WO2015143163A1 - Coalescing a discontinuous oleophilic phase in aqueous mixtures with zwiterionic particles - Google Patents

Abstract

Described herein is a device for coalescing a discontinuous oleophilic phase from an aqueous mixture, the device comprising: a vessel adapted to support upward flow of the aqueous mixture, the vessel having an upper portion comprising a retaining means adapted to retain a coalescing media within the vessel while allowing liquids to pass through; and the coalescing media retained within the vessel, the coalescing media comprising a plurality of buoyant surface-modified inorganic particles wherein at least a portion of the surface of each inorganic particle comprises an organic moiety, wherein upward flow of the aqueous mixture will cause the coalescing media to form a predominantly stationary self-assembled packed bed against the retaining means.

Description

COALESCING A DISCONTINUOUS OLEOPHILIC PHASE IN AQUEOUS MIXTURES WITH ZWITERIONIC PARTICLES

TECHNICAL FIELD

[0001] An device for coalescing a discontinuous oleophilic phase from an aqueous mixture is described along with methods thereof.

BACKGROUND

[0002] An oleophilic phase dispersed in an aqueous phase can be found in the waste streams from a number of different processes, including treatment of produced water from conventional oil production, separation of hydrocarbon/complexing agent in water emulsions in hydrometallurgy applications, treatment of industrial wastewater containing oil wastes, and treatment of food processing wastewater. Conventional treatments for these types of waste streams involve a primary density-driven operation (e.g., corrugated plate interceptors, desanding hydrocyclones, deoiling hydro cyclones) to remove the bulk oleophilic phase, large droplets of the dispersed oleophilic phase, and bulk solids; secondary operations such as flotation (e.g., induced gas flotation, dissolved gas/air flotation) to remove smaller droplets of the dispersed oleophilic phase; and tertiary operations (e.g., walnut shell filters) to polish the aqueous phase.

SUMMARY

[0003] There is a desire for effective and robust processes for removal of a discontinuous oleophilic phase from an aqueous mixture in high flux applications. In one embodiment, the method enables reduced operating cost, improved tolerance for upsets in process fluid concentration and composition, and/or a reduced footprint and weight.

[0004] In one aspect, a device for coalescing a discontinuous oleophilic phase from an aqueous mixture is provided, the device comprising:

a vessel adapted to support upward flow of the aqueous mixture, the vessel having an upper portion comprising a retaining means adapted to retain a coalescing media within the vessel while allowing liquids to pass through; and the coalescing media retained within the vessel, the coalescing media comprising a plurality of buoyant surface-modified inorganic particles wherein at least a portion of the surface of each inorganic particle comprises an organic moiety, wherein upward flow of the aqueous mixture will cause the coalescing media to form a predominantly stationary self-assembled packed bed against the retaining means.

[0005] In another aspect, a method of coalescing a discontinuous oleophilic phase of an aqueous mixture is provided, comprising:

providing the coalescing device as described above; and

delivering the aqueous mixture to the coalescing device.

[0006] In yet another aspect, an oleophilic liquid coalescing device is provided comprising a packed bed for coalescing an oleophilic phase, the bed comprising a plurality of buoyant surface-modified inorganic particles wherein at least a portion of the surface of each inorganic particle comprises an organic compound.

[0007] The above summary is not intended to describe each embodiment. The details of one or more embodiments of the invention are also set forth in the description below. Other features, objects, and advantages will be apparent from the description and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In the accompanying drawing:

[0009] Fig. 1 is a perspective view of vessel 10; and

[0010] Fig. 2 is the particle size analysis of Field Sample 2 and effluent from Example 7.

DETAILED DESCRIPTION

[0011] Definitions

[0012] As used herein, the term

"a", "an", and "the" are used interchangeably and mean one or more; and

"and/or" is used to indicate one or both stated cases may occur, for example A and/or B includes, (A and B) and (A or B).

[0013] As used herein, the term "organic group" means a hydrocarbon group (with optional elements other than carbon and hydrogen, such as oxygen, nitrogen, sulfur, and silicon) that is classified as an aliphatic group, cyclic group, or combination of aliphatic and cyclic groups (e.g., alkaryl and aralkyl groups). The term "aliphatic group" means a saturated or unsaturated linear or branched hydrocarbon group. This term is used to encompass alkyl, alkenyl, and alkynyl groups, for example. The term "alkynyl group" means an unsaturated, linear or branched hydrocarbon group with one or more carbon- carbon triple bonds. The term "cyclic group" means a closed ring hydrocarbon group that is classified as an alicyclic group, aromatic group, or heterocyclic group. The term "alicyclic group" means a cyclic hydrocarbon group having properties resembling those of aliphatic groups. The term "aromatic group" or "aryl group" means a mono- or polynuclear aromatic hydrocarbon group. The term "heterocyclic group" means a closed ring hydrocarbon in which one or more of the atoms in the ring is an element other than carbon (e.g., nitrogen, oxygen, sulfur, etc.). A group that may be the same or different is referred to as being "independently" something.

[0014] The term "alkyl" refers to a monovalent group that is a radical of an alkane and includes groups that are linear, branched, cyclic, bi cyclic, or a combination thereof. In some embodiments, the alkyl groups contain 1 to 20 carbon atoms, 1 to 10 carbon atoms, 1 to 6 carbon atoms, 1 to 4 carbon atoms, or 1 to 3 carbon atoms. Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, n-butyl, n-pentyl, isobutyl, t-butyl, isopropyl, n-octyl, n-heptyl, ethylhexyl, cyclopentyl, cyclohexyl, cycloheptyl, adamantyl, norbornyl, and the like.

[0015] The term "alkylene" refers to a divalent group that is a radical of an alkane and includes groups that are linear, branched, cyclic, bicyclic, or a combination thereof. Unless otherwise indicated, the alkylene group typically has 1 to 30 carbon atoms. In some embodiments, the al kylene group has 1 to 20 carbon atoms, 1 to 10 carbon atoms, I to 6 carbon atoms, or 1 to 4 carbon atoms. Examples of alkylene groups include, but are not limited to, methylene, ethylene, 1 ,3-propylene, 1 ,2-propylene, 1 ,4-butylene, 1 ,4- cyclohexylene, and 1 ,4-cyclohexyldimethylene.

[0016] The term "alkoxy" refers to a monovalent group having an oxy group bonded directly to an alkyl group.

[0017] The term "aryl" refers to a monovalent group that is aromatic and, optionally, carbocyclic. The aryl has at least one aromatic ring. Any additional rings can be unsaturated, partially saturated, saturated, or aromatic. Optionally, the aromatic ring can have one or more additional carbocyclic rings that are fused to the aromatic ring. Unless otherwise indicated, the aryl groups typically contain from 6 to 30 carbon atoms. In some embodiments, the aryl groups contain 6 to 20, 6 to 18, 6 to 16, 6 to 12, or 6 to 10 carbon atoms. Examples of an aryl group include phenyl, naphthyl, biphenyl, phenanthryl, and anthracyl.

[0018] The term "aryiene" refers to a divalent group that is aromatic and, optionally, carbocyclic. The arylene has at least one aromatic ring. Any additional rings can be unsaturated, partially saturated, or saturated. Optionally, an aromatic ring can have one or more additional carbocyclic rings that are fused to the aromatic ring. Unless otherwise indicated, aryiene groups often have 6 to 20 carbon atoms, 6 to 18 carbon atoms, 6 to 16 carbon atoms, 6 to 12 carbon atoms, or 6 to 10 carbon atoms.

[0019] The term "aralkyl" refers to a monovalent group that is an alkyl group substituted with an aryl group (e.g., as in a benzyl group). The term "alkaryl" refers to a monovalent group that is an aryl substituted with an alkyl group (e.g., as in a tolyi group). Unless otherwise indicated, for both groups, the alkyl portion often has 1 to 10 carbon atoms, 1 to 6 carbon atoms, or 1 to 4 carbon atoms and an aryl portion often has 6 to 20 carbon atoms, 6 to 18 carbon atoms, 6 to 16 carbon atoms, 6 to 12 carbon atoms, or 6 to 10 carbon atoms.

[0020] The term "aralkylene" refers to a divalent group that is an alkylene group substituted with an aryl group or an alkylene group attached to an arylene group. The term "alkarylene" refers to a divalent group that is an arylene group substituted with an alkyl group or an arylene group attached to an alkylene group. Unless otherwise indicated, for both groups, the alkyl or alkylene portion typically has from 1 to 20 carbon atoms, 1 to 10 carbon atoms, 1 to 6 carbon atoms, or 1 to 4 carbon atoms. Unless otherwise indicated, for both groups, the aryl or arylene portion typically has from 6 to 20 carbon atoms, 6 to 18 carbon atoms, 6 to 16 carbon atoms, 6 to 12 carbon atoms, or 6 to 10 carbon atoms.

[0021] The term "perfiuorinated alkyl group" or "perfluoroalkyl group" refers to an alkane group having all C-H bonds replaced with C-F bonds.

[0022] The term "silyl" refers to a monovalent group of formula -Si(R^c)j where R^c is a hydrolyzable group or a non-hydrolyzable group. In many embodiments, the silyl group is a "hydrolyzable silyl." group, which means that the silyl group contains at least, one R° group that is a hydrolyzable group.

[0023] The term "hydrolyzable group" refers to a group that can react with water having a pH of 1 to 10 under conditions of atmospheric pressure. The hydrolyzable group is often converted to a hydroxy! group when it reacts. The hydroxyl group often undergoes further reactions. Typical hydrolyzable groups include, but are not limited to, alkoxy, aryloxy, araikyloxy, alkaryloxy, acyloxy, or halo. As used herein, the term is often used in reference to one of more groups bonded to a silicon atom in a silyl group.

