion. Removal 1341 of solvent form silica sols yields a nanopwder. Relatively larger colloidal silica particles (100 1342 ¨ 150 nm) may be prepared but form less stable dispersion. Colloidal silica particles up to 1343 800 nm have been prepared using various chemical reactions.
Precipitated silica is a porous 1344 amorphous form of silica made by precipitation of sodium silicate.
Precipitated silica particles 1345 consist of primary particles (5 ¨ 50 nm) which form larger aggregates (100 ¨500 nm) and 1346 agglomerates (1 ¨ 100 pm). Precipitated silica is porous with pore size less than 30 nm and 1347 high specific surface area (25 -700 m2/g). Silica gel particles are commonly used as 1348 desiccant and generally available in three grades: low density, regular density, and 1349 intermediate density. Regular density silica gel is made in an acid medium, which gives high 1350 surface area (7 5 0 m2/g), small primary particles having small pore diameters (2.2-2.6 nm), 1351 and a pore volume of 0.3 7-0.4 0 mL/g. Intermediate density silica gel consists of larger 1352 primary particles having a lower surface area (3 0 0 ¨ 350 m2/g), larger pore volumes (0.9 ¨
1353 1.1 mL/g), and larger average pore diameters (1 2-1 6 nm). Low density silica gel has lower 1354 surface areas (1 0 0 ¨ 200 m2/g) but larger average pore diameters (1 8 ¨
2 2 nm) and larger 1355 pore volumes (1.4-2.0 mL/g). Silica aerogel is derived from silica gel and prepared by 1356 extracting the liquid from the gel framework. The liquid is removed using a variety of 1357 techniques such as supercritical drying, freeze drying, solvent exchange, and calcination.
1358 Mesoporous silica is prepared by reacting tetraethyl orthosilicate or analogue in the presence 1359 of a structure-directing agent. Mesoporous silica is also prepared using sodium silicate.
1360 Using a template method, mesoporous silica with a variety of pore sizes may be prepared 1361 by changing the size of the host which may include surfactant micelles, polymers, and 1362 nanoparticles. The template host is later removed to yield a porous solid which has large 1363 surface area of pore volume. MCM-type mesostructured silica is prepared in the presence 1364 of cationic templates such as long-chain quaternary ammonium compounds under basic 1365 conditions. MOM-type silica contains either hexagonally-ordered cylindrical pore structure or 1366 cubic pore structure. The diameter of the channels formed by hexagonally ordered cylindrical 1367 pores can be controlled by changing the length of the template molecule. SBA-type 1368 mesostructured silica is prepared in the presence of non-ionic triblock polymers as template.
1369 SBA-type silica contains either hexagonally ordered cylindrical pore structure or a body-1370 centered cubic structure of spherical pores. The channels (between 2 ¨
30 nm) are the result 1371 of self-assembled block-copolymers. MSU-type mesostructured silica is prepared using 1372 block polymer surfactants and form 3D worm-hole porous framework with poorly defined 1373 crystallographic symmetry. KSW-type mesostructured silica contains 2D
orthorhombic pore 1374 structure. FSM-type mesostructured silica contains 2D hexagonal pore structure. Both KSW-1375 type silica and FSM-type silica are formed via deposition of layered intermediates composed 1376 of fragmented silicate sheets and cationic surfactants. HMM-type mesostructured silica 1377 contains hierarchically-ordered pore structure. Spherical mesoporous silica particles with 1378 controllable pore size between 4 ¨ 15 nm and particle diameter between 20 ¨80 nm involved 1379 simultaneous hydrolysis of tetra-orthosilicate to form silica and polymerization of styrene into 1380 polystyrene. The material becomes mesoporous after removal of polystyrene by calcination.
1381 It is also possible to coat various inorganic and organic materials with a layer of silica. Metal 1382 oxides such as iron oxide may be coated with silica through silicate precipitation, hydrolysis 1383 of silicate precursors, or both.
1384 The surface of silica particles may be cleaned using a variety of solvents. Silica may be 1385 cleaned with water at ambient temperature or elevated temperature. The use of both acids 1386 and bases is useful when surface impurities must be removed. Radiative energy may also 1387 be used to clean the surface of silica as well as other metal oxides and metals.
1388 Polymers are prepared through various chemical reactions including free-radical 1389 polymerization, condensation polymerization, and Ziegler-Natta polymerization. Other 1390 polymerization techniques include living polymerization reactions such as reversible 1391 addition-fragmentation chain transfer polymerization and atomic transfer radical 1392 polymerization which offer much greater control of the product by introducing polymerization 1393 pathways wherein a stable radical intermediate exists. The polymerization reaction can be 1394 performed in a variety of environments including bulk polymerization, solution 1395 polymerization, and dispersed phase polymerization which encompasses at least two 1396 immiscible phases. Dispersed phase polymerization or heterogeneous polymerization 1397 includes techniques such as micro-emulsion polymerization, mini-emulsion polymerization, 1398 emulsion polymerization, and suspension polymerization. Polymerization reactions in 1399 dispersed phase are especially useful in preparing latex particles.
Many different surface 1400 groups can be installed onto the surface of latex particles during the polymerization process 1401 by carefully selecting a suitable surfactant, a suitable initiator, and reaction conditions. A
1402 surfactant may optionally react onto the surface of the particle if it contains an appropriate 1403 reactive moiety. By using appropriate start material, latex particles with specific surface 1404 functionality are readily produced. The presence of a continuous phase, especially water, 1405 also improves heat exchange and inherent safety.
1406 In dispersed phase polymerization, reactive monomers are polymerization within an 1407 immiscible continuous phase resulting in dispersed polymer particles.
Dispersed polymer 1408 particles can range from about 1 nm to greater than 1 mm, depending .on the reaction 1409 conditions and level of stabilization provided to particles. This form of polymerization is very 1410 versatile and numerous types of surface groups including surface functionalities which switch 1411 from a non-ionic state to an ionic state or from an ionic state to a non-ionic state upon 1412 exposure or removal to an appropriate trigger be installed onto the surface of polymer 1413 particles. Polymer particles with switchable surface groups may be prepared by using both 1414 reactive and non-reactive, with respect to the polymerization reaction, surfactants which 1415 additionally comprise a chemical moiety capable of reversibly converting between an ionic 1416 state and a non-ionic state. Furthermore, a chemical moiety capable of reversibly converting 1417 between an ionic state and a non-ionic state may be installed on the surface of the polymer 1418 latex particles using an appropriate initiator. Moreover, both homopolymers and copolymers 1419 may be prepared using one or more monomers comprising a chemical moiety capable of 1420 reversibly converting between an ionic state and a non-ionic state.
1421 Suspension polymerization is polymerization process which relies on continuous mechanical 1422 agitation to produced dispersed droplets of monomer or monomer solution.
Smooth 1423 translucent spherical particles are produced when the polymer is soluble in the monomer.
1424 However, when the polymer has poor solubility in the monomer, irregular and porous 1425 particles may result. This effect may be induced by adding an additional diluent to the 1426 monomer. Removal of the unreactive monomer after polymerization results in porous 1427 particles. Suspension polymerization may be used to prepare particles from 100 nm to 5 mm, 1428 depending on the stirring intensity, volume fraction of monomer, and additional effects 1429 provided by surfactants, if present. During suspension polymerization, chain growth 1430 proceeds within dispersed monomer droplet at a similar rate as bulk or solution 1431 polymerization processes.
1432 During emulsion polymerization, initiation occurs in the continuous phase; also known as 1433 homogeneous nucleation. Small oligomers are initially formed within the continuous phase 1434 but rapidly begin to lose solubility as the polymerization reaction continues. When a 1435 surfactant is present above its critical micelle concentration, micelles are present. Reacting 1436 oligomers eventually migrate into micelles where the surfactant molecules provide a more 1437 compatible environment. When no surfactant is present, reacting oligomers organize into 1438 nucleated micelles. Once nucleated, polymer particles undergo substantial chain growth 1439 sustained by monomer diffusion. Nucleation occurs within surfactant micelles and polymer 1440 chain growth is sustained by monomer diffusion from droplets through the continuous phase 1441 into nucleated micelles. Through emulsion polymerization, high-molecular weight polymers 1442 are produced without negatively affecting conversion. The rate of emulsion polymerization is 1443 unaffected by conversion and emulsion polymerization processes can run to high conversion 1444 without the depressed rate of polymerization observed in bulk polymerization when 1445 molecular weight is high. Emulsion polymerization produces latex nanoparticles with specific 1446 functional groups by using different monomers, initiators, and surfactants. Latex particles 1447 made using emulsion polymerization are generally spherical between 100 ¨ 2000 nm. The 1448 size of the particles interferes with light and scattering results in opaque latex product. In 1449 contrast, during bulk and solution polymerization, the increasing molecular weight of the 1450 polymer reduces the ability of remaining monomers to diffuse. In addition, emulsion 1451 polymerization can produce latex particles which are very uniform in size. However, 1452 homogeneous nucleation can occur during emulsion polymerization for certain monomers 1453 and polymerization conditions; especially if the monomer exhibits at least partially water-1454 solubility (e.g. styrene in water). Furthermore, coalescence and Ostwald ripening can occur 1455 during emulsion polymerization which adversely affect the quality of the resulting latex. Mini-1456 emulsion polymerization is a related process which typically requires high energy methods 1457 of emulsification. Addition of a material which very insoluble in the continuous phase (e.g.
1458 hexadecane in water) provides added stability against diffusion processes.
1459 In miniemulsion or nanoemulsion polymerization, unlike emulsion polymerization, droplet 1460 nucleation occurs within individual reactant droplets. Prevalent droplet nucleation can only 1461 occur if the surface area of the monomer droplets is large compared with that of the micelles, 1462 and this requires submicron droplet size. Therefore, the reactant monomer phase is 1463 dispersed in the continuous phase using high-energy methods such as ultrasound 1464 sonication, high-pressure flow through a restricted orifice, and other specialized means.
1465 Monomer droplet must be stabilized against diffusion degradation (Ostwald Ripening) by 1466 adding a substance with adequate solubility in the dispersed phase but extremely low 1467 solubility in the continuous phase. Monomer droplet must also be stabilized against 1468 coagulation degradation using surfactants or fine bi-wetting particles. Latex made through 1469 miniemulsion polymerization typically consists of particles between 10 ¨500 nm and also 1470 appear opaque. Nanoemulsion polymerization represents the extreme lower limit of 1471 miniemulsion polymerization and produces particles which are typically between 10 ¨ 100 1472 nm and appear translucent. Unlike conventional emulsions, microemulsions are 1473 thermodynamically stable isotropic mixtures which form spontaneously without the need for 1474 high-energy emulsification processes. Microemulsion polymerization produces latex 1475 particles between 10 ¨ 50 nm.
1476 Various materials may be incorporated within latex particles using dispersed phase 1477 polymerization by initially dispersing or suspending the material within the dispersed 1478 monomer droplets before polymerization. Materials which are incorporated may include solid 1479 particles including iron oxide and iron oxide nanoparticles which are superparamagnetic. In 1480 order to disperse solids particles effectively, the rate of sedimentation must be insignificant 1481 compared to the length of the polymerization process. Furthermore, the wettability of the 1482 particle must be compatible with the dispersed phase. The wettability of particles including 1483 iron oxide may be altered using a compound which reacts with the surface, such as a silane 1484 coupling agent, or a compound which adsorbs strongly to the particle, such as carboxylate 1485 or phosphate.
1486 Cellulose is an organic compound which consists of a polysaccharide chain of monomeric 1487 glucose units. Cellulose is an important natural polymer found in the cell wall of plants and 1488 other organisms. Cellulose is hydrophilic, insoluble in water and most organic solvents, 1489 chiral, and biodegradable. Cellulose is available in various forms including nanocrystalline 1490 cellulose, powered cellulose, and cellulose fibres. Cellulose is available in various molecular 1491 weight. The hydroxyl groups of cellulose can be partially or fully reacted with various 1492 reagents to afford derivatives with useful properties like mainly cellulose esters and cellulose 1493 ethers.
1494 5.0 Surface Functionalization 1495 Silane coupling agents are compounds whose molecules contain functional groups that bond 1496 with both organic and inorganic materials. The structure of a silane coupling agents typically 1497 contain two types of reactive functional groups: reactive groups which form chemical bonds 1498 with inorganic materials including glass, metals, silica, and other minerals; and reactive 1499 groups that form chemical bonds with organic materials such as synthetic resins including 1500 vinyl groups, epoxy groups, amino groups, methacryloxy groups, mecapto groups, halo 1501 groups, and others. A silane coupling agent acts as an intermediary and may be effectively 1502 used to bond organic materials and inorganic materials together improving the mechanical 1503 strength of composite materials which contain both inorganic materials and organic 1504 materials. When a silane coupling agent is used on the surface on an inorganic particle, an 1505 organic moiety corresponding to the silane coupling agent may be grafted onto the surface 1506 of the particle. Silane agents are therefore useful for resin modification and surface 1507 modification.
1508 Silane coupling agents react with water to form silanol groups and oligomers are formed 1509 through partial condensation; the silanol oligomers are capable of hydrogen bonding to the 1510 surface of many inorganic materials and metallic materials. Silane coupling reagents and 1511 related chemical compounds can provide improved adhesion when transitioning between 1512 organic materials such as plastics and inorganic materials such as silcates. Silane coupling 1513 agents improve wettability or miscibility of the plastic or resin by forming chemical bonds or 1514 hydrogen bonds.
1515 Slane coupling agents include silicon oligomers, silanes, and silylating agents. Silicone 1516 oligomers include organic functional groups as well as alkoxy groups (similar to silane 1517 coupling agents). Silicone oligomers are more multifunctional than silanes, and can be used 1518 as an oligomeric coupling agent for resin modification or as a functional coating agent.
1519 Silanes include alkoxy silanes containing methyl groups, long-chain alkyl groups, phenyl 1520 groups and other organic groups. Silanes are used in a wide variety of fields; they can be 1521 used for surface modification of inorganic materials to impart water repellency and have 1522 many other uses. Silylating agents are used in organic synthesis in the manufacture of 1523 pharmaceuticals and agrichemicals, and in electronics manufacturing.
Silylating agents can 1524 be used to introduce organosilyl groups into organic or inorganic materials where they act 1525 as protecting groups for active hydrogens. Different types of alkyl groups vary in their 1526 bulkiness and ease of separation; by using the proper alkyl groups, the user can gain better 1527 control over the organic synthesis reaction.
1528 Silane coupling agents are compounds whose molecules contain functional groups that bond 1529 with both organic and inorganic materials. A variety of silane coupling agent can acts as an 1530 intermediary which helps bonds organic materials to inorganic materials. Silane coupling 1531 agents are available with various functional groups including vinyl, halo, epoxy, styryl, 1532 methacryloxy, acryloxy, amino, isocyanurate, ureide, mercapto, sulfide, and isocyanate.
1533 Silane coupling agents are effective on a variety of inorganic material including glass, silica, 1534 aluminum oxide, talc, clay, aluminum, aluminum hydroxide, mica, asbestos, titanium oxide, 1535 zinc oxide, and iron oxide. Silane coupling agents with appropriate functional groups are also 1536 compatible with thermoplastic resins, thermosetting resins, and elastomers.
1537 Silane coupling agents react with water undergoing hydrolysis to form silanol groups while 1538 oligomers are formed through partial condensation. The silanol oligomers are hydrogen 1539 bonded to the surface of the inorganic material. Finally, the inorganic material put through a 1540 drying process and robust chemical bonds are formed through a dehydration condensation 1541 reaction. Silane coupling agents are commonly used in the form of a dilute aqueous solution.
1542 The silane coupling agent contains hydrolysable alkoxy groups with react with inorganic 1543 materials. When these groups are hydrolyzed, silanol groups are formed which adhere and 1544 bond to hydroxyl groups on the surface of the inorganic material.
Silane coupling agents may 1545 be used in almost any organic solvent. The hydrolyzable alkoxy groups include methoxy and 1546 ethoxy groups. Methoxy groups and ethoxy groups have different hydrolytic properties, and 1547 are thus used for different types of applications; exchange occurs when ethanol or methanol 1548 are used as solvent.
1549 Silane coupling agents are typically used as dilute solutions. Silane coupling agents contains 1550 hydrolyzable alkoxy groups which react with inorganic materials. When these groups are 1551 hydrolyzed, silanol groups are formed which adhere and bond to hydroxyl groups on the 1552 surface of the inorganic material. Typically, concentration for silane coupling agent is 1553 between 0.1 ¨ 2.0 vol%. Various solvents are effective including water, alcohol, and organic 1554 solvents. The pH of the silane coupling agent may be adjusted using acetic acid. A 0.1 ¨ 2.0 1555 vol% of acetic acid will promote hydrolysis of the silane and stabilize the resulting silanol in 1556 solution. Addition of silane coupling agents is typically controlled to prevent formation of 1557 colloidal particles. Particulate material, fibrous materials, and well as surfaces are coated 1558 with silane coupling agent. In a general process, the substrate is first washed; then dipped 1559 into the hydrolysis solution; and subsequently removed from excess liquid. Both 1560 concentrated solutions of silane coupling agent (with about 1 wt%
water) and silane coupling 1561 agent diluted in a solvent may be used and to coat inorganic material.

1563 6.0 Switchable Surface Charge 1564 An Arrhenius base is a chemical substance which dissociates in water, thereby adopting an 1565 ionic state, and increases the concentration of hydroxide ions. A salt is produced when an 1566 acid reacts with a base. Strong bases such as sodium hydroxide dissociate completely while 1567 less basic substances may only partially dissociate. The extent of ionization depends on the 1568 basicity of the substance as well as the pH of the aqueous solution.
In the presence of a 1569 stronger base, a weaker base may remain non-dissociated. A basic substance which is not 1570 dissociated is non-ionic while a basic substance which is fully dissociated is ionic.
1571 BOH OH- + B+
1572 An Arrhenius acid is a chemical substance which dissociates in water, thereby adopting an 1573 ionic state, in water and increases the concentration of hydrogen ions or more specifically 1574 hydronium ions. Strong acids such as hydrochloric acid dissociate completely while less 1575 acidic substances may only partially dissociate. The extent of ionization depends on the 1576 acidity of the substance as well as the pH of the aqueous solution. In the presence of a 1577 stronger acid, a weaker acid may remain non-dissociated. An acidic substance which is not 1578 dissociated is non-ionic while an acidic substance which is fully dissociated is ionic.
1579 AH <-3 A- + H+
1580 Nitrogen bases such as primary amines, secondary amines, tertiary amine, amidines, and 1581 guanidines are known to react with carbon dioxide in the presence of water; forming an ionic 1582 bicarbonate salt with carbonic acid. This reaction is reversible and the free base is restored 1583 upon removal of dissolved carbon dioxide. Primary and secondary amines are less suitable 1584 in certain applications due to carbamate formation which, unlike bicarbonate formation, is 1585 not reversed upon removal of carbon dioxide from the solution.
Guanidines and amidine are 1586 stronger bases compared to amines.
1587 Phenol is more acidic compared to other alcohols because the phenoxide ion is stabilized to 1588 some extent by the aromatic ring; the negative charge on the oxygen atom is delocalized.
1589 The stability of the phenoxide ion may be stabilized through inductive effects and resonance 1590 effects by adding additional substituents to the aromatic ring.
Specifically, adding electron 1591 donating groups to the meta- positions of the aromatic ring or by adding electron withdrawing 1592 groups to the ortho- and/or para- position. The acidity of phenol may be enhanced by 1593 installing electron withdrawing groups in the ortho- and/or para-positions of the aromatic ring 1594 (relative to the phenol) in order to stabilize the phenoxide ion.
Electron withdrawing groups, 1595 include ¨NO2, ¨NR3+, ¨NH3, -S03H, ¨CN, ¨CF3, ¨0013, ¨COCI, ¨COOH, ¨COOR, ¨COR, 1596 ¨CHO, ¨Cl, ¨Br, ¨F, ¨I, ¨ CONR2, CONHR, and ¨CONH2. Halogens are very electronegative 1597 and are very strongly electron withdrawing due to inductive effects.
Other functional groups 1598 such as ¨NR3+, ¨NH3, ¨0013 and ¨CF3 also have strong inductive effect but lack orbitals or 1599 electron pairs which can overlap and therefore cannot contribute to resonance effect. The 1600 most effective electron withdrawing groups, such as ¨NO2, ¨ON, ¨S03H, -CHO, ¨COR, -1601 COOH, and ¨CONH2, contribute to both inductive effect and resonance effect. The acidity of 1602 phenol may be enhanced by installing electron donating groups in the meta- positions of the 1603 aromatic ring (relative to the phenol) in order to stabilize the phenoxide ion. Electron donating 1604 groups include ¨0-, ¨NR2, ¨NHR, ¨NH2, ¨OH, ¨OR, ¨NHCOR, ¨000R, -R, -Ar, and -1605 CHCR2. Alkyl groups have very limited inductive effect. The most effective electron 1606 withdrawing groups, such as ¨0-, ¨NR2, ¨NHR, ¨NH2, ¨OH, ¨OR, ¨NHCOR, and ¨OCOR, 1607 contribute to both inductive effect and resonance effect.
1608 Water is a unique molecule which dissociates into hydroxide and hydronium ions; and 1609 therefore functions both as acid and base. The strength of an acid is characterized using its 1610 acid dissociation constant. Conversely the strength of a base is characterized using its base 1611 dissociation constant. Pure water has a pKa of 15.7 and results in a pH of 7 when the 1612 concentration of both hydroxide ion and hydronium ions is equal. When a base and an acid 1613 react together, an ionic salt is formed consisting of the conjugate base and the conjugate 1614 acid. A gas that liberates hydronium or hydrogen ions is employed to trigger a switch in 1615 particle surface charge. Carbonic acid is produced from dissolving carbon dioxide in water;
1616 carbon dioxide is particularly preferred as the trigger. When particles with switchable surface 1617 charge comprises a reversible surface functionality which is a base, the addition of the gas 1618 and liberation of hydronium ions causes the reversible surface functionality to convert to its 1619 ionic state. When carbon dioxide is used, the reaction between carbonic acid and the base 1620 surface functionality produces a bicarbonate salt. Conversely, when particles with switchable 1621 surface charge comprises a reversible surface functionality which is an acid, the addition of 1622 the gas and liberation of hydronium ions causes the reversible surface functionality to its 1623 non-ionic state. When carbon dioxide is used, the reaction between carbonic acid and the 1624 conjugate base of the acid surface functionality produces the protonated acid. Dissolved 1625 carbon dioxide is readily removed by heating and/or sparging with an inert gas such as 1626 nitrogen or air which contains low carbon dioxide concentration. When carbon dioxide is 1627 expelled from the solution, its effect is also reversed. Flue gas has low to moderate carbon 1628 dioxide concentration depending on its source. As such, low carbon dioxide flue gas may be 1629 used to remove dissolved carbon dioxide; however, acidic components such as sulfur dioxide 1630 must be first removed.
1631 Other gases that liberate hydrogen ions include carbon disulfide and carbonyl sulfide, and 1632 are expected to behave similarly to carbon dioxide. However, removal of such dissolved 1633 gases from solution is expected to be more difficult. In some embodiments of the invention, 1634 alternative gases that liberate hydrogen ions are used instead of carbon dioxide, or in 1635 combination with carbon dioxide, or in combination with each other.
Alternative gases that 1636 liberate hydronium ions are less preferred because of the added costs of supplying them and 1637 recapturing them, if recapturing is appropriate. However, in some applications one or more 1638 such alternative gases may be readily available and therefore add little to no extra cost.
1639 Gases such as hydrogen cyanide and hydrogen chloride are less preferred triggers because 1640 of their toxicity and difficult removal.

1642 7.0 Particles with Switchable Surface Charge for Osmotic Processes 1643 Although water permeates spontaneously through a semi-permeable membrane in forward 1644 osmosis, this does not mean that forward osmosis is more energy efficient, as a separation 1645 process, compared to other membrane processes. Forward osmosis is simultaneously both 1646 a separation process and a mixing process. The water molecules that transport across the 1647 membrane from a feed solution mixes with the draw solution in order to reduce its chemical 1648 potential. In order to obtain fresh water as a product, subsequent separation of the diluted 1649 draw medium is required in the forward osmosis process. Therefore, the ability to separate 1650 or regenerate the draw solution is of critical importance in related processes. Regenerating 1651 the draw solution may be achieved through reverse osmosis wherein the draw solution is 1652 concentrated across a semi-permeable membrane driven by hydraulic pressure. Methods 1653 used to separate solutes from a diluted draw solution include liquid-liquid separation of an 1654 immiscible solute, thermal decomposition of an unstable solute, and magnetic separation of 1655 a magnetically susceptible solute. Alternatively, according to the present invention, 1656 separation of insoluble particles from a liquid is possible using conventional filtration without 1657 resorting to reverse osmosis or nanofiltration, both which require substantially more energy 1658 and maintenance.
1659 The present invention relates to a dispersion for use in a membrane process comprising 1660 responsive particles with switchable surface charge. Specifically, the present invention 1661 employs responsive particles with switchable surface charge to modulate the osmotic 1662 concentration of a solution; taking advantage of solid-liquid separation processes, which may 1663 be employed to separate said responsive particles with switchable surface charge from said 1664 solution. In general, solid-liquid separation processes based on size exclusion are more 1665 effective and more efficient compared to liquid-liquid separation processes. Size exclusion 1666 separation processes are more versatile and applicable to a variety of solids. Liquid-liquid 1667 separations, on the other hand, are based on differences between the properties of the 1668 specific liquids such as solubility (e.g. in extraction); volatility or boiling point (e.g. in 1669 volatilization, evaporation, simple distillation, fractional distillation, flash distillation, etc...);
1670 and mobility in different media (e.g, in chromatography). Typically, liquid-liquid separations 1671 are less effective than solid-liquid separations. Complete separation using extraction, 1672 distillation, or chromatography is typically difficult, especially at large scale. Liquid-liquid 1673 separation process are also less efficient, often requiring large capital costs for equipment 1674 and incurring significant operating costs. Solids are also much easier to handle compared to 1675 fluids which deform under stress and are therefore more easily transported and contained if 1676 exposed to the environment.
1677 The responsive particles of the present invention comprise: an insoluble particle and a 1678 surface functionality; wherein the surface functionality reversibly converts between an ionic 1679 state and a non-ionic state. Responsive particles with said surface functionality have 1680 switchable surface charge which depends on the instant state of said surface functionality.
1681 Responsive particles with switchable surface charge are prepared by placing the appropriate 1682 surface functionality onto the insoluble particles through chemical bonding, physical 1683 entanglement, chemisorption, physisorption, or combinations thereof. In certain 1684 embodiments of the present invention, the insoluble particles and the surface functionality 1685 are linked through chemical bonding, physical entanglement, chemisorption, physisorption, 1686 or combinations thereof. Specifically, a covalent chemical bond may be formed in order to 1687 attach a surface functionality to an insoluble particle.
Alternatively, said surface functionality 1688 may be immobilized onto said insoluble particle through other interactions such as physical 1689 entanglement; for example, within a cross-linked polymer matrix.
Chemical structures are 1690 capable of specific interactions as result of attractive intermolecular forces (e.g. hydrogen 1691 bonding, dipole interactions, induced dipole interactions, and van der Waals forces).
1692 Chemical compounds can therefore adsorb onto a surface through physical or chemical 1693 adsorption. In practical terms, responsive particles with switchable surface charge comprise 1694 an insoluble particle with a surface functionality which does not detach from said insoluble 1695 particle under normal operating conditions.
1696 The conductivity of a fluid can be influenced by the presence of electrolytes. Although pure 1697 water exhibits very poor conductivity, addition of a small amount of electrolyte dramatically 1698 increases the electrolyte solution's ability to conduct electricity.
For strong electrolytes (i.e.
1699 salts, strong acids, and strong bases) the molar conductivity depends only weakly on 1700 concentration. However, for weak electrolytes (i.e. incompletely dissociated electrolytes), the 1701 molar conductivity strongly depends on concentration. Non-ionic solutes have little impact 1702 on electrolytic conductivity. In one embodiment of the present invention, the conductivity of 1703 the dispersion comprising responsive particles with switchable surface charge increases 1704 when the surface functionality is converted to its ionic state. In another embodiment of the 1705 present invention, the conductivity of the dispersion comprising responsive particles with 1706 switchable surface charge decreases when the surface functionality is converted to its non-1707 ionic state.
1708 Non-ionic solutes increase ionic strength. However, charged solutes which dissociate have 1709 a much greater impact on ionic strength as more than one dissolved species is generated.
1710 In one embodiment of the present invention, the ionic strength of the dispersion comprising 1711 responsive particles with switchable surface charge increases when the surface functionality 1712 is converted to its ionic state. In another embodiment of the present invention, the ionic 1713 strength of the dispersion comprising responsive particles with switchable surface charge 1714 decreases when the surface functionality is converted to its non-ionic state.
1715 A substance in solid state typically has greater density compared to its liquid, gas, and 1716 plasma states. When dispersed in a fluid, unless the solid is sufficiently small or its specific 1717 gravity is otherwise similar to its dispersion media, solid particles begin to separate under 1718 gravity. Very small particles may remain dispersed in a fluid due to Brownian motion of fluid 1719 molecules which continuously collide with particles. Larger particles are less affected by 1720 collisions with fluid molecules. The Knudsen number provides an indication whether a 1721 particle of a certain size is within the continuous regime, the statistical regime, or a transition 1722 between the continuous and statistical regimes. In one embodiment of the present invention, 1723 the responsive particles with switchable surface charge remain suspended under continuous 1724 agitation. In a further embodiment of the present invention, the responsive particles remain 1725 suspended in a dispersion by mechanical agitation, gas flotation, or pumping.
1726 Insoluble particles refer to discrete solid units of matter which comprises a material which 1727 has limited solubility, including materials which are only sparingly soluble. The solubility of 1728 one material in another is determined by the balance of intermolecular forces between the 1729 solvent and solute as well as to the entropy change which accompanies solvation; factors 1730 such as temperature will alter this balance and change the effective solubility of the material.
1731 Solubility may also strongly depend on other factors such as pH, concentration of common 1732 dissolved ions, presence of choatropes, etc. In practical terms, a material which has a 1733 solubility less than 0.1 g per 100 mL of solvent, under operating conditions, is considered 1734 insoluble.
1735 In certain embodiments of the present invention, the insoluble particles comprise an 1736 inorganic solid, a synthetic polymer, a natural polymer, or a natural polymer derivative. In 1737 one embodiment of the present invention, the inorganic solid comprises a silicate or an 1738 aluminosilicate. Silicates and aluminosilicates are materials found in nature as various 1739 polymorphs or engineered with specific properties. In a further embodiment of the present 1740 invention, the silicate comprises silica. Silica or silicon dioxide has numerous crystalline 1741 polymorphs as well as amorphous polymorphs. In a preferred embodiment of the present 1742 invention, the insoluble particle comprises quartz, colloidal silica, silica gel, precipitated silica, 1743 mesoporous silica, or fumed silica. In a most preferred embodiment of the present invention, 1744 the insoluble particle comprises colloidal silica. Responsive particles with switchable surface 1745 charge were prepared, according to Examples Al ¨ A4 and Examples A7 ¨
A17, from 1746 colloidal silica, silica gel, precipitated silica, mesoporous silica, fumed silica, and silica-1747 coated iron oxide nanoparticles. Responsive particles with switchable surface charge are 1748 prepared by chemical functionalization of subnnicron fumed silica particles (FIG. 1) or 1749 microscopic colloidal silica particles and silica gel particles (FIG.
2).
1750 In another embodiment of the present invention, the insoluble particle comprises a synthetic 1751 polymer. In a further embodiment of the present invention, the synthetic polymer comprises 1752 poly(acrylonitrile butadiene styrene), cross-linked polyethylene, poly(ethylene vinyl acetate), 1753 poly(methyl methacrylate), polyamide, polybutylene, polybutylene terephthalate, 1754 polycarbonate, poly(ether ether ketone), polyester, polyethylene, poly(ethylene 1755 terephthalate), polyimide, poly(lactic acid), poly(oxymethylene), poly(phenyl ether), 1756 polypropylene, polystyrene, polysulfone, poly(tetrafluoroethylene), polyurethane, polyvinyl 1757 chloride, poly(vinylidene chloride), poly(styrene maleic anhydride), poly(styrene-1758 acrylonitrile), cyanoacrylate resin, epoxy resin, phenol formaldehyde resin, urea 1759 formaldehyde resin, or silicone resin. In a preferred embodiment of the present invention, 1760 the synthetic polymer comprises polystyrene. Responsive particles with switchable surface 1761 charge were prepared, according to Examples B1 ¨B9, through emulsion polymerization of 1762 styrene, methyl methacrylate, or both.

