CN116585912A - High-selectivity polyamide nano composite membrane for lithium-magnesium separation and preparation method thereof - Google Patents
High-selectivity polyamide nano composite membrane for lithium-magnesium separation and preparation method thereof Download PDFInfo
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- 239000004952 Polyamide Substances 0.000 title claims abstract description 204
- 229920002647 polyamide Polymers 0.000 title claims abstract description 204
- 238000000926 separation method Methods 0.000 title claims abstract description 72
- 239000012528 membrane Substances 0.000 title claims abstract description 71
- 238000002360 preparation method Methods 0.000 title claims abstract description 27
- GCICAPWZNUIIDV-UHFFFAOYSA-N lithium magnesium Chemical compound [Li].[Mg] GCICAPWZNUIIDV-UHFFFAOYSA-N 0.000 title claims abstract description 21
- 239000002114 nanocomposite Substances 0.000 title abstract description 22
- 239000000412 dendrimer Substances 0.000 claims abstract description 47
- 229920000736 dendritic polymer Polymers 0.000 claims abstract description 47
- 238000000034 method Methods 0.000 claims abstract description 14
- 125000001931 aliphatic group Chemical group 0.000 claims abstract description 10
- 239000002120 nanofilm Substances 0.000 claims abstract description 10
- 125000003118 aryl group Chemical group 0.000 claims abstract description 6
- 229920002521 macromolecule Polymers 0.000 claims description 37
- 239000000243 solution Substances 0.000 claims description 34
- 229920002492 poly(sulfone) Polymers 0.000 claims description 21
- 238000012695 Interfacial polymerization Methods 0.000 claims description 18
- 230000005611 electricity Effects 0.000 claims description 18
- LPXPTNMVRIOKMN-UHFFFAOYSA-M sodium nitrite Chemical compound [Na+].[O-]N=O LPXPTNMVRIOKMN-UHFFFAOYSA-M 0.000 claims description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 16
- 239000007864 aqueous solution Substances 0.000 claims description 9
- 235000010288 sodium nitrite Nutrition 0.000 claims description 9
- 238000005859 coupling reaction Methods 0.000 claims description 6
- 238000001338 self-assembly Methods 0.000 claims description 3
- 238000002791 soaking Methods 0.000 claims description 2
- 239000011777 magnesium Substances 0.000 abstract description 19
- 238000012216 screening Methods 0.000 abstract description 11
- 230000014759 maintenance of location Effects 0.000 abstract description 9
- 230000004907 flux Effects 0.000 abstract description 7
- 239000002131 composite material Substances 0.000 abstract description 6
- 150000001408 amides Chemical class 0.000 abstract 1
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 25
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 description 14
- GLUUGHFHXGJENI-UHFFFAOYSA-N Piperazine Chemical compound C1CNCCN1 GLUUGHFHXGJENI-UHFFFAOYSA-N 0.000 description 12
- 150000002500 ions Chemical class 0.000 description 11
- 238000012360 testing method Methods 0.000 description 10
- 238000001728 nano-filtration Methods 0.000 description 9
- 238000010438 heat treatment Methods 0.000 description 8
- 238000011056 performance test Methods 0.000 description 8
- 150000003839 salts Chemical class 0.000 description 8
- 239000002904 solvent Substances 0.000 description 8
- 238000005406 washing Methods 0.000 description 8
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 7
- 229910052744 lithium Inorganic materials 0.000 description 7
- 230000002093 peripheral effect Effects 0.000 description 7
- 125000003277 amino group Chemical group 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- 239000000178 monomer Substances 0.000 description 6
- UWCPYKQBIPYOLX-UHFFFAOYSA-N benzene-1,3,5-tricarbonyl chloride Chemical compound ClC(=O)C1=CC(C(Cl)=O)=CC(C(Cl)=O)=C1 UWCPYKQBIPYOLX-UHFFFAOYSA-N 0.000 description 5
- 238000009826 distribution Methods 0.000 description 5
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 4
- 150000001412 amines Chemical class 0.000 description 4
- 239000008346 aqueous phase Substances 0.000 description 4
- 239000012267 brine Substances 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- 229910052749 magnesium Inorganic materials 0.000 description 4
- 230000001105 regulatory effect Effects 0.000 description 4
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 description 4
- 150000001263 acyl chlorides Chemical class 0.000 description 3
- 125000002490 anilino group Chemical group [H]N(*)C1=C([H])C([H])=C([H])C([H])=C1[H] 0.000 description 3