[0024] The term "non-hydrolyzable group" refers to a group that cannot react with water having a pH of 1 to 10 under conditions of atmospheric pressure. Typical non- hydrolyzable groups include, but are not limited to, a!ky!, aryi, aralkyl, and alkary!. As used herein, the term is often used in reference to one or more groups bonded to a silicon atom in a silyl group.

[0025] The term "alkoxy" refers to a monovalent group having an oxy group bonded directly to an alkyl group.

[0026] The term "aryloxy" refers to a monovalent group having an oxy group bonded directly to an aryi group.

[0027] The terms "araikyloxy" and "alkaryloxy" refer to a monovalent group having an oxy group bonded directly to an aralkyl group or an alkaryl group, respectively.

[0028] The term "acyloxy" refers to a monovalent group of the formula -0(CO)R^tJ where R^b is alkyl, aryi, aralkyl, or alkaryl. Suitable alkyl R^b groups often have 1 to 10 carbon atoms, 1 to 6 carbon atoms, or 1 to 4 carbon atoms. Suitable aryi R^tJ groups often have 6 to 12 carbon atoms such as, for example, phenyl. Suitable aralkyl and alkaryl R^b groups often have an alkyl group with 1 to 10 carbon atoms, 1 to 6 carbon atoms, or 1 to 4 carbon atoms and an aryi having 6 to 12 carbon atoms.

[0029] The term "halo" refers to a halogen atom such as fluoro, bromo, iodo, or chloro. When part of a reactive silyl, the halo group is often chloro.

[0030] The term "reactive group" refers to a functionality that will react with itself and/or another molecule (e.g., through polymerizing or crosslinking) to form a polymeric network. Such group can also be referred to as a "polymerizable group." The polymerizable group often includes a group that can undergo a free radical reaction such as an ethylenically unsaturated group. Alternatively, the polymerizable group can undergo a hydrolysis and/or condensation reaction. Such polymerizable groups include hydrolyzable silyl groups. Additionally, the term "reactive group" refers to a first group that can react with a second group on the surface of an inorganic particle to attach the first group to inorganic particle though the formation of a covalent bond. Such group can also be referred to as a "substrate-reactive group." The substrate-reactive group typically includes a hydro lyzable silyl group.

[0031] The term "(meth)acryloyloxy group" includes an acryloyloxy group (-O-(CO)- CH=CH₂) and a methacryloyloxy group (-0-(CO)-C(CH₃)=CH₂).

[0032] The term "(meth)acryloylamino group" includes an acryloylamino group (-NR- (CO)-CH=CH₂) and a methacryloylamino group (-NR-(CO)-C(CH₃)=CH₂) including embodiments wherein the amide nitrogen is bonded to a hydrogen, methyl group, or ethyl group (R is H, methyl, or ethyl).

[0033] The term "brush copolymer" refers to a copolymer where at least one of the repeat units is derived from a macromonomer. Macromonomers are polymeric chains (typically, with at least 10 repeat units) that have a polymerizable group (e.g., an ethylenically unsaturated group) at one end.

[0034] Substitution is anticipated on the organic groups of the complexes of the present disclosure. As a means of simplifying the discussion and recitation of certain terminology used throughout this application, the terms "group" and "moiety" are used to differentiate between chemical species that allow for substitution or that may be substituted and those that do not allow or may not be so substituted. Thus, when the term "group" is used to describe a chemical substituent, the described chemical material includes the unsubstituted group and that group with O, N, Si, or S atoms, for example, in the chain (as in an alkoxy group) as well as carbonyl groups or other conventional substitution. Where the term "moiety" is used to describe a chemical compound or substituent, only an unsubstituted chemical material is intended to be included. For example, the phrase "alkyl group" is intended to include not only pure open chain saturated hydrocarbon alkyl substituents, such as methyl, ethyl, propyl, t-butyl, and the like, but also alkyl substituents bearing further substituents known in the art, such as hydroxy, alkoxy, alkylsulfonyl, halogen atoms, cyano, nitro, amino, carboxyl, etc. Thus, "alkyl group" includes ether groups, haloalkyls, nitroalkyls, carboxyalkyls, hydroxy alky Is, sulfoalkyls, etc. On the other hand, the phrase "alkyl moiety" is limited to the inclusion of only pure open chain saturated hydrocarbon alkyl substituents, such as methyl, ethyl, propyl, t-butyl, and the like.

[0035] As used herein, "hydrophilic surface" is used to refer to a surface on which drops of water or aqueous solutions exhibit a static water contact angle of less than 90°. [0036] As used herein, "oleophilic surface" is used to refer to a surface on which drops of hydrocarbon solutions (e.g., oil) exhibit a static contact angle of less than 90°.

[0037] Also herein, recitation of ranges by endpoints includes all numbers subsumed within that range (e.g., 1 to 10 includes 1.4, 1.9, 2.33, 5.75, 9.98, etc.).

[0038] Also herein, recitation of "at least one" includes all numbers of one and greater

(e.g., at least 2, at least 4, at least 6, at least 8, at least 10, at least 25, at least 50, at least

100, etc.).

[0039] Discontinuous Oleophilic Coalescence and/or Removal

[0040] Removal of a discontinuous oleophilic phase (e.g., oil) from a waste stream comprising an aqueous continuous phase may be necessary for reuse of the aqueous phase and/or release of the stream into a sewage treatment plant or the environment. If a substantial fraction of the oleophilic phase in a waste stream consists of large droplets, or may be coagulated or flocculated into large droplets via chemical treatment, conventional gravitational settling devices and/or hydrocyclones are employed. Gravitational settling devices tend to effectively separate droplets larger than 50-100 microns. Gravitational settling devices are governed by Stokes' Law, which states that the velocity of a droplet rising through a fluid is directly proportional to the square of the radius of the droplet and to the difference in density between the droplet and the continuous phase, and inversely proportional to the viscosity of the continuous phase. These density-driven techniques are effective as long as among other things, there is a sufficiently large density difference between the phases, the droplets are of sufficiently large size, and there is sufficient residence time in the vessel. However, residence time determines the effectiveness of these apparatuses, and required residence time increases with the square of the droplet radius. As a result, when handling small diameter droplets, these apparatuses can become prohibitively large and heavy. Hydrocyclones rely on centripetal forces and tend to be used for removal of droplets with diameters of 10-20 microns and up, depending on the waste stream and vessel design. Hydrocyclones require a much smaller footprint than a gravitational setting device, but also require that the waste stream (or process liquid) be delivered at certain flow rates and pressures. Variability in flow rate and/or pressure affects the efficiency of the apparatus. Flotation devices can be used to remove smaller droplet sizes down to about 5 microns in diameter with appropriate chemical additions (or flocculants), and down to about 25 microns without the use of flocculants. Commercial flotation units are available which generate either large bubbles or small bubbles. The large bubble units have a large footprint, while the small bubble units are higher in removal efficiency, but also more expensive. Compact flotation units that combine the mechanisms of bubble interception and centripetal forces have much smaller footprints, but sacrifice efficiency. Variability in the feed, flow rate and chemical dosage can affect the efficiency of these apparatuses. Nutshell filters can be used to capture fine droplets with diameters of 1-5 microns in the interstitial spaces of the depth filter, however, these filters can become overwhelmed when used with waste streams comprising large oleophilic droplet sizes. Additionally, these filter units require frequent high pressure backwash operation to fluidize the bed and remove material trapped in the interstitial spaces in the bed and in the cake.

[0041] In the present disclosure a novel coalescing technique is described, wherein buoyant particles coalesce a discontinuous oleophilic phase, which can then be more easily retrieved and/or removed from an aqueous phase. Ideally, the present invention could be utilized for removal of large, small, and/or fine oleophilic droplets.

[0042] Use of coalescing technology to treat aqueous waste streams is known. For example, U.S. Pat. No. 3,231,091 (Kingsbury et al.) discloses separating viscous oil from ballast water on ships using a particular wire mesh and G.B. Pat. No. 2083370 (Sakai) discloses an apparatus for oil-water separation using a polymeric gel which is water insoluble and oil-repelling to coalesce the dispersed oil.

[0043] In the present disclosure, buoyant particles form a media bed in which, prior to flooding of the vessel chamber, the majority of the buoyant particles float above the surface of the process liquid. The process liquid is pumped into the bottom of a vessel chamber and flows vertically upward through the media bed, which self-assembles into a packed structure against a constraining screen. As the process liquid passes through the media bed, the discontinuous oleophilic phase coalesces within the media bed, forming larger droplets. The effluent containing the larger droplets can then optionally, be collected and separated in any density-driven separation process known to those skilled in the art (e.g. settling tank).

[0044] Process liquid

[0045] The process liquid of the present disclosure is a mixture comprising at least a continuous predominantly aqueous phase and a discontinuous oleophilic phase. As used herein predominantly aqueous refers to a solution comprising water , but may also comprise small amounts of organic solvents that have miscibility with water such as alcohols, benzene, toluene, ethylbenzene and xylene, and other volatile compounds, so long as there are two phases (the continuous aqueous phase and a discontinuous oleophilic phase) present in the process liquid. As used herein an oleophilic phase refers to a substance that is hydrophobic and lipophilic, and commonly hydrocarbon in composition. This phase may comprise saturates (which are largely saturated hydrocarbons), aromatics, resins, and/or asphaltenes. The mixture may also comprise solids, surfactants, salts, metal ions, biological species, and organic solvents miscible with water.

[0046] The oleophilic phase is discontinuous in the mixture, comprising small droplets having a first average diameter. Exemplary first average diameters include at least 1, 5, or even 10 μιη (micrometers); and at most 25, 30, 40 or even 50 μιη. Upon interaction with the media bed of the present disclosure, the discontinuous oleophilic phase coalesces, forming droplets having second average diameter. The second average diameter is larger than the first average diameter. In one embodiment, the second average diameter is at least 1.5, 2, 4, or even 10 times larger than the first average diameter. Exemplary second average diameters include at least 100 μιη, 200 μιη, 400 μιη, or even 500 μιη; and at most 750 μιη, 1000 μιη, 3000 μιη, or even 5000 μιη, or more. The average diameter can be determined using any particle size technique known in the art, including for example, laser diffraction particle size distribution.