1763 In another embodiment of the invention, the responsive particles comprises iron oxide 1764 particles coated with silica iron oxide particles coated with polystyrene. Magnetically 1765 susceptible responsive particles with switchable surface charge were prepared, according to 1766 Examples A15 and Example B8. In Example A15, iron oxide nanoparticles were by first 1767 coated with silica and subsequently treated with a silane coupling agent. In Example B8, 1768 iron oxide nanoparticles were incorporated into polymer particles prepared using 1769 miniemulsion polymerization by first dispersing iron oxide nanoparticles, modified to have 1770 hydrophobic surface, into monomer droplets prior to polymerization. In a further embodiment 1771 of the invention, the responsive particle comprising iron oxide particles are separated under 1772 an applied magnetic field generated by a permanent magnet or an electromagnet.
1773 In yet another embodiment of the present invention, the insoluble particle comprises a natural 1774 polymer. In a further embodiment of the present invention, the natural polymer comprises 1775 cellulose, chitin, poly(lactic acid), poly(3-hydroxybutyrate), or poly(hydroxyalkanoate). In a 1776 preferred embodiment of the present invention, the natural polymer comprises cellulose.
1777 Responsive particles with switchable surface charge were prepared, according to Example 1778 Ni, from nanocrystalline cellulose.
1779 In yet another embodiment of the present invention, the natural polymer derivative comprises 1780 carbonaceous material. Responsive particles with switchable surface charge were prepared, 1781 according to Example N2, from cellulose which is converted from a natural polymer into a 1782 carbonaceous material.
1783 In certain embodiments of the present invention, the responsive particle comprises a surface 1784 functionality which reversibly converts to its ionic state upon contact with a trigger in the 1785 presence of water. In one embodiment of the present invention, the trigger is 002, NO2, 1786 COS, or CS2. In a most preferred embodiment of the present invention, the trigger is 002. In 1787 one embodiments of the present invention, the surface functionality comprises a nitrogen 1788 base wherein contact with a trigger in the presence of water protonates said nitrogen base.
1789 In a further embodiment of the present invention, the surface functionality comprises, in its 1790 non-ionic state: an amidine, a guanidine, or a tertiary amine; and, in its ionic state: an 1791 amidinium, a guanidinium, or a tertiary aminium.

In a preferred embodiment of the present invention, the surface functionality has the following 1793 structure in its non-ionic state:

I E

1795 where is the surface of the insoluble particle;
1796 where Ri and R2 are independently:
1797 H;

a substituted or unsubstituted Ci to 08 aliphatic group that is linear, branched, or cyclic, optionally wherein one or more C of the alkyl group is replaced by {¨Si(R92--0-4 up 1800 to and ncluding eight C being replaced by eight {¨Si(R92-0¨};

a substituted or unsubstituted CnS6 group where n and m are independently a number 1802 from 0 to 8 and n+m is a number from 1 to 8;

a substituted or unsubstituted C4 to 08 aryl group wherein aryl is optionally heteroaryl, 1804 optionally wherein one or more C is replaced by 1¨Si(R92-0-1;

a substituted or unsubstituted aryl group having 4 to 8 ring atoms, optionally including one 1806 or more {¨Si(R92-0---}, wherein aryl is optionally heteroaryl;

a ¨(Si(R92-0)p--- chain in which p is from 1 to 8 which is terminated by H, or is 1808 terminated by a substituted or unsubstituted Ci to 08 aliphatic and/or aryl group; or a substituted or unsubstituted (Ci to 08 aliphatic)-(C4 to 08 aryl) group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by a {¨Si(R1 )2-0-1811 };

wherein R1 is a substituted or unsubstituted Ci to 08 aliphatic group, a substituted or unsubstituted Ci to Cs alkoxy, a substituted or unsubstituted 04 to Cs aryl wherein aryl is optionally heteroaryl, a substituted or unsubstituted aliphatic-alkoxy, a substituted or 1815 unsubstituted aliphatic-aryl, or a substituted or unsubstituted alkoxy-aryl group;
1816 where E is:

a substituted or unsubstituted Ci to 08 aliphatic group that is linear, branched, or cyclic, optionally wherein one or more C of the alkyl group is replaced by {¨Si(R10)2-0¨} up 1819 to and including 8 C being replaced by 8 {¨Si(R10)2--0¨};

a substituted or unsubstituted CnSim group where n and m are independently a number 1821 from 0 to 8 and n+m is a number from 1 to 8;

a substituted or unsubstituted 04 to 08 aryl group wherein aryl is optionally heteroaryl, 1823 optionally wherein one or more C is replaced by 1¨Si(R10)2-0-1;

a substituted or unsubstituted aryl group having 4 to 8 ring atoms, optionally including one 1825 or more {¨Si(R1 )2-0¨}, wherein aryl is optionally heteroaryl;
1826 a ¨(Si(R1 )2-0)p¨ chain in which p is from 1 to 8; or a substituted or unsubstituted (Ci to 08 aliphatic)-(C4 to 08 aryl) group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by a {¨Si(R10)2-0-1829 }; and wherein R1 is a substituted or unsubstituted Ci to 08 aliphatic group, a substituted or unsubstituted Ci to 08 alkoxy, a substituted or unsubstituted C4 to C8 aryl wherein aryl is optionally heteroaryl, a substituted or unsubstituted aliphatic-alkoxy, a substituted or 1833 unsubstituted aliphatic-aryl, or a substituted or unsubstituted alkoxy-aryl group; and wherein a substituent is independently: alkyl; alkenyl; alkynyl; aryl; aryl-halide; heteroaryl;

cycloalkyl; Si(alkyl)3; Si(alkoxy)3; halo; alkoxyl; amino; alkylamino;
alkenylamino; amide;

hydroxyl; thioether; alkylcarbonyl; alkylcarbonyloxy; arylcarbonyloxy;
alkoxycarbonyloxy;

aryloxycarbonyloxy; carbonate; alkoxycarbonyl; aminocarbonyl;
alkylthiocarbonyl; amidine, 1838 phosphate; phosphate ester; phosphonato; phosphinato; cyano; acylamino;
imino;

3.839 sulfhydryl; alkylthio; arylthio; thiocarboxylate; dithiocarboxylate;
sulfate; sulfato; sulfonate;
1840 sulfamoyl; sulfonamide; nitro; nitrile; azido; heterocyclyl; ether;
ester; silicon-containing 1841 moieties; thioester; or a combination thereof. In a further embodiment of the present 1842 invention, the surface functionality has the following structure in its ionic state:

I

1843 .
1844 In a most preferred embodiment of the present invention, the surface functionality has the 1845 following structure, in its non-ionic state:

Ii - E - N
\

1847 where ¨ is the surface of the insoluble particle;
1848 where R-1 and R2 are independently: .
1849 H;
1850 a substituted or unsubstituted Ci to 08 aliphatic group that is linear, branched, or cyclic, 1851 optionally wherein one or more C of the alkyl group is replaced by {¨Si(R1 )2-0¨} up 1852 to and ncluding eight C being replaced by eight 1¨Si(R10)2-0--1;
1853 a substituted or unsubstituted CnSim group where n and m are independently a number 1854 from 0 to 8 and n+m is a number from 1 to 8;

1855 a substituted or unsubstituted C4 to 08 aryl group wherein aryl is optionally heteroaryl, 1856 optionally wherein one or more C is replaced by {¨Si(R1 )2-0--};
1857 a substituted or unsubstituted aryl group having 4 to 8 ring atoms, optionally including one 1858 or more {¨Si(R1 )2-0¨}, wherein aryl is optionally heteroaryl;
1859 a ¨(Si(R10)2-0)p¨ chain in which p is from 1 to 8 which is terminated by H, or is 1860 terminated by a substituted or unsubstituted Ci to 08 aliphatic and/or aryl group; or 1861 a substituted or unsubstituted (Ci to 08 aliphatic)-(C4 to 08 aryl) group wherein aryl is 1862 optionally heteroaryl, optionally wherein one or more C is replaced by a {¨Si(R1 )2-0-1863 };
1864 wherein Rio is a substituted or unsubstituted Ci to 08 aliphatic group, a substituted or 1865 unsubstituted Ci to 08 alkoxy, a substituted or unsubstituted 04 to 08 aryl wherein aryl is 1866 optionally heteroaryl, a substituted or unsubstituted aliphatic-alkoxy, a substituted or 1867 unsubstituted aliphatic-aryl, or a substituted or unsubstituted alkoxy-aryl group;
1868 where E is:
1869 a substituted or unsubstituted C-1 to 08 aliphatic group that is linear, branched, or cyclic, 1870 optionally wherein one or more C of the alkyl group is replaced by {¨Si(R1 )2-0¨} up 1871 to and including 8 C being replaced by 8 {¨Si(R1 )2-0¨};
1872 a substituted or unsubstituted CnSim group where n and m are independently a number 1873 from 0 to 8 and n+nn is a number from 1 to 8;
1874 a substituted or unsubstituted 04 to 08 aryl group wherein aryl is optionally heteroaryl, 1875 optionally wherein one or more C is replaced by {¨Si(R1 )2-0¨};
1876 a substituted or unsubstituted aryl group having 4 to 8 ring atoms, optionally including one 1877 or more {¨Si(R1 )2-0--}, wherein aryl is optionally heteroaryl;
1878 a ¨(Si(R1 )2-0)p¨ chain in which p is from 1 to 8; or 1879 a substituted or unsubstituted (Ci to 08 aliphatic)-(C4 to C8 aryl) group wherein aryl is 1880 optionally heteroaryl, optionally wherein one or more C is replaced by a {¨Si(R1 )2-0-1881 }; and 1882 wherein R1 is a substituted or unsubstituted Ci to C8 aliphatic group, a substituted or 1883 unsubstituted Ci to 08 alkoxy, a substituted or unsubstituted 04 to 08 aryl wherein aryl is 1884 optionally heteroaryl, a substituted or unsubstituted aliphatic-alkoxy, a substituted or 1885 unsubstituted aliphatic-aryl, or a substituted or unsubstituted alkoxy-aryl group; and 1886 wherein a substituent is independently: alkyl; alkenyl; alkynyl; aryl;
aryl-halide; heteroaryl;
1887 cycloalkyl; Si(alkyl)3; Si(alkoxy)3; halo; alkoxyl; amino; alkylamino;
alkenylamino; amide;
1888 hydroxyl; thioether; alkylcarbonyl; alkylcarbonyloxy; arylcarbonyloxy;
alkoxycarbonyloxy;
1889 aryloxycarbonyloxy; carbonate; alkoxycarbonyl; aminocarbonyl;
alkylthiocarbonyl; amidine, 1890 phosphate; phosphate ester; phosphonato; phosphinato; cyano; acylamino;
imino;
1891 sulfhydryl; alkylthio; arylthio; thiocarboxylate; dithiocarboxylate;
sulfate; sulfato; sulfonate;
1892 sulfamoyl; sulfonamide; nitro; nitrile; azido; heterocyclyl; ether;
ester; silicon-containing 1893 moieties; thioester; or a combination thereof. In a further embodiment of the present 1894 invention, the surface functionality has the following structure, in its ionic state:

a /
E NH

1896 In a less preferred embodiment of the present invention, the surface functionality has the 1897 following structure in its non-ionic state:

-1899 where is the surface of the insoluble particle;
1900 where Ri and R2 are independently:
1901 H;

a substituted or unsubstituted Ci to 08 aliphatic group that is linear, branched, or cyclic, optionally wherein one or more C of the alkyl group is replaced by {¨Si(R10)2-0¨} up 1904 to and ncluding eight C being replaced by eight {¨Si(R1 )2-0¨};

a substituted or unsubstituted CnSim group where n and m are independently a number 1906 from 0 to 8 and n+m is a number from 1 to 8;

a substituted or unsubstituted 04 to 08 aryl group wherein aryl is optionally heteroaryl, 1908 optionally wherein one or more C is replaced by {¨Si(R10)2-0¨};

a substituted or unsubstituted aryl group having 4 to 8 ring atoms, optionally including one 1910 or more {¨Si(R10)2-0¨}, wherein aryl is optionally heteroaryl;

a ¨(Si(R1 )2-0)p¨ chain in which p is from 1 to 8 which is terminated by H, or is 1912 terminated by a substituted or unsubstituted Ci to 08 aliphatic and/or aryl group; or a substituted or unsubstituted (C, to C8 aliphatic)-(C4 to 08 aryl) group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by a{¨Si(R1 )2-0-1915 };

wherein R1 is a substituted or unsubstituted Ci to 08 aliphatic group, a substituted or unsubstituted Ci to 08 alkoxy, a substituted or unsubstituted 04 to 08 aryl wherein aryl is optionally heteroaryl, a substituted or unsubstituted aliphatic-alkoxy, a substituted or 1919 unsubstituted aliphatic-aryl, or a substituted or unsubstituted alkoxy-aryl group;
1920 where E is:

a substituted or unsubstituted Ci to Ca aliphatic group that is linear, branched, or cyclic, optionally wherein one or more C of the alkyl group is replaced by {¨Si(R1 )2-0--} up 1923 to and including 8 C being replaced by 8 {¨Si(R1 )2-0¨};

a substituted or unsubstituted CnSim group where n and m are independently a number 1925 from 0 to 8 and n+m is a number from 1 to 8;

a substituted or unsubstituted C4 to 08 aryl group wherein aryl is optionally heteroaryl, 1927 optionally wherein one or more C is replaced by {¨Si(11110)2-0¨};

a substituted or unsubstituted aryl group having 4 to 8 ring atoms, optionally including one 1929 or more {¨Si(R92-0¨}, wherein aryl is optionally heteroaryl;
1930 a ¨(Si(R1 )2-0)p¨ chain in which p is from 1 to 8; or a substituted or unsubstituted (Ci to C8 aliphatic)-(C4 to C8 aryl) group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by a {¨Si(R92-0-1933 }; and wherein Rl is a substituted or unsubstituted Ci to C8 aliphatic group, a substituted or unsubstituted Ci to 08 alkoxy, a substituted or unsubstituted C4 to C8 aryl wherein aryl is optionally heteroaryl, a substituted or unsubstituted aliphatic-alkoxy, a substituted or 1937 unsubstituted aliphatic-aryl, or a substituted or unsubstituted alkoxy-aryl group; and wherein a substituent is independently: alkyl; alkenyl; alkynyl; aryl; aryl-halide; heteroaryl;

cycloalkyl; Si(alkyl)3; Si(alkoxy)3; halo; alkoxyl; amino; alkylamino;
alkenylamino; amide;

hydroxyl; thioether; alkylcarbonyl; alkylcarbonyloxy; arylcarbonyloxy;
alkoxycarbonyloxy;

aryloxycarbonyloxy; carbonate; alkoxycarbonyl; aminocarbonyl;
alkylthiocarbonyl; amidine, 1942 phosphate; phosphate ester; phosphonato; phosphinato; cyano; acylamino;
imino;

sulfhydryl; alkylthio; arylthio; thiocarboxylate; dithiocarboxylate;
sulfate; sulfato; sulfonate;

sulfamoyl; sulfonamide; nitro; nitrile; azido; heterocyclyl; ether; ester;
silicon-containing 1945 moieties; thioester; or a combination thereof. In a further embodiment of the present 1946 invention, the surface functionality has the following structure in its ionic state:

-E-N NHj 1948 Responsive particles with switchable surface charge comprising a surface functionality which 1949 reversibly converts to its ionic state upon contact with a trigger, in the presence of water, 1950 were prepared, according to Examples Al ¨ A4 and Examples A7 ¨ A16, by reaction of 1951 different silica particles with the appropriate silane coupling agent;
and, when necessary, 1952 ' subsequently performing chemical reactions to transform the surface functional groups.
1953 Responsive particles with switchable surface charge prepared according to Examples Al -1954 A4 and Examples A7 ¨ Al 6 comprise a surface functionality which is a base and converts 1955 to its ionic state upon contact with a trigger in the presence of water. Responsive particles 1956 with switchable surface charge prepared according to Examples Al ¨ A4 and Examples 1957 A7 ¨ A16 comprise a nitrogen base surface functionality which is protonated upon 1958 application of the trigger, in the presence of water, resulting in a cationic surface charge; and 1959 deprotonated upon removal of the trigger, resulting in a non-ionic surface charge.
1960 Responsive particles with switchable surface charge prepared according to Example A3 and 1961 Examples A7 ¨A16 comprise a surface functionality which is a tertiary amine which converts 1962 into a tertiary aminium upon application of the trigger, in the presence of water, resulting in 1963 cationic surface charge; and which converts back into a tertiary amine upon removal of the 1964 trigger, resulting in non-ionic surface charge. Responsive particles with switchable surface 1965 charge prepared according to Example A4 comprise a surface functionality which is an 1966 amidine which converts into an amidinium upon application of the trigger, in the presence of 1967 water, resulting in cationic surface charge; and which converts back into a tertiary amine 1968 upon removal of the trigger, resulting in non-ionic surface charge.

In certain embodiments of the present invention, the responsive particle comprises a surface functionality which reversibly converts to its non-ionic state upon contact with a trigger in the presence of water. In one embodiment of the present invention, the trigger is 002, NO2, 1972 COS, or CS2. In a preferred embodiment of the present invention, the trigger is CO2.

In one embodiment of the present invention, the surface functionality comprises an oxygen 1974 acid wherein upon contact with a trigger in the presence of water protonates said oxygen acid. In a further embodiment of the present invention, the surface functionality comprises, in its non-ionic state: a 2-nitrophenol; and, in its ionic state: 2-nitrophenoxide. In a further embodiment of the present invention, the surface functionality has the following structure in 1978 its ionic state:

F- E

1980 where ¨ is the surface of the insoluble particle;
1981 where Q is ¨000¨, ¨00¨, ¨NOC¨, or ¨NHOC¨, 1982 where R1 and R4 are independently:

H; nitro; sulfa; amnnonio; cyano; trihalomethyl; carbonyl; haloformyl; a substituted or unsubstituted Ci to 08 alkoxycarbonyl; a substituted or unsubstituted alto 08 alkylformyl;
1985 formyl; halo; or a substituted or unsubstituted Ci to C8 carbamoyl;
and 1986 where R2 and R3 are independently:

H; alkyl; alkenyl; aryl; amino; hydroxy; a substituted or unsubstituted Ci to C8 alkylhydroxy;

a substituted or unsubstituted Ci to 08 carboxyamido; or a substituted or unsubstituted 1989 Ci to C8 alkanyloxy;

1990 wherein at least one or more of R', R2, R3, and R4 is not H; and 1991 where E is:
1992 a substituted or unsubstituted Ci to 08 alkoxycarbonyl;
1993 a substituted or unsubstituted Ci to 08 carbamoyl;

a substituted or unsubstituted Ci to 08 aliphatic group that is linear, branched, or cyclic, optionally wherein one or more C of the alkyl group is replaced by {¨Si(R10)2-0--} up 1996 to and including 8 C being replaced by 8 {¨Si(R92-0¨};

a substituted or unsubstituted CnSim group where n and m are independently a number 1998 from 0 to 8 and n+m is a number from 1 to 8;

a substituted or unsubstituted C4 to 08 aryl group wherein aryl is optionally heteroaryl, 2000 optionally wherein one or more C is replaced by {¨Si(R10)2-0--};

a substituted or unsubstituted aryl group having 4 to 8 ring atoms, optionally including one 2002 or more {¨Si(R92-0¨}, wherein aryl is optionally heteroaryl;
2003 a ¨(Si(R10)2-0)p¨ chain in which p is from 1 to 8; or a substituted or unsubstituted (C, to 08 aliphatic)-(C4 to 08 aryl) group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by a {¨Si(R92-0-2006 }; and wherein R1 is a substituted or unsubstituted Ci to 08 aliphatic group, a substituted or unsubstituted Ci to Cs alkoxy, a substituted or unsubstituted C4 to 08 aryl wherein aryl is optionally heteroaryl, a substituted or unsubstituted aliphatic-alkoxy, a substituted or 2010 unsubstituted aliphatic-aryl, or a substituted or unsubstituted alkoxy-aryl group; and wherein a substituent is independently: alkyl; alkenyl; alkynyl; aryl; aryl-halide; heteroaryl;

cycloalkyl; Si(alkyl)3; Si(alkoxy)3; halo; alkoxyl; amino; alkylamino;
alkenylamino; amide;

hydroxyl; thioether; alkylcarbonyl; alkylcarbonyloxy; arylcarbonyloxy;
alkoxycarbonyloxy;

aryloxycarbonyloxy; carbonate; alkoxycarbonyl; aminocarbonyl;
alkylthiocarbonyl; amidine, 2015 phosphate; phosphate ester; phosphonato; phosphinato; cyano; acylamino;
imino;

2016 sulfhydryl; alkylthio; arylthio; thiocarboxylate; dithiocarboxylate;
sulfate; sulfato; sulfonate;
2017 sulfamoyl; sulfonamide; nitro; nitrite; azido; heterocyclyl; ether;
ester; silicon-containing 2018 moieties; thioester; or a combination thereof. In a further embodiment of the present 2019 invention, the surface functionality has the following structure in its non-ionic state:
RJ
-.., HE -Q

2020 .

2022 In a preferred embodiment of the present invention, the surface functionality has the following 2023 structure in its ionic state:

\
40 OC) I

2025 where ¨ is the surface of the insoluble particle;
2026 where R1 is:

H; nitro; sulfo; ammonio; cyano; trihalomethyl; carbonyl; haloformyl; a substituted or unsubstituted Ci to C8 alkoxycarbonyl; a substituted or unsubstituted Ci to C8 alkylformyl;
2029 formyl; halo; or a substituted or unsubstituted Ci to 08 carbamoyl;
2030 where R2 and R3 are independently:

H; alkyl; alkenyl; aryl; amino; hydroxy; a substituted or unsubstituted C-1 to 08 alkylhydroxy;

a substituted or unsubstituted Ci to C8 carboxyamido; or a substituted or unsubstituted 2033 Ci to Cs alkanyloxy; and 2034 where E is:
2035 a substituted or unsubstituted Ci to C8 alkoxycarbonyl;
2036 a substituted or unsubstituted Ci to 08 carbamoyl;

a substituted or unsubstituted Ci to 08 aliphatic group that is linear, branched, or cyclic, optionally wherein one or more C of the alkyl group is replaced by {¨Si(R92-0¨} up 2039 to and including 8 C being replaced by 8 {¨Si(R92-0¨};

a substituted or unsubstituted CnSim group where n and m are independently a number 2041 from 0 to 8 and n+m is a number from 1 to 8;

a substituted or unsubstituted 04 to 08 aryl group wherein aryl is optionally heteroaryl, 2043 optionally wherein one or more C is replaced by {¨Si(R1 )2-0¨};

a substituted or unsubstituted aryl group having 4 to 8 ring atoms, optionally including one 2045 or more {¨Si(R192-0¨}, wherein aryl is optionally heteroaryl;
2046 a ¨(Si(R92---0)p¨ chain in which p is from 1 to 8; or a substituted or unsubstituted (C, to 08 aliphatic)-(C4 to 08 aryl) group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by a {¨Si(R192-0-2049 }; and wherein Rio is a substituted or unsubstituted C1 to 08 aliphatic group, a substituted or unsubstituted C-1 to C8 alkoxy, a substituted or unsubstituted 04 to 08 aryl wherein aryl is optionally heteroaryl, a substituted or unsubstituted aliphatic-alkoxy, a substituted or 2053 unsubstituted aliphatic-aryl, or a substituted or unsubstituted alkoxy-aryl group; and wherein a substituent is independently: alkyl; alkenyl; alkynyl; aryl; aryl-halide; heteroaryl;

cycloalkyl; Si(alkyl)3; Si(alkoxy)3; halo; alkoxyl; amino; alkylamino;
alkenylamino; amide;

hydroxyl; thioether; alkylcarbonyl; alkylcarbonyloxy; arylcarbonyloxy;
alkoxycarbonyloxy;

2057 aryloxycarbonyloxy; carbonate; alkoxycarbonyl; aminocarbonyl;
alkylthiocarbonyl; amidine, 2058 phosphate; phosphate ester; phosphonato; phosphinato; cyano; acylamino;
imino;
2059 sulfhydryl; alkylthio; arylthio; thiocarboxylate; dithiocarboxylate;
sulfate; sulfato; sulfonate;
2060 sulfamoyl; sulfonamide; nitro; nitrile; azido; heterocyclyl; ether;
ester; silicon-containing 2061 moieties; thioester; or a combination thereof. In a further embodiment of the present 2062 invention, the surface functionality has the following structure in its non-ionic state:

II
HE¨ 0 2064 In another preferred embodiment of the present invention, the surface functionality has the 2065 following structure in its ionic state:

HE¨ N

2067 where wvwJ is the surface of the insoluble particle;
2068 where R1 is:
2069 H; nitro; sulfo; ammonio; cyano; trihalomethyl; carbonyl; haloformyl;
a substituted or 2070 unsubstituted Ci to C8 alkoxycarbonyl; a substituted or unsubstituted Ci to C8 alkylformyl;
2071 formyl; halo; or a substituted or unsubstituted Ci to C8 carbamoyl;
and 2072 where R2 and R3 are independently:

H; alkyl; alkenyl; aryl; amino; hydroxy; a substituted or unsubstituted Ci to Cs alkylhydroxy;

a substituted or unsubstituted Ci to Cs carboxyamido; or a substituted or unsubstituted 2075 Ci to 08 alkanyloxy; and 2076 where E is:
2077 a substituted or unsubstituted Ci to 08 alkoxycarbonyl;
2078 or a substituted or unsubstituted Ci to Cs carbamoyl a substituted or unsubstituted Ci to Cs aliphatic group that is linear, branched, or cyclic, optionally wherein one or more C of the alkyl group is replaced by {¨Si(R1 )2-0¨} up 2081 to and including 8 C being replaced by 8 a substituted or unsubstituted CnSim group where n and m are independently a number 2083 from 0 to 8 and n+m is a number from 1 to 8;

a substituted or unsubstituted 04 to Cs aryl group wherein aryl is optionally heteroaryl, 2085 optionally wherein one or more C is replaced by {¨Si(R10)2-0--};

a substituted or unsubstituted aryl group having 4 to 8 ring atoms, optionally including one 2087 or more {¨Si(R1 )2-0¨}, wherein aryl is optionally heteroaryl;
2088 a ¨(Si(R1 )2-0)p¨ chain in which p is from 1 to 8; or a substituted or unsubstituted (C, to Cs aliphatic)-(C4 to Cs aryl) group wherein aryl is 2090 optionally heteroaryl, optionally wherein one or more C is replaced by a s i 0)2-0-2091 1; and wherein R1 is a substituted or unsubstituted Ci to 08 aliphatic group, a substituted or unsubstituted Ci to Cs alkoxy, a substituted or unsubstituted C4 to 08 aryl wherein aryl is optionally heteroaryl, a substituted or unsubstituted aliphatic-alkoxy, a substituted or 2095 unsubstituted aliphatic-aryl, or a substituted or unsubstituted alkoxy-aryl group; and wherein a substituent is independently: alkyl; alkenyl; alkynyl; aryl; aryl-halide; heteroaryl;

cycloalkyl; Si(alkyl)3; Si(alkoxy)3; halo; alkoxyl; amino; alkylamino;
alkenylamino; amide;

hydroxyl; thioether; alkylcarbonyl; alkylcarbonyloxy; arylcarbonyloxy;
alkoxycarbonyloxy;

2099 aryloxycarbonyloxy; carbonate; alkoxycarbonyl; aminocarbonyl;
alkylthiocarbonyl; amidine, 2100 phosphate; phosphate ester; phosphonato; phosphinato; cyano; acylamino;
imino;
2101 sulfhydryl; alkylthio; arylthio; thiocarboxylate; dithiocarboxylate;
sulfate; sulfato; sulfonate;
2102 sulfamoyl; sulfonamide; nitro; nitrile; azido; heterocyclyl; ether;
ester; silicon-containing 2103 moieties; thioester; or a combination thereof. In a further embodiment of the present 2104 invention, the surface functionality has the following structure in its non-ionic state:

OH
HE- N

2106 Responsive particles with switchable surface charge comprising a surface functionality which 2107 reversibly converts to its non-ionic state upon contact with a trigger, in the presence of water 2108 were prepared, according to Examples A17 and B9, by reaction of silica particles with a 2109 silane coupling agent followed by chemical functional group transformation. Responsive 2110 particles with switchable surface charge prepared according to Examples A17 and B9 2111 comprise a surface functionality which is an acid and converts to its non-ionic state upon 2112 contact with a trigger in the presence of water. Responsive particles with switchable surface 2113 charge prepared according to Examples A17 and B9 comprise an oxygen acid surface 2114 functionality which is protonated upon contact with a trigger, resulting in a non-ionic surface 2115 charge; and deprotonated upon removal of the trigger, resulting in an anionic Surface charge.
2116 Responsive particles with switchable surface charge prepared according to Examples A17 2117 and B9 comprise a surface functionality which, in its ionic state, is a 2-nitrophenoxide.
2118 It is possible to prepare particles with more or less surface groups by adjusting the amount 2119 the silane coupling agent, the reactivity of the active silane coupling agent, the reaction time, 2120 and the reaction conditions. Additional functional groups may be installed by repeating the 2121 coupling reaction with silane coupling agent multiple times as in Example A8. Surface 2122 functionality coverage of silica particles reaches up to 10 groups/nm2, but more typically 2123 between 1 ¨ 5 groups/nm2. Increasing number of charges associated with each particle is 2124 accomplished, according to Examples A9 and Example A10, using surface functionality 2125 which comprises more than one charged moiety.
2126 7.1 Surface Charge 2127 The responsive particles of the present invention comprise switchable surface charge; upon 2128 specific conditions, the surface charge may be adopt a strongly positive charge, a weakly 2129 positive charge, a strongly negative charge, a weakly negative.
charge, or limited surface 2130 charge close to neutrality. The responsive particles of the present invention are capable of 2131 adopting, under different conditions, at least two distinct states with contrasting surface 2132 charge. The responsive particles of the present invention are capable of reversibly converting 2133 between the different states. Responsive particles with surface functionality Which is basic 2134 have positive zeta potential due to formation of cationic surface charge in its ionic state.
2135 Conversely, particles with surface functionality which is acidic have negative zeta potential 2136 due to formation of anionic surface charge in its ionic state. In one embodiment of the present 2137 invention, the intensity of the surface charge of responsive particles with switchable surface 2138 charge is greater when the surface functionality is in ionic state and lesser when the 2139 surface functionality is in non-ionic state. A zeta potential value of greater intensity 2140 indicates more surface charge while a zeta potential value of lesser intensity indicates less 2141 surface charge. The zeta potential of responsive particles with switchable surface charge 2142 was measured, according to Example Cl (see Table 3 and Table 4).
2143 Colloidal silica particle with switchable surface charge prepared using amidine surface 2144 functionality (El in Table 3) and tertiary amine surface functionality (E2 in Table 3) have 2145 positive zeta potential in their ionic state. Colloidal silica particles with primary amine surface 2146 functionality (Example A2) and secondary amine functionality (Example A3) also exhibit 2147 positive zeta potential in their ionic state (+25 mV and +30 mV, respectively). The absolute 2148 value for zeta potential is greater for particles prepared with amidine surface functionality 2149 compared to amine surface functionality, due to the increased basicity of the amidine surface 2150 functionality compared to the tertiary amine surface functionality.
The zeta potential is even 2151 greater for particles prepared with guanidine surface functionality compared to amidine 2152 surface functionality, due to the increased basicity of the guanidine surface functionality.

2153 Upon removal of the trigger, the surface functional groups of colloidal silica particles with 2154 switchable surface charge convert to their non-ionic state which leads to depressed zeta 2155 potential. Colloidal silica particles functionalized with amidine, guanidine, and tertiary amine 2156 surface functionality are capable of reversibly converting between ionic and non-ionic sate.
2157 Colloidal silica particles prepared using primary amine surface functionality and silica 2158 particles prepared using secondary amine surface functionality do no fully revert to its non-2159 ionic state due to formation of carbamate salt which is less reversible than formation of 2160 bicarbonate salt.
2161 In certain samples, the zeta potential of particles with basic surface group have slightly 2162 negative zeta potential after removal of trigger (El and E2 in Table 3). The surface of silica 2163 is covered by silanol groups which react with silane coupling agents;
the zeta potential of 2164 unmodified silica is about -40 mV. However, unreacted silanol groups contribute to surface 2165 charge and lowers zeta potential, as silanol is acidic. This surface charge may be eliminated 2166 by replacing silanol surface groups with non-polar surface groups using the appropriate 2167 silane coupling agent. Surface groups which do not induce significant surface charge are 2168 installed on the surface of silica particles, according to Example A5.
Colloidal silica particles 2169 treated accordingly exhibit very limited surface charge (E6 in Table 3). Colloidal silica 2170 particles with switchable surface charge were prepared with a surface functionality which 2171 reversible converts between ionic state and non-ionic state were further treated to replace 2172 unreacted silanol groups with surface functionality which is not responsive; according to 2173 Example A7. Colloidal silica particles with both basic surface functionality (tertiary amine or 2174 amidine) and alkyl functionality exhibited positive zeta potential in its ionic state and limited 2175 surface charge in its non-ionic state (E7 and E8 in Table 3).
2176 The surface charge of responsible particle with switchable surface charge can be increased 2177 by increasing the number of charges of each individual surface groups which reversibly 2178 converts between an ionic state and a non-ionic state. The zeta potential of functionalized 2179 colloidal silica particles intensifies when the coverage of ionic surface groups increases. (E2 2180 ¨ E4 in Table 3). Colloidal silica particles with greater coverage of surface functionality were 2181 prepared according to Example A8. The zeta potential may also be intensified by installing 2182 surface functionality with more than one moiety which can reversibly convert between ionic 2183 state and non-ionic state on the surface of particles (E9 and El 0 in Table 3). Colloidal silica 2184 particles comprising polyamines surface functionality were prepared according to Example 2185 A9 and Example A10. The surface charge of responsible particle with switchable surface 2186 charge can be increased by increasing the coverage of surface functionality which reversibly 2187 converts between an ionic state and a non-ionic state. Colloidal silica particles with greater 2188 coverage of surface functionality were prepared according to Example A8. Colloidal silica 2189 particles with switchable surface charge prepared using 2-nitrophenoxide surface 2190 functionality (El 1 and El 2 in Table 3) have negative zeta potential in their ionic state. Upon 2191 application of a trigger, the surface functionality convert to their non-ionic state; however, 2192 residual silanols surface groups lead to slightly negative zeta potential in its non-ionic state 2193 (Ell in table 3). Additional coverage with non-ionic group supress effect of silanol and 2194 functionalized particles exhibited limited zeta potential in its non-ion state (E12 in Table 3).
2195 Fumed silica particles functionalized with tertiary amine surface functionality, according to 2196 Example All, exhibited switchable surface charge (E13 in Table 3).
Flash silica particles 2197 with tertiary amine surface functionality, prepared according to Examples Al2, exhibited 2198 switchable surface charge (E14 in Table 3). Silica gel particles with tertiary amine surface 2199 functionality, prepared according to Examples A13, exhibited switchable surface charge 2200 (E15 in Table 3).
2201 Table 3 ¨ Zeta potential of various colloidal silica-based particles with switchable surface 2202 charge in both ionic and non-ionic state.
Sample Surface Functionality Zeta Potential in Ionic Zeta Potential in Non-State Ionic State E1 Amidine / Amidinium +40 mV -5 mV
E2 Tertiary Amine / Aminium +35 mV -5 mV
E3 Tertiary Amine / Aminium +40 mV 0 mV
E4 Tertiary Amine / Aminium +45 mV 0 mV
E6 Alkyl n/a 0 mV
E7 Tertiary Amine / Aminium +35 mV 0 mV
+ Alkyl E8 Amidine / Amidinium + +45 mV 0 mV
Alkyl E9 Poly Tertiary Amine / +55 mV +5 mV
Aminium El 0 Poly Tertiary Amine! + 50 mV 0 mV
Aminium Ell 2-Nitrophenoxide / 2- -40 mV -10 mV
Nitrophenol E12 2-Nitrophenoxide / 2- -35 mV 0 mV
Nitrophenol + Alkyl E13 Tertiary Amine / Arninium +45 mV 0 mV
El 4 Tertiary Amine / Am iniu m +35 mV +10 mV
E15 Tertiary Amine / Aminium +35 mV +5 mV

2204 Polymer particles, such as polystyrene, poly(methyl-methacrylate), and copolymers thereof, 2205 with switchable surface charge were prepared according to Examples B1 ¨
B9 using 2206 emulsion polymerization and miniemulsion polymerization. Switchable surface charges were 2207 installed on the surface of polymer particles using with a surfactant with switchable charge, 2208 according to Examples B1 ¨ B4, and Example B9; an initiator with switchable charge, 2209 according to Example B5; a monomer with switchable charge, according to Examples B6 2210 ¨ B7; or a combination thereof. During the heterogeneous polymerization process, charged 2211 species are concentrated at the interface with water and remain at the surface of polymer 2212 particles after the polymerization reaction is complete.
2213 Polystyrene particles with switchable surface charge prepared using amidine surface 2214 functionality (F1 ¨ F5 in Table 4) have positive zeta potential in their ionic state; upon removal 2215 of the trigger, silica particles with switchable surface charge exhibited reduced zeta potential 2216 as amidine surface functionality is converted to its non-ionic state.
Polystyrene particles 2217 prepared via emulsion polymerization using surfactant with switchable charge (F1 in Table 2218 4), initiator with switchable charge (F2 in Table 4), and monomer with switchable charge (F3 2219 in Table 4), were all capable of converting between ionic and non-ionc surface charge.
2220 However, polystyrene particles with switchable surface charge showed slightly positive zeta 2221 potential in their non-ionic state. The surface of pure polystyrene is non-ionic and 2222 hydrophobic. The residual positive charge of polystyrene particles is eliminated (F4 and F5 2223 in Table 4) when the surfactant used during emulsion polymerization comprises hydrophilic 2224 linkers (-CH2CH20-). Further reduction of zeta potential for responsive particles in non-ionic 2225 state was achieved by replacing 2,2'-azobis-{2-(2-imidazolin-2-yl)propanel-dihydrochloride 2226 with 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dibicarbonate. Polystyrene particles with 2227 switchable surface charge prepared using nitrophenoxide surface functionality (F6 in Table 2228 4) have negative zeta potential in their ionic state; upon application of a trigger, polystyrene 2229 particles with switchable surface charge exhibited limited zeta potential as 2-nitrophenoxide 2230 surface functionality is converted to its non-ionic state.
2231 Table 4 ¨ Zeta potential of polystyrene particles with switchable surface charge in both ionic 2232 and non-ionic state.
Sample Surface Functionality Zeta Potential in Ionic Zeta Potential in Non-State Ionic State Fl Amidine / Amidinium +45 mV +10 mV
F2 Amidine / Amidinium +45 mV +10 mV
F3 Amidine / Amidinium +40 mV +5 mV
F4 Amidine / Amidinium +45 mV 0 mV
F5 Amidine / Amidinium +50 mV 0 mV
F6 2-Nitrophenioxide / 2- -40 mV 0 mV
Nitrophenol 2234 Nanocrystalline cellulose particles with tertiary amine functionality, prepared according to 2235 Example Ni, exhibited a zeta potential of +40 mV in its ionic state and a zeta potential of -5 2236 mV in its non-ionic state. Carbon particles with tertiary amine functionality, prepared 2237 according to Example N2, exhibited a zeta potential of +35 mV in its ionic state and a zeta 2238 potential of 5 mV in its non-ionic state.
2239 The zeta-potential of various responsive particles with switchable surface charge, prepared 2240 according to the Examples provided, are presented in FIG. 3. FIG. 3 shows that is it possible 2241 to prepared responsive particles with switchable surface charge having a tunable range of 2242 properties such as surface charge.

2243 Responsive particles with switchable surface charge are dispersed in water or other fluid 2244 when provided with sufficient agitation. There are various methods of dispersing particles.
2245 Responsive particles with switchable surface charge are dispersed in an aqueous phase by 2246 manual mixing, ultrasonic treatment, high-shear mixing, or combination thereof. Responsive 2247 particle with switchable surface charge are more readily dispersed when surface functionality 2248 is in ionic form compared to when surface functionality is in non-ionic form. The increase 2249 surface charge enhanced colloidal stability of responsive particles.
2250 7.2 Electrolytic Conductivity 2251 Electrolytic conductivity of dispersions prepared using particles with switchable surface 2252 charge was measured according to Example C2 (see Table 5). The electrolytic conductivity 2253 of dispersions prepared with particles with switchable surface charge is greatly increased 2254 when the surface functionality is in its ionic state compared to when the surface functionality 2255 is in its non-ionic state. High-quality deionized water has a conductivity of about 5.5 pS/m, 2256 typical drinking water in has a conductivity of 5 ¨ 50 mS/m; sea water has conductivity of 2257 about 5 S/m, depending on salinity.
2258 The electrolytic conductivity of dispersed colloidal silica particles with switchable surface 2259 charge in their ionic state increases with concentration (G1 in Table

5); the increase in 2260 concentration also increases conductivity when particles are in their non-ionic state but to a 2261 much lesser extent. Colloidal silica particles with switchable surface charge functionalized 2262 using polyamine surface groups (G3 in Table 5) were more effective at increasing electrolytic 2263 conductivity compared to particles switchable surface charge functionalized using 2264 monoamine surface groups (G2 in Table 5). Silica particles with switchable surface charge 2265 functionalized using 2-nitrophenoxide surface groups were also effective in raising 2266 conductivity in its ionic state (G4 in Table 5). Fumed silica particles with switchable surface 2267 charge prepared using tertiary amine surface functionality behaved similarly, exhibiting 2268 increased conductivity in its ionic state and depressed conductivity in its non-ionic state (G5 2269 in Table 5).
2270 Porous silica particles with switchable surface charge, including flash silica particles (G6 in 2271 Table 5) and silica gel particles (G7 in Table 5), prepared using tertiary amine surface 2272 functionality exhibited increased conductivity in its ionic state and depressed conductivity in 2273 its non-ionic state. Porous silica particles were less effective compared to colloidal silica 2274 particles functionalized similarly.
2275 Table 5 ¨ Electrolytic conductivity of dispersions prepared using silica particles with 2276 switchable surface charge in both ionic and non-ionic state.
Sample Conc. (g/mL) Conductivity in Ionic State Conductivity in Non-Ionic State G1 0.01 Low Very low 0.05 Moderate Low 0.10 High Low 0.25 High Low G2 0.05 Moderate Very low 0.10 Moderate Low G3 0.05 Moderate Very low 0.10 High Low G4 0.05 Moderate Very low 0.10 Moderate Low G5 0.05 Moderate Low 0.10 Moderate Low G6 0.05 Moderate Low 0.10 Moderate Low G7 0.05 Moderate Low 0.10 Moderate Low 2278 The electrolytic conductivity of dispersed polystyrene particles with switchable surface 2279 charge in their ionic state increased with concentration (H1 in Table

6). Polystyrene particles 2280 with switchable surface charge prepared via emulsion polymerization using initiator with 2281 switchable charge, prepared according to Example B5, and using monomer with switchable 2282 charge, prepared according to Example B6, were also effective in raising electrolytic 2283 conductivity (H2 and H3 in Table 6, respectively).

2284 Table 6 ¨ Electrolytic conductivity of dispersions prepared using polystyrene particles with 2285 switchable surface charge in both ionic and non-ionic state.
Sample Conc. (g/mL) Conductivity in Ionic State Conductivity in Non-Ionic State H1 0.01 Low Very low 0.05 Moderate Very low 0.10 High Low 0.25 High Low H2 0.10 High Low H3 0.10 High Low 2287 Dispersions of nanocrystalline cellulose particles with switchable surface charge, prepared 2288 with tertiary amine surface functionality according to Example Ni, were also effective in 2289 increasing electrolytic conductivity in its ionic state; but resulted in limited conductivity in its 2290 non-ionic state.
2291 The electrolytic conductivity of various dispersions prepared using responsive particles with 2292 switchable surface charge, prepared according to the Examples provided, is presented in 2293 FIG. 4. FIG. 4 shows that is it possible to prepared responsive particles with switchable 2294 surface charge having a tunable range of properties such as electrolytic conductivity.
2295 7.3 Osmotic Performance 2296 The suitability of responsive particles with switchable surface charge for separations based 2297 on an osmotic process was evaluated in Example C3 (see Table 7). In order to achieve flux 2298 across the membrane, the osmotic gradient must be sufficient. The salinity of water varies 2299 depending on the source. Freshwater sources, such as pond, lakes, rivers, streams, and 2300 aquafers, typically contains water with salinity less than 0.5 %.
Brackish water sources, such 2301 as estuaries, mangroves, swamps, brackish lakes and seas, and brackish swamps, typically 2302 contains water with salinity between 0.05 and 3 %. Saline water sources, such as seawater 2303 and salt lakes, typically contain water with salinity between 3 ¨ 5 %.
Brine from industrial 2304 sources may have salinity much greater than 5 %.

2305 In one embodiment of the present invention, the ionic strength of a dispersion comprising 2306 responsive particles with switchable surface charge increases when the surface functionality 2307 is converted to its ionic state and decreases when the surface functionality is converted to 2308 its non-ionic state.
2309 Responsive particles with switchable surface charge dispersed in deionized water provided 2310 sufficient osmotic pressure to drive solvent from various electrolyte solutions across the 2311 membrane into the dispersion of colloidal silica particles with switchable surface charge. Flux 2312 was evaluate in Example C4 (see Table 7).
2313 Unmodified colloidal silica particles were not capable of driving movement of solvent across 2314 the membrane, even at very high concentration. Dispersions of colloidal silica particles with 2315 switchable surface charge comprising tertiary amine surface functionality were effective in 2316 driving solvent flux (J1 in Table 7) from an electrolyte solution (0.01 g/ml NaCl); higher 2317 concentration of dispersed particles was required to drive solvent flux from more 2318 concentrated electrolyte solution (0.05 g/ml NaCI). Dispersions of colloidal silica particles 2319 with switchable surface charge comprising polyamine surface functionality required lower 2320 concentration to achieve similar solvent flux (J2 in Table 7).
Dispersions of fumed silica 2321 particles with switchable surface charge comprising tertiary amine surface functionality (J3 2322 in Table 7).
2323 Suspensions of flash silica particles with switchable surface charge comprising tertiary 2324 surface functionality (J4 in Table 7) and suspensions of silica gel particles with switchable 2325 surface charge comprising tertiary surface functionality (J5 in Table

7) were both capable of 2326 driving solvent flux but were less effective compared to functionalized colloidal silica particles 2327 and fumed silica particles (J1 and J3 in Table 7, respectively). All functionalized silica 2328 particles exhibited very low solvent flux when in non-ionic state.
2329 Polystyrene particles with switchable surface charge comprising amidine surface 2330 functionality, prepared according to Example B3, were capable of driving solvent flux in its 2331 ionic state (J6 in Table 7) but were not as effective, at the same concentration, in its non-2332 ionic state.

2333 Dispersion of nanocrystalline cellulose particles with switchable surface comprising tertiary 2334 amine surface functionality, prepared according to Example El, were capable of driving 2335 solvent flux in its ionic state (J7 in Table 7) but were not as effective, at the same 2336 concentration, in its non-ionic state.
2337 Table 7 - Water flux across membrane from electrolyte solution driven by dispersions 2338 prepared using particles with switchable surface charge in ionic state.
Sample Particle Concentration (g/ml) NaC1 Concentration (g/ml) Flux J1 0.05 0.01 Low 0.10 0.01 Moderate 0.20 0.01 High 0.35 0.01 High 0.05 0.05 Low 0.10 0.05 Low 0.20 0.05 Moderate 0.35 0.05 High J2 0.10 0.05 Moderate 0.20 0.05 High J3 0.10 0.05 Moderate 0.20 0.05 Moderate J4 0.20 0.05 Low 0.35 0.05 Moderate J5 0.20 0.05 Low 0.35 0.05 Moderate J6 0.10 0.05 Low 0.20 0.05 Moderate J7 0.10 0.05 Low 0.20 0.05 Moderate 2340 7.4 Particle Separation 2341 Functionalized particles are insoluble and, unlike soluble chemical compounds, may be 2342 separated from a liquid without the use of reverse osmosis or nanofiltration. Responsive 2343 particles with switchable surface charge have a specific gravity typically greater than any 2344 solvent; and thus the responsive particles sediment under the force of gravity. Alternatively, 2345 if the responsive particles have a specific gravity lesser than the solvent, then the responsive 2346 particles will rise. Sufficiently small particles are less affected by momentum diffusivity and 2347 more affected by thermal diffusivity. The separation of responsive particles with negligible 2348 gravity settling rate is possible using in a centrifuge which can generate a driving force much 2349 greater than gravity and effectively separate responsive particles with hydrodynamic size 2350 less than approximately 0.5 pm.
2351 Responsive particles with switchable surface charge are effectively separated by size 2352 exclusion processes, such as screening and filtration, due to the finite size of solids which is 2353 typically much greater than both solvent molecules and solute molecules. Filtration of 2354 responsive particles with switchable surface charge from dispersions thereof is enhanced by 2355 means for switching the responsive particles with switchable surface charge to non-ionic 2356 state wherein aggregation of responsive particles is promoted. In one embodiment of the 2357 present invention, the responsive particles with switchable surface charge are separated by 2358 sedimentation or by centrifuging. Responsive particles with switchable surface charge exhibit 2359 different rates of sedimentation due to differences in particle morphology (e.g. size, shape, 2360 and structure). Sedimentation is driven by the force of gravity while separation in a centrifuge 2361 is driven by a centrifugal force generated by continuous acceleration around a central axis.
2362 Dispersions of responsive particles with hydrodynamic size less than approximately 0.5 pm 2363 generally remain dispersed for long periods of time due to the negligible effect of gravity.
2364 Submicron responsive particles with switchable surface charge remain dispersed for 2365 prolonged periods and the resulting dispersion is clear with a blueish hue, as shown in FIG.
2366 5-A. A particle, depending on its size, may be in the continuum regime, the free molecular 2367 regime, or the transition regime. Particles of comparable size to the distance solvent 2368 molecules travel between collisions with other solvent molecule are consequently influenced 2369 by solvent-particles interactions. Particles dispersed in a fluid undergo irregular random 2370 motion due to bombardment by surrounding fluid molecules; the interaction between solvent 2371 molecules and particles of comparable size leads to Brownian motion.
Dispersions of 2372 responsive particles with switchable surface charge greater than approximately 1 pm are 2373 opaque. The sedimentation rate of responsive particles with switchable surface charge less 2374 than approximately 10 pm is limited, as shown in FIG. 5-B. The sedimentation rate of 2375 responsive particles with switchable surface charge may be tuned by varying the size of the 2376 insoluble particle. Alternatively, the sedimentation rate of responsive particles with 2377 switchable surface charge may be tuned by varying its effective density by incorporating 2378 materials which have high density materials such as iron oxide or barium sulphate into 2379 responsive particles with switchable surface charge. The settling rate of responsive particles 2380 with switchable surface charge is enhanced when individual particles form aggregate 2381 masses. Aggregation of responsive particles is more pronounced when the surface 2382 functionality is switched from ionic state, which provides electrostatic stabilization, to non-2383 ionic state, which reduces the level of electrostatic stabilization.
2384 Larger responsive particles with switchable surface charge prepared from silica gel particles 2385 or flash silica particles, with hydrodynamic size greater than approximately 50 pm, remain 2386 suspended only with sustained agitation, as shown in FIG. 5-C; and settle under gravity 2387 within 1 h without agitation. The settling rate of responsive particles with switchable surface 2388 charge of large hydrodynamic size was similar in both ionic and non-ionic states.
2389 Intermediate responsive particles with switchable surface charge with hydrodynamic size 2390 between approximately 1 ¨ 50 pm displayed slower settling rate, as shown in FIG. 5-B; but 2391 were nevertheless separated under gravity within 48 h. The settling rate of responsive 2392 particles of intermediate hydrodynamic size was greater when surface functionality is in its 2393 non-ionic state. Hydrodynamic size of responsive particles with switchable surface charge 2394 prepared from silica gel particles and flash silica particles increased slightly after converting 2395 to its surface functionality from ionic state to non-ionic state.
2396 Dispersions prepared using colloidal particles with switchable surface charge are much more 2397 stable against sedimentation. The time required for various responsive particles with 2398 switchable surface charge to settle under the force gravity was determined according to 2399 Example D1 (see Table 8). Responsive particles with switchable surface charge prepared 2400 using colloidal silica particles do not sediment within 48 h (K1 ¨ K4 in Table 8). Similarly, 2401 polystyrene latex particles did not sediment within 48 h (K5 ¨ K8 in Table 8). Colloidal 2402 stability of responsive particles with switchable surface charge in ionic state is due in large 2403 part to electrostatic stabilization which prevents particles from forming larger aggregates;
2404 particles functionalized with switchable surface charge are more stable when the switchable 2405 surface charge is in its ionic state and less stable when the switchable surface charge is in 2406 its non-ionic state. Colloidal stability of functionalized particles is reduced after supressing 2407 surface charge. Responsive particles having significant gravity settling rate are effectively 2408 separated by sedimentation.
2409 Table 8 ¨ Settling time for functionalized particles with switchable surface charge in both 2410 ionic and non-ionic state.
Sample State Approximate Hydrodynamic Diameter Time to Settle K1 Ionic 20 nm > 48 h Non-ionic 1.5 pm <24 h K2 Ionic 50 nm > 48 h Non-ionic 35 pm < 12 h K3 Ionic 100 nm > 48 h Non-ionic 300 pm < 1 h K4 Ionic 200 nm > 48 h Non-ionic 500 pm <1 h K5 Ionic 20 nm > 48 h Non-ionic 1.5 pm <24 h K6 Ionic 50 nm > 48 h Non-ionic 35 pm <12 h K7 Ionic 100 nm > 48 h Non-ionic 300 pm <1 h K8 Ionic 200 nm > 48 h Non-ionic 500 pm <1 h 2412 Changes to particle surface charge also affects wettability; particles are made more 2413 hydrophobic by replacing hydrophilic functional groups present on the surface with less 2414 hydrophilic functional groups. Ionic groups are hydrophilic and switching the charge of 2415 functionalized particles to non-ionic state decreases the affinity of the surface for water.