[0047] Set-up

[0048] In one embodiment, the buoyant media particles are confined within a vessel. One exemplary vessel is depicted in Fig. 1, which is used for illustrative purposes and is not drawn to scale. Vessel 10 comprises inlet port 12 and outlet port 14. The ports may or may not comprise a valve for directing liquid flow. There is an upper retaining means 16 located in the upper portion of the vessel and optional lower retaining means 18. The vessel may optionally comprise drain valve 17, which is typically closed during use and is used for example for sludge removal. During use, process liquid is moved from inlet port 12 into the vessel. Fluid flows through media bed 20 and then out of the vessel via outlet port 14. In one embodiment, during cleaning, drain valve 17 is opened and fluid is moved in the reverse direction at a sufficiently high flowrate to disrupt the packing of the bed, entering via the outlet port 14, passing through the buoyant media and out the drain valve 17.

[0049] The vessel shape and size is not particularly limiting, however, the vessel should be large enough to handle the desired volume of liquid to be treated. Exemplary volume sizes may include laboratory bench scale (as small as 50 mL) and industrial scale (as large as 25 to 100 cubic meters or even larger).

[0050] The location of the inlet port and outlet port and optional drain valve are not particularly limited so long as the inlet port and outlet port are fluidly connected with the buoyant particles therebetween during use. In one embodiment, the inlet port is positioned between the lowest point of the vessel and the upstream face of the media bed, while the outlet port is positioned above the retaining means. In one example, the inlet port may be located at the lowest point of the vessel and the outlet port may be located on the side of the vessel.

[0051] The retaining means are foraminous materials having holes (or openings) smaller than the diameter of the buoyant particles, confining the buoyant particles, while allowing unencumbered fluid flow out of the vessel. The upper retaining means 16 is located in the upper portion of the vessel, ideally near the outlet port of the vessel. Upper retaining means 16 is used to confine media bed 20, preventing the buoyant particles from flowing out the vessel through outlet port 14 during use. Lower retaining means 18, is optional and could be used, for example, to confine the buoyant particles during backwashing of the media bed, preventing the buoyant particles from being flushed out through drain valve 17. Such retaining means spans the interior of the vessel and can include, for example, a screen, a frit, nonwoven, or other foraminous material. The foraminous materials may have openings having a smallest open span of at least 10 μιη, 15 μιη, 20 μιη, 30 μιη, 40 μιη, or even 50 μιη; and at most 100 μιη, 150 μιη, 250 μιη, 500 μιη, 1000 μιη, 1500 μιη, 1700 μιη, 2500 μιη, or even 5000 μιη, or even more.

[0052] Particles

[0053] The media bed of the present disclosure is formed by buoyant particles. In other words, the particles have a density less than that of the continuous phase of the process liquid (or mixture). The density of the particles is less than 0.9, 0.8, 0.7, 0.6, 0.5, 0.2, or even 0.125 g/cc (grams/cubic centimeter); and no greater than 1 g/cc. It is advantageous that the buoyant particles have a density which is at least 5%, 10%, 20%, or even 30%> less than the density of the continuous phase, such that the particles are sufficiently buoyant to rise rapidly in the quiescent continuous aqueous phase. For any particular mixture and process, it may be desirable to tailor the buoyancy of the particles to control the rate of sloughing from the upstream surface if there are cake-forming solids present in the mixture.

[0054] The particles of the media bed comprise inorganic particles. The inorganic particles comprise metal oxides. Such metal oxides include, for example, silicon dioxide (silica), zirconia, titania, ceria, alumina, iron oxide, zinc oxide, vanadia, antimony oxide, and tin oxide. Although the metal oxide may be essentially pure, it may contain small amounts of stabilizing ion such as ammonium and alkaline metal ions, or it may be a combination of metal oxides such as a combination of titania and silica. In one embodiment, the inorganic particles may comprise other inorganic salts such as calcium carbonate. Because of the surface-modification chemistries disclosed herein, in one embodiment, the inorganic particles of the present disclosure comprise silicon dioxide (silica).

[0055] In one embodiment, the inorganic particle comprises a hollow core, for example, a glass bubble or a ceramic bubble.

[0056] The inorganic particles used in the present disclosure can comprise any known shape including oblate-shaped, flake-shaped or irregular. However, it is preferable that the inorganic particles comprise a spherical or substantially spherical shape (i.e., sphericity of at least 0.9), which assists in packing of the particles and reducing the incidence of channeling in the media bed.

[0057] The inorganic particles have an average diameter of the particle of at least 15 μιη (microns), 25 μιη, 50 μιη, 75 μιη, 100 μιη, or even 150 μιη; at most about 300 μιη, 500 μιη, 1000 μιη, 2 mm, 3 mm, or even 5 mm (millimeters) depending on the inorganic particle used. For the purposes of the present disclosure, the average diameter can be measured using a technique known in the art including laser diffraction particle size distribution or calibrated microscopy.

[0058] In one embodiment, the inorganic particles have a size distribution of diameters. The inorganic particles of the present disclosure may comprise a unimodal or multimodal (e.g., bimodal) size distribution. [0059] The inorganic particle is modified or coated with an organic compound to provide different surface properties to the inorganic particle to assist in improved coalescing of a discontinuous oleophilic phase. In one embodiment, the surface of the inorganic nanoparticle is irreversibly associated (e.g., is covalently-bonded) with an organic compound.

[0060] Generally the inorganic particles are reacted, such that at least 2%, 5%, 10%, 20%, 25%o, 50%o, 75%), or even 100% of the surface of the inorganic particle is modified. In one embodiment at least a monolayer of the organic compound is bonded to the inorganic particle surface through siloxane bonds. As used herein, "at least a monolayer of an organic compound" includes a monolayer or a thicker layer of molecules, covalently bonded (through siloxane bonds, Si-O-Si) to the surface of an inorganic particle.

[0061] In one embodiment, the organically-surface-modified inorganic particles are hydrophilic and preferably water-wet. Although not wanting to be bound by theory, it is believed that a hydrophilic surface retains a layer of bound water molecules when immersed in water or exposed to suitable humidity levels. This layer of bound water acts as a lubricant, and prevents strong adhesion of the oleophilic layer to the surface of the buoyant particle. Hydrophilic buoyant particle surfaces exhibit resistance to fouling when exposed to an aqueous solution comprising an oleophilic phase, and can be readily cleaned without damage to the substrate should fouling occur.

[0062] A water-wet surface is a surface preferentially wet by water rather than by the oleophilic phase. More precisely, a surface treatment that is applied to a surface of constant cross-sectional perimeter and area and that is water-wet exhibits positive advancing and receding adhesion tensions when that surface is introduced to and removed from an oil-water interface on a Wilhelmy plate balance. Adhesion tension is defined by the Young equation: Adhesion Tension = ywo cos Θ = ysw - yso, where ywo is the interfacial tension between the aqueous and oleophilic phases, ysw is the interfacial tension between the solid and the aqueous phase, yso is the interfacial tension between the solid and the oleophilic phase, and Θ is the contact angle of wetting. A preferred surface or surface treatment of these buoyant media, when evaluated in a format compatible with Wilhelmy measurement (e.g. on a plate, fiber or sphere of identical chemical composition as the substrate and surface treatment of the buoyant particles), will exhibit positive advancing and receding adhesion tensions in this test when it is introduced to the Wilhelmy plate measurement either from a dry state or if it is introduced to the test after being allowed to come to an equilibrium state of hydration by preconditioning with water exposure. For a given combination of oleophilic phase and aqueous phase composition, preferred values of advancing and receding adhesion tensions are greater than 0 dynes/cm, more preferably greater than 10 dynes/cm, 20 dynes/cm, 30 dynes/cm and most preferably greater than 40 dynes/cm.

[0063] In one embodiment, the inorganic particle may be modified with an amphiphilic modification, and/or a zwitterionic modification onto the surface of the inorganic particle.

[0064] Zwitterionic

[0065] In one embodiment, the surface of the inorganic particle is modified with a sulfonate-functional coating composition, wherein the sulfonate-functional coating composition includes a zwitterionic compound having sulfonate-functional groups and alkoxysilane groups and/or silanol-functional groups. The zwitterionic compounds used in the modification of the inorganic particles have the following Formula (I) wherein:

(R¹0)p-Si(R²)_q-W-N⁺(R³)(R⁴)-(CH₂)m-S03- (I)

wherein:

each R¹ is independently a hydrogen, methyl group, or ethyl group;

each R² is independently a methyl group or an ethyl group;

each R³ and R⁴ is independently a saturated or unsaturated, straight chain, branched, or cyclic organic group, which may be joined together, optionally with atoms of the group W, to form a ring;

W is an organic linking group;

p and m are integers of 1 to 3;

q is 0 or 1 ; and

p+q=3.

[0066] The organic linking group W of Formula (I) is preferably selected from saturated or unsaturated, straight chain, branched, or cyclic organic groups. The linking group W is preferably an alkylene group, which may include carbonyl groups, urethane groups, urea groups, heteroatoms such as oxygen, nitrogen, and sulfur, and combinations thereof. Examples of suitable linking groups W include alkylene groups, cycloalkylene groups, alkyl-substituted cycloalkylene groups, hydroxy-substituted alkylene groups, hydroxy- substituted mono-oxa alkylene groups, divalent hydrocarbon groups having mono-oxa backbone substitution, divalent hydrocarbon groups having mono-thia backbone substitution, divalent hydrocarbon groups having monooxo-thia backbone substitution, divalent hydrocarbon groups having dioxo-thia backbone substitution, arylene groups, arylalkylene groups, alkylarylene groups and substituted alkylarylene groups.

[0067] Suitable examples of zwitterionic compounds of Formula (I) are described in U.S. Patent No. 5,936,703 (Miyazaki et al.) and International Publication Nos. WO 2007/146680 and WO 2009/119690, and include the following zwitterionic functional groups (-W-N⁺(R³)(R⁴)-(CH₂)m-S03 ):

Su^oa sy lm¾s»sl^m sat®

S«?fe¾lk 1 ammomum sals

[0068] In certain embodiments, the zwitterionic compounds have the following Formula (II) wherein:

(R¹0)p-Si(R²)_q-CH₂CH₂CH₂-N⁺(CH3)₂-(CH₂)m-S03- (Π)

wherein:

each R¹ is independently a hydrogen, methyl group, or ethyl group; each R² is independently a methyl group or an ethyl group;

p and m are integers of 1 to 3;

q is 0 or 1 ; and

p+q=3.

[0069] Suitable examples of zwitterionic compounds of Formula (II) are described in U.S.

Patent No. 5,936,703 (Miyazaki et al), including, for example:

(CH30)3Si-CH₂CH2CH2-N⁺(CH3)2-CH2CH2CH₂-S03-; and

(CH3CH20)2Si(CH3)-CH2CH2CH2-N⁺(CH3)2-CH2CH₂CH2-S03-.

[0070] Other examples of suitable zwitterionic compounds, which can be used to modify the inorganic particles include the following:

[0071] U.S. Pat. App. No. 2012-0273000, herein incorporated by reference, discloses such zwitterionic compounds and chemistries disclosed above. [0072] Amphiphilic

[0073] In another embodiment, the surface of the inorganic particle is modified with a reactive polyoxazoline (POx) having a perfluorinated alkyl group to generate amphiphilic coatings. The polyoxazo lines are employed as the hydrophilic component, and a perfluorinated alkyl group is employed as the hydrophobic component.

[0074] An exemplary polymerizable or substrate -reactive polyoxazoline includes:

[0075] where R¹ is selected from H, an alkyl group, an aryl group, and combinations thereof. For example, R¹ is a (Cl-C20)alkyl group (such as methyl and ethyl), a (C6- C12)aryl group, a (C6-C12)ar(Cl-C20)alkyl group, or a (Cl-C20)alk(C6-C12)aryl group.

[0076] R² is R^f-Y-(CH₂)x- where Y is selected from a bond, -S(0)₂-N(CH₃)-, -S(0)₂- N(CH₂CH₃)-, -S(0)₂-0- -S(0)₂- -C(O)-, -C(0)-S- -C(0)-0- -C(0)-NH- -C(O)- N(CH₃)-, -C(0)-N(CH₂CH₃) -, -(CH₂CH₂0)_y-, -0-, and -0-C(0)-CH=CH-C(0)-0-. In certain embodiments, Y is selected from a bond, -S(0)₂-N(CH₃)-, -C(0)-NH-, and - (CH₂CH₂0)x-. In certain embodiments, x is an integer from 2 to 20. In certain embodiments, x is 2 to 10. In certain embodiments, x is 2 to 6. In certain embodiments, R^f is a perfluorinated alkyl group. In certain embodiments, R^f is a perfluorinated (Cl- C5)alkyl group. In certain embodiments, R^f is a perfluorinated C4 alkyl group.

[0077] In certain embodiments, n is an integer of greater than 10. In certain embodiments, n is no greater than 500. In certain embodiments, n is 20 to 100.

[0078] R³ is a reactive group (e.g., a polymerizable group and/or a substrate-reactive group). For example, a polymerizable group such as an ethylenically unsaturated group selected from a vinyl group, a vinylether group, a (meth)acryloyloxy group, and a (meth)acryloylamino group (including embodiments wherein the nitrogen is optionally substituted with methyl or ethyl). For example a substrate -reactive group such as an organic group containing a hydrolyzable silyl group that provides functionality for bonding to a inorganic particle surface. In one embodiment R³ is selected from a (meth)acryloyloxy group, a (meth)acryloylamino group, a trialkoxysilylalkylthio group, and a trialkyoxysilylalkylamino group. [0079] In one embodiment R³ is of the formula -W-Si(R⁹)₃ wherein W is an organic group and each R⁹ group is independently selected from an alkyl group, an aryl group, or a combination thereof (an alkaryl group or an aralkyl group) and a hydrolyzable group; and at least one R⁹ is a hydrolyzable group. In certain embodiments, the hydrolyzable group is selected from a halo, an alkoxy group, and an acyloxy group. In certain embodiments, the hydrolyzable group is selected from a halo, a (Cl-C4)alkoxy group, and a (Cl-C4)acyloxy group. In certain embodiments, all three R⁹ groups are hydrolyzable groups. In certain embodiments, all three R⁹ groups are the same.

[0080] In certain embodiments, W is selected from an alkylene group, an arylene group, and a combination thereof (i.e., an alkarylene group or an aralkylene group), optionally including -0-, -C(O)-, -NR-, -S-, or a combination thereof, wherein R is H, methyl, or ethyl. Such optional group is typically not directly bonded to the silyl group. In certain embodiments, W is selected from a (Cl-C20)alkylene group, a (C6-C12)arylene group, and combination thereof, optionally including -0-, -C(O)-, -NR-, -S-, or a combination thereof. For example, W can be of the divalent group of formula -N(R)-R⁷- or -S-R⁸- where R⁷ and R⁸ are each an alkylene group and R is H, methyl, or ethyl.

[0081] Examples of substrate -reactive groups include trialkoxysilylalkylamino (including embodiments wherein the nitrogen is optionally substituted with methyl or ethyl) and trialkoxysilylalkylthio. Such groups are not only substrate-reactive but may also be polymerizable and form a network.

[0082] In certain embodiments, the trialkoxysilylalkylamino group is of the formula -N(R)-R⁷-Si(OR⁴)(OR⁵)(OR⁶), wherein R is H, methyl, or ethyl, and each R⁴, R⁵, and R⁶ is an alkyl group, and R⁷ is an alkylene group. In certain embodiments, the trialkoxysilylalkylamino group is of the formula -N(R)-CH₂CH₂CH₂-Si(OR⁴)(OR⁵)(OR⁶), wherein R is H, methyl, or ethyl, and each R⁴, R⁵, and R⁶ is an alkyl group, preferably methyl or ethyl.

[0083] In certain embodiments, the trialkoxysilylalkylthio group is of the formula

-S-R⁸-Si(OR⁴)(OR⁵)(OR⁶), wherein each R⁴, R⁵, and R⁶ is an alkyl group, and R⁸ is an alkylene group. In certain embodiments, the trialkoxysilylalkylthio is of the formula -S- CH₂CH₂CH₂-Si(OR⁴)(OR⁵)(OR⁶), wherein R is H, methyl, or ethyl, and each R⁴, R⁵, and R⁶ is an alkyl group, preferably methyl or ethyl. [0084] In certain embodiments, y is an integer equal to at least 1. In certain embodiments, y is no greater than 20. In certain embodiments, y is 1 to 5.

[0085] In some embodiments, the inorganic particle is selected to have a group that can react with the polyoxazoline. For example, the particle can have a glass or ceramic- containing surface that has silanol groups that can undergo a condensation reaction with group R³ selected from a trialkoxysilylalkylthio or a trialkoxysilylamino group. The product of this reaction results in the formation of a -Si-O-Si- bond between the polyoxazoline and the substrate. Further discussion of the surface modification can be found in U.S. Prov. Appl. No. 61/739150 filed 19 Dec 2012, herein incorporated by reference.

[0086] In one embodiment, the inorganic particles are first reacted with a surface reactive group which can then be surface modified with an oxazoline, particularly a 2-oxazoline that includes an R¹ group at the 2-position. The oxazoline is subjected to a ring opening reaction in a suitable solvent (e.g., acetonitrile) in the presence of an initiator (e.g., methyl trifluoromethansulfonate (i.e., methyl triflate), perfluorobutyl ethylene triflate, perfluorobutyl sulfonamide triflate, methyl toluene sulfonate (i.e., methyl tosylate), and methyl iodide) with heating (e.g., at a temperature of 80 °C), and subsequently modified to include a polymerizable group (e.g., upon reaction with (meth)acrylic acid in the presence of a base (e.g., triethylamine)).

[0087] In one embodiment, the surface modification is derived from a copolymer derived from a monomer mixture comprising monomers having the formulas:

(A) (B) wherein:

Q is O or N;

R¹⁰ is H or CHs;

R¹¹ is an organic group comprising a hydrolyzable silyl group; R¹² is H or CH₃; and

P is:

wherein:

R¹ is selected from H, an alkyl group, an aryl group, and a combination thereof;

R² is selected from an alkyl group, an aryl group, a combination thereof, and a R^f-Y-(CH2)x- group;

R^f is a perfluorinated alkyl group;

Y is selected from a bond, -S(0)₂-N(CH₃)-, -S(0)₂-N(CH₂CH₃)-, -S(0)₂-0-, -S(0)₂- -C(O)-, -C(0)-S-, -C(0)-0- -C(0)-NH-, -C(0)-N(CH₃)-, -C(0)-N(CH₂CH₃)-, -(CH₂CH₂0)_y-, -0-, and

-0-C(0)-CH=CH-C(0)-0-;

n is an integer of greater than 2;

x is an integer of at least 2; and

y is an integer of at least 1.