2416 Sufficiently hydrophobic particles can attach onto air bubbles which rise to the surface, as 2417 shown in FIG. 5-D. In such cases, it is possible to separate particles by flotation, according 2418 to Example 02.
2419 In one embodiment of the present invention, the responsive particles with switchable surface 2420 charge are separated by screening or filtration. The responsive particles with switchable 2421 surface charge of the present invention, prepared with different morphology, were separated 2422 by size exclusion. Filtration of responsive particles with switchable surface charge is possible 2423 both when surface functionality is in ionic state and when surface functionality is in non-ionic 2424 states. The filtration process was more efficient when responsive particles with switchable 2425 surface charge are in non-ionic state. Effective separation of responsive particles is possible 2426 using a mesh screen with opening smaller than responsive particles.
Aggregates of 2427 responsive particles with switchable surface charge are formed when surface charge is 2428 converted to its non-ionic state. Responsive particles with switchable surface are effective 2429 separated using a gravity filtration or vacuum filtration, according to Example D3.
2430 Aggregates of responsive particles with switchable surface are more efficiently separated by 2431 filtration. Larger aggregates are removed using filter media with larger pore size or using a 2432 bag filter.
2433 Magnetically susceptible responsive particles with switchable surface charge were prepared 2434 by functionalizing a magnetic material, according to Example A15, or by emulsion 2435 polymerization, according to Example B8. Both methods produced responsive particles with 2436 switchable surface charge that were also magnetically responsive and were effectively 2437 separated under an applied magnetic field, according to Example D4.
Separation of 2438 magnetic particles with switchable surface charge using a permanent magnet is shown in 2439 FIG. 6. After magnetic separation, either the magnetically recovered particles are removed 2440 from the fluid or the fluid is removed from the magnetically recovered particles. Once the 2441 magnetically recovered responsive particles are removed from an applied magnetic field, the 2442 responsive particles are re-dispersed in a suitable fluid by providing sufficient agitation.
2443 However, magnetic particles can retain residual magnetization which hinders re-dispersion.
2444 In one embodiment of the present invention, the magnetically susceptible responsive 2445 particles with switchable surface charge are separated under an applied magnetic field. In 2446 another embodiment of the present invention, the magnetically susceptible responsive 2447 particles with switchable surface charge are dispersed when the surface functionality of 2448 responsive particles is in ionic state.
2449 8.0 System Embodiments 2450 Different elements of various embodiments of the present invention are illustrated in FIG. 7 2451 - 14. It will be understood by those skilled in the art that this description is made with 2452 reference to the preferred embodiments and that it is possible to make other embodiments 2453 employing the principles of the invention which fall within its spirit and scope as defined by 2454 the claims appended hereto. All such modifications as would be obvious to one skilled in the 2455 art are intended to be included within the scope of the following claims.
2456 The present invention relates to a system comprising an aqueous dispersion of responsive 2457 particles with switchable surface charge; means for switching responsive particles from ionic 2458 state to non-ionic state or from non-ionic state to ionic state; and means for separating the 2459 responsive particles from said aqueous dispersion. FIG. 7 shows a diagram of systems 2460 comprising aqueous dispersion (1) comprising responsive particles with switchable surface 2461 charge (2, 3, 4, 5). The aqueous dispersion (1) has reduced electrolytic conductivity and ionic 2462 strength when responsive particles are in non-ionic state (2, 5). The aqueous dispersion (1) 2463 has elevated electrolytic conductivity and ionic strength when the responsive particles are in 2464 ionic state (3, 4).
2465 In one embodiment of the present invention, the responsive particles (2, 3) comprise an 2466 insoluble particle and a surface functionality which is a base wherein upon contact with a 2467 trigger protonates said base; the aqueous dispersion (1) comprising responsive particles (2, 2468 3) has high ionic strength when said trigger is added to said aqueous dispersion (1) and has 2469 low ionic strength when said trigger is removed from said aqueous dispersion (1). In a further 2470 embodiment of the present invention, means for switching the responsive particles from non-2471 ionic state (2) to ionic state (3) comprises means for adding the trigger to the aqueous 2472 dispersion (1) and means for switching the responsive particles from ionic state (3) to non-2473 ionic state (2) comprises means for removing said trigger from said aqueous dispersion (1).
2474 In certain embodiments of the present invention, the surface functionality of the responsive 2475 particles (2, 3) comprises a nitrogen base. In a preferred embodiment of the present 2476 invention, the responsive particles in non-ionic state (2) comprise a surface functionality 2477 which is an amidine, a guanidine, or a tertiary amine and said responsive particles in ionic 2478 state (3) comprise a surface functionality which is an annidinium, a guanidinium, or a tertiary 2479 aminium.
2480 In another embodiment of the present invention, the responsive particles (4, 5) comprise an 2481 insoluble particle and a surface functionality which is an acid;
wherein upon contact with a 2482 trigger protonates said acid; the aqueous dispersion (1) comprising responsive particles (4, 2483 5) has reduced electrolytic conductivity and ionic strength when said trigger is added to said 2484 aqueous dispersion (1) and high ionic strength when said trigger is removed from said 2485 aqueous dispersion (1). In a further embodiment of the present invention, means for 2486 switching the responsive particles from non-ionic state (5) to ionic state (4) comprises means 2487 for adding the trigger to the aqueous dispersion (1) and means for switching the responsive 2488 particles from ionic state (4) to non-ionic state (5) comprises means for removing said trigger 2489 from said aqueous dispersion (1). In certain embodiments of the present invention, the 2490 surface functionality of the responsive particles (4, 5) comprises an oxygen acid. In a 2491 preferred embodiment of the present invention, the responsive particles in non-ionic state 2492 (5) comprise a surface functionality which is a 2-nitrophenol and the responsive particles in 2493 ionic state (4) comprise a surface functionality which is 2-nitrophenoxide. In another 2494 embodiment of the present invention, the trigger comprises CO2, NO2, COS, or CS2. In a 2495 further embodiment of the present invention, means for adding the trigger to the aqueous 2496 dispersion (1) comprises: bubbling said trigger into said aqueous dispersion, adding a trigger 2497 solution saturated with said trigger, mixing said aqueous dispersion under an atmosphere 2498 containing said trigger, or combinations thereof. In a yet further embodiment of the present 2499 invention, means for removing the trigger from the aqueous dispersion (1) comprises heating 2500 said aqueous dispersion, sparing said aqueous dispersion with a flushing gas, exposing said 2501 aqueous dispersion to vacuum or partial vacuum, agitating said aqueous dispersion, 2502 sonicating said aqueous dispersion, or combinations thereof. In a further embodiment of the 2503 present invention, the flushing gas comprises: air, N2, or other gas with low concentration of 2504 002, NO2, COS, and CS2.
2505 8.1 System for Modulate the Electrochemical Gradient 2506 The present invention further relates to a system for modulating the electrochemical gradient 2507 across a membrane comprising an aqueous dispersion of responsive particles with 2508 switchable surface charge. FIG. 8 shows a diagram of a system for modulating the 2509 electrochemical gradient across a membrane (6) comprising an aqueous dispersion (7, 9) 2510 comprising responsive particles with switchable surface charge and a feed solution (8), said 2511 aqueous dispersion (7, 9) is located on one side of said membrane (6) while said feed 2512 solution (8) is located on the opposing side of said membrane (6); as well as means for 2513 switching the surface charge (10) of said responsive particles from non-ionic state to ionic 2514 state and means for switching the surface charge (11) of said responsive particles from ionic 2515 state to non-ionic state. In one embodiment of the present invention, the system for 2516 modulating the electrochemical gradient across a membrane (6) comprises: an aqueous 2517 dispersion (7, 9) comprising responsive particles with switchable surface charge; means for 2518 contacting a feed solution (8) with said membrane (6); means for switching (10) the surface 2519 charge of said responsive particles from non-ionic state to ionic state; and means for 2520 switching (1 1 ) the surface charge of said responsive particles from ionic state to non-ionic 2521 state; wherein said aqueous dispersion (7, 9) is located on one side of said membrane (6) 2522 and said feed solution (8) is on the opposing side of said membrane (6). The imbalance 2523 created across the membrane (6) when the feed solution (8) is placed in contact with one 2524 side of membrane and the aqueous dispersion (7, 9) comprising responsive particles with 2525 switchable surface charge is on the opposing side of said membrane (6) causes both an 2526 electrical gradient to exist due to a difference in charged species between the aqueous 2527 dispersion (7, 9) and the feed solution (8), as well as a concentration gradient to exist due to 2528 a difference in dissolved species between the aqueous dispersion (7, 9) and the feed solution 2529 (8). In a further embodiment of the present invention, the pore size of the membrane (6) is 2530 smaller than the responsive particles with switchable surface charge of the aqueous 2531 dispersion (7, 9) and restricts said responsive particles of the aqueous dispersion (7, 9) to 2532 one side of the membrane (6). Due to the size of the pores of the membrane (6), responsive 2533 particles with switchable surface charge cannot pass through said membrane (6) and are 2534 restricted to one side of said membrane (6).
2535 Any material present in the feed solution (8) larger than the pore size of the membrane (6) 2536 is also impeded and restricted to one side by said membrane (6). When the feed solution (8) 2537 and the aqueous dispersion (7, 9), comprising responsive particles with switchable surface 2538 charge, are placed on opposite sides of the membrane (6), charged ions present in said feed 2539 solution (8) or said aqueous dispersion (7, 9) begin to diffuse across said membrane (6); in 2540 addition, other charged and dissolved species will also diffuse across said membrane (6) 2541 until an electrochemical equilibrium is reached; that is, when the electrical gradient between 2542 said feed solution (8) and said aqueous dispersion (7, 9) is balanced by its concentration 2543 gradient. The direction and rate of diffusion is dependent on the physiochemical properties 2544 of both the feed solution (8) and the aqueous dispersion (7, 9). The aqueous dispersion (7) 2545 comprising responsive particles in ionic state has a greater concentration of charged species 2546 compared to the aqueous dispersion (9) comprising responsive particles in non-ionic state;
2547 the aqueous dispersion (9) comprising responsive particles in non-ionic state has a lower 2548 concentration of charged species compared to the aqueous dispersion (7) comprising 2549 responsive particles in non-ionic state. The electrochemical gradient between the feed 2550 solution (8) and the aqueous dispersion (7, 9) is modulated through means for switching (10) 2551 the surface charge of said responsive particles from non-ionic state to ionic state and means 2552 for switching (11) the surface charge of said responsive particles from ionic state to non-ionic 2553 state. Ionic species with electrostatic charge will migrate towards a region with opposite 2554 electrostatic charge in order to achieve electrostatic neutrality.
Anionic species from the feed 2555 solution (8) are attracted to an aqueous dispersion (7, 9) comprising responsive particles 2556 with switchable surface charge wherein the surface functionality is a base which results in 2557 positive surface charge; and means for switching (10) the responsive particles from non-2558 ionic state to ionic state comprises addition of the trigger; and means for switching (11) the 2559 responsive particles from ionic state to non-ionic state comprises removal of said trigger.
2560 Conversely, cationic species from the feed solution (8) are attracted to an aqueous 2561 dispersion (7, 9) comprising responsive particles with switchable surface charge wherein 2562 surface functionality is an acid which results in negative surface charge; and means for 2563 switching (11) the responsive particles from ionic state to non-ionic state comprises addition 2564 of the trigger; and means for switching (10) the responsive particles from non-ionic state to 2565 ionic state comprises removal of said trigger. The net flow of ionic species across the 2566 membrane (6) is controlled by modulating the electrochemical gradient across said 2567 membrane (6) by switching the surface charge of responsive particles used to prepare the 2568 aqueous dispersion (7, 9) between non-ionic state and ionic state.

2569 A related system for modulating the electrochemical gradient across a membrane is provided 2570 by the present invention when both the feed solution and the aqueous ,dispersion of 2571 responsive particles are on the same side of the membrane. FIG. 13 shows a diagram of a 2572 system for modulating the electrochemical gradient across a membrane (31) comprising a 2573 feed solution (32), a receiving solution (34), and an aqueous dispersion (33, 35) comprising 2574 responsive particles with switchable surface charge; said aqueous dispersion (33, 35) and 2575 said feed solution (32) are located on the side of said membrane (31) while said receiving 2576 solution is located on the opposing side of said membrane; as well as means for switching 2577 the surface charge (36) of said responsive particles from non-ionic state to ionic state and 2578 means for switching the surface charge (37) of said responsive particles from ionic state to 2579 non-ionic state. In another embodiment of the present invention, the system for modulating 2580 the electrochemical gradient across a membrane (31) comprises: an aqueous dispersion 2581 (33, 35) comprising responsive particles with switchable surface charge; a receiving solution 2582 (34); means for contacting a feed solution (32) with said membrane (31); means for switching 2583 (36) the surface charge of said responsive particles from non-ionic state to ionic state; and 2584 means for switching (37) the surface charge of said responsive particles from ionic state to 2585 non-ionic state; wherein said feed solution (32) and said aqueous dispersion (33, 35) are 2586 located on one side of said membrane (31) and said receiving solution (34) is on the 2587 opposing side of said membrane (31). In a further embodiment of the present invention, the 2588 pore size of the membrane (31) is smaller than the responsive particles of the aqueous 2589 dispersion (33, 35) and restricts said responsive particles as well any material present in the 2590 feed solution (32) or the receiving solution (34) larger than the pore size of said membrane 2591 (31) to one side of said membrane (31). When the combined feed solution (32) and aqueous 2592 dispersion (33, 35), comprising responsive particles with switchable surface charge, are 2593 placed on the same side of the membrane (31) and the receiving solution (34) is placed on 2594 the opposing side of said membrane (31), charged ions present in said feed solution (32) or 2595 said receiving solution (34) begin to diffuse across the membrane (31); in addition, other 2596 species will also diffuse across said membrane (31) until an electrochemical equilibrium is 2597 reached, when the electrical gradient across said membrane (31) is balanced by the 2598 concentration gradient across said membrane (31). The direction and rate of diffusion is 2599 dependent on the physiochemical properties of both the combined feed solution (32) and 2600 aqueous dispersion (33, 35) and the receiving solution (34). The aqueous dispersion (33) 2601 comprising responsive particles in ionic state has a greater concentration of charged species 2602 compared to the aqueous dispersion (35) comprising responsive particles in non-ionic state;
2603 the aqueous dispersion (35) comprising responsive particles in non-ionic state has a lower 2604 concentration of charged species compared to the aqueous dispersion (33) comprising 2605 responsive particles in non-ionic state. The electrochemical gradient between the combined 2606 feed solution (32) and aqueous dispersion (33, 35) and the receiving solution (34) is 2607 modulated through means for switching (36) the surface charge of said responsive particles 2608 from non-ionic state to ionic state and means for switching (37) the surface charge of said 2609 responsive particles from ionic state to non-ionic state. Ionic species with electrostatic charge 2610 will migrate towards a region with opposite electrostatic charge in order to achieve 2611 electrostatic neutrality. Cationic species from the feed solution (32) are repelled from an 2612 aqueous dispersion (33, 35) comprising responsive particles with switchable surface charge 2613 wherein the surface functionality is a base which results in positive surface charge; and 2614 means for switching (36) the responsive particles from non-ionic state to ionic state 2615 comprises addition of the trigger; and means for switching (37) the responsive particles from 2616 ionic state to non-ionic state comprises removal of said trigger.
Conversely, anionic species 2617 from the feed solution (32) are attracted to an aqueous dispersion (33, 35) comprising 2618 responsive particles with switchable surface charge wherein surface functionality is an acid 2619 which results in negative surface charge; and means for switching (37) the responsive 2620 particles from ionic state to non-ionic state comprises addition of the trigger; and means for 2621 switching (36) the responsive particles from non-ionic state to ionic state comprises removal 2622 of said trigger.
2623 Another similar system for modulating the electrochemical gradient across a membrane is 2624 provided by the present invention, wherein a first aqueous dispersion comprising responsive 2625 particles with switchable surface charge is present on one side of said membrane and a 2626 second aqueous dispersion comprising responsive particles with switchable surface charge 2627 is provided on the opposing side of said membrane.
2628 In another embodiment of the present invention, the responsive particles comprise an 2629 insoluble particle and a surface functionality which is a base and wherein means for switching 2630 (10, 36) the responsive particles from non-ionic state to ionic state comprises means for 2631 adding a trigger and means for switching (11, 37) the responsive particles from ionic state to 2632 non-ionic state comprises means for removing said trigger. In certain embodiments of the 2633 present invention, the surface functionality comprises a nitrogen base wherein contact with 2634 the trigger in the presence of water protonates said nitrogen base. In preferred embodiments 2635 of the present invention, the surface functionality, in non-ionic state, comprises: an amidine, 2636 a guanidine, or a tertiary amine; and, in ionic state, comprises: an amidinium, a guanidium, 2637 or a tertiary aminium. In another embodiment of the present invention, the responsive 2638 particles comprise an insoluble particle and a surface functionality which is an acid and 2639 wherein means for switching (11, 37) the responsive particles from ionic state to non-ionic 2640 state comprises addition of a trigger; and means for switching (10, 36) the responsive 2641 particles from non-ionic state to ionic state comprises removal of said trigger. In specific 2642 embodiments of the present invention, the surface functionality comprises an oxygen acid 2643 wherein contact with the trigger in the presence of water protonates said oxygen acid. In 2644 preferred embodiments of the present invention, the surface functionality, in ionic state, 2645 comprises 2-nitrophenoxide; and, in non-ionic state, comprises 2-nitrophenol. In certain 2646 embodiments of the present invention, the trigger comprises CO2, NO2, COS, or CS2. In a 2647 preferred embodiment of the present invention, the trigger is CO2. In yet another embodiment 2648 of the present invention, means for adding the trigger to the aqueous dispersion (7, 8, 33, 2649 35) comprises: bubbling said trigger into said aqueous dispersion (7,

8, 33, 35), adding a 2650 trigger solution saturated with said trigger, mixing said aqueous dispersion (7, 8, 33, 35) 2651 under said trigger, or combinations thereof. In a yet further embodiment of the present 2652 invention, means for removing the trigger from the aqueous dispersion (7, 8, 33, 35) 2653 comprises: heating said aqueous dispersion (7, 8, 33, 35), sparing said aqueous dispersion 2654 (7, 8, 33, 35) with a flushing gas, exposing said aqueous dispersion (7, 8, 33, 35) to vacuum 2655 or partial vacuum, agitating said aqueous dispersion (7, 8, 33, 35), sonicating said aqueous 2656 dispersion (7, 8, 33, 35), or combinations thereof. In a further embodiment of the present 2657 invention, the flushing gas comprises: air, N2, or other gas with low concentration of CO2, 2658 NO2, COS, and CS2.
2659 In another embodiment of the present invention, the system for modulating the 2660 electrochemical gradient across a membrane further comprises means for separating the 2661 responsive particles with switchable surface charge from the aqueous dispersion. In certain 2662 embodiments of the present invention, means for separating the responsive particles from 2663 the aqueous dispersion comprises: sedimentation, centrifugation, flotation, gravity filtration, 2664 pressure filtration, vacuum filtration, or combinations thereof. In a further embodiment of the 2665 present invention, the responsive particles with switchable surface charge are magnetically 2666 susceptible and means for separating said responsive particles comprises:
a permanent 2667 magnet, an electromagnet, or a high-gradient magnetic separator. In yet a further 2668 embodiment of the present invention, the responsive particles with switchable surface charge 2669 are in ionic state and means for separating said responsive particles comprises an electric 2670 field.
2671 When a feed solution with high concentration of dissolved ions is placed on one side of a 2672 membrane and an aqueous dispersion of responsive particles, comprising switchable 2673 surface charge with cationic (basic) surface functionality in ionic state, is placed on the 2674 opposing side of said membrane, an electrochemical gradient is generated; causing anionic 2675 species to migrate along the electrical potential gradient, from said feed solution across said 2676 membrane into said aqueous dispersion of responsive particles, and cationic species to 2677 migrate in the reverse direction; in addition, other dissolved solutes diffuse across the 2678 membrane, driven by the concentration gradient generated by diffusing ionic species along 2679 said electrical potential gradient. Conversely, when an aqueous dispersion of responsive 2680 particles, comprising switchable surface charge with anionic (acidic) surface functionality in 2681 ionic state is placed on the opposing side of the membrane from the feed solution an 2682 electrochemical gradient is generated; causing cationic species to migrate along the 2683 electrical potential gradient, from said feed solution across said membrane into said aqueous 2684 dispersion of responsive particles, and anionic species to migrate in the reverse direction;
2685 again, other dissolved solutes diffuse across the membrane, driven by the concentration 2686 gradient generated by diffusion of ionic species along electrical potential gradient.
2687 Alternatively, when a feed solution with high concentration of dissolved ions is combined with 2688 an aqueous dispersion of responsive particles, comprising switchable surface charge with 2689 cationic surface functionality in ionic state, and placed on one side of a membrane and a 2690 receiving solution is placed on the opposing side of said membrane, an electrochemical 2691 gradient is generated; causing cationic species to migrate away from said feed solution and 2692 said aqueous dispersion of responsive particles across said membrane into to the receiving 2693 solution and anionic species to migrate in the reverse direction;
again, other dissolved 2694 solutes diffuse across the membrane, driven by the concentration gradient generated by 2695 diffusion of ionic species along electrical potential gradient. The system effectively directs 2696 the movement of charged ions across a membrane by modulating the electrochemical 2697 gradient across said membrane using responsive particles with switchable surface charge.
2698 In one embodiment of the present invention, the system for modulating the electrochemical 2699 gradient across a membrane is for reducing or increasing the ionic strength of an aqueous 2700 solution wherein the feed solution comprises water, dissolved species, and dispersed solids.
2701 In another embodiment of the present invention, the system for modulating the 2702 electrochemical gradient across a membrane is for reducing or increasing the concentration 2703 of multivalent ions in an aqueous solution wherein the feed solution comprises water, 2704 dissolved species, and dispersed solids. The system of the present invention, by modulating 2705 the electrochemical gradient across the membrane, can exchange multivalent ions, such as 2706 calcium and sulfate, on one side of said membrane with monovalent ions, such as sodium 2707 and chloride, from the opposing side of said membrane. The system, by modulating the 2708 electrochemical potential across the membrane, can drive ions across the membrane along 2709 the modulated electrochemical gradient and deliver specific charged ions to a receiving 2710 solution. The system, by modulating the electrochemical potential across the membrane, can 2711 drive ions across the membrane along the modulated electrochemical gradient and remove 2712 specific charged ions from a feed solution. In a specific embodiment of the present invention, 2713 the system for modulating the electrochemical gradient is useful for treating bituminous sand 2714 extraction tailings. Bituminous sand extraction tailings contain dispersed mineral solids such 2715 as clay. Treated tailings contain high concentration of divalent and multivalent cations which 2716 causes dispersed clay particles to aggregate together and settle rapidly. In another specific 2717 embodiment of the present invention, the system for modulating the electrochemical gradient 2718 is useful for treating industrial process water. Treated industrial process water contains lower 2719 concentration of specific ions such as divalent and multivalent cations which causes reduced 2720 bitumen extraction efficiency for bituminous sands.
2721 8.2 System for Modulate the Osmotic Gradient 2722 The present invention further relates to a system for modulating the osmotic gradient across 2723 a membrane comprising an aqueous dispersion of responsive particles with switchable 2724 surface charge. FIG. 9 shows a diagram of a system for modulating the osmotic gradient 2725 across a membrane (12) comprising an aqueous dispersion (13, 17), comprising responsive 2726 particles with switchable surface charge, on one side of said membrane (12); a feed solution 2727 (14) on the opposing side of said membrane (12); means for switching (18) the surface 2728 charge of said responsive particles from its non-ionic state to its ionic state; and means for 2729 switching (16) the surface charge of said responsive particles from its ionic state to its non-2730 ionic state. In one embodiment of the present invention, the system for modulating the 2731 osmotic gradient across a membrane (12) comprises: an aqueous dispersion (13, 17) 2732 comprising responsive particles with switchable surface charge; means for contacting the 2733 feed solution with said membrane (12), means for switching (18) the surface charge of said 2734 responsive particles with switchable surface charge from its non-ionic state to its ionic state;
2735 and means for switching (16) the surface charge of said responsive particles with switchable 2736 surface charge from its ionic state to its non-ionic state; wherein means for switching (18) 2737 the surface charge of said responsive particles with switchable surface charge from non-2738 ionic to ionic sate raises the ionic strength of the aqueous dispersion (17); and wherein said 2739 aqueous dispersion (13, 17) is located on one side of said membrane (12) and said feed 2740 solution (14) is on the opposing side of said membrane (12). Means for switching (18) the 2741 surface charge of responsive particles with switchable surface charge from non-ionic to ionic 2742 sate increases the number of ionic species in solution and increases the ionic strength of the 2743 aqueous dispersion (17), comprising responsive particles with switchable surface charge in 2744 its ionic sate. The imbalance created across the membrane (12) when the feed solution (14) 2745 is placed in contact with one side of membrane and the aqueous dispersion (13, 17) 2746 comprising responsive particles with switchable surface charge is on the opposing side of 2747 said membrane (12) causes an osmotic gradient to exist across the membrane (12). In a 2748 further embodiment of the present invention, the membrane (12) is selectively permeable for 2749 water. The pore size of the membrane (12) is smaller than both the responsive particles of 2750 the aqueous dispersion (13, 17) and dissolved ions in the feed solution (14) but allows 2751 solvent molecules such as water to permeate across said membrane (12).
2752 When the feed solution (14) and the aqueous dispersion (13, 17), comprising responsive 2753 particles with switchable surface charge, are placed on opposite sides of said membrane 2754 (12), water molecules in said feed solution (14) or said aqueous dispersion (13, 17) begin to 2755 diffuse across the membrane (12); until osmotic pressure is equal on both sides of said 2756 membrane (12). The osmotic pressure of the aqueous dispersion (13, 17) must exceed that 2757 of the feed solution (14) in order to generate a sufficient osmotic gradient to drive water flux 2758 from said feed solution (14) across the membrane (12) into the aqueous dispersion (13, 17).
2759 Otherwise, when the ionic pressure of the feed solution (14) exceeds that of the aqueous 2760 dispersion (13, 17), the osmotic gradient is reversed and drives water flux from said aqueous 2761 dispersion (13, 17) to said feed solution (14). The osmotic pressure increases when the 2762 molar concentration of solutes is increased. The ionic strength is a measure of the number 2763 of ions and therefore contributes to osmotic pressure. Ionic compounds are especially good 2764 at raising osmotic pressure as they dissociate into ions in water. The ionic strength of the 2765 aqueous dispersion (13), comprising responsive particles with switchable surface charge in 2766 non-ionic state, can be increased though means for switching (18) the surface charge of said 2767 responsive particles from non-ionic state to ionic state; the increase in surface charge raises 2768 the ionic strength of the aqueous dispersion (17) comprising an aqueous dispersion of 2769 responsive particles with switchable surface charge in ionic state.
The ionic strength of the 2770 aqueous dispersion (17), comprising responsive particles with switchable surface charge in 2771 ionic state, can be decreased though means for switching (16) the surface charge of said 2772 responsive particles from ionic state to non-ionic state; the decrease in surface charge lowers 2773 the ionic strength of the aqueous dispersion (13) comprising an aqueous dispersion of 2774 responsive particles with switchable surface charge in non-ionic state. By means of switching 2775 (16, 18) the surface charge of the responsive particles with switchable surface charge, the 2776 osmotic gradient between the aqueous dispersion (13, 17) and the feed solution (14) is 2777 modulated. Upon increasing the ionic strength of the aqueous dispersion (17), water from 2778 the feed solution (14) with lower ionic strength permeates across the membrane (12) to said 2779 aqueous dispersion (17) with greater ionic strength comprising responsive particles with 2780 switchable surface charge in ionic state. The difference in ionic strength, between the 2781 aqueous dispersion (13) comprising responsive particles in non-ionic state and the aqueous 2782 dispersion (17) comprising responsive particles in ionic state, required to generate water flux 2783 across the membrane (12) is determined by properties of the feed solution (14) and the 2784 performance of said membrane (12).