[0088] R¹¹ is -Z-Si(R¹³) each R¹³ group is independently a hydrolyzable group or a non- hydrolyzable group (e.g., an alkyl group, an aryl group, or a combination thereof (i.e., an alkaryl group or an aralkyl group)). In certain embodiments, each R¹³ is independently selected from an alkyl group, an aryl group, a combination thereof, and a hydrolyzable group; and at least one R¹³ is a hydrolyzable group. In certain embodiments, the hydrolyzable group is selected from a halo, an alkoxy group, and an acyloxy group. In certain embodiments, the hydrolyzable group is selected from a halo, a (Cl-C4)alkoxy group, and a (Cl-C4)acyloxy group.

[0089] In certain embodiments, Z is selected from an alkylene group, an arylene group, and a combination thereof (i.e., an alkarylene group or an aralkylene group), optionally including -0-, -C(O)-, -NR- (wherein R can be H, methyl, or ethyl, and is typically, H), -S-, or a combination thereof, within the chain. In this context, "within" means that such atoms or groups are not directly bonded to the silyl group or the -C(0)Q- group. In certain embodiments, Z is selected from a (Cl-C20)alkylene group, a (C6-C12)arylene group, and a combination thereof, optionally including -0-, -C(O)-, -NR- (wherein R can be H, methyl, or ethyl, and is typically, H), -S-, or a combination thereof, within the chain.

[0090] In certain embodiments, R¹ is selected from H, an alkyl group, an aryl group, and combinations thereof. In certain embodiments, R¹ is H, a (Cl-C20)alkyl group, a (C6- C12)aryl group, a (C6-C12)ar(Cl-C20)alkyl group, or a (Cl-C20)alk(C6-C12)aryl group. In certain embodiments, R¹ is selected from H, methyl, and ethyl.

[0091] In certain embodiments, R2 is selected from an alkyl group, an aryl group, and a R^f-Y-(CH2)x- group. In certain embodiments, R² is a R^f-Y-(CH₂)x- group.

[0092] In certain embodiments, Y is selected from a bond, -S(0)₂-N(CH3)-,

-S(0)₂-N(CH₂CH₃)-, -S(0)₂-0-, -S(0)₂- -C(O)-, -C(0)-S- -C(0)-0- -C(0)-NH- -C(0)-N(CH₃)-, -C(0)-N(CH₂CH₃)-, -(CH₂CH₂0)y-, -0-, and -0-C(0)-CH=CH- C(0)-0- In certain embodiments, Y is selected from a bond, -S(0)₂-N(CH₃)-, -C(O)-

[0093] In certain embodiments, R^f is a perfluorinated alkyl group. In certain embodiments, R^f is a perfluorinated (Cl-C8)alkyl group. In certain embodiments, R^f is a perfluorinated (Cl-C5)alkyl group or a perfluorinated (Cl-C4)alkyl group. In certain embodiments, R^f is a perfluorinated C4 alkyl group.

[0094] In certain embodiments, n is an integer of greater than 2. In certain embodiments, n is greater than 10. In certain embodiments, n is at least 20. In certain embodiments, n is no greater than 500. In certain embodiments, n is no greater than 100. In certain embodiments, n is 20 to 100.

[0095] In certain embodiments, x is an integer of at least 2. In certain embodiments, x is no greater than 20. In certain embodiments x is no greater than 10. In certain embodiments, x is no greater than 6.

[0096] In certain embodiments, y is an integer of at least 1. In certain embodiments, y is no greater than 20. In certain embodiments, y is no greater than 5.

[0097] Such amphiphilic surface modification is disclosed in U.S. Prov. Appl. No. 61/739162. Filed 19 Dec 2012, herein incorporated by reference.

[0098] Preparation of Modified Inorganic Particles [0099] The inorganic particles can be modified with the above-mentioned organic compounds by preparing a solution of the organic compound, using for example, water, alcohol, or another solvent and optionally, additional additives to, for example, adjust the pH or facilitate adhesion to the surface or durability of the coating as needed. The inorganic particle can be coated by or immersed in the solution and then dried. Typically, the modified particles are baked at temperatures of 20 °C to 150 °C in a recirculating oven. Optionally, an inert gas may be circulated. The temperature may be increased to speed the drying process, but care must be exercised to avoid damage to the inorganic particles.

[00100] In another embodiment, the inorganic particle may first be coated or reacted with a bonding or adhesion layer comprising a polymerizable group and optionally a substrate-reactive group, and subsequently reacted with a hydrophilic, ampiphilic and/or zwitterionic organic compound comprising a polymerizable group. For example, in one embodiment, the inorganic particle could first be functionalized with a coupling agent comprising both a polymerizable group and a substrate -reactive group, such as a silane coupling agent as known in the art, e.g., methacryloxypropyl trimethoxy silane. After treatment with the coupling agent, the treated particles could then be combined with or coated with, for example, a hydrophilic, ampiphilic and/or zwitterionic organic compound comprising a polymerizable group and an appropriate initiator for covalent grafting via thermal or actinic reaction, yielding a buoyant surface-modified particle.

[00101] Method

[00102] In the present disclosure, the buoyant particles are placed within the vessel and a process fluid is delivered into the vessel, allowing the floating bed of buoyant particles to form and pack (e.g., randomly pack) as it is lifted by the rising meniscus of the process liquid. As the process liquid fills the vessel, the media bed is finally constrained against an upper retaining means, forming a packed media bed, which is predominantly stationary. Ideally, the buoyant particles have a density much lower than the density of the continuous phase, causing the buoyant particles to tightly pack against the upper retaining means. In one embodiment, the particles pack so tightly that upon draining of liquid from the vessel, the media bed stays in place against the upper retaining means.

[00103] As the process liquid continues to fill the vessel, the interstitial volume in the media bed floods with fluid until the media bed is fully wetted and filtrate exits the upper retaining means. In one embodiment, the media bed has a porosity of greater than 0 and no greater than 0.5, 0.45, 0.4, 0.38, or even 0.36.

[00104] As the process fluid flows vertically up through the media bed, the discontinuous oleophilic phase coalesces in the media bed and due to density differences and flow-driven transport fluid movement, rises to the top of the vessel, where it can exit the outlet as effluent.

[00105] Advantageously, if the process liquid comprises dirt or other particulates, these may, under their own weight, drop and settle to the bottom of the vessel and be drained via a drain valve.

[00106] In one embodiment, a procedure for backwashing can be used to aid in the lifetime of the media bed, by cleaning and/or refreshing the media bed. Backwashing of media beds is known in the art. Briefly, backwashing may consist of draining the sludge and some portion of the liquid from the bottom of the vessel, closing the drain valve, filling the vessel with clean water from the outlet port with a sufficient volumetric flow rate to dislodge the strata of the packed bed, allowing the bed to reform, and then repeating the procedure. Pressurized air may also be employed to further agitate the media to cause any bound oleophilic phase or debris to release from the surface of the media. Such backwashing techniques, and other types of backwashing techniques for cleaning media beds are known in the art.

[00107] In one embodiment, the vessel is coupled with a classic density-driven separation unit operation (e.g. a quiescent oil trap, a corrugated plate interceptor, a settling tank or a hydrocyclone) located downstream of the coalescing vessel to collect and concentrate the oleophilic droplets.

[00108] In one embodiment, it is envisioned that a treatment train comprising the present disclosure including multiple stages with decreasing media size could be implemented.

[00109] Although not wanting to be limited by theory it is believed, that there are four different mechanisms that govern how a droplet moves through and interacts with a buoyant particle media bed: inertia impaction, settling/buoyancy, interception and Brownian diffusion. For aqueous mixtures comprising small oleophilic droplets having only slight differences in density with the bulk aqueous phase moving at low flow velocities through a media bed, inertia impaction of the droplets with the media bed is negligible because the momentum associated with inertia is small. Increases in the size of the droplet, density difference with the bulk phase, or flow velocity increase the likelihood of inertia impaction. The settling/buoyancy mechanism refers to the gravitational sedimentation of droplets denser than the bulk aqueous phase or buoyancy of the droplets lighter than the bulk aqueous phase. Droplets with a density greater or lighter than the bulk aqueous phase tend to deviate from fluid streamlines due to the gravitational force or buoyancy force. If the deviation of the droplet is sufficient enough to intercept a surface of a buoyant particle in the residence time that it takes for the droplet to traverse any given volume element of the bed, then a coalescence event may occur. The gravitational force or buoyancy force decreases with the decreasing square of the radius of the droplet, so this mechanism reduces in importance as droplets get smaller. Droplets smaller than those in the size regime where the settling/buoyancy mechanism dominates, but larger than the range where Brownian motion dominates tend to be swept through the bed on streamlines. Larger droplets in this regime may largely remain in their streamlines, yet may intercept the walls or boundary layers of the buoyant media, which may promote a coalescence event. Smaller droplets in this regime may not be intercepted by either following streamline or Brownian diffusion, therefore such droplets may have a low chance of experiencing a coalescence. Colloidal (sub-micron) particles exhibit diffusion due to Brownian motion, and the likelihood of a given droplet finding a media particle surface in the residence time necessary to traverse any given volume element of the bed increases as the diameter of the colloidal particle decreases.

[00110] The four factors described above contribute additively to the removal efficiency of coalescence of a droplet of any given size. As a result, theory predicts that for an exemplary appropriately sized buoyant particle and a given media bed, removal efficiency may exhibit a minimum for droplet diameters near the boundary between the Brownian motion and interception regimes and may asymptotically approach 100% removal efficiency for larger droplet diameters. In actual operation, coalescence may depend on the droplet size distribution within the bulk aqueous phase. A threshold cut-off diameter may be defined such that a majority of the droplets have diameters larger than this threshold in the process liquid. The efficiency of a media bed comprising the buoyant particles disclosed herein can be tailored by the threshold cut-off diameter that is selected. [00111] The buoyant media bed has several factors that can be controlled to achieve a target threshold cut-off diameter at a particular efficiency. These factors include: the droplet size distribution in the feed, the pressure drop allowable across the bed, the flowrate or flux, the bed depth, porosity of the media bed, and average diameter and size distribution of the buoyant particles of the media bed. A target threshold cut-off diameter may be defined by first inspecting the feed droplet distribution. A typical real-life constraint may be the allowable total oil and grease concentration in the effluent from the process, and by inspecting the droplet size distribution of the feed, it is possible to determine what threshold cut-off diameter might be specified in order to coalesce sufficient oleophilic droplets to meet that total oil and grease target. Once that threshold is identified, then other process constraints must be considered: allowable footprint, volumetric flowrate of process stream, and allowable pressure drop, among others. Each of the design factors then is optimized to best meet all process constraints.

[00112] Using this theory, a target cut-off threshold diameter can be determined and the particle size of the buoyant inorganic particle is selected to achieve efficient removal of the oleophilic phase. In one embodiment, the inorganic particles have an average diameter that is at least 1.5, 2, 5, 10, 20 or even 25 times larger and at most 50, 100, 150 or even 200 times larger than a target cut-off threshold diameter of the average diameter of the discontinuous oleophilic phase.

[00113] The depth of the media bed required is a function of the average diameter of the buoyant particles, the volumetric flow rate of the mixture through the media bed, the target threshold cut-off diameter for coalescence of oleophilic droplets, the targeted efficiency of that coalescence, and the allowable pressure drop across the media bed. These variables are not independent. To increase the efficiency of removal at a given threshold cut-off diameter, the media bed depth can be increased, the flow rate can be reduced, and/or the average diameter of the buoyant particle can be reduced. Pressure drop is directly proportional to media bed depth and the square of fluid velocity.

[00114] Regarding the surface modification of the inorganic particles, although not wanting to be limited by theory, it is believed that when inorganic particles comprise an ampiphilic surface modification, the surface comprises mixed domains of hydrophilic and microscopic oleophobic regions. Upon contact, an oleophilic droplet can adhere to an oleophilic domain of the modified inorganic particle but has poor or no adhesion with the surrounding hydrophilic areas. Consequently, as more oleophilic droplets coalesce with the initial droplet, it is believed that area of "pinning" associated with the attachment site on the oleophilic domain limits the force of adhesion between the droplet and the surface, and this in turn limits the amount of shear force that the coalesced droplet can withstand before the enlarged oleophilic droplet is swept away by the flow of the bulk mixture. Oleophilic droplets of sufficient size also experience shear and are impeded by interactions with the media interfaces as they move through the packed bed and pass through the narrow interstitial pores of the media bed. This shear deforms the interface of the oleophilic droplet. When two oleophilic droplets interact when the interface is sufficiently deformed, coalescence can occur.

[00115] Although not wanting to be limited by theory, it is believed that when inorganic particles comprise a zwitterionic surface modification, there is a hydrated surface which prevents the oleophilic droplets from strongly adhering to the modified inorganic particle. In this embodiment, the coalescence does not rely on wetting any substantial area of the media with the oleophilic phase. The coalescence in this case is predominantly a result of deformation of oleophilic droplets due to imposed shear in the interstitial pores and collisions between deformed droplets due to the impeding of the upward velocity of droplets as they encounter and penetrate into the bed.

[00116] Advantageously, the present disclosure enables a reduced weight compared to for example hematite media (e.g. density of less thanl g/cc compared to as much as 5 g/cc for hematite media). Further, low pressure regeneration cycles can be used because the media bed does not require fluidization of a bed of dense media. There is potentially a reduced footprint because the requirement for high backwash fluidization pressure does not constrain the bed depth. Further, there is improved mechanical durability because calcined inorganic material (e.g. glass or ceramic) will be amorphous and roughly spherical. Thus, these materials will have few to no crystal planes for fracture, and no "lever arm" for other particles in the bed to torque that might aid fracture. This process is inherently a density-driven mechanism for separation of many types of debris as well as coalescence of an oleophilic phase. Many types of debris are typically more dense than both the buoyant media and the continuous phase. As a result, cake formation, and associated increase in pressure drop, are significantly retarded because solids that might otherwise be prone to cake formation slough off the upstream face as sludge. When the oleophilic phase has entrained dense solids, the oleophilic phase can be trapped in that sludge. Because the bottom of the media bed is the upstream face, advantages, including higher flux and improved tolerance for upsets (e.g., presence of solids) that might occur during use may be realized.

[00117] In some embodiments, the buoyant particles having an organically- modified surface using the chemistries disclosed herein may show reduced biofilm formation for certain organisms, which can be advantageous when used for coalescing the discontinuous oleophilic phase from a variety of wastewater applications.

[00118] In one embodiment, an article for coalescing a discontinuous oleophilic phase of a mixture is described, wherein the article comprises a vessel having an inlet port, an outlet port, and a media bed formed by buoyant particles having a density less than the mixture and the article has the capability to coalesce an oleophilic phase.

[00119] The method of the present disclosure can be used, for example in treatment of produced water from conventional oil production, separation of hydrocarbon/complexing agent in water emulsions in hydrometallurgy applications, treatment of industrial wastewater containing oil wastes, and treatment of food processing wastewater.

EXAMPLES

[00120] Advantages and embodiments of this disclosure are further illustrated by the following examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this invention. In these examples, all percentages, proportions and ratios are by weight unless otherwise indicated.

[00121] All materials are commercially available, for example from Sigma-Aldrich

Chemical Company; Milwaukee, WI, or known to those skilled in the art unless otherwise stated or apparent.

[00122] These abbreviations are used in the following examples: g = gram, kg = kilogram, min = minute, mol = mole; cm = centimeter, mm = millimeter, ml = milliliter, L = liter, psi = pounds per square inch, and wt = weight. Raw Materials

[00123] Methods

[00124] Modification of Inorganic Particles

[00125] A 0.1% solution of an organo-silane compound in isopropyl alcohol was made using each of the organo-silanes disclosed in the Raw Materials table above. The inorganic particles were added to the 0.1% solution of an organo-silane compound to form a mixture. The mixture was shaken on a shaker overnight at room temperature. The mixture was filtered to collect the particles, which were then transferred to an aluminum pan and allowed to dry to visual dryness. The particles were then baked in an oven at 100 °C overnight. The particles were then removed from the oven and allowed to cool.

[00126] Modification of a Microscope Slide

[00127] A microscope slide was modified as follows: A microscope slide (2 inches x 3 inches, Corning Plain Microscope Slides, VWR Scientific Inc., Brisbane, CA, USA) was immersed in a 0.1% solution of an organo-silane compound in isopropyl alcohol and allowed to soak overnight. The microscope slide was removed from the solution and baked in an oven at 100 °C overnight. The microscope slide was removed from the oven and allowed to cool.

[00128] Plastic Vessel Method: A housing (Polyclear II, F-40C Beach Filter Products, Inc., Glen Rock, PA) was disassembled and the Clyform P/N EL40 media pack for compressed air & gas was removed. The housing then was custom-modified with a 60- mesh 304 stainless steel frit (McMaster-Carr, Elmhurst, Illinois ) at the outlet of the housing, and an optional 60-mesh 304 stainless steel frit (McMaster-Carr, Elmhurst, Illinois, if specified) was used at the inlet. The housing was operated so that the buoyant particles floated at the top of the housing, held in the housing by the mesh frit, and a surrogate solution (or process liquid) was delivered from the bottom of the housing. The inlet port was fluidly connected via #16 Viton tubing (Masterflex 96412-16, Cole-Parmer, Vernon Hills, Illinois) to a container containing the stirring surrogate solution. A peristaltic pump (available under the trade designation "SCILOG FILTERTEC" normal flow filtration system, SciLog, Inc., Middleton, WI) was used to feed the surrogate solution from the container into the housing at a given flow rate. The specified buoyant particles were added to the housing to fill it halfway before sealing. Upon filling of the housing with the surrogate solution, the buoyant particles formed a media bed having a diameter of 47 mm and a height of about 3 inches (76 mm). The filtrate exited the media bed, then exited the outlet of the housing. The outlet was fluidly connected to a modified separatory funnel, which acted as an oil trap, collecting the coalesced oleophilic droplets at the top of the funnel, while the clarified water was sent to waste. Sample ports were available immediately after the housing outlet and after the oil trap for collection of sample (typically 25 ml.) A pressure transducer (SciPres, SciLog, Inc., Middleton, WI) was located upstream of the housing and was used to monitor the pressure of the system during use.

[00129] Glass Vessel Method: A custom-designed glass housing consisting of an upper section and a lower section connected by clamped flanges and a gasket was prepared. The upper section had a removable cap with an exit port into which a 60-mesh 304 stainless steel frit (McMaster-Carr, Elmhurst, Illinois) was fitted. Beneath the cap, the upper section consisted of a vertical cylindrical tube with a 27 mm inner diameter which flared at the top end to accommodate said cap and at the bottom end to accommodate the flange. The lower section of the glass vessel consisted of a flanged, 6 inch tall vessel with an inlet port on the side and a drain valve at the bottom. The housing was operated so that the buoyant particles floated at the top of the housing, held in the housing by the mesh frit. A surrogate solution (or process liquid) was delivered from the inlet port in the lower section of the glass vessel. The inlet port was fluidly connected via tubing to container containing the stirring surrogate solution and a peristaltic pump (available under the trade designation "SCILOG FILTERTEC", SciLog, Inc., Middleton, WI) was used to feed the surrogate solution into the housing at a given flow rate. The specified buoyant particles were added to the housing. Upon filling of the housing with the surrogate solution, the buoyant particles formed a media bed having a diameter of 27 mm and a height of about 17 inches (432 mm). The filtrate exited the media bed, then exited the outlet of the housing. The outlet was fluidly connected to a modified 2L separatory funnel, which acted as an oil trap, collecting the coalesced oleophilic droplets at the top of the funnel, while the clarified water was sent to waste. Sample ports were available immediately after the housing outlet and after the oil trap for collection of sample (typically 25 ml.) A pressure transducer (SciPres, SciLog, Inc., Middleton, WI) was located upstream of the housing, and was used to monitor the pressure of the system during use.