2785 A related system for modulating the osmotic gradient across a membrane is provided by the 2786 present invention when both the feed solution and the aqueous dispersion of responsive 2787 particles are on the same side of the membrane. FIG. 14 shows a diagram of a system for 2788 modulating the osmotic gradient across a membrane (38) comprising an aqueous dispersion 2789 (40, 42) comprising responsive particles with switchable surface charge; an exchange 2790 solution (41); a feed solution (39), said aqueous dispersion (40, 42) and feed solution (40) 2791 are located on one side of said membrane (38) while said exchange solution (41) is located 2792 on the opposing side of said membrane (38); means for switching (44) the surface charge 2793 of said responsive particles from its non-ionic state to its ionic state; and means for switching 2794 (45) the surface charge of said responsive particles from its ionic state to its non-ionic state.
2795 In one embodiment of the present invention, the system for modulating the osmotic gradient 2796 across a membrane (38) comprises: an aqueous dispersion (40, 42) comprising responsive 2797 particles with switchable surface charge; means for contacting the feed solution with said 2798 membrane (38), means for switching (44) the surface charge of said responsive particles 2799 with switchable surface charge from its non-ionic state to its ionic state; and means for 2800 switching (45) the surface charge of said responsive particles with switchable surface charge 2801 from its ionic state to its non-ionic state; wherein means for switching (44) the surface charge 2802 of said responsive particles with switchable surface charge from non-ionic to ionic sate raises 2803 the ionic strength of said aqueous dispersion (42).
2804 Means for switching (44) the surface charge of responsive particles with switchable surface 2805 charge from non-ionic to ionic sate increases the number of ionic species in solution and 2806 increases the ionic strength of the aqueous dispersion (42) comprising responsive particles 2807 with switchable surface charge in its ionic sate. The imbalance created across the membrane 2808 (38) when the exchange solution (41) is placed in contact with one side of membrane and 2809 the aqueous dispersion (40, 42), comprising responsive particles with switchable surface 2810 charge, and said feed solution are on the opposing side of said membrane (38) causes an 2811 osmotic gradient to exist across the membrane (38). In a further embodiment of the present 2812 invention, the membrane (38) is selectively permeable for water. The pore size of the 2813 membrane (38) is smaller than both the responsive particles of the aqueous dispersion (40, 2814 42) and dissolved ions in the feed solution (40) and in the exchange solution (41) but allows 2815 solvent molecules such as water to permeate across said membrane (38).
The osmotic 2816 pressure of the aqueous dispersion (40, 42) and the feed solution (39) must exceed that of 2817 the exchange solution (41) in order to generate a sufficient osmotic gradient to drive water 2818 flux from said exchange solution (41) across the membrane (38) into the feed solution (39) 2819 and aqueous dispersion (40, 42). Otherwise, when the ionic pressure of the exchange 2820 solution (41) exceeds that of feed solution (39) and the aqueous dispersion (40, 42), the 2821 osmotic gradient is reversed and drives water flux from said feed solution (39) and said 2822 aqueous dispersion (40, 42). The osmotic pressure increases when the molar concentration 2823 of solutes is increased. The ionic strength is a measure of the number of ions and therefore 2824 contributes to osmotic pressure. The ionic strength of the aqueous dispersion (40), 2825 comprising responsive particles with switchable surface charge in non-ionic state, can be 2826 increased though means for switching (44) the surface charge of said responsive particles 2827 from non-ionic state to ionic state; the increase in surface charge raises the ionic strength of 2828 the aqueous dispersion (42) comprising an aqueous dispersion of responsive particles with 2829 switchable surface charge in ionic state. The ionic strength of the aqueous dispersion (42), 2830 comprising responsive particles with switchable surface charge in ionic state, can be 2831 decreased though means for switching (45) the surface charge of said responsive particles 2832 from ionic state to non-ionic state; the decrease in surface charge lowers the ionic strength 2833 of the aqueous dispersion (40) comprising an aqueous dispersion of responsive particles 2834 with switchable surface charge in non-ionic state. By means of switching (44, 45) the surface 2835 charge of the responsive particles with switchable surface charge, the osmotic gradient 2836 between the exchange solution (41) and both the feed solution (14) and the aqueous 2837 dispersion (40, 42) is modulated. Upon increasing the ionic strength of the aqueous 2838 dispersion (42), water from the exchange solution (41) with lower ionic strength permeates 2839 across the membrane (38) to said aqueous dispersion (42) with greater ionic strength 2840 comprising responsive particles with switchable surface charge in ionic state. The difference 2841 in ionic strength, between the aqueous dispersion (40) comprising responsive particles in 2842 non-ionic state and the aqueous dispersion (42) comprising responsive particles in ionic 2843 state, required to generate water flux across the membrane (38) is determined by properties 2844 of the feed solution (39), the exchange solution (41), and the performance of said membrane 2845 (38).

2846 In another embodiment of the present invention, the responsive particles comprise an 2847 insoluble particle and a surface functionality which is a base and wherein means for switching 2848 (18, 44) the responsive particles from non-ionic state to ionic state comprises means for 2849 adding a trigger and means for switching (16, 45) the responsive particles from ionic state to 2850 non-ionic state comprises means for removing said trigger. In certain embodiments of the 2851 present invention, the surface functionality comprises a nitrogen base wherein contact with 2852 the trigger in the presence of water protonates said nitrogen base. In preferred embodiments 2853 of the present invention, the surface functionality, in non-ionic state, comprises: an amidine, 2854 a guanidine, or a tertiary amine; and, in ionic state, comprises: an amidinium, a guanidium, 2855 or a tertiary aminium. In another embodiment of the present invention, the responsive 2856 particles comprise an insoluble particle and a surface functionality which is an acid and 2857 wherein means for switching (16, 45) the responsive particles from ionic state to non-ionic 2858 state comprises means for adding a trigger; and means for switching (18, 44) the responsive 2859 particles from non-ionic state to ionic state comprises means for removing said trigger. In 2860 another embodiment of the present invention, the responsive particles comprise an insoluble 2861 particle and a surface functionality which is an acid and wherein means for switching (16, 2862 45) the responsive particles from ionic state to non-ionic state comprises addition of a trigger;
2863 and means for switching (18, 44) the responsive particles from non-ionic state to ionic state 2864 comprises removal of said trigger. In certain embodiments of the present invention, the 2865 surface functionality comprises an oxygen acid wherein contact with the trigger in the 2866 presence of water protonates said oxygen acid. In preferred embodiments of the present 2867 invention, the surface functionality, in ionic state, comprises 2-nitrophenoxide; and, in non-2868 ionic state, comprises 2-nitrophenol. In certain embodiment of the present invention, the 2869 trigger comprises 002, NO2, COS, or CS2. In a preferred embodiment of the present 2870 invention, the trigger is 002. In a further embodiment of the present invention, means for 2871 adding the trigger to the aqueous dispersion (13, 17, 40, 42) comprises: bubbling said trigger 2872 into said aqueous dispersion (13, 17, 40, 42), adding a trigger solution saturated with said 2873 trigger, mixing said aqueous dispersion (13, 17, 40, 42) under said trigger, or combinations 2874 thereof. In a yet further embodiment of the present invention, means for removing the trigger 2875 from the aqueous dispersion (13, 17, 40, 42) comprises: heating said aqueous dispersion 2876 (13, 17, 40, 42), sparing said aqueous dispersion (13, 17, 40, 42) with a flushing gas, 2877 exposing said aqueous dispersion (13, 17, 40, 42) to vacuum or partial vacuum, agitating 2878 said aqueous dispersion (13, 17, 40, 42), sonicating said aqueous dispersion (13, 17, 40, 2879 42), or combinations thereof. In a further embodiment of the present invention, the flushing 2880 gas comprises: air, N2, or other gas with low concentration of 002, NO2, COS, and CS2.
2881 In another embodiment of the present invention, the system for modulating the osmotic 2882 gradient across a membrane further comprises means for separating the responsive 2883 particles with switchable surface charge from the aqueous dispersion. In certain 2884 embodiments of the present invention, means for separating the responsive particles from 2885 the aqueous dispersion comprises: sedimentation, centrifugation, flotation, gravity filtration, 2886 pressure filtration, vacuum filtration, or combinations thereof. In a further embodiment of the 2887 present invention, the responsive particles with switchable surface charge are magnetically 2888 susceptible and means for separating said responsive particles comprises: a permanent 2889 magnet, an electromagnet, or a high-gradient magnetic separator. In yet a further 2890 embodiment of the present invention, the responsive particles with switchable surface charge 2891 are in ionic state and means for separating said responsive particles comprises an electric 2892 field.
2893 The system for modulating the osmotic gradient across a membrane is useful in producing 2894 permeate water which is relatively pure depending on the performance of the membrane 2895 selectively permeable for water. High performance membranes are extremely effective with 2896 greater than 99% rejection. Less effective membranes achieve lower rejection level. The 2897 feed solution (14, 39) may be brackish water, saline water, or brine water. The feed solution 2898 (14, 39) may also be seawater, industrial wastewater, or runoff. In one embodiment of the 2899 present invention, the feed solution is brackish water, saline water, or brine water. In a further 2900 embodiment of the present invention, the feed solution is seawater, industrial wastewater, or 2901 runoff. Permeate water from feed solution such as brackish water, saline water, brine water, 2902 seawater, industrial wastewater, and runoff has less impurities because impurities are less 2903 likely to pass through the membrane. The effectiveness of a system for modulating the 2904 osmotic gradient across a membrane in treating water is dependent on the ionic strength of 2905 aqueous dispersion comprising responsive particle witch switchable surface charge. The 2906 ionic strength of the aqueous dispersion may be supplemented using contemporary 2907 electrolytes. In one embodiment of the present invention, the system for modulating the 2908 osmotic gradient is used to treat water.

2909 The system of the present invention, by modulating the osmotic gradient across the 2910 membrane, can exchange solvent molecules, such as water, from opposing sides of said 2911 membrane. The system, by modulating the osmotic gradient across a membrane, can drive 2912 water across said membrane along the modulated osmotic gradient.
2913 Permeated water may be separated from an aqueous dispersion of responsive particles with 2914 switchable surface charge through a variety of methods such as sedimentation, flotation, or 2915 combinations thereof. Additionally, magnetically susceptible responsive particles with 2916 switchable surface charge may be separated under an applied magnetic field generated by 2917 a permanent magnet or an electromagnet. The responsive surface charge of responsive 2918 particles with switchable surface charge facilitates the separation of said responsive particles 2919 from dispersions thereof. In addition to the effect of surface charge which is determined by 2920 the surface functionality of said responsive particles, means for separating responsive 2921 particles witch switchable surface charge is also dependent on the properties of the particle 2922 such as wettability.
2923 The present invention also relates to means for separating the responsive particles with 2924 switchable surface charge from a dispersion thereof. The separation of particles with different 2925 specific gravity is possible using gravity. FIG. 10 shows a diagram of means for separating 2926 responsive particles with switchable surface charge from an aqueous dispersion (15) by 2927 sedimentation and means for separating responsive particles with switchable surface charge 2928 from said dispersion (15) by flotation. Means for separating the responsive particles from a 2929 dispersion (15) comprises: a sedimentation vessel (21) or a flotation cell (24); and means or 2930 switching the surface charge (19) of responsive particles with switchable surface from ionic 2931 state (3, 4) to non-ionic state (2, 5). The dispersion (20), after switching surface charge, 2932 comprises responsive particles with switchable surface charge in non-ionic state (2, 5) which 2933 have enhanced rate of sedimentation, due to increased aggregation as result of the modified 2934 wettability (i.e. more hydrophobic), compared to responsive particles with switchable surface 2935 in ionic state (3, 4). The process of sedimentation is driven by the force of gravity and 2936 produces a sediment (22) of responsive particles with switchable surface charge in non-ionic 2937 state (2, 4) and treated water (23); the treated water (23) has less impurities compared to 2938 the feed solution (8) and is substantially free of responsive particles. Means of separating 2939 responsive particles from the dispersion (15) by sedimentation also comprises means of 2940 removing the sediment (22) from treated water (23). Treated water (23) may be removed 2941 from the sedimentation vessel (21) using a pump with inlet located away from the sediment 2942 (22). The sediment (22) may be removed using a pump with inlet located close to the 2943 sediment. Other methods may be used to separate the sediment (22) from the treated water 2944 (23). Centrifugation is a similar process used to separate materials with different specific 2945 gravity under a centrifugal force; with greater force, the separation of responsive particles is 2946 faster. The aqueous dispersion (20), after switching surface charge, comprises responsive 2947 particles with switchable surface charge in non-ionic state (2, 5) which attach onto the 2948 surface of rising gas bubbles as result if the modified wettability (i.e. more hydrophobic). The 2949 process of flotation is driven by particle attachment onto rising gas bubbles and produces a 2950 froth (26), rich in responsive particles with switchable surface charge in non-ionic state (2, 2951 5). Means of separating responsive particles from the dispersion (15) by flotation also 2952 comprises means of removing the froth (25) rich in responsive particles from treated water 2953 (23). The froth (25) may be skimmed off the surface of treated water (23) using a suitable 2954 mechanism such as a rake. After removing the froth (25), treated water (23) remains in the 2955 flotation cell (24). It is important that the gas bubbles are produced using a gas that does not 2956 switch the surface charge of responsive particles with switchable surface charge in non-ionic 2957 state (2, 5) to responsive particles with switchable surface charge in ionic state (3, 4). In 2958 certain embodiments of the present invention, means for separating the responsive particles 2959 with switchable surface charge from a dispersion comprises:
sedimentation, centrifugation, 2960 or flotation.
2961 The separation of materials of different size is possible using size exclusion processes 2962 wherein materials which are above a certain size are removed. FIG. 11 shows a diagram of 2963 means for separating the responsive particles with switchable surface charge from an 2964 aqueous dispersion (20) with responsive particles with switchable surface charge in non-2965 ionic state (2, 5) by filtration. Responsive particles with switchable surface charge in non-2966 ionic state form larger aggregates which facilitates filtration. Means for separating the 2967 responsive particles by filtration comprises a filter (26), the aqueous dispersion (20) 2968 comprising responsive particles with switchable surface in non-ionic state (2, 5), and means 2969 to drive said aqueous dispersion (20) through said filter (26). The filtration process may be 2970 driven by gravity, vacuum, or hydraulic pressure. The filter (26) restricts the movement of 2971 particles but allows treated water (23) to pass. After filtration, the filtrate consists of treated 2972 water (23) substantially free of responsive particles which are retained by the filter (26).
2973 Means of separating responsive particles from aqueous dispersion by filtration also 2974 comprises means of removing retained particles (27). Filtration may operate in a dead-end 2975 configuration where the aqueous dispersion (20) is passed through the filter (26) or cross-2976 flow filtration where the aqueous dispersion (20) is passed across the surface of the filter 2977 (26). In certain embodiments of the present invention, means for separating the responsive 2978 particles with switchable surface charge from a dispersion comprises:
gravity filtration, 2979 pressure filtration, or vacuum filtration. In a preferred embodiment of the invention, the filter 2980 (27) is a screen.
2981 Alternatively, magnetically susceptible responsive particles with switchable surface charge 2982 may be separated under an applied magnetic field. FIG. 12 shows a diagram of means for 2983 separating responsive particles with switchable surface charge, comprising a magnetically 2984 susceptible material, under a magnet field (28). In a further embodiment of the invention, the 2985 magnet field (28) is generated by a permanent magnet, an electromagnet, or a high-gradient 2986 magnetic separator. Under an applied magnetic field, the magnetically susceptible 2987 responsive particles with switchable surface charge are collected. A
solution essentially free 2988 of particles (23) is left as the magnetically collected responsive particles (29) are separated.
2989 Ideally, a superparamagnetic material is only magnetically responsive under an applied 2990 magnetic field and such superparamagnetic particles may be re-dispersed after removing 2991 the magnetic field. However, magnetically collected responsive particles with switchable 2992 surface charge (29) are sometimes difficult to re-disperse due to residual magnetization.
2993 Dispersing responsive particles with switchable surface charge is assisted by means 2994 switching the surface charge (17) of magnetically collected responsive particles with 2995 switchable surface charge (29) from non-ionic state to ionic state.
The electrostatic charge 2996 of magnetically collected responsive particles (29) provided when surface functionality is in 2997 ionic state enhances electrostatic repulsion between dispersed particles which improves 2998 colloidal stability of responsive particles with switchable surface charge. Alternatively, 2999 responsive particles with switchable surface charge may be separated under an applied 3000 electric field.
3001 9.0 Method Embodiments 3002 The present invention further relates to a method for modulating an osmotic gradient or an 3003 electrochemical gradient across a membrane. In one embodiment of the invention, the 3004 method for modulating an osmotic gradient or an electrochemical gradient across a 3005 membrane comprises: a. providing an aqueous dispersion comprising responsive particles 3006 with switchable surface charge on one side of said membrane; b. providing a solution on the 3007 opposing side of said membrane; and c. switching the surface charge of said responsive 3008 particles from non-ionic state to ionic state or switching the surface charge of said responsive 3009 particles from ionic state to non-ionic state.
3010 An electrochemical gradient is present when there is a difference in the balance of ionic 3011 species across a membrane. The ionic strength of the aqueous dispersion comprising 3012 responsive particles with switchable surface charge on side of the membrane can be 3013 switched 3014 In one embodiment of the invention, the aqueous dispersion has a greater ionic strength than 3015 said solution and said aqueous dispersion has a lower ionic strength when said responsive 3016 particles are in non-ionic state. In another embodiment of the invention, the aqueous 3017 dispersion has a greater osmotic pressure than said solution when said responsive particles 3018 are in ionic state and said aqueous dispersion has a lower osmotic pressure when said 3019 responsive particles are in non-ionic state. In a further embodiment of the invention, the 3020 membrane pore size is smaller than said responsive particles. In a yet further embodiment 3021 of the invention, the membrane is selectively permeable for water.
3022 In another embodiment of the present invention, the responsive particles comprise an 3023 insoluble particle and a surface functionality which is a base and wherein: switching the 3024 responsive particles from non-ionic state to ionic state comprises addition of a trigger; and 3025 switching the responsive particles from ionic state to non-ionic state comprises removal of 3026 said trigger. In certain embodiments of the present invention, the surface functionality 3027 comprises a nitrogen base wherein contact with the trigger in the presence of water 3028 protonates said nitrogen base. In preferred embodiments of the present invention, the 3029 surface functionality comprises, in ionic state, an amidinium, a guanidinium, or a tertiary 3030 aminium; and in its non-ionic state, an amidine, a guanidine, or a tertiary amine. In another 3031 embodiment of the present invention, the responsive particles comprise an insoluble particle 3032 and a surface functionality which is an acid and wherein: switching the responsive particles 3033 from ionic state to non-ionic state comprises addition of a trigger;
and switching the 3034 responsive particles from non-ionic state to ionic state comprises removal of said trigger. In 3035 certain embodiments of the present invention, the surface functionality comprises an oxygen 3036 acid wherein contact with the trigger in the presence of water protonates said oxygen acid.
3037 In preferred embodiments of the present invention, the surface functionality, in ionic state, 3038 comprises 2-nitrophenoxide; and, in non-ionic state, comprises 2-nitrophenol. In certain 3039 embodiment of the present invention, the trigger comprises 002, NO2, COS, or CS2. In a 3040 preferred embodiment of the present invention, the trigger is 002. In a further embodiment 3041 of the present invention, means for adding the trigger to the aqueous dispersion comprises:
3042 bubbling said trigger into said aqueous dispersion, adding a trigger solution saturated with 3043 said trigger, mixing said aqueous under said trigger, or combinations thereof. In a yet further 3044 embodiment of the present invention, means for removing the trigger from the aqueous 3045 dispersion comprises: heating said aqueous dispersion, sparing said aqueous dispersion 3046 with a flushing gas, exposing said aqueous dispersion to vacuum or partial vacuum, agitating 3047 said aqueous dispersion, sonicating said aqueous dispersion, or combinations thereof. In a 3048 further embodiment of the present invention, the flushing gas comprises: air, N2, or other gas 3049 with low concentration of 002, NO2, nns, and 0S2.
3050 In another embodiment of the present invention, the method further comprises separating 3051 the responsive particles from the aqueous dispersion. In certain embodiments of the present 3052 invention, separating the responsive particles comprises:
sedimentation, centrifugation, 3053 flotation, gravity filtration, vacuum filtration, or combinations thereof. In a further embodiment 3054 of the present invention, the responsive particles with switchable surface charge are 3055 magnetically susceptible and separating said responsive particles comprises: a permanent 3056 magnet, an electromagnet, or a high-gradient magnetic separator. In yet a further 3057 embodiment of the present invention, the responsive particles with switchable surface charge 3058 are in ionic state and separating said responsive particles comprises an electric field.
3059 In one embodiment of the invention, the method is useful for concentrating an aqueous 3060 solution wherein the solution comprises water and dissolved species.
In another embodiment 3061 of the invention, the method is useful for concentrating an aqueous suspension wherein the 3062 solution comprises water and dispersed solids. In another embodiment of the invention, the 3063 method is useful for desalinating water.

3065 Deionized water (> 18 MO/cm) was used throughout and supplied from a Thermo Fischer 3066 Barnstead Nanopure ultrapure water purification system. Carbon dioxide (CAS 124-38-9; 4.0 3067 Grade; Praxair), nitrogen (CAS 7727-37-9; 4.8 Grade; Praxair), and argon (CAS 7440-37-1;
3068 4.8 Grade; Praxair) were used as received.
3069 Inhibitors (4-tert-butylcatechol and monomethyl ether hydroquinone) were removed from 3070 styrene (CAS 100-42-5; 99%; Sigma-Aldrich S4972), divinyibenzene (CAS
1321-74-0; 80%;
3071 Aldrich 414565), methyl methacrylate (CAS 80-62-6; 99%; Aldrich M55909), and 2-3072 (diethyl)aminoethyl methacrylate (CAS 105-16-8; 99%; Aldrich 408980) using a prepacked 3073 column (Aldrich 306320). Various silica particles may be conditioned before use by 3074 immersing particles in a 1% HCI acid solution for 4 h and subsequently immersing particles 3075 in deionized water at 60 C. Silica particles were recovered using a Hettich Rotanta 460R
3076 high-speed centrifuge and dried in an oven at 110 C for 12 h.
3077 Example Al: 3.1 g colloidal silica particles (CAS 7631-86-9; Aldrich 718483) were well-3078 dispersed in 150 ml toluene (CAS 108-88-3; ACS grade; Fischer Chemical) and charged into 3079 a round-bottom flask equipped with magnetic stirrer under nitrogen.
3.0 ml of (3-3080 aminopropyl)triethoxysilane (CAS 919-30-2; 99%; Aldrich 440140) and 10 ml of ethanol 3081. (CAS 64-17-5; 99%; Commercial Alcohols) were added to the reaction mixture. After stirring 3082 the reaction mixture at ambient temperature for 24 h, functionalized particles were recovered 3083 using a centrifuge and washed with excess ethanol. Solids were recovered using centrifuge 3084 and transferred to an oven at to 120 C for 2 h. Dried particles were washed with excess 3085 toluene and ethanol, dried under nitrogen, and stored in a desiccator.
3086 Example A2: 3.2 g colloidal silica particles (CAS 7631-86-9; Aldrich 718483) were well-3087 dispersed in 150 ml toluene (CAS 108-88-3; ACS grade; Fischer Chemical) and charged into 3088 a round-bottom flask equipped with magnetic stirrer under nitrogen.
1.0 ml of (3-3089 (ethylamino)propy)trimethoxysilane (CAS 3069-25-8; 98%; Aldrich 551635) was added to 3090 the reaction mixture. After stirring the reaction mixture at ambient temperature for 24 h, 3091 functionalized particles were recovered using a centrifuge and washed with excess methanol 3092 (CAS 67-56-1; ACS Grade; Fisher Chemical). Solids were recovered using centrifuge and 3093 transferred to an oven at to 120 C for 2 h. Dried particles were washed with excess toluene 3094 and methanol, dried under nitrogen, and stored in a desiccator.
3095 Example A3: 3.1 g colloidal silica particles (CAS 7631-86-9; Aldrich 718483) were well-3096 dispersed in 150 ml toluene (CAS 108-88-3; ACS grade; Fischer Chemical) and charged into 3097 a round-bottom flask equipped with magnetic stirrer under nitrogen.
1.8 ml of (3-(N,N-3098 diethylamino)propyI)-trimethoxysilane (CAS 41051-80-3; 98%; Aldrich 679356) was added 3099 to the reaction mixture. After stirring the reaction mixture at ambient temperature for 24 h, 3100 functionalized particles were recovered using a centrifuge and washed with excess methanol 3101 (CAS 67-56-1; ACS Grade; Fisher Chemical). Solids were recovered using centrifuge and 3102 transferred to an oven at to 120 C for 2 h. Dried particles were washed with excess toluene 3103 and methanol, dried under nitrogen, and stored in a desiccator.
3104 Example A4: 2.8 g colloidal silica particles with primary amine surface functionality, 3105 prepared according to Example 1, and 50 ml methanol (CAS 67-56-1; ACS
Grade; Fisher 3106 Chemical) were charged into a 100 .mL round-bottom flask equipped with magnetic stirrer 3107 under nitrogen. 2.0 ml N,N-dimethylacetamide dimethylacetal (CAS 18871-66-4; 90%;
3108 Aldrich) was added to the reaction mixture. After stirring the reaction mixture at ambient 3109 temperature for 10 h, particles were recovered using a centrifuge, washed with excess 3110 ethanol, and dried in an oven at 70 C under reduced pressure. Dried particles were crushed 3111 to yield a white free-slowing powder and stored in a desiccator.
3112 Example A5: 3.1 g colloidal silica particles (CAS 7631-86-9; Aldrich 718483) were well-3113 dispersed in 50 ml toluene (CAS 108-88-3; ACS grade; Fischer Chemical) and charged into 3114 a 150 ml round-bottom flask equipped with magnetic stirrer under nitrogen. 2.0 ml of 3115 (propyl)trimethoxysilane (CAS 41051-80-3; 98%; Aldrich 679356) was added to the reaction 3116 mixture. After stirring the reaction mixture at ambient temperature for 24 h, functionalized 3117 particles were recovered using a centrifuge and washed with excess ethanol. Solids were 3118 recovered using centrifuge and transferred to an oven at to 120 C for 2 h. Dry particles were 3119 washed with excess toluene and methanol (CAS 67-56-1; ACS Grade; Fisher Chemical).
3120 Example A6: 3.0 g colloidal silica particles (CAS 7631-86-9; Aldrich 718483) were well-3121 dispersed in 150 ml toluene (CAS 108-88-3; ACS grade; Fischer Chemical) and charged into 3122 a round-bottom flask equipped with magnetic stirrer and reflux condenser under nitrogen.

3123 3.0 ml of (3-bromopropyl)trimethoxysilane (CAS 51826-90-5; 97%;
Aldrich 18265) was 3124 added to the reaction mixture. After stirring the reaction mixture at ambient temperature for 3125 24 h, functionalized particles were recovered using a centrifuge and washed with excess 3126 ethanol. Solids were recovered using centrifuge and transferred to an oven at to 120 C for 2 3127 h. Dry particles were washed with excess toluene and methanol (CAS 67-56-1; ACS Grade;
3128 Fisher Chemical) dried under nitrogen, and stored in a desiccator.
3129 Example A7: 3.1 g colloidal silica particles (CAS 7631-86-9; Aldrich 718483) were well-3130 dispersed in 150 ml toluene (CAS 108-88-3; ACS grade; Fischer Chemical) and charged into 3131 a round-bottom flask equipped with magnetic stirrer under nitrogen.
1.8 ml of (3-(N,N-3132 diethylamino)propyI)-trimethoxysilane (CAS 41051-80-3; 98%; Aldrich 679356) was added 3133 to the reaction mixture. After stirring the reaction mixture at ambient temperature for 24 h, 3134 functionalized particles were recovered using a centrifuge and washed with excess methanol 3135 (CAS 67-56-1; ACS Grade; Fisher Chemical). Solids were recovered using centrifuge and 3136 transferred to an oven at to 120 C for 2 h.
3137 2.9 g of recovered functionalized colloidal silica particles were well-dispersed in 50 ml 3138 toluene and charged into a 150 ml round-bottom flask equipped with magnetic stirrer under 3139 nitrogen. 2.0 ml of (propy)trimethoxysilane (CAS 41051-80-3; 98%;
Aldrich 679356) was 3140 added to the reaction mixture. After stirring the reaction mixture at ambient temperature for 3141 24 h, functionalized particles were recovered using a centrifuge and washed with excess 3142 ethanol. Solids were recovered using centrifuge and transferred to an oven at to 120 C for 2 3143 h. Dry particles were washed with excess toluene and methanol.
3144 Example A8: 6.1 g colloidal silica particles (CAS 7631-86-9; Aldrich 718483) were well-3145 dispersed in 150 ml toluene (CAS 108-88-3; ACS grade; Fischer Chemical) and charged into 3146 a round-bottom flask equipped with magnetic stirrer under nitrogen.
1.8 ml of (3-(N,N-3147 diethylamino)propyI)-trimethoxysilane (CAS 41051-80-3; 98%; Aldrich 679356) was added 3148 to the reaction mixture. After stirring the reaction mixture at ambient temperature for 8 h, 3149 functionalized particles were recovered using a centrifuge and washed with excess methanol 3150 (CAS 67-56-1; ACS Grade; Fisher Chemical). Solids were recovered using centrifuge and 3151 transferred to an oven at to 120 C for 2 h.