[00130] Turbidity

[00131] The turbidity of a given solution was determined by collecting a sample from the sample port and analyzing with a turbidimeter (Micro 100 available from HF Scientific, Fort Myers, FL). The results are reported in NTU (Nephelometric Turbidity Units).

[00132] Total Organic Carbon (TOC)

[00133] The total organic carbon of a given solution was determined by collecting a sample from the sample port and analyzing with a total organic carbon analyzer (TOC-L CSN available from Shimadzu Scientific Instruments, Columbia, MD) to measure both the dispersed and dissolved organics.

[00134] Particle Size

[00135] The particle size of the oleophilic phase was determined by collecting a sample and analyzing with a laser diffraction, scattering particle size distribution analyzer (LA-300, Horiba/STEC Inc., Santa Clara, CA).

[00136] Samples

[00137] Surrogate 1 :

[00138] The Oleophilic phase was prepared by combining 80 g Dioctyl sulfosuccinate sodium salt (Cytec, Woodland Park, NJ,) 160 g Naphthenic acid (TCI Co., LTD, Toshima, Japan,) 600 g ethanol (200 proof pure Ethanol, Koptec Co. King of Prussia, PA,) 20 g Mineral oil (Kaydol, Sonneborn, Parsippany, NJ,) 30 g Kerosene (Low Odor Kerosene, Alfa Aesar, Ward Hill, MA,) 10 g Xylene (Xylenes ACS grade, EMD Co. (Merck, Darmstadt, Germany,) and 5 mg Sudan III (Sigma-Aldrich, Saint Louis, MO,) and shaking until all of the solids were dissolved.

[00139] An aqueous emulsion was prepared by combining 20 g NaCl (Sigma-

Aldrich Company, Saint Louis, MO,) 2 g CaCk (Sigma-Aldrich Company, Saint Louis, MO,) and 9 g Oleophilic phase (above) into 2 L deionized water and using 5 mL IN NaOH Sigma-Aldrich Company, Saint Louis, MO) to adjust the pH to 6.5.

[00140] Surrogate 2:

[00141] The aqueous emulsion was prepared as in Surrogate 1 and 500 mg of ISO

12103-1 Al Ultrafme Test Dust (Powder Technology Inc., Burnsville, MN) was added. The sample was shear mixed in a homogenizer (Turrax T-18, Cole-Parmer, Vernon Hills, IL) at 20,000 rpm for 60 sec in a 2 L jar. The sample comprised 250 ppm solids.

[00142] Surrogate 3:

[00143] Oleophilic phase was prepared by mixing a 20 volume % solution of 2- hydroxy-5-nonylacetophenone oxime in hydrocarbon diluents (available under the trade designation "LIX 84-1" from BASF Corp. Tucson, Tucson, AZ) with 80 volume % of a solvent extraction diluent (available under the trade designation "ORFOM SX 80" from Chevron Philips Chemical Co., LLC, The Woodlands, TX.)

[00144] Aqueous phase was prepared by adjusting the pH of 1 L deionized water to

1.8 using 50% sulfuric acid (Alfa Aesar, Ward Hill, MA.) To the acidified water, 10.3 g FeSO₄-7H₂0 granular (J.T. Baker Center Valley, PA) and 24.3 g of CuS0₄ 5H₂0 (Alfa Aesar, Ward Hill, MA) was added. The solution was stirred on a hot plate and heated to 60 °C as needed.

[00145] The Oleophilic phase and the Aqueous phase were mixed in the mixing vessel described below as follows to make Surrogate 3. The mixing vessel comprised a baffled, glass mixing vessel fabricated from heavy wall glass tubing approximately 15 cm high by 10 cm wide with a bottom take-off valve was made from glass tubing. The walls of the vessel had been modified to include 4 baffles that protruded approximately 1 cm into the vessel space. A 1.75 inch (44.5 mm) diameter slotted, polypropylene impeller on a 10 cm stainless steel shaft was used, as described in BASF monograph D/EVH 017e "Standard quality control test of LIX™ reagents," dated August 2012 . The impeller was mounted on a variable speed mixer and stand. 450 ml of the Aqueous phase was added to the mixing vessel. The impeller was positioned just below the surface of the Aqueous phase and the motor was stirred at 2000 rpm (revolutions per minute). 135 ml of the Oleophilic phase was added to the vessel. After the addition of the Oleophilic phase, the mixture was stirred 2000 rpm for 3 minutes. Then, the stirrer was stopped and the phases were allowed to separate for 5 minutes. The resulting aqueous phase was drained into a beaker and used as Surrogate 3.

[00146] Field Sample 1 : Sample of crude oil having a 22 ° API gravity.

[00147] Field Sample 2: Sample of waste water produced from oil production operations

[00148] Comparative Example 1

[00149] The Plastic Vessel Method, with the optional 60-mesh 304 stainless steel frit at the inlet, was used with the Inorganic Particles, and Surrogate 1 was used as the process liquid. The flow rate was 26 ml/min, which corresponded to a flux of 899 L/m²/hr. Samples of the solution were taken from the process stream for turbidity measurements, as described above. Samples were taken from right before the housing inlet, right after the housing outlet, and after the oil trap. The inlet solution had a turbidity of 1055 NTU. The turbidity results are shown in Table 1 along with the pressure drop. A coalesced oleophilic phase started to appear in the oil trap after about 8.7 L of filtrate was passed through the media bed.

Table 1

[00150] The TOC of Surrogate 1 was tested as well as a sample, which was taken right after the outlet port during the run. Surrogate 1 comprised miscible organics, such as ethanol, xylene, and Sudan III, which would not be coalesced and removed with the packed bed of buoyant particles. Discounting the TOC contribution of these miscible components (xylene, ethanol, and Sudan III ) and assuming complete removal of the dispersed oleophilic phase in Surrogate 1 would have resulted in a 32.2% reduction in TOC. The TOC was reduced from 2462 ppm (initial) to 1772 ppm (after treatment through the packed bed), a 28.0% reduction in TOC.

[00151] Example 2

[00152] The Plastic Vessel Method was used with the Inorganic Particles, and Surrogate 3 was used as the process liquid. Shown in Table 2 below are the results from two samples run at 26 ml/min (flux = 899 LMH) and one sample run at 100 ml/min (flux = 3458 LMH.) One data point for each sample was taken about 5 to 10 minutes after starting each experiment. Samples were taken immediately upstream of the housing inlet and immediately downstream from the housing outlet. Table 2

[00153] Passing through the media bed dropped the turbidity effectively, leaving the effluent visibly clear and producing oleophilic droplets on the surface of the collected volume. Increasing the flow rate by a factor of four did not impact the turbidity reduction, and only very slightly increased the pressure drop on the system

[00154] The effluent of samples 2 and 3 was visually very clean and transparent, even with a large pathlength of -8-10 inches (the diameter of the collection beaker), and coalesced oleophilic was present in significant quantities on the meniscus.

[00155] Example 3

[00156] The Inorganic Particles were modified with the C4-Pox silane following the

Modification of Inorganic Particles described above. The Plastic Vessel Method was used with the modified Inorganic Particles and Surrogate 1 was used as the process liquid. The flow rate was 26 ml/min, which corresponded to a flux of 899 L/m²/hr. Samples of the solution were taken from the process stream for turbidity measurements, as described above. Samples were taken from right before the housing inlet, right after the housing outlet, and after the oil trap. The inlet solution had a turbidity of 1059 NTU. The turbidity results are shown in Table 3 along with the pressure drop. A coalesced oleophilic phase started to appear in the oil trap after about 8 L of filtrate was passed through the media bed. Table 3

[00157] This example differed from Comparative Example 1 in the behavior after breakthrough of spalled oleophilic droplets was observed downstream of the packed bed in two ways. The absolute turbidity downstream of the oil trap was reduced by an order of magnitude. Also, a significant difference between the turbidity of the outlet from the oil trap and that of the outlet from the packed bed was observed for this case, but not for Comparative Example 1. These observations are consistent with improved coalescence and more efficient use of the oil trap in this Example compared to the media used in Comparative Example 1.

[00158] Example 4

[00159] Example 4 was carried out in the same manner as Example 3, except that

Surrogate 2 was used in place of Surrogate 1. The inlet solution had a turbidity that exceeded the upper limit of the turbidimeter, which was 1100 NTU. The turbidity results are shown in Table 4 along with the pressure drop. Table 4

[00160] The added solids in the surrogate appeared to change the nature of the mixture, stabilizing the oil-water interface of the oleophilic phase. The upstream face of the packed bed of buoyant particles seemed to "reject" the solids-laden oleophilic phase, which manifested as a settled cake of sludge in the vessel upstream of the media bed. Additionally, the coalesced oleophilic droplets that spalled off the media bed were noticeably larger (at least a millimeter or more, based on visual observation) than those observed in Example 3.

[00161] Example 5

[00162] The inorganic particles were modified with the zwitterionic silane following the Modification of Inorganic Particles described above. The Glass Vessel Method was used with the modified Inorganic Particles and Surrogate 1 was used as the process liquid. The flow rate was 26 ml/min, which corresponded to a flux of 899 L/m²/hr. Samples of the solution were taken from the process stream for turbidity measurements, as described above. Samples were taken from right after the housing outlet, and after the oil trap. The turbidity results are shown in Table 5 along with the pressure drop. A coalesced oleophilic phase started to appear in the oil trap after about 18 L of filtrate was passed through the media bed.

Table 5

[00163] Example 6

[00164] Example 6 was carried out in the same manner as Example 5, except that

Surrogate 2 was used in place of Surrogate 1. The inlet solution had a turbidity of that exceeded the upper limit of the turbidimeter, which was 1100 NTU. The turbidity results are shown in Table 6 along with the pressure drop.