3152 3.2 g previously functionalized particles were well-dispersed in 150 ml toluene and charged 3153 into a round-bottom flask equipped with magnetic stirrer under nitrogen. 1.8 ml of (3-(N,N-3154 diethylamino)propyI)-trimethoxysilane was added to the reaction mixture. After stirring the 3155 reaction mixture at ambient temperature for 8 h, functionalized particles were recovered 3156 using a centrifuge and washed with excess methanol. Solids were recovered using centrifuge 3157 and transferred to an oven at to 120 C for 2 h.
3158 1.5 g previously functionalized particles were well-dispersed in 150 ml toluene and charged 3159 into a round-bottom flask equipped with magnetic stirrer under nitrogen. 1.8 ml of (3-(N,N-3160 diethylamino)propyI)-trimethoxysilane was added to the reaction mixture. After stirring the 3161 reaction mixture at ambient temperature for 8 h, functionalized particles were recovered 3162 using a centrifuge and washed with excess methanol. Solids were recovered using centrifuge 3163 and transferred to an oven at to 120 C for 2 h. Dried particles were washed with excess 3164 methanol, dried under nitrogen, and stored in a desiccator.
3165 Example A9: 3.1 g colloidal silica particles (CAS 7631-86-9; Aldrich 718483) were well-3166 dispersed in 150 ml toluene (CAS 108-88-3; ACS grade; Fischer Chemical) and charged into 3167 a 250 ml round-bottom flask equipped with magnetic stirrer under nitrogen. 2.4 ml (3-3168 glycidyloxypropyI)-trimethoxysilane (CAS-2530-83-8; 98%; Aldrich 440167) was added to 3169 the reaction mixture. After stirring the reaction mixture at ambient temperature for 24 h, 3170 functionalized particles were recovered using a centrifuge and washed with excess ethanol.
3171 Solids were recovered using centrifuge and transferred to an oven at to 120 C for 2 h. Dry 3172 particles were washed with excess toluene and methanol (CAS 67-56-1; ACS
Grade; Fisher 3173 Chemical).
3174 2.5 g of the epoxy-functionalized silica particles were well-dispersed in 150 ml toluene and 3175 charged into a 250 ml round-bottom flask equipped with magnetic stirrer under nitrogen. The 3176 reaction mixture was cooled in an ice water bath. 2.0 ml N,N-diethyl-N'-3177 methylethylenediamine (CAS 104-79-0; 97%; Aldrich 308099) was slowly added to the 3178 reaction mixture. After stirring the reaction mixture at for 24 h, functionalized particles were 3179 recovered using a centrifuge and washed with excess ethanol. Solids were recovered using 3180 centrifuge and transferred to an oven at to 120 C for 2 h. Dry particles were washed with 3181 excess toluene and methanol.

3182 Example A10: 3.1 g colloidal silica particles (CAS 7631-86-9; Aldrich 718483) were well-3183 dispersed in 150 ml toluene (CAS 108-88-3; ACS grade; Fischer Chemical) and charged into 3184 a 150 ml round-bottom flask equipped with magnetic stirrer under nitrogen. 3.5 ml 3185 (vinyl)trimethoxysilane (CAS-2768-02-7; 98%, Aldrich 235768) was added to the reaction 3186 mixture. The reaction mixture was immersed in an oil bath and heated to reflux for 24 h while 3187 the condenser feed was kept at 70 C. After cooling to ambient temperature, functionalized 3188 particles were recovered using a centrifuge and washed with excess methanol (CAS 67-56-3189 1; ACS Grade; Fisher Chemical). Solids were recovered using centrifuge and transferred to 3190 an oven at to 80 C for 2 h and stored in a desiccator.
3191 0.8 g of vinyl-functionalized particles were well-dispersed in 10 ml deionized water and 3192 charged into a 100 ml round- bottom flask equipped with a magnetic stirrer under nitrogen.
3193 2.1 g 2-(diethyl)aminoethyl methacrylate (CAS 105-16-8; 99%; Aldrich 408980) was 3194 dissolved in 5 mL of CO2-saturated deionized water and added to the reaction mixture. The 3195 reaction mixture was immersed in an oil bath and heated to 70 C. 0.06 g of 2,2'-azobis[2-3196 (2-imidazolin-2-yl)propane] was dissolved in 5 mL of 002-saturated deionized water and 3197 added to the reaction mixture. The reaction was left for 24 h.
3198 Example All: 3.0 g fumed silica particles (CAS 112945-52-5; Aldrich S5505) were well-3199 dispersed in 150 ml toluene (CAS 108-88-3; ACS grade; Fischer Chemical) and charged into 3200 a round-bottom flask equipped with magnetic stirrer under nitrogen.
2.1 ml of (3-(N,N-3201 diethylamino)propyI)-trimethoxysilane (CAS 41051-80-3; 98%; Aldrich 679356) was added 3202 to the reaction mixture. After stirring the reaction mixture at ambient temperature for 24 h, 3203 functionalized particles were recovered using a centrifuge and washed with excess methanol 3204 (CAS 67-56-1; ACS Grade; Fisher Chemical). Solids were recovered using centrifuge and 3205 transferred to an oven at to 120 C for 2 h. Dried particles were washed with excess toluene 3206 and methanol, dried under nitrogen, and stored in a desiccator.
3207 2.9 g of the amine-functionalized silica particles were well-dispersed in 50 ml toluene and 3208 charged into a 150 ml round-bottom flask equipped with magnetic stirrer under nitrogen. 1.0 3209 ml trimethoxymethylsilane (CAS 1185-55-3; 98%; Aldrich 246174) was slowly added to the 3210 reaction mixture. After stirring the reaction mixture at for 24 h, functionalized particles were 3211 recovered using a centrifuge and washed with excess ethanol. Solids were recovered using 3212 centrifuge and transferred to an oven at to 120 C for 2 h. Dry particles were washed with 3213 excess toluene and methanol.
3214 Example Al2: 5.1 g flash silica particles (CAS 112926-00-8; Supelco 97728) were well-3215 dispersed in 150 ml toluene (CAS 108-88-3; ACS grade; Fischer Chemical) and charged into 3216 a round-bottom flask equipped with magnetic stirrer under nitrogen.
3.3 ml of (3-(N,N-3217 diethylamino)propyI)-trimethoxysilane (CAS 41051-80-3; 98%; Aldrich 679356) was added 3218 to the reaction mixture. After stirring the reaction mixture at ambient temperature for 24 h, 3219 functionalized particles were recovered using a centrifuge and washed with excess methanol 3220 (CAS 67-56-1; ACS Grade; Fisher Chemical). Solids were recovered using centrifuge and 3221 transferred to an oven at to 120 C for 2 h. Dried particles were washed with excess toluene 3222 and methanol, dried under nitrogen, and stored in a desiccator.
3223 2.9 g of the amine-functionalized silica particles were well-dispersed in 50 ml toluene and 3224 charged into a 150 ml round-bottom flask equipped with magnetic stirrer under nitrogen. 1.0 3225 ml trimethoxymethylsilane (CAS 1185-55-3; 98%; Aldrich 246174) was slowly added to the 3226 reaction mixture. After stirring the reaction mixture at for 24 h, functionalized particles were 3227 recovered using a centrifuge and washed with excess ethanol. Solids were recovered using 3228 centrifuge and transferred to an oven at to 120 C for 2 h. Dry particles were washed with 3229 excess toluene and methanol.
3230 Example A13: 5.0 g silica gel particles (CAS 112926-00-8; Sigma-Aldrich 236810) were 3231 well-dispersed in 150 ml toluene (CAS 108-88-3; ACS grade; Fischer Chemical) and charged 3232 into a round-bottom flask equipped with magnetic stirrer under nitrogen. 3.4 ml of (3-(N,N-3233 diethylamino)propyl)trimethoxysilane (CAS 41051-80-3; 98%; Aldrich 679356) was added to 3234 the reaction mixture. After stirring the reaction mixture at ambient temperature for 24 h, 3235 functionalized particles were recovered using a centrifuge and washed with excess methanol 3236 (CAS 67-56-1; ACS Grade; Fisher Chemical). Solids were recovered using centrifuge and 3237 transferred to an oven at to 120 C for 2 h. Dried particles were washed with excess toluene 3238 and methanol, dried under nitrogen, and stored in a desiccator.
3239 2.9 g of the amine-functionalized silica particles were well-dispersed in 50 ml toluene and 3240 charged into a 150 ml round-bottom flask equipped with magnetic stirrer under nitrogen. 1.0 3241 ml trimethoxymethylsilane (CAS 1185-55-3; 98%; Aldrich 246174) was slowly added to the 3242 reaction mixture. After stirring the reaction mixture at for 24 h, functionalized particles were 3243 recovered using a centrifuge and washed with excess ethanol. Solids were recovered using 3244 centrifuge and transferred to an oven at to 120 C for 2 h. Dry particles were washed with 3245 excess toluene and methanol.
3246 Example A14: 2.0 g Pluronic 123 (CAS 9003-11-6; Aldrich 435465), 70 ml of hydrochloric 3247 acid (CAS 7647-01-0; ACS Plus; Fisher Chemical), and 400 ml deionized water were 3248 charged into a 1 L Erlenmeyer flask equipped with a magnetic stirrer.
After the polymer 3249 dissolved, 26.4 g tetraethyl-orthosilicate (CAS 78-10-4; 98%; Aldrich 131903) was added.
3250 The reaction mixture was immersed in an oil bath at 35 C. After stirring for 24 h, stirring was 3251 discontinued and the solution was heated to 80 C for 24 hours. The reaction mixture was 3252 cooled by adding 400 mL of deionized water. Particles were recovered using a centrifuge, 3253 washed excess deionized water, dried in an oven at to 80 C for 2 h, and stored in a 3254 desiccator. Calcination of the recovered particles was performed by heating at 1.2 C/min to 3255 550 C; particles were help at 200 C for 1 h and at 550 C for 6 h.
Calcinated particles were 3256 washed with methanol, dried in an oven at to 80 C for 2 h, and stored in a desiccator.
3257 A 4 M sodium hydroxide (CAS 1310-7302; ACS grade; Fisher Chemical) solution was 3258 prepared, charged into a 250 ml round bottom flask equipped with a magnetic stirrer and 3259 reflux condenser under nitrogen, and placed in a water bath at 50 C.
2-choloethylamine 3260 hydrochloride (CAS 870-24-6; 99%; Aldrich C40200) was added to the NaOH
solution and 3261 stirred for 2 h. The product was recovered by distillation and immediately cooled in an ice 3262 bath.
3263 1.0 g of SBA-type mesostructured silica particles, 2.0 g of aziridine, and 50 ml toluene (CAS
3264 108-88-3; ACS grade; Fischer Chemical) were charged into a 150 ml round-bottom flask 3265 equipped with magnetic stirrer under nitrogen. A few drops of glacial acetic acid (CAS 61-3266 19-7; ACS Grade; Fischer Chemical) were added to the reaction mixture.
After stirring the 3267 reaction mixture at ambient temperature for 24 h, functionalized particles were recovered 3268 using a centrifuge and washed excess toluene and methanol (CAS 67-56-1;
ACS Grade;
3269 Fisher Chemical). Solids were recovered using centrifuge and transferred to an oven at to 3270 120 C for 2 h.

3271 0.9 g of the amine-functionalized silica particles were well-dispersed in 50 ml toluene and 3272 charged into a 150 ml round-bottom flask equipped with magnetic stirrer under nitrogen. 0.5 3273 ml trimethoxymethylsilane (CAS 1185-55-3; 98%; Aldrich 246174) was slowly added to the 3274 reaction mixture. After stirring the reaction mixture at for 24 h, functionalized particles were 3275 recovered using a centrifuge and washed with excess ethanol. Solids were recovered using 3276 centrifuge and transferred to an oven at to 120 C for 2 h. Dry particles were washed with 3277 excess toluene and methanol.
3278 Example A15: 1.9 g iron oxide nanoparticles (CAS 1317-61-9; 50¨ 100 nm; Aldrich 637106) 3279 were well-dispersed in 100 ml of ethanol (CAS 64-17-5; 99%; Commercial Alcohols) and 3280 charged into a 250 ml round bottom flask equipped with an overhead stirrer. 0.5 g tetraethyl-3281 orthosilicate (CAS 78-10-4; 98%; Aldrich 131903) was dissolved in 15 ml ethanol and added 3282 to the reaction mixture. 13 mL ammonium hydroxide solution (CAS 7664-41-7; 30%; Fischer 3283 Chemical) was added dropwise into the reaction mixture. The reaction was stirred at ambient 3284 temperature. After for 5 h, magnetic particles were separated using a strong magnet, rinsed 3285 with ethanol, dried in an oven at 110 C, and stored in a desiccator.
3286 Coated iron oxide nanoparticles were well-dispersed in 100 mL of deionized water and 3287 charged into a 250 mL round-bottom flask equipped with an overhead stirrer. The pH of the 3288 suspension was raised to 9.5 using 0.1 M sodium hydroxide (CAS 1310-7302;
ACS grade;
3289 Fisher Chemical) solution. The reaction mixture was heated to 90 C. A
0.1 M sodium 3290 metasilicate (CAS 6834-92-0; Aldrich 307815) solution was prepared using deionized water.
3291 10 ml of the 0.1 M sodium silicate solution and 0.1 M sulfuric acid (CAS 7664-93-9; Fischer 3292 Chemical) were added concurrently dropwise to the reaction mixture over a period of 1 h 3293 while maintaining the solution pH at 9.5. The reaction mixture was stirred for 1 h and 3294 subsequently cooled to ambient temperature. Magnetic particles were separated using a 3295 strong magnet, rinsed with deionized water, dried in an oven at 110 C, and stored in a 3296 desiccator.
3297 1.8 g silica-coated iron oxide nanoparticles were well-dispersed in 150 ml toluene (CAS 108-3298 88-3; ACS grade; Fischer Chemical) and charged into a round-bottom flask equipped with 3299 magnetic stirrer under nitrogen. 3.4 ml of (3-(N,N-diethylamino)propyI)-trimethoxysilane 3300 (CAS 41051-80-3; 98%; Aldrich 679356) was added to the reaction mixture. After stirring the 3301 reaction mixture at ambient temperature for 24 h, functionalized particles were recovered 3302 using a centrifuge and washed with excess methanol (CAS 67-56-1; ACS
Grade; Fisher 3303 Chemical). Solids were recovered using centrifuge and transferred to an oven at to 120 C
3304 for 2 h. Dried particles were washed with excess toluene and methanol, dried under nitrogen, 3305 and stored in a desiccator.
3306 1.8 g of the amine-functionalized silica particles were well-dispersed in 50 ml toluene and 3307 charged into a 150 ml round-bottom flask equipped with magnetic stirrer under nitrogen. 1.0 3308 ml trimethoxymethylsilane (CAS 1185-55-3; 98%; Aldrich 246174) was slowly added to the 3309 reaction mixture. After stirring the reaction mixture at for 24 h, functionalized particles were 3310 recovered using a centrifuge and washed with excess ethanol. Solids were recovered using 3311 centrifuge and transferred to an oven at to 120 C for 2 h. Dry particles were washed with 3312 excess toluene and methanol, dried under nitrogen, and stored in a desiccator.
3313 Example A16: 4.7 g tetraethyl-orthosilicate (CAS 78-10-4; 98%; Aldrich 131903) was 3314 dissolved in 11 ml ethanol (CAS 64-17-5; 99%; Commercial Alcohols) and charged into a 3315 100 ml round-bottom flask equipped with a magnetic stirrer. A solution was prepared with 3316 1.9 g ammonium fluoride (CAS 12125-01-8; 99%; Sigma-Aldrich 216011), 25 ml ammonium 3317 hydroxide solution (CAS 7664-41-7; 30%; Fischer Chemical), and 100 ml deionized water.
3318 0.4 ml of the ammonium fluoride/hydroxide solution was added to a mixture of 67 ml 3319 deionized water and 11 ml ethanol. The diluted ammonium fluoride/hydroxide solution was 3320 added to the reaction mixture. The reaction mixture was stirred for 5 min. and transferred to 3321 a small Petri dish. After 30 min, the gel was transferred to beaker and immersed in ethanol, 3322 and left at ambient temperature for 48 h. The gel was washed with excess ethanol which is 3323 gradually replaced with toluene (CAS 108-88-3; ACS grade; Fischer Chemical).
3324 1.6 ml of (3-(N,N-diethylamino)propyI)-trimethoxysilane (CAS 41051-80-3; 98%; Aldrich 3325 679356) was diluted in 20 ml ethanol and added to the gel. After stirring the reaction mixture 3326 at ambient temperature for 24 h, the gel was washed with toluene. After repeating three 3327 times, the gel was washed with pentane (CAS 109-66-0; 99%; Fisher Chemical). Pentane 3328 was removed from gel by evaporation in a fume hood, washed with additional ethanol, dried 3329 in an oven at 110 C, and stored in a desiccator. Recovered particles were crushed into 3330 smaller particles of variable size using a mortar and pestle.

3331 2.0 g of the amine-functionalized silica particles were well-dispersed in 50 ml toluene and 3332 charged into a 150 ml round-bottom flask equipped with magnetic stirrer under nitrogen. 1.5 3333 ml trimethoxymethylsilane (CAS 1185-55-3; 98%; Aldrich 246174) was slowly added to the 3334 reaction mixture. After stirring the reaction mixture at for 24 h, functionalized particles were 3335 recovered using a centrifuge and washed with excess ethanol. Solids were recovered using 3336 centrifuge and transferred to an oven at to 120 C for 2 h. Dry particles were washed with 3337 excess toluene and methanol, dried under nitrogen, and stored in a desiccator.
3338 Example A17: 3.3 g 4-hydroxy-3-nitrobenzoic acid (CAS 616-82-0; 98%;
Aldrich 228575), 3339 thionyl chloride (CAS 7719-09-7; 97%; Sigma-Aldrich 320536), 150 ml anhydrous benzene 3340 (CAS 71-43-2; 99.8%; Sigma-Aldrich 401765), and a few drops of N,N-dimethylforamide 3341 (CAS 68-12-2; 99%, Sigma D4551) were charged into a 250 ml round-bottom flask equipped 3342 with a magnetic stirrer under nitrogen. The reaction mixture was immersed in an oil bath and 3343 heated to 50 C for 6 h. After cooling to ambient temperature, the reaction mixture was placed 3344 in a rotary evaporator under reduced pressure to yield a yellow residue.
3345 2.3 g of the recovered 4-hydroxy-3-nitrobenzoyl chloride, 2.8 g colloidal silica particles with 3346 primary amine surface functionality, prepared according to Example 1, and 50 ml of diethyl 3347 ether (CAS 60-29-7; 99%; Sigma-Aldrich 346136) were charged into a 150 ml round-bottom 3348 flask. After stirring the reaction mixture at ambient temperature for 24 h, functionalized 3349 particles were recovered using a centrifuge and washed with excess methanol (CAS 67-56-3350 1; ACS Grade; Fisher Chemical). Solids were recovered using centrifuge and transferred to 3351 an oven at to 120 C for 2 h. Dried particles were washed with excess toluene and ethanol, 3352 dried under nitrogen, and stored in a desiccator.
3353 Example B1: 1.5 g Dodecylamine (CAS 124-22-1; 99%; Aldrich 325163) and 1.0 ml N,N-3354 dimethylacetamide dimethyl acetal (CAS 18871-66-4; 90%; Aldrich 261483) were charged 3355 in a 50 ml round-bottom flask equipped with magnetic stirrer under nitrogen. The reaction 3356 mixture was stirred for 24 h at ambient temperature. The reaction mixture was dissolved into 3357 30 ml diethyl ether (CAS 60-29-7; 99%; Sigma-Aldrich 346136). A white precipitate formed 3358 after addition of carbon dioxide and a drop of deionized water and was separated by filtration 3359 to yield N'-dodecyl-N,N-dimethylacetamidiniunn bicarbonate.

3360 6.26 g methyl methacrylate, 0.014 g N'-dodecyl-N,N-dimethylacetamidinium bicarbonate, 3361 and 18 mL of CO2-saturated deionized water were charged into a 50 mL
round-bottomed 3362 flask equipped with magnetic stirrer under carbon dioxide. The reaction mixture was 3363 emulsified using a Fisher Scientific high-speed homogenizer. The reaction mixture was 3364 placed in a water bath heated to 70 C. In a separate vial, 2,2'-azobis[2-(2-imidazolin-2-3365 yl)propane] (VA-061; Wako Pure Chemical Industries Limited) was dissolved in 2 ml of CO2-3366 saturated deionized water carbonated water and added to the reaction mixture. The reaction 3367 was left for 24 h. The latex product appeared white and opaque. Solids were concentrated 3368 using a high-speed centrifuge and dispersed in deionized water. The concentrated solids 3369 were placed in a dialysis tube (MW cut-off: 1200 g/mol; Sigma D9652) and placed in 3370 deionized water for 48 h. Latex particles are destabilized by heating the latex to 50 C and 3371 sparging with nitrogen. The particle aggregates are recovered by filtration, washed with 3372 deionized water, and dried under nitrogen.
3373 Example B2: 2.1 g styrene, 0.1 g divinylbenzene, 0.11 g N'-dodecyl-N,N-3374 dimethylacetamidinium bicarbonate, and 7 mL deionized water were charged into a 50 ml 3375 round-bottom flask equipped with a magnetic stirrer and reflux condenser under carbon 3376 dioxide. The reaction mixture was emulsified using a Fisher Scientific high-speed 3377 homogenizer. The reaction mixture was placed in a water bath heated to 70 C. In a separate 3378 vial, 0.3 g 2,2'-azobis[2-(2-imidazolin-2-yl)propane] (VA-061; Wako Pure Chemical 3379 Industries Limited) was dissolved in 3 mL deionized water and added to the reaction mixture.
3380 The reaction was left for 24 h. The latex product appeared white and opaque. Solids were 3381 concentrated using a high-speed centrifuge and dispersed in deionized water. The 3382 concentrated solids were placed in a dialysis tube (MW cut-off: 1200 g/mol; Sigma D9652) 3383 and placed in deionized water for 48 h. Latex particles are destabilized by heating the latex 3384 to 50 C and sparging with nitrogen. The particle aggregated are recovered by filtration, 3385 washed with deionized water, and dried under nitrogen.
3386 Example B3: 1.5 g di(ethylene glycol) hexyl ether (CAS 112-59-4; 98%;
Aldrich 300284), 3387 1.6 g p-toluenesulphonyl chloride (CAS 98-59-9; 99%; Sigma-Aldrich 98-59-9), and 100 ml 3388 tetrahydrofuran (CAS 109-99-9; 99%; Sigma-Aldrich 360589) were charge into a 250 ml 3389 round-bottom flask equipped with a magnetic stirrer. The reaction mixture was cooled in an 3390 ice water bath. Triethylamine (CAS 121-44-8; 99%; Sigma-Aldrich T0886)) was slowly added 3391 to the reaction mixture dropwise. The reaction mixture was stirred for 24 h. A white precipitate 3392 formed and was removed by filtration through a Buchner funnel. The filtrate was transferred 3393 to a separatory funnel and washed with several portions of saturated aqueous sodium 3394 bicarbonate, distilled water, and saturated aqueous sodium chloride.
The organic layer was 3395 collected, dried over magnesium sulfate, filtered, and concentrated in a rotary evaporator 3396 under reduced pressure to yield a clear faintly yellow residue.
3397 1.9 g of the alkyl ether tosylate derivative, 50 ml dimethylformamide (CAS 68-12-2; 99%;
3398 Sigma-Aldrich 227056), and 1.3 g potassium phthalimide (CAS 1074-82-4;
98%; Aldrich 3399 160385) were charged into a 250 ml round-bottom flask equipped with a magnetic stirrer.
3400 The reaction mixture was immersed in an oil bath and heated to 100 C for 12 h. After cooling, 3401 the reaction mixture consisted of a white precipitate in a clear yellow solution.
3402 Dimethylformamide was removed by distillation under reduced pressure.
Diethyl ether (CAS
3403 60-29-7; 99%; Sigma-Aldrich 346136) was added to the residue and the reaction mixture 3404 was placed in a refrigerator at 4 C for 48 h. The solids were removed by filtration through a 3405 Biichner funnel. The filtrate was concentrated in a rotary evaporator under reduced pressure, 3406 dissolved in ethyl acetate (CAS 141-78-6; ACS Grade; Fischer Chemical) and transferred to 3407 a separatory funnel. The crude product was washed with several portions of deionized water 3408 and saturated aqueous sodium chloride. The organic layer was collected, dried over 3409 magnesium sulfate, filtered, and concentrated in a rotary evaporator at reduced pressure to 3410 yield a clear yellow residue.
3411 1.5 g of the alkyl ether phthalimide derivative and 50 ml ethanol (CAS
64-17-5; 99%;
3412 Commercial Alcohols) were charged into a large 250 ml round-bottom flask equipped with 3413 magnetic stirrer. 3.0 ml hydrazine monohydrate (CAS 7803-57-8; 98%;
Sigma-Aldrich 3414 207942) was added to the reaction mixture. The reaction mixture was heated to reflux for 4 3415 h. A large amount of white precipitate formed. The reaction mixture was concentrated in a 3416 rotary evaporator under reduced pressure. Diethyl ether was added to the residue and well 3417 mixed. The solids were removed by vacuum filtration through a Buchner funnel. The filtrate 3418 was concentrated in a rotary evaporator under reduced pressure to yield a clear pale yellow 3419 liquid residue.

3420 0.5 g alkyl ether amine derivative and 1.0 ml N,N-dimethylacetamide dimethyl acetal (CAS
3421 18871-66-4; 90%; Aldrich 261483) were charged in a 50 ml round-bottom flask equipped 3422 with magnetic stirrer under nitrogen. The reaction mixture was stirred for 24 h at ambient 3423 temperature. The reaction mixture was concentrated in a rotary evaporator under reduced 3424 pressure to yield N'-3,6-dioxadodecyl-N,N -dimethylacetamidium.
3425 2.1 g styrene, 0.1 g divinylbenzene, 0.11 g N'-3,6-dioxadodecyl-N,N-dimethylacetamidium, 3426 and 7 mL deionized water were charged into a 50 ml round-bottom flask equipped with a 3427 magnetic stirrer and reflux condenser under carbon dioxide. The reaction mixture was 3428 emulsified using a Fisher Scientific high-speed homogenizer. The reaction mixture was 3429 placed in a water bath heated to 70 C. In a separate vial, 0.3 g 2,2'-azobis[2-(2-imidazolin-3430 2-yl)propane] (VA-061; Wako Pure Chemical Industries Limited) was dissolved in 3 mL
3431 deionized water and added to the reaction mixture. The reaction was left for 24 h. The latex 3432 product appeared yellow and opaque. Solids were concentrated using a high-speed 3433 centrifuge and dispersed in deionized water. The concentrated solids were placed in a 3434 dialysis tube (MW cut-off: 1200 g/mol; Sigma D9652) and placed in deionized water for 48 3435 h. Latex particles are destabilized by heating the latex to 50 C and sparging with nitrogen.
3436 The particle aggregates are recovered by filtration washed with deionized water, and dried 3437 under nitrogen.
3438 Example B4: 1.9 g Oleylamine (CAS 112-90-3; 98%; Aldrich HT-0A100) and 2.0 ml N,N-3439 dinnethylacetannide dimethyl acetal (CAS 18871-66-4; 90%; Aldrich 261483) were charged 3440 in a 50 ml round-bottom flask equipped with magnetic stirrer under nitrogen. The reaction 3441 mixture was stirred for 24 h at ambient temperature. The reaction mixture was dissolved into 3442 30 ml diethyl ether (CAS 60-29-7; 99%; Sigma-Aldrich 346136). A white precipitate formed 3443 after addition of carbon dioxide and a drop of deionized water and was separated by filtration 3444 to yield N'-hexadecene-N,N-dimethylacetamidinium bicarbonate.
3445 2.1 g styrene, 0.1 g divinylbenzene, 0.11 g N'-octadecene-N,N-dimethyl-acetamidinium 3446 bicarbonate, and 7 mL deionized water were charged into a 50 ml round-bottom flask 3447 equipped with a magnetic stirrer and reflux condenser under carbon dioxide. The reaction 3448 mixture was emulsified using a Fisher Scientific high-speed homogenizer. The reaction 3449 mixture was placed in a water bath heated to 70 C. In a separate vial, 0.3 g 2,2'-azobis[2-3450 (2-imidazolin-2-yl)propane] (VA-061; Wako Pure Chemical Industries Limited) was 3451 dissolved in 3 mL deionized water and added to the reaction mixture.
The reaction was left 3452 for 24 h. The latex product appeared white and opaque. Solids were concentrated using a 3453 high-speed centrifuge and dispersed in deionized water. The concentrated solids were 3454 placed in a dialysis tube (MW cut-off: 1200 g/mol; Sigma D9652) and placed in deionized 3455 water for 48 h. Latex particles are destabilized by heating the latex to 50 C and sparging 3456 with nitrogen. The particle aggregates are recovered by filtration, washed with deionized 3457 water, and dried under nitrogen.
3458 Example B5: 4.2 g styrene, 0.1 g divinylbenzene, and 60 mL of 002-saturated deionized 3459 water were charged into 100 mL round-bottomed flask equipped with a magnetic stirrer and 3460 a reflux condenser under carbon dioxide. The reaction mixture was placed in a water bath 3461 heated to 70 C. 0.11 g of 2,2'-azobis[2-(2-imidazolin-2-yl)propane]
(VA-061; Wako Pure 3462 Chemical Industries Limited) dissolved in 10 mL of 002-saturated deionized water was 3463 added to the reaction mixture. The reaction was left for 24 h. The latex product appeared 3464 white and opaque. Solids were concentrated using a high-speed centrifuge and dispersed in 3465 deionized water. The concentrated solids were placed in a dialysis tube (MW cut-off: 1200 3466 g/mol; Sigma D9652) and placed in deionized water for 48 h. Latex particles are destabilized 3467 by heating the latex to 50 C and sparging with nitrogen. The particle aggregates are 3468 recovered by filtration, washed with deionized water, and dried under nitrogen.
3469 Example B6: 2.2 g styrene, 0.1 g divinylbenzene, 0.1 g methyl methacrylate, and 100 mL of 3470 002-saturated deionized water were charged into a 250 mL round-bottom flask equipped 3471 with a magnetic stirrer and a reflux condenser under carbon dioxide.
The reaction mixture =
3472 was placed in a water bath heated to 70 C. 0.21 g 2-(diethyl)aminoethyl methacrylate was 3473 dissolved in 5 mL of 002-saturated deionized water and added to the reaction mixture. 0.06 3474 g of 2,2'-azobis[2-(2-imidazolin-2-yl)propane] was dissolved in 5 mL
of 002-saturated 3475 deionized water and added to the reaction mixture. The reaction was left for 24 h. The latex 3476 product appeared white and opaque. Solids were concentrated using a high-speed 3477 centrifuge and dispersed in deionized water. Latex particles are destabilized by heating the 3478 latex to 50 C and sparging with nitrogen. The particle aggregates are recovered by filtration 3479 and dried under nitrogen.