Table 6

[00165] The effluent from the oil trap did not exhibit an additional reduction in turbidity relative to the buoyant bed alone, but appeared to be less noisy. No evidence of spalling (discharge of large oleophilic droplets) of coalesced oleophilic droplets was observed off the downstream face of the media bed. Although not wanting to be limited by theory, it is believed that the presence of the added solids in the process liquid stabilized the oil-water interface of the oleophilic droplets. The upstream face of the media bed seemed to "reject" the solids-laden oil, which manifested as a settled cake of sludge in the vessel upstream of the media bed that appeared early in the run ( about 2 L filtrate).

[00166] Example 7

[00167] Example 7 was carried out in the same manner as Example 5, except that

Field Sample 2 was used in place of Surrogate 1. The inlet solution had a turbidity of 26.7 NTU. The turbidity results are shown in Table 7 along with the pressure drop.

Table 7

[00168] The turbidity of the effluent from the oil trap was not largely reduced from the effluent from the packed bed, but was less noisy. No spalled oleophilic droplets were observed in the oil trap.

[00169] Particle size measurement of the Field Sample 2 and the effluent from the media bed are shown in Fig. 2. The resulting effluent had a particle size distribution with a peak around 1 micron, whereas Field Sample 2 had a broad distribution that includes much larger particles. It is believed that the turbidity observed in the effluent (sampled right after the outlet port) was due to scattering since Field Sample 2 had a fraction of droplets less than 10 microns, centered around ~1 micron. As shown in Fig. 2, the packed bed, appeared to coalesce (or remove) droplets larger than 10 microns.

[00170] Example 7 A

[00171] The cleanability of the media bed after being challenged with 5 gallons of

Field Sample 2 was demonstrated as follows. Upon completion of Example 7, the unprocessed process liquid remaining upstream of the media bed was drained through the drain valve. The valve was closed and deionized water, which was introduced via the outlet port, was used to rinse and dislodge the buoyant particles from up against the upper retaining means. This deionized water rinse also dislodged a significant quantity of coalesced oleophilic droplets into the washwater. The rinsed buoyant particles reassembled in the vessel once the washwater was turned off, and the visually black washwater was collected in a glass jar by opening the drain valve. More deionized water was introduced into the glass vessel via the outlet port and drain valve was opened. This water flushed the rinsed media out the drain valve, and this washwater and rinsed media were collected in a second glass jar. Visual comparison of the two jars showed that the collected crude oil was in the wash water jar, while the rinsed media showed no visual evidence of crude oil.

[00172] Comparative Example 8

[00173] An unmodified microscope slide (2 inches x 3 inches, Corning Plain

Microscope Slides, VWR Scientific Inc, Brisbane, CA) was smeared with the Field Sample 1 to make a coating having roughly a uniform thickness. The soiled microscope slide was immersed into a beaker of deionized water and visually observed. [00174] Upon immersion, the soiling immediately started to lift from the microscope slide, coalescing into droplets. Within 30 seconds of soaking and a few seconds of mild agitation, all of the soiling had been removed from the microscope slide surface.

[00175] Example 9

[00176] A microscope slide was modified with C4-Pox-silane using the procedure as described in the Modification of a Microscope Slide (above.) The modified microscope slide was smeared with the Field Sample 1 to make a coating having roughly a uniform thickness. The soiled modified microscope slide was immersed into a beaker of deionized water and visually observed.

[00177] Near complete removal of the soiling from the surface of the modified microscope slide was observed after a few seconds of soaking followed by mild agitation.

[00178] Example 10

[00179] A microscope slide was modified with C4-Sulfonamide-Pox-silane using the procedure as described in the Modification of a Microscope Slide (above). The modified microscope slide was smeared with the Field Sample 1 to make a coating having roughly a uniform thickness. The soiled modified microscope slide was immersed into a beaker of deionized water and visually observed.

[00180] Near complete removal of the soiling from the surface of the modified microscope slide was observed after a few seconds of soaking followed by mild agitation as in Example 9.

[00181] Example 11

[00182] Comparative Examples 1 and Examples 3-6 from above, were run over the course of several days, and the flowrate was shut off each evening and re-started in the morning. Shown in Table 8 is a summary of the number of shutdowns in flow and the filtrate volume at the shutdown point. The packing of the buoyant particles within the media bed appeared insensitive to the presence of flow (or lack thereof). No settling or distortion of the media bed was observed visually as a result of process shut-downs and restarts. Furthermore, the turbidity measurements did not reflect spikes in the turbidity as might be expected if the media bed did not retain a packed geometry even when there was no flow. Table 8

[00183] Prophetic Example 1 : Resistance of Media Treated with Amphiphilic

Polyoxazoline-FluorochemicalSilane-functional Copolymers to Development of Biofilm

[00184] The Inorganic Particles are modified with the C4- sulfonamide-Pox silane following the Modification of Inorganic Particles described above. The modified inorganic particles are sterilized by immersing in 70% ethanol and placed into the sterilized CDC reactor. The reactor is filled with sterile dilute Bacto trypic soy broth (TSB, Becton, Dickinson and Co., Sparks, MD). 10% TSB (3 g TSB per liter) is used. The reactor is inoculated with a culture of S. epidermidis (ATCC# 35984) or E. coli (ATCC# 25922). The system is incubated at 37°C for 24 hours, after 24 hours, sterile 10% TSB is passed through the reactor at a rate of approximately 11.5 mL/ min for an additional 24 hours to facilitate biofilm growth.

[00185] The modified inorganic particles and adherent biofilm are removed from the reactor, rinsed by immersing 5 times in phosphate buffered saline (PBS), and stained with 1% crystal violet in water for 1 minute. Then the inorganic particles are rinsed by dipping 30 times in PBS to remove excess crystal violet and placed in ethanol. Crystal violet is eluted from the inorganic particles by vortexing for approximately 10 seconds, and the absorbance of the ethanol solutions is measured at 590 nm using a spectrophotometer to estimate the amount of biofilm adhered to the modified inorganic particles. See Example 7 of PCT application US2013/074259 (Thompson et al.), which showed reduced biofilm formation for S. epidermidis and E. coli relative to a primed polyethylene terephthalate (PET) film control, whereas a surface that is merely hydrophilic only exhibited reduced biofilm formation for S. epidermidis. [00186] Foreseeable modifications and alterations of this invention will be apparent to those skilled in the art without departing from the scope and spirit of this invention. This invention should not be restricted to the embodiments that are set forth in this application for illustrative purposes. To the extent that there is a conflict or discrepancy between this specification and the disclosures incorporated by reference herein, this specification will control.

Claims

What is claimed is:

1. A device for coalescing a discontinuous oleophilic phase from an aqueous mixture, the device comprising:

a vessel adapted to support upward flow of the aqueous mixture, the vessel having an upper portion comprising a retaining means adapted to retain a coalescing media within the vessel while allowing liquids to pass through; and

the coalescing media retained within the vessel, the coalescing media comprising a plurality of buoyant surface-modified inorganic particles wherein at least a portion of the surface of each inorganic particle comprises an organic moiety, wherein upward flow of the aqueous mixture will cause the coalescing media to form a predominantly stationary packed bed against the retaining means.

2. The device of claim 1, wherein at least a portion of the total surface area of the buoyant surface-modified inorganic particles is hydrophilic.

3. The device of any one of the previous claims, wherein at least a portion of total surface area of the buoyant surface-modified inorganic particles is oleophilic.

4. The device of any one of the previous claims, wherein the buoyant surface-modified inorganic particles are selected from at least one of glass and ceramic.

5. The device of any one of the previous claims, wherein the surface modification on the inorganic particles comprise at least one of: an amphiphilic modification, and a zwitterionic modification.

6. The device of claim 5, wherein the amphiphilic modification is C4-Pox silane.

7. The device of claim 5, wherein the zwitterionic modification is of the following Formula:

(R¹0)p-Si(R²)_q-W-N⁺(R³)(R⁴)-(CH₂)m-S03- wherein:

each R¹ is independently a hydrogen, methyl group, or ethyl group; each R² is independently a methyl group or an ethyl group;

each R³ and R⁴ is independently a saturated or unsaturated, straight chain, branched, or cyclic organic group, which may be joined together, optionally with atoms of the group W, to form a ring;

W is an organic linking group;

p and m are integers of 1 to 3;

q is 0 or 1 ; and

p+q=3.

8. The device of any one of the previous claims, wherein the buoyant surface-modified inorganic particles have an average diameter of from 15 micrometers to 3000 micrometers.

9. The device of any one of the previous claims, wherein the buoyant surface-modified inorganic particles have an average diameter that is 1.5 to 200 times larger than a target cut-off threshold diameter of the average diameter of the discontinuous oleophilic phase.

10. The device of any one of the previous claims, wherein the buoyant surface-modified inorganic particles have a distribution of diameters around the average diameter of the buoyant surface-modified inorganic particles.

11. The device of any one of the previous claims, wherein the buoyant surface-modified inorganic particles have a bimodal or multimodal distribution of diameters.

12. The device of any one of the previous claims, whereby the packed bed has a porosity of no greater than 0.5.

13. A method of coalescing a discontinuous oleophilic phase of an aqueous mixture, comprising:

providing the coalescing device of any one of claims 1-12; and

delivering the aqueous mixture to the coalescing device.

14. An oleophilic liquid coalescing device comprising a packed bed for coalescing an oleophilic phase, the bed comprising a plurality of buoyant surface-modified inorganic particles wherein at least a portion of the surface of each inorganic particle comprises an organic compound.

15. The device of claim 14, wherein the buoyant surface-modified inorganic particles comprise at least one of: an amphiphilic modification, and a zwitterionic modification.