3480 Example B7: 2.0 g 2-(diethyl)aminoethyl methacrylate and 18 ml deionized water were 3481 charged into a 250 mL round-bottom flask equipped with a magnetic stirrer and a reflux 3482 condenser under nitrogen. Concentrated hydrochloric acid (CAS 7647-01-0; ACS Plus;
3483 Fisher Chemical) was added to adjust pH was to 6Ø 0.052 g styrene, 0.046 g N-tert-butyl-3484 N-(1-diethylphosphono-2,2-dimethylpropyl) nitroxide (CAS 188526-94-5;
85%; Arkema), and 3485 0.035 g 2,2'-azobis42-(2-imidazolin-2-yl)propane]clihydrochloride (VA-044; Wako Pure 3486 Chemical Industries Limited) were added to the reaction mixture and immersed in an oil bath 3487 heated to 90 C. In a separate flask, a solution was prepared with 0.1 g methyl methacrylate, 3488 1.0 g styrene, and 100 g of deionized water. The second solution was added to the reaction 3489 mixture after 15 min of immersing the reaction mixture in the hot oil bath at 90 C. The 3490 reaction was left for 6 h. Solids were concentrated using a high-speed centrifuge and 3491 dispersed in deionized water. The concentrated solids were placed in a dialysis tube (MW
3492 cut-off: 1200 g/mol; Sigma D9652) and placed in deionized water for 48 h. Latex particles 3493 are destabilized by heating the latex to 50 C and sparging with nitrogen. The particle 3494 aggregates are recovered by filtration, washed with deionized water, and dried under 3495 nitrogen.
3496 Example B8: 1.9 g iron oxide nanoparticles (CAS 1317-61-9; 97%;
Aldrich 637106), 0.5 g 3497 of oleic acid (CAS 112-80-1; 99%; Sigma-Aldrich 01008), and 50 ml of deionized water were 3498 charged into a 100 ml round-bottom flask equipped with an overhead stirrer. The reaction 3499 mixture was placed in a water bath at 70 C for 1 h. Magnetic particles were separated using 3500 a strong magnet, washed with excess deionized water and ethanol (CAS 64-17-5; 99%;
3501 Commercial Alcohols) (CAS 64-17-5; 99%; Commercial Alcohols), dried in an oven at 110 3502 C, and stored in a desiccator.
3503 0.1 g N'-dodecyl-N,N-dimethylacetamidinium bicarbonate and 30 mL of CO2-saturated 3504 deionized water were charged into a 100 ml round-bottom flask equipped with an overhead 3505 stirrer under carbon dioxide. 0.7 g of oleic-acid coated iron oxide nanoparticles were well-3506 dispersed in a mixture of 1.0 g of styrene and 0.1 g cyclohexane (CAS
110-82-7; 99.5%;
3507 Sigma-Aldrich 33117) and added to the reaction mixture. The reaction mixture was 3508 emulsified using a Fisher Scientific high-speed homogenizer and subsequently sonicated 3509 using a sonic dismembrator. The reaction mixture was placed in a water bath heated to 70 3510 C. In a separate vial, 0.3 g 2,2'-azobis[2-(2-imidazolin-2-yl)propane] (VA-061; Wako Pure 3511 Chemical Industries Limited) was dissolved in 3 mL deionized water and added to the 3512 reaction mixture. The reaction was left for 24 h. The latex product is dark brown and opaque.
3513 Magnetically-responsive solids were recovered using a strong rare-earth magnet.
3514 Example B9: 5.2 g 4-hydroxy-3-nitrobenzoic acid (CAS 616-82-0; 98%;
Aldrich 228575), 7.3 3515 g 1-octanol (CAS 111-87-5; 99%; Sigma-Aldrich 472328), 0.05 g p-toluenesulfonic acid (CAS
3516 6192-52-5; 98%; Sigma-Aldrich T35920), and 200 ml toluene (CAS 108-88-3;
ACS grade;
3517 Fischer Chemical) were charged into a 500 ml round-bottom flask equipped with a magnetic 3518 stirrer, condenser, and Dean-Stark trap. The reaction mixture was heated to reflux. After 24 3519 h, the reaction mixture was cooled to ambient temperature and place in a rotary evaporator 3520 under reduced pressure. Diethyl ether (CAS 60-29-7; 99%; Sigma-Aldrich 346136) and 0.1 3521 M potassium hydroxide (CAS 1310-58-3; 90%; Sigma-Aldrich 484016) solution prepared in 3522 ethanol (CAS 64-17-5; 99%; Commercial Alcohols) was added to the residue.
An orange 3523 solid precipitated and was recovered by filtration, washed with diethyl ether, and dried under 3524 nitrogen, and stored in a desiccator.
3525 2.1 g styrene, 0.1 g divinylbenzene, 0.11 g of the orange solid, and 7 mL deionized water 3526 were charged into a 50 ml round-bottom flask equipped with a magnetic stirrer and reflux 3527 condenser under nitrogen. The reaction mixture was emulsified using a Fisher Scientific 3528 high-speed homogenizer. The reaction mixture was placed in a water bath heated to 70 C.
3529 In a separate vial, 0.1 g potassium persulfate (CAS 7727-21-1; 99%;
Sigma-Aldrich 216224) 3530 was dissolved in 3 mL deionized water and added to the reaction mixture. The reaction stirred 3531 for 24 h. Solids were concentrated using a high-speed centrifuge and dispersed in deionized 3532 water. Latex particles are destabilized by treating with carbon dioxide gas. The particle 3533 aggregates were recovered by filtration, washed with deionized water, dried under nitrogen, 3534 and stored in a desiccator.
3535 Example Cl: A 0.01 M solution of electrolyte was prepared using potassium chloride and 3536 deionized water. A 0.01 M solution of hydrochloric acid (CAS 7647-01-0; ACS Plus; Fisher 3537 Chemical) and a 0.01 M solution of sodium hydroxide sodium hydroxide (CAS 1310-7302;
3538 ACS grade; Fisher Chemical) were prepared. Zeta potential was measured using a Malvern 3539 Instruments Zetasizer Nano at 20 C. Samples were well dispersed in electrolyte solution by 3540 placing in an ultrasonic bath for 60 s. Surface charge for larger silica particles was measured 3541 by streaming potential using Anton Paar SurPASS instrument; 1.0 g of dry functionalized 3542 particles were packed inside a cylindrical tube and placed inside the instrument.
3543 Silica particles functionalized with switchable surface charge were prepared according to 3544 Examples A1-A17 by reacting silica particles with appropriate silane coupling agents and, 3545 where necessary, subsequently converted in a functional group capable of converting 3546 between its ionic state and non-ionic state. 0.05 g of functionalized silica was dispersed into 3547 10 ml of 10 mM KCI solution and saturated with CO2 gas. Zeta potential of functionalized 3548 particle dispersions was measured. The dispersion of functionalized silica particles were 3549 immersed into a water bath at 50 C and sparged with air to remove dissolved CO2. After 3550 cooling back to ambient temperature, the zeta-potential of functionalized particle dispersions 3551 was measured. This procedure was repeated several times alternating between 002-3552 saturated solution and 002-deficient solution.
3553 Polymer particles functionalized with switchable surface charge were prepared according to 3554 Examples B1-B9. The product latex samples were diluted into 10 mM KCI
solution and 3555 saturated with carbon dioxide. Zeta potential of functionalized particle dispersions was 3556 measured. The dispersion of functionalized silica particles were immersed into a water bath 3557 at 50 C and sparged with air to remove dissolved carbon dioxide. After cooling back to 3558 ambient temperature, the zeta-potential of functionalized particle dispersions was measured.
3559 This procedure was repeated several times alternating between 002-saturated solution and 3560 002-deficient solution.
3561 Example C2: Silica particles functionalized with switchable surface charge were prepared 3562 by reacting silica particles with appropriate silane coupling agents and, where necessary, 3563 subsequently converted in a functional group capable of converting between its ionic state 3564 and non-ionic state. Polystyrene particles were prepared via emulsion polymerization using 3565 surfactants with switchable charge.
3566 A know amount of particles switchable surface charge was dispersed in deionized water by 3567 first placing in vortex mixer for 1 min. and subsequently placing sample in an ultrasonic bath 3568 for 15 minutes. "High" conductivity indicated an average electrolytic conductivity reading 3569 greater than 10 mS/cm. "Moderate" conductivity indicated an average electrolytic 3570 conductivity between 1 ¨ 10 mS/cm. "Low" conductivity indicated an average electrolytic 3571 conductivity between 0.1 ¨ 1 niS/cm. "Very low" conductivity indicated an average electrolytic 3572 conductivity less than 100 pS/cm.
3573 Example C3: Silica particles functionalized with switchable surface charge were prepared 3574 by reacting silica particles with appropriate silane coupling agents and, where necessary, 3575 subsequently converted in a functional group capable of converting between its ionic state 3576 and non-ionic state. Polystyrene particles were prepared via emulsion polymerization using 3577 surfactants with switchable charge. Electrolyte solutions were prepared using sodium 3578 chloride (CAS 7647-14-5; 99%; Acros Organics) and deionized water.
Cellulose membrane 3579 dialysis tubing (MW cut-off: 1200 g/mol; Sigma D9652) was used.
3580 Dispersions of particles with switchable surface charge were prepared using silica particles 3581 comprising surface functionality which reversibly converts from ionic to non-ionic state and 3582 polymer particles comprising surface functionality which reversibly converts from ionic to 3583 non-ionic state. Dispersions prepared using particles with basic surface functionality were 3584 saturated with carbon dioxide by exposing the dispersion to a stream of carbon dioxide gas.
3585 Dispersions prepared using particles with acidic surface functionality were sparged with 3586 nitrogen to remove any dissolved carbon dioxide. The dispersion was transferred into dialysis 3587 tubing and sealed with clips. The dialysis tube charged with dispersion comprising 3588 responsive particles with switchable surface charge was immersed in large beaker 3589 containing an electrolyte solution. The movement of water across the membrane was tracked 3590 by mass. The procedure was repeated using electrolyte solutions of different concentration 3591 and using different dispersions with different particle concentration.
3592 In addition, an electrolyte solution was charged into dialysis tubing and sealed with clips. The 3593 dialysis tube charged with an electrolyte solution and immersed in a large beaker containing 3594 a dispersion of particles with switchable surface charge. Dispersions prepared using particles 3595 with basic surface functionality were saturated with carbon dioxide by exposing the 3596 dispersion to a stream of carbon dioxide gas. Dispersions prepared using particles with acidic 3597 surface functionality were sparged with nitrogen to remove any dissolved carbon dioxide.
3598 The movement of water across the membrane was tracked by mass. The procedure was 3599 repeated using electrolyte solutions of different concentration and using different dispersions 3600 with different particle concentration. "Low" water flux indicated an average net movement of 3601 water less than 1 ml/h. "Moderate" water flux indicated an average net movement of water 3602 between 10 ¨ 10 ml/h. "High" water flux indicated an average net movement of water greater 3603 than 100 ml/h.
3604 Example Dl: Particles with switchable surface charge were prepared from silica and 3605 polymer particles with different surface functionality which reversibly converts between an 3606 ionic state and a non-ionic state. Dispersion samples were prepared using 0.5 g particles 3607 with switchable surface charge and 25 ml deionized water in small test tubes under nitrogen.
3608 The test tubes were shaken, placed in a vortex mixer for 10 s, and finally immersed in an 3609 ultrasonic bath for 10 minutes. The rate of sedimentation of functionalized was tracked by 3610 bed height as a function of time. The hydrodynamic particle size was measured using a 3611 Malvern Instruments Mastersizer 3000 instrument at 20 C. The dispersion samples were 3612 exposed to carbon dioxide gas and sealed under carbon dioxide. The rate of sedimentation 3613 of functionalized was tracked by bed height as a function of time. The hydrodynamic particle 3614 size was measured using a Malvern Instruments Mastersizer 3000 instrument at 20 C.
3615 After settling, free water was decanted or carefully siphoned from the surface to yield 3616 particles with switchable surface charge. Remaining particles with switchable surface charge 3617 were dried under ambient conditions.
3618 Example D2: Particles with switchable surface charge were prepared from silica and 3619 polymer particles with different surface functionality which reversibly converts between an 3620 ionic state and a non-ionic state.
3621 Dispersion samples were prepared using particles with basic surface functionality and 3622 carbon dioxide saturated water. The dispersion was transferred to a Buchner funnel with a 3623 fritted glass bottom. The dispersion samples were exposed to a stream of carbon dioxide 3624 gas. Solids-rich froth was collected from the surface using a skimmer and dried under 3625 ambient conditions.
3626 Dispersion samples were prepared using particles with acidic surface functionality and 3627 deionized water. The dispersion was transferred to a Buchner funnel with a fritted glass 3628 bottom. The dispersion samples were exposed to a stream of nitrogen.
Solids-rich froth was 3629 collected from the surface using a skimmer and dried under ambient conditions.

3630 Example D3: Silica particles functionalized with switchable surface charge were prepared 3631 by reacting silica particles with appropriate silane coupling agents and, where necessary, 3632 subsequently converted in a functional group capable of converting between its ionic state 3633 and non-ionic state. Polystyrene particles were prepared via emulsion polymerization using 3634 surfactants with switchable charge.
3635 A dispersion of functionalized particles was prepared using carbon dioxide saturated water.
3636 Coarse porosity filter paper (P8 Grade; Fisher Scientific S47573) and medium porosity filter 3637 paper (P5 Grade; Fisher Scientific S47574) were used to separate solids.
3638 Example 04: Magnetic particles with switchable surface charge were prepared by coating 3639 iron oxide with silica and subsequently grating surface group which are capable of reversibly 3640 converting between ionic and non-ionic state. Magnetic particles with switchable surface 3641 charge were also prepared by miniemulsion polymerization of styrene using surfactants 3642 which are capable of reversibly converting between ionic and non-ionic state. Both samples 3643 were placed beside a strong rare-earth metal magnet. The amount of solids recovered was 3644 determined gravimetrically after drying recovered particle in an oven at 70 C under reduced 3645 pressure.
3646 Example Ni: A 0.01 M solution of hydrochloric acid (CAS 7647-01-0; ACS
Plus; Fisher 3647 Chemical), a 0.01 M solution of sodium hydroxide sodium hydroxide (CAS
1310-7302; ACS
3648 grade; Fisher Chemical), and a saturated solution of sodium chloride (CAS 7647-14-5; 99%;
3649 Acros Organics) were prepared.
3650 1.2 g nanocrystalline cellulose (AITF) was well-dispersed in 100 ml water and charged into 3651 a 250 ml round bottom flask equipped with magnetic stirrer under nitrogen. 0.015 g (2,2,6,6-3652 Tetramethylpiperidin-1-yl)oxyl (CAS 2564-83-2; 99%; Aldrich 426369), and 0.35 g sodium 3653 bromide (CAS 7647-15-6; 98%; Sigma-Aldrich 746401) were added to the reaction mixture.
3654 8.5 ml sodium hypochlorite solution (7681-52-9; 10 - 15 %; Sigma-Aldrich 425044) was 3655 added dropwise slowly. The pH of the suspension was maintained at 10.0 by adding NaOH
3656 solution. The reaction mixture was stirred for 1 h at ambient temperature. 5.0 ml methanol 3657 (CAS 67-56-1; ACS Grade; Fisher Chemical) was added and the pH was adjusted to 7.0 by 3658 adding HCI solution. Solids were concentrated using high speed centrifuge and washed with 3659 deionized water. The concentrated solids were placed in a dialysis tube (MW cut-off: 1200 3660 g/mol; Sigma D9652) and placed in deionized water for 48 h.
3661 0.35 g oxidized nanocrystalline cellulose was well-dispersed in 20 mL
2-(N-morpholino)-3662 ethanesulfonic acid buffer with pH of 5.0 (CAS 4432-31-9; 99%; Sigma M3671) and charged 3663 into a 100 ml round-bottom flask equipped with a magnetic stirrer under nitrogen. 0.60 g N-3664 (3-dimethylaminopropyI)-N'-ethylcarbodiimide hydrochloride (CAS 25952-53-8; Sigma-3665 Aldrich E7750) and 0.35 g N-hydroxysuccinimide (CAS 6066-82-6; 98%;
Aldrich 130672) 3666 were added to the reaction mixture. The reaction mixture was stirred for 15 minutes at 3667 ambient temperature. 10 ml 3-(diethylamino)propylamine (CAS 104-78-9;
99%; Aldrich 3668 549975) was added to the reaction mixture was stirred for 24 h at ambient temperature.
3669 Solids were concentrated using high speed centrifuge and washed with deionized water. The 3670 concentrated solids were placed in a dialysis tube (MW cut-off: 1200 g/mol; Sigma D9652) 3671 and placed in saturated NaCI solution for 24 h followed by deionized water for 24 h.
3672 Recovered particles were dried under nitrogen and stored in a dessicator. The zeta-potential 3673 of recovered particles was measured in both ionic and non-ionic state.
The electrolytic 3674 conductivity of recovered particles was measured in both ionic and non-ionic state.
3675 Example N2: 3.5 g carbon (CAS 7440-44-0; < 100 nm; Aldrich 633100) was dispersed into 3676 100 ml concentrated nitric acid (CAS 7697-37-2; ACS grade; Fisher Chemical) and charged 3677 into a 250 ml round-bottom flask equipped with a magnetic stirrer and reflux condenser. The 3678 reaction mixture was immersed in an oil bath and heated to reflux.
After 12 h, the reaction 3679 mixture was cooled to ambient temperature. Solids were separated by filtration, rinsed with 3680 deionized water, and dried in an oven at 110 C.
3681 Oxidized carbon was dispersed in 100 ml toluene (CAS 108-88-3; ACS grade;
Fischer 3682 Chemical) and charged into a 250 ml round-bottom flask equipped with a magnetic stirrer 3683 and reflux condenser. 2.0 ml N,N-diethyl-N'-methylethylenediamine (CAS
104-79-0; 97%;
3684 Aldrich 308099) was added to the reaction mixture. The reaction mixture was immersed in 3685 an oil bath and heated to reflux. After 4 h, the reaction mixture was cooled to ambient 3686 temperature. Solids were separated by filtration, dispersed in toluene, and heated to reflux 3687 for an additional 24 h. Solids were separated by filtration, dispersed in toluene, and heated 3688 to reflux for an additional 24 h. Solids were separated by filtration, washed with toluene, and 3689 dried in an oven at 110 C. The zeta-potential of recovered particles was measured in both 3690 ionic and non-ionic state. The electrolytic conductivity of recovered particles was measured 3691 in both ionic and non-ionic state.
'

Claims

I CLAIM:

1. A dispersion for use in a membrane process comprising responsive particles with switchable surface charge.

2. The dispersion of claim 1 wherein the responsive particles comprise:
an insoluble particle, and a surface functionality;
wherein the surface functionality reversibly converts between an ionic state and a non-ionic state.

3. The dispersion of claim 2 wherein the insoluble particle and surface functionality are linked through chemical bonding, physical entanglement, chemisorption, physisorption, or combinations thereof.

4. The dispersion of claim 2 wherein electrolytic conductivity increases when the surface functionality is converted to its ionic state.

5. The dispersion of claim 2 wherein electrolytic conductivity decreases when the surface functionality is converted to its non-ionic state.

6. The dispersion of claim 2 wherein ionic strength increases when the surface functionality is converted to its ionic state.

7. The dispersion of claim 2 wherein ionic strength decreases when the surface functionality is converted to its non-ionic state

8. The dispersion of claim 1 wherein the responsive particles remain suspended under continuous agitation.

9. The dispersion of claim 8 wherein the responsive particles are suspended by mechanical agitation, gas flotation, or pumping.

10. The dispersion of claim 2 wherein the insoluble particle comprises an inorganic solid, a synthetic polymer, a natural polymer, or a natural polymer derivative.

11. The dispersion of claim 10 wherein the insoluble particle comprises silica.

12. The dispersion of claim 11 wherein the insoluble particle comprises colloidal silica, silica gel, precipitated silica, mesoporous silica, or fumed silica.

13. The dispersion of claim 10 wherein the insoluble particle comprises iron oxide coated with silica or iron oxide coated with polystyrene.

14. The dispersion of claim 13 wherein the responsive particles are separated under an applied magnetic field generated by a permanent magnet or an electromagnet.

15. The dispersion of claim 10 wherein the insoluble particle comprises carbonaceous material.

16. The dispersion of claim 10 wherein the synthetic polymer comprises poly(acrylonitrile butadiene styrene), cross-linked polyethylene, poly(ethylene vinyl acetate), poly(methyl methacrylate), polyamide, polybutylene, polybutylene terephthalate, polycarbonate, poly(ether ether ketone), polyester, polyethylene, poly(ethylene terephthalate), polyimide, poly(lactic acid), poly(oxymethylene), poly(phenyl ether), polypropylene, polystyrene, polysulfone, poly(tetrafluoroethylene), polyurethane, polyvinyl chloride, poly(vinylidene chloride), poly(styrene maleic anhydride), poly(styrene-acrylonitrile), cyanoacrylate resin, epoxy resin, phenol formaldehyde resin, urea formaldehyde resin, or silicone resin.

17. The dispersion of claim 16 wherein the synthetic polymer comprises polystyrene.

18. The dispersion of claim 10 wherein the natural polymer comprises cellulose, cellulose ethers, cellulose esters, chitin, poly(lactic acid), poly(3-hydroxybutyrate), or poly(hydroxyaIkanoate).

19. The dispersion of claim 18 wherein the natural polymer comprises cellulose, cellulose ether, or cellulose ester.

20. The dispersion of claim 2 wherein the surface functionality reversibly converts to its ionic state upon contact with a trigger in the presence of water.

21. The dispersion of claim 20 wherein the trigger comprises CO2, NO2, COS, or CS2.

22. The dispersion of claim 20 wherein the surface functionality comprises a nitrogen base wherein contact with the trigger in the presence of water protonates said nitrogen base.

23. The dispersion of claim 22 wherein the surface functionality, in its non-ionic state, comprises: an amidine, a guanidine, or a tertiary amine.

24. The dispersion of claim 22 wherein the surface functionality, in its ionic state, comprises:
an amidinium, a guanidinium, or a tertiary aminium.

25. The dispersion of claim 23 wherein the surface functionality has the following structure in its non-ionic state:
where ~ is surface the surface of the insoluble particle;
where R1 and R2 are independently:
H;
a substituted or unsubstituted C1 to C8 aliphatic group that is linear, branched, or cyclic, optionally wherein one or more C of the alkyl group is replaced by {¨Si(R10)2¨
O-} up to and including eight C being replaced by eight {¨Si(R10)2-O¨};
a substituted or unsubstituted C n Si m group where n and m are independently a number from 0 to 8 and n+m is a number from 1 to 8;
a substituted or unsubstituted C4 to C8 aryl group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by {¨Si(R10)2-O¨};
a substituted or unsubstituted aryl group having 4 to 8 ring atoms, optionally including one or more {¨Si(R10)2-O-}, wherein aryl is optionally heteroaryl;
a ¨(Si(R10)2-O)p¨ chain in which p is from 1 to 8 which is terminated by H, or is terminated by a substituted or unsubstituted C1 to C8 aliphatic and/or aryl group; or a substituted or unsubstituted (C1 to C8 aliphatic)-(C4 to C8 aryl) group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by a {¨Si(R10)2-O¨};
wherein R10 is a substituted or unsubstituted C1 to C8 aliphatic group, a substituted or unsubstituted C1 to C8 alkoxy, a substituted or unsubstituted C4 to C8 aryl wherein aryl is optionally heteroaryl, a substituted or unsubstituted aliphatic-alkoxy, a substituted or unsubstituted aliphatic-aryl, or a substituted or unsubstituted alkoxy-aryl group;
where E is:
a substituted or unsubstituted C1 to C8 aliphatic group that is linear, branched, or cyclic, optionally wherein one or more C of the alkyl group is replaced by {¨Si(R10)2-O¨} up to and including 8 C being replaced by 8 {¨Si(R10)2-O¨};
a substituted or unsubstituted C n Si m group where n and m are independently a number from 0 to 8 and n+m is a number from 1 to 8;
a substituted or unsubstituted C4 to C8 aryl group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by {¨Si(R10)2-O¨};
a substituted or unsubstituted aryl group having 4 to 8 ring atoms, optionally including one or more {¨Si(R10)2-O-}, wherein aryl is optionally heteroaryl;
a ¨(Si(R10)2-O)p¨ chain in which p is from 1 to 8; or a substituted or unsubstituted (C1 to C8 aliphatic)-(C4 to C8 aryl) group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by a {¨Si(R10)2-O¨}; and wherein R10 is a substituted or unsubstituted C1 to C8 aliphatic group, a substituted or unsubstituted C1 to C8 alkoxy, a substituted or unsubstituted C4 to C8 aryl wherein aryl is optionally heteroaryl, a substituted or unsubstituted aliphatic-alkoxy, a substituted or unsubstituted aliphatic-aryl, or a substituted or unsubstituted alkoxy-aryl group; and wherein a substituent is independently: alkyl; alkenyl; alkynyl; aryl; aryl-halide;
heteroaryl; cycloalkyl; Si(alkyl)3; Si(alkoxy)3; halo; alkoxyl; amino;
alkylamino;

alkenylamino; amide; hydroxyl; thioether; alkylcarbonyl; alkylcarbonyloxy;
arylcarbonyloxy; alkoxycarbonyloxy; aryloxycarbonyloxy; carbonate;
alkoxycarbonyl;
aminocarbonyl; alkylthiocarbonyl; amidine, phosphate; phosphate ester;
phosphonato;
phosphinato; cyano; acylamino; imino; sulfhydryl; alkylthio; arylthio;
thiocarboxylate;
dithiocarboxylate; sulfate; sulfato; sulfonate; sulfamoyl; sulfonamide; nitro;
nitrile; azido;
heterocyclyl; ether; ester; silicon-containing moieties; thioester; or a combination thereof.

26. The dispersion of claim 23 wherein the surface functionality has the following structure in its non-ionic state:
where ~ is the surface of the insoluble particle;
where R1 and R2 are independently:
H;
a substituted or unsubstituted C1 to C8 aliphatic group that is linear, branched, or cyclic, optionally wherein one or more C of the alkyl group is replaced by {¨Si(R10)2-O¨} up to and including eight C being replaced by eight {¨Si(R10)2-O¨};
a substituted or unsubstituted C n Si m group where n and m are independently a number from 0 to 8 and n+m is a number from 1 to 8;
a substituted or unsubstituted C4 to C8 aryl group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by {¨Si(R10)2-O¨};
a substituted or unsubstituted aryl group having 4 to 8 ring atoms, optionally including one or more {¨Si(R10)2-O¨}, wherein aryl is optionally heteroaryl;

a ¨(Si(R10)2-O)p¨ chain in which p is from 1 to 8 which is terminated by H, or is terminated by a substituted or unsubstituted C1 to C8 aliphatic and/or aryl group; or a substituted or unsubstituted (C1 to C8 aliphatic)-(C4 to C8 aryl) group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by a {¨Si(R10)2-O-};
wherein R10 is a substituted or unsubstituted C1 to C8 aliphatic group, a substituted or unsubstituted C1 to C8 alkoxy, a substituted or unsubstituted C4 to C8 aryl wherein aryl is optionally heteroaryl, a substituted or unsubstituted aliphatic-alkoxy, a substituted or unsubstituted aliphatic-aryl, or a substituted or unsubstituted alkoxy-aryl group;
where E is:
a substituted or unsubstituted C1 to C8 aliphatic group that is linear, branched, or cyclic, optionally wherein one or more C of the alkyl group is replaced by {¨Si(R10)2-O-} up to and including 8 C being replaced by 8 {¨Si(R10)2-O¨};
a substituted or unsubstituted C n Si m group where n and m are independently a number from 0 to 8 and n+m is a number from 1 to 8;
a substituted or unsubstituted C4 to C8 aryl group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by {¨Si(R10)2-O¨};
a substituted or unsubstituted aryl group having 4 to 8 ring atoms, optionally including one or more {¨Si(R10)2-O¨}, wherein aryl is optionally heteroaryl;
a ¨(Si(R10)2-O)p¨ chain in which p is from 1 to 8; or a substituted or unsubstituted (CI. to C8 aliphatic)-(C4 to C8 aryl) group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by a {¨Si(R10)2-O¨}; and wherein R10 is a substituted or unsubstituted C1 to C8 aliphatic group, a substituted or unsubstituted C1 to C8 alkoxy, a substituted or unsubstituted C4 to C8 aryl wherein aryl is optionally heteroaryl, a substituted or unsubstituted aliphatic-alkoxy, a substituted or unsubstituted aliphatic-aryl, or a substituted or unsubstituted alkoxy-aryl group; and wherein a substituent is independently: alkyl; alkenyl; alkynyl; aryl; aryl-halide;
heteroaryl; cycloalkyl; Si(alkyl)3; Si(alkoxy)3; halo; alkoxyl; amino;
alkylamino;
alkenylamino; amide; hydroxyl; thioether; alkylcarbonyl; alkylcarbonyloxy;
arylcarbonyloxy; aIkoxycarbonyloxy; aryloxycarbonyloxy; carbonate;
alkoxycarbonyl;
aminocarbonyl; alkylthiocarbonyl; amidine, phosphate; phosphate ester;
phosphonato;
phosphinato; cyano; acylamino; imino; sulfhydryl; alkylthio; arylthio;
thiocarboxylate;
dithiocarboxylate; sulfate; sulfato; sulfonate; sulfamoyl; sulfonamide; nitro;
nitrile; azido;
heterocyclyl; ether; ester; silicon-containing moieties; thioester; or a combination thereof.

27. The dispersion of claim 23 wherein the surface functionality has the following structure in its non-ionic state:
where ~ is the surface of the insoluble particle;
where R1 and R2 are independently:
H;
a substituted or unsubstituted C1 to C8 aliphatic group that is linear, branched, or cyclic, optionally wherein one or more C of the alkyl group is replaced by {¨Si(R10)2-O¨} up to and including eight C being replaced by eight {¨Si(R10)2-O--};
a substituted or unsubstituted C n Si m group where n and m are independently a number from 0 to 8 and n+m is a number from 1 to 8;

a substituted or unsubstituted C4 to C8 aryl group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by {¨Si(R12)-O¨};
a substituted or unsubstituted aryl group having 4 to 8 ring atoms, optionally including one or more {¨Si(R10)2-O¨}, wherein aryl is optionally heteroaryl;
a --(Si(R10)2-O)p-- chain in which p is from 1 to 8 which is terminated by H, or is terminated by a substituted or unsubstituted C1 to C8 aliphatic and/or aryl group; or a substituted or unsubstituted (C1 to C8 aliphatic)-(C4 to C8 aryl) group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by a {¨Si(R10)2-O-};
wherein R10 is a substituted or unsubstituted C1 to C8 aliphatic group, a substituted or unsubstituted C1 to C8 alkoxy, a substituted or unsubstituted C4 to C8 aryl wherein aryl is optionally heteroaryl, a substituted or unsubstituted aliphatic-alkoxy, a substituted or unsubstituted aliphatic-aryl, or a substituted or unsubstituted alkoxy-aryl group;
where E is:
a substituted or unsubstituted C1 to C8 aliphatic group that is linear, branched, or cyclic, optionally wherein one or more C of the alkyl group is replaced by {¨Si(R10)2-O¨} up to and including 8 C being replaced by 8 {¨Si(R10)2-O¨};
a substituted or unsubstituted C n Si m group where n and m are independently a number from 0 to 8 and n+m is a number from 1 to 8;
a substituted or unsubstituted C4 to C8 aryl group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by {¨Si(R10)2-O¨};
a substituted or unsubstituted aryl group haying 4 to 8 ring atoms, optionally including one or more {¨Si(R10)2-O¨}, wherein aryl is optionally heteroaryl;
a ¨(Si(R10)2-O)p¨ chain in which p is from 1 to 8; or a substituted or unsubstituted (C1 to C8 aliphatic)-(C4 to C8 aryl) group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by a {-Si(R10)2-O-}; and wherein R10 is a substituted or unsubstituted C1 to C8 aliphatic group, a substituted or unsubstituted C1 to C8 alkoxy, a substituted or unsubstituted C4 to C8 aryl wherein aryl is optionally heteroaryl, a substituted or unsubstituted aliphatic-alkoxy, a substituted or unsubstituted aliphatic-aryl, or a substituted or unsubstituted alkoxy-aryl group; and wherein a substituent is independently: alkyl; alkenyl; alkynyl; aryl; aryl-halide;
heteroaryl; cycloalkyl; Si(alkyl)3; Si(alkoxy)3; halo; alkoxyl; amino;
alkylamino;
alkenylamino; amide; hydroxyl; thioether; alkylcarbonyl; alkylcarbonyloxy;
arylcarbonyloxy; alkoxycarbonyloxy; aryloxycarbonyloxy; carbonate;
alkoxycarbonyl;
aminocarbonyl; alkylthiocarbonyl; amidine, phosphate; phosphate ester;
phosphonato;
phosphinato; cyano; acylamino; imino; sulfhydryl; alkylthio; arylthio;
thiocarboxylate;
dithiocarboxylate; sulfate; sulfato; sulfonate; sulfamoyl; sulfonamide; nitro;
nitrile; azido;
heterocyclyl; ether; ester; silicon-containing moieties; thioester; or a combination thereof.

28. The dispersion of claim 22 wherein the surface functionality, in its non-ionic state, comprises:
where ~ is the surface of the insoluble particle; where y and z are independently between 0 and 12; and x is between 1 and 12.

29. The dispersion of claim 22 wherein the surface functionality, in its non-ionic state, comprises:
where ~ is the surface of the insoluble particle; where y and z are independently between 0 and 12; and x is between 1 and 12.

30. The dispersion of claim 22 wherein the surface functionality, in its non-ionic state, comprises:
where ~ is the surface of the insoluble particle; where y and z are independently between 0 and 12; and x is between 1 and 12.

31. The dispersion of claim 2 wherein the surface functionality reversibly converts to its non-ionic state upon contact with a trigger in the presence of water.

32. The dispersion of claim 31 wherein the trigger comprises CO2, NO2, COS, or CS2.

33. The dispersion of claim 31 wherein the surface functionality comprises an oxygen acid wherein contact with the trigger in the presence of water protonates said oxygen acid.

34. The dispersion of claim 33 wherein the surface functionality comprises, in its ionic state, a 2-nitro phenoxide.

35. The dispersion of claim 33 wherein the surface functionality comprises, in its non-ionic state, a 2-nitrophenol.

36. The dispersion of claim 34 wherein the surface functionality has the following structure, in its ionic state:
where ~ is the surface of the insoluble particle;
where Q is ¨OOC¨, ¨OC¨, ¨NOC¨, or ¨NHOC¨, where R1 and R4 are independently:
H; nitro; sulfo; ammonio; cyano; trihalomethyl; carbonyl; haloformyl; a substituted or unsubstituted C1 to C8 alkoxycarbonyl; a substituted or unsubstituted C1 to alkylformyl; formyl; halo; or a substituted or unsubstituted C1 to C8 carbamoyl; and where R2 and R3 are independently:
H; alkyl; alkenyl; aryl; amino; hydroxy; a substituted or unsubstituted C1 to alkylhydroxy; a substituted or unsubstituted C1 to C8 carboxyamido; or a substituted or unsubstituted C1 to C8 alkanyloxy;
wherein at least one or more of R1, R2, R3, and R4 is not H; and where E is:
a substituted or unsubstituted C1 to C8 alkoxycarbonyl;
or a substituted or unsubstituted C1 to C8 carbamoyl a substituted or unsubstituted C1 to C8 aliphatic group that is linear, branched, or cyclic, optionally wherein one or more C of the alkyl group is replaced by {¨
Si(R10)2¨O¨} up to and including 8 C being replaced by 8 {¨Si(R10)2-O¨};

a substituted or unsubstituted C n Si m group where n and m are independently a number from 0 to 8 and n+m is a number from 1 to 8;
a substituted or unsubstituted C4 to C8 aryl group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by {¨Si(R10)2-O¨};
a substituted or unsubstituted aryl group having 4 to 8 ring atoms, optionally including one or more {¨Si(R10)2-O¨}, wherein aryl is optionally heteroaryl;
a ¨(Si(R10)2-O)p¨ chain in which p is from 1 to 8; or a substituted or unsubstituted (C1 to C8 aliphatic)-(C4 to C8 aryl) group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by a {¨
Si(R10)2-O¨}; and wherein R10 is a substituted or unsubstituted C1 to C8 aliphatic group, a substituted or unsubstituted C1 to C8 alkoxy, a substituted or unsubstituted C4 to C8 aryl wherein aryl is optionally heteroaryl, a substituted or unsubstituted aliphatic-alkoxy, a substituted or unsubstituted aliphatic-aryl, or a substituted or unsubstituted alkoxy-aryl group; and wherein a substituent is independently: alkyl; alkenyl; alkynyl; aryl; aryl-halide;
heteroaryl; cycloalkyl; Si(alkyl)i; Si(alkoxy)i; halo; alkoxyl; amino;
alkylamino;
alkenylamino; amide; hydroxyl; thioether; alkylcarbonyl; alkylcarbonyloxy;
arylcarbonyloxy; alkoxycarbonyloxy; aryloxycarbonyloxy; carbonate;
alkoxycarbonyl;
aminocarbonyl; alkylthiocarbonyl; amidine, phosphate; phosphate ester;
phosphonato;
phosphinato; cyano; acylamino; imino; sulfhydryl; alkylthio; arylthio;
thiocarboxylate;
dithiocarboxylate; sulfate; sulfato; sulfonate; sulfamoyl; sulfonamide; nitro;
nitrile; azido;
heterocyclyl; ether; ester; silicon-containing moieties; thioester; or a combination thereof.

37. The dispersion of claim 34 wherein the surface functionality has the following structure, in its ionic state:

where ~ is the surface of the insoluble particle;
where R1 is:
H; nitro; sulfo; ammonio; cyano; trihalomethyl; carbonyl; haloformyl; a substituted or unsubstituted C1 to C8 alkoxycarbonyl; a substituted or unsubstituted C1 to alkylformyl; formyl; halo; or a substituted or unsubstituted C1 to C8 carbamoyl; and where R2 and R3 are independently:
H; alkyl; alkenyl; aryl; amino; hydroxy; a substituted or unsubstituted C1 to alkylhydroxy; a substituted or unsubstituted C1 to C8 carboxyamido; or a substituted or unsubstituted C1 to C8 alkanyloxy;
where E is:
a substituted or unsubstituted C1 to C8 alkoxycarbonyl;
a substituted or unsubstituted C1 to C8 carbamoyl;
a substituted or unsubstituted C1 to C8 aliphatic group that is linear, branched, or cyclic, optionally wherein one or more C of the alkyl group is replaced by {-Si(R10)2-O-} up to and including 8 C being replaced by 8 {-Si(R10)2-O-};
a substituted or unsubstituted C n Si m group where n and m are independently a number from 0 to 8 and n+m is a number from 1 to 8;
a substituted or unsubstituted C4 to C8 aryl group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by {-Si(R10)2-O-};
a substituted or unsubstituted aryl group having 4 to 8 ring atoms, optionally including one or more {-Si(R10)2-O-}, wherein aryl is optionally heteroaryl;

a -(Si(R10)2-O)p- chain in which p is from 1 to 8; or a substituted or unsubstituted (C1 to C8 aliphatic)-(C4 to C8 aryl) group wherein aryl is optionally heteroaryl, optionally wherein one or more C is replaced by a {-Si(R10)2-O-};
wherein R10 is a substituted or unsubstituted C1 to C8 aliphatic group, a substituted or unsubstituted C1 to C8 alkoxy, a substituted or unsubstituted C4 to C8 aryl wherein aryl is optionally heteroaryl, a substituted or unsubstituted aliphatic-alkoxy, a substituted or unsubstituted aliphatic-aryl, or a substituted or unsubstituted alkoxy-aryl group; and wherein a substituent is independently: alkyl; alkenyl; alkynyl; aryl; aryl-halide;
heteroaryl; cycloalkyl; Si(alkyl)3; Si(alkoxy)3; halo; alkoxyl; amino;
alkylamino;
alkenylamino; amide; hydroxyl; thioether; alkylcarbonyl; alkylcarbonyloxy;
arylcarbonyloxy; alkoxycarbonyloxy; aryloxycarbonyloxy; carbonate;
alkoxycarbonyl;
aminocarbonyl; alkylthiocarbonyl; amidine, phosphate; phosphate ester;
phosphonato;
phosphinato; cyano; acylamino; imino; sulfhydryl; alkylthio; arylthio;
thiocarboxylate;
dithiocarboxylate; sulfate; sulfato; sulfonate; sulfamoyl; sulfonamide; nitro;
nitrile; azido;
heterocyclyl; ether; ester; silicon-containing moieties; thioester; or a combination thereof.

38. The dispersion of claim 31 wherein the surface functionality has the following structure, in its ionic state:
where ~ is the surface of the insoluble particle; where y and z are independently between 0 and 12; and x is between 1 and 12.

39. The dispersion of claim 31 wherein the surface functionality has the following structure, in its ionic state:
where ~ is the surface of the insoluble particle; where y and z are independently between 0 and 12; and x is between 1 and 12.

40. A system comprising:
i. an aqueous dispersion comprising responsive particles with switchable surface charge;
ii. means for switching said responsive particles from ionic state to non-ionic state or from non-ionic state to ionic state; and wherein said aqueous dispersion has high ionic strength when the responsive particles are in ionic state and said aqueous dispersion has low ionic strength when the responsive particles are in non-ionic state.

41. The system of claim 40 wherein:
i. the responsive particles comprise: an insoluble particle and a surface functionality which is a base wherein addition of a trigger to the aqueous dispersion protonates said base; and ii. said aqueous dispersion has high ionic strength when said trigger is added to said aqueous dispersion and low ionic strength when said trigger is removed from the aqueous dispersion.

42. The system of claim 41 wherein:
i. means for switching the responsive particles from non-ionic state to ionic state comprises means for adding the trigger to the aqueous dispersion; and ii. means for switching said responsive particles from ionic state to non-ionic state comprises means for removing said trigger from said aqueous dispersion.

43. The system of claim 41 wherein the surface functionality comprises a nitrogen base.

44. The system of claim 42 wherein:
i. in non-ionic state, the surface functionality comprises: an amidine, a guanidine, or a tertiary amine; and ii. in ionic state, said surface functionality comprises: an amidinium, a guanidinium, or a tertiary aminium.

45. The system of claim 40 wherein:
i. the responsive particles comprise: an insoluble particle and a surface functionality which is an acid wherein addition of a trigger to the aqueous dispersion protonates said acid; and said aqueous dispersion has low ionic strength when said trigger is added to said aqueous dispersion and said aqueous dispersion has low ionic strength when said trigger is removed from said aqueous dispersion.

46. The system of claim 45 wherein:
means for switching the responsive particles from ionic state to non-ionic state comprises addition of a trigger to said aqueous dispersion; and means for switching said responsive particles from non-ionic state to ionic state comprises removal of said trigger to said aqueous dispersion.

47. The system of claim 45 wherein the surface functionality comprises an oxygen acid.

48. The system of claim 47 wherein:
in ionic state, the surface functionality comprises 2-nitrophenoxide; and in non-ionic state, said surface functionality comprises 2-nitrophenol.

49. The system of claim 41 or claim 45 wherein the trigger comprises CO2, NO2, COS, or CS2.

50. The system of claim 49 wherein means for adding the trigger to the aqueous dispersion comprises: bubbling said trigger into said aqueous dispersion, adding a trigger solution saturated with said trigger, mixing said aqueous dispersion under said trigger, or combinations thereof.

51. The system of claim 49 wherein means for removing the trigger from the aqueous dispersion comprises: heating said aqueous dispersion, sparing said aqueous dispersion with a flushing gas, exposing said aqueous dispersion to vacuum or partial vacuum, agitating said aqueous dispersion, sonicating said aqueous dispersion, or combinations thereof.

52. The system of claim 51, wherein the flushing gas comprises: air, N2, or other gas with low concentration of CO2, NO2, COS, and CS2.

53. The system of claim 40 further comprising means for separating the responsive particles with switchable surface charge from the aqueous dispersion.

54. The system of claim 53 wherein means for separating the responsive particles with switchable surface charge from the aqueous dispersion comprises:
sedimentation, centrifugation, flotation, gravity filtration, vacuum filtration, or combinations thereof.

55. The system of claim 53 wherein the responsive particles with switchable surface charge are magnetically susceptible and means for separating said responsive particles comprises: a permanent magnet, an electromagnet, or a high-gradient magnetic separator.

56. The system of claim 53 wherein the responsive particles with switchable surface charge are in ionic state and means for separating said responsive particles comprises an electric field.

57. A system for modulating the electrochemical gradient across a membrane comprising:
i. an aqueous dispersion comprising responsive particles with switchable surface charge;
ii. means for contacting a feed solution with said membrane;
iii. means for switching the surface charge of said responsive particles from non-ionic state to ionic state; and iv. means for switching the surface charge of said responsive particles from ionic state to non-ionic state.

58. The system of claim 57 wherein the membrane pore size is smaller than the size of the responsive particles.

59. The system of claim 57 wherein the aqueous dispersion is located on one side of the membrane and the feed solution is on the opposing side of said membrane.

60. The system of claim 57, further comprising a receiving solution;
wherein:
i. the aqueous dispersion is located on one side of the membrane and the feed solution is on the same side of said membrane; and ii. said receiving solution is located on the opposing side of said membrane.

61. The system of claim 57 wherein the responsive particles comprise an insoluble particle and a surface functionality which is a base and wherein:
i. means for switching the responsive particles from non-ionic state to ionic state comprises addition of a trigger; and ii. means for switching the responsive particles from ionic state to non-ionic state comprises removal of said trigger.

62. The system of claim 61 wherein the surface functionality comprises a nitrogen base wherein contact with the trigger in the presence of water protonates said nitrogen base.

63. The system of claim 62 wherein:
i. in non-ionic state, the surface functionality comprises: an amidine, a guanidine, or a tertiary amine; and, ii. in ionic state, said surface functionality comprises: an amidinium, a guanidium, or a tertiary aminium.

64. The system of claim 57 wherein the responsive particles comprise an insoluble particle and a surface functionality which is an acid and wherein:
i. means for switching the responsive particles from ionic state to non-ionic state comprises addition of a trigger; and ii. means for switching the responsive particles from non-ionic state to ionic state comprises removal of said trigger.

65. The system of claim 64 wherein the surface functionality comprises an oxygen acid wherein contact with the trigger in the presence of water protonates said oxygen acid.

66. The system of claim 65 wherein:
i. in ionic state, the surface functionality comprises 2-nitrophenoxide; and, ii. in non-ionic state, said surface functionality comprises 2-nitrophenol.

67. The system of claim 61 and claim 64 wherein the trigger comprises CO2, NO2, COS, or CS2.

68. The system of claim 67 wherein means for adding the trigger to the aqueous dispersion comprises: bubbling said trigger into said aqueous dispersion, adding a trigger solution saturated with said trigger, mixing said aqueous dispersion under said trigger, or combinations thereof.

69. The system of claim 67 wherein means for removing the trigger from the aqueous dispersion comprises: heating said aqueous dispersion, sparing said aqueous dispersion with a flushing gas, exposing said aqueous dispersion to vacuum or partial vacuum, agitating said aqueous dispersion, sonicating said aqueous dispersion, or combinations thereof.

70. The system of claim 69 wherein the flushing gas comprises: air, N2, or other gas with low concentration of CO2, NO2, COS, and CS2.

71. The system of claim 57 further comprising means for separating the responsive particles with switchable surface charge from the aqueous dispersion.

72. The system of claim 71 wherein means for separating the responsive particles with switchable surface charge comprises: sedimentation, centrifugation, flotation, gravity filtration, vacuum filtration, or combinations thereof.

73. The system of claim 71 wherein the responsive particles with switchable surface charge are magnetically susceptible and means for separating said responsive particles comprises: a permanent magnet, an electromagnet, or a high-gradient magnetic separator.

74. The system of claim 71 wherein the responsive particles with switchable surface charge are in ionic state and means for separating said responsive particles comprises an electric field.

75. The system of claim 57 for use in reducing or increasing the ionic strength of an aqueous solution wherein the feed solution comprises water, dissolved species, and dispersed solids.

76. The system of claim 75 for use in treating industrial process water.

77. The system of claim 57 for use in reducing or increasing the concentration of multivalent ions in an aqueous solution wherein the feed solution comprises water, dissolved species, and dispersed solids.

78. The system of claim 77 for use in treating bituminous sand extraction tailings.

79. A system for modulating the osmotic gradient across a membrane, comprising:
i. an aqueous dispersion comprising responsive particles with switchable surface charge;
ii. means for contacting a feed solution with said membrane;
iii. means for switching the surface charge of said responsive particles from its non-ionic state to its ionic state; and iv. means for switching the surface charge of said responsive particles from its ionic state to its non-ionic state;
wherein means for switching the surface charge of said responsive particles with switchable surface charge from non-ionic state to ionic state raises the ionic strength of said aqueous dispersion above the ionic strength of said feed solution.

80. The system of claim 79 wherein the membrane is selectively permeable for water.

81. The system of claim 79 wherein:
i. the aqueous dispersion is located on one side of the membrane and the feed solution is on the opposing side of said membrane; and ii. wherein means for contacting said feed solution with said membrane permits water from said feed solution to permeate through said membrane into said aqueous dispersion comprising responsive particles with switchable surface charge along the osmotic gradient generated by the difference in ionic strength between said feed solution and said aqueous dispersion when said responsive particles with switchable surface charge are in its ionic state.

82. The system of claim 79 further comprising an exchange solution;
i. wherein both the aqueous dispersion and the feed solution are on one side of the membrane while said exchange solution is located on the opposing side of said membrane; and ii. wherein means for contacting said feed solution with said membrane permits flow of water from said exchange solution through said membrane into said feed solution and said aqueous dispersion comprising responsive particles with switchable surface charge along the osmotic gradient generated by the difference in ionic strength between said feed solution and said draw medium when said responsive particles with switchable surface charge are in its ionic state.

83. The system of claim 79 wherein the responsive particles comprise an insoluble particle and a surface functionality which is a base and wherein:

i. means for switching said responsive particles from non-ionic state to ionic state comprises addition of a trigger; and ii. means for switching said responsive particles from ionic state to non-ionic state comprises removal of said trigger.

84. The system of claim 83 wherein the surface functionality comprises a nitrogen base wherein contact with the trigger in the presence of water protonates said nitrogen base.

85. The system of claim 84 wherein:
i. in non-ionic state, the surface functionality comprises: an amidine, a guanidine, or a tertiary amine; and, ii. in ionic state, said surface functionality comprises: an amidinium, a guanidinium, or a tertiary aminium.

86. The system of claim 79 wherein the responsive particles comprise an insoluble particle and a surface functionality which is an acid and wherein:
i. means for switching the responsive particles from ionic state to non-ionic state comprises addition of a trigger; and ii. means for switching said responsive particles from non-ionic state to ionic state comprises removal of said trigger.

87. The system of claim 83 wherein the surface functionality comprises an oxygen acid wherein contact with the trigger in the presence of water protonates said oxygen acid.

88. The system of claim 84 wherein:
i. in its ionic state, the surface functionality comprises a 2-nitrophenoxide; and, ii. in its non-ionic state, said surface functionality comprises a 2-nitrophenol.

89. The system of claim 83 and claim 86 wherein the trigger comprises CO2, NO2, COS, or CS2.

90. The system of claim 89 wherein means for adding the trigger to the aqueous dispersion comprises: bubbling said trigger into said aqueous dispersion, adding a trigger solution saturated with said trigger, mixing said aqueous dispersion under said trigger, or combinations thereof.

91. The system of claim 89 wherein means for removing the trigger from the aqueous dispersion comprises: heating said aqueous dispersion, sparing said aqueous dispersion with a flushing gas, exposing said aqueous dispersion to vacuum or partial vacuum, agitating said aqueous dispersion, sonicating said aqueous dispersion, or combinations thereof.

92. The system of claim 91 wherein the flushing gas comprises: air, N2, or other gas with low concentration of CO2, NO2, COS, and CS2.

93. The system of claim 79 further comprising means for separating the responsive particles with switchable surface charge from the aqueous dispersion.

94. The system of claim 93 wherein means for separating the responsive particles comprises:
sedimentation, centrifugation, flotation, gravity filtration, vacuum filtration, or combinations thereof.

95. The system of claim 93 wherein the responsive particles are magnetically susceptible and means for separating said responsive particles with switchable surface charge comprises:
a permanent magnet, an electromagnet, or a high-gradient magnetic separator.

96. The system of claim 93 wherein the responsive particles with switchable surface charge are in ionic state and means for separating said responsive particles with switchable surface charge comprises: an electric field.

97. The system of claim 79 wherein the feed solution comprises: water, dissolved species, or dispersed solids.

98. The system of claim 97 wherein the feed solution is brackish water, saline water, or brine water.

99. The system of claim 98 wherein the feed solution is seawater, industrial wastewater, or runoff water.

100. The system of claim 79 for water treatment.

101. The system of claim 79 for desalination.

102. The system of claim 79 for selective separation of water.

103. A method for modulating an osmotic gradient or an electrochemical gradient across a membrane comprising:
a. providing an aqueous dispersion comprising responsive particles with switchable surface charge on one side of said membrane;
b. providing a solution on the opposing side of said membrane; and c. switching the surface charge of said responsive particles from non-ionic state to ionic state or switching the surface charge of said responsive particles from ionic state to non-ionic state.

104. The method of claim 103 wherein the aqueous dispersion has a greater electrolytic conductivity than the solution and said aqueous dispersion has a lower electrolytic conductivity when said responsive particles are in non-ionic state.

105. The method of claim 103 wherein the aqueous dispersion has a greater ionic strength than the solution when said responsive particles are in ionic state and said aqueous dispersion has a lower ionic strength when said responsive particles are in non-ionic state.

106. The method of claim 103 wherein the membrane pore size is smaller than the responsive particles.

107. The method of claim 106 wherein the membrane is selectively permeable for water.

108. The method of claim 103 wherein the responsive particles comprise an insoluble particle and a surface functionality which is a base and wherein:
i. switching said responsive particles from non-ionic state to ionic state comprises addition of a trigger; and ii. switching said responsive particles from ionic state to non-ionic state comprises removal of said trigger.

109. The method of claim 108 wherein the surface functionality comprises a nitrogen base wherein contact with the trigger in the presence of water protonates said nitrogen base.

110. The method of claim 109 wherein:
i. in non-ionic state, the surface functionality comprises an amidine, a guanidine, or a tertiary amine; and, ii. in ionic state, said surface functionality comprises an amidinium, a guanidinium, or a tertiary aminium.

111. The method of claim 103 wherein the responsive particles comprise an insoluble particle and a surface functionality which is an acid and wherein:
i. switching said responsive particles from ionic state to non-ionic state comprises addition of a trigger; and ii. switching said responsive particles from non-ionic state to ionic state comprises removal of said trigger.

112. The method of claim 111 wherein the surface functionality comprises an oxygen acid wherein contact with the trigger in the presence of water protonates said oxygen acid.

113. The method of claim 112 wherein:
i. in its ionic state, the surface functionality comprises a 2-nitrophenoxide.
ii. in its non-ionic state, said surface functionality comprises a 2-nitrophenol.

114. The method of claim 108 and claim 111 wherein the trigger comprises CO2, NO2, COS, or CS2.

115. The method of claim 114 wherein addition of the trigger to the aqueous dispersion comprises: bubbling said trigger into said aqueous dispersion, adding a trigger solution saturated with said trigger, mixing said aqueous dispersion under said trigger, or combinations thereof.

116. The method of claim 114 wherein removal of the trigger from the aqueous dispersion comprises: heating said aqueous dispersion, sparing said aqueous dispersion with a flushing gas, exposing said aqueous dispersion to vacuum or partial vacuum, agitating said aqueous dispersion, sonicating said aqueous dispersion, or combinations thereof.

117. The method of claim 116 wherein the flushing gas comprises: air, N2, or other gas with low concentration of CO2, NO2, COS, and CS2.

118. The method of claim 103 further comprising:
d. separating the responsive particles with switchable surface charge from the aqueous dispersion.

119. The method of claim 118 wherein separating the responsive particles with switchable surface charge comprises: sedimentation, centrifugation, flotation, gravity filtration, vacuum filtration, or combinations thereof.

120. The method of claim 118 wherein the responsive particles with switchable surface charge are magnetically susceptible and separating said responsive particles with switchable surface charge comprises: a permanent magnet, an electromagnet, or a high-gradient magnetic separator.

121. The method of claim 118 wherein the responsive particles with switchable surface charge are in ionic state and separating said responsive particles with switchable surface charge comprises: an electric field.

122. The method of claim 103 for concentrating an aqueous solution wherein the solution comprises water and dissolved species.

123. The method of claim 103 for concentrating an aqueous suspension wherein the solution comprises water and dispersed solids.

124. The method of claim 103 for desalinating water.

125. The method of claim 103 for treating industrial process water.