- 150000001768 cations Chemical class 0.000 description 3
- 230000001276 controlling effect Effects 0.000 description 3
- 238000013461 design Methods 0.000 description 3
- 238000011161 development Methods 0.000 description 3
- 238000009792 diffusion process Methods 0.000 description 3
- 239000002090 nanochannel Substances 0.000 description 3
- 230000035699 permeability Effects 0.000 description 3
- 239000012071 phase Substances 0.000 description 3
- 239000011148 porous material Substances 0.000 description 3
- 238000011160 research Methods 0.000 description 3
- 239000012266 salt solution Substances 0.000 description 3
- 238000005728 strengthening Methods 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000002708 enhancing effect Effects 0.000 description 2
- 239000012527 feed solution Substances 0.000 description 2
- 230000036571 hydration Effects 0.000 description 2
- 238000006703 hydration reaction Methods 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000004745 nonwoven fabric Substances 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000007873 sieving Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 239000012085 test solution Substances 0.000 description 2
- 238000000108 ultra-filtration Methods 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- 150000001335 aliphatic alkanes Chemical class 0.000 description 1
- 150000001336 alkenes Chemical class 0.000 description 1
- 239000003945 anionic surfactant Substances 0.000 description 1
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- AASBQTIDAQOQAV-UHFFFAOYSA-N cyclobutane-1,2,3,4-tetracarbonyl chloride Chemical compound ClC(=O)C1C(C(Cl)=O)C(C(Cl)=O)C1C(Cl)=O AASBQTIDAQOQAV-UHFFFAOYSA-N 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000005595 deprotonation Effects 0.000 description 1
- 238000010537 deprotonation reaction Methods 0.000 description 1
- 238000010612 desalination reaction Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000666 effect on cation Effects 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000013183 functionalized metal-organic framework Substances 0.000 description 1
- 229910001385 heavy metal Inorganic materials 0.000 description 1
- 238000004255 ion exchange chromatography Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000002715 modification method Methods 0.000 description 1
- JRZJOMJEPLMPRA-UHFFFAOYSA-N olefin Natural products CCCCCCCC=C JRZJOMJEPLMPRA-UHFFFAOYSA-N 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- -1 phosphodiester compound Chemical class 0.000 description 1
- 229920006122 polyamide resin Polymers 0.000 description 1
- 230000005588 protonation Effects 0.000 description 1
- 150000003242 quaternary ammonium salts Chemical class 0.000 description 1
- 238000007348 radical reaction Methods 0.000 description 1
- 150000003254 radicals Chemical class 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- DAJSVUQLFFJUSX-UHFFFAOYSA-M sodium;dodecane-1-sulfonate Chemical compound [Na+].CCCCCCCCCCCCS([O-])(=O)=O DAJSVUQLFFJUSX-UHFFFAOYSA-M 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- MBYLVOKEDDQJDY-UHFFFAOYSA-N tris(2-aminoethyl)amine Chemical compound NCCN(CCN)CCN MBYLVOKEDDQJDY-UHFFFAOYSA-N 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/56—Polyamides, e.g. polyester-amides
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/12—Composite membranes; Ultra-thin membranes
- B01D69/125—In situ manufacturing by polymerisation, polycondensation, cross-linking or chemical reaction
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/66—Polymers having sulfur in the main chain, with or without nitrogen, oxygen or carbon only
- B01D71/68—Polysulfones; Polyethersulfones
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F5/00—Softening water; Preventing scale; Adding scale preventatives or scale removers to water, e.g. adding sequestering agents
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B26/00—Obtaining alkali, alkaline earth metals or magnesium
- C22B26/10—Obtaining alkali metals
- C22B26/12—Obtaining lithium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
- C22B7/006—Wet processes
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/20—Heavy metals or heavy metal compounds
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Abstract
The invention relates to a high-selectivity polyamide nano composite membrane for lithium-magnesium separation and a preparation method thereof. The polyamide nanometer film is formed by combining a lower layer and an upper layer through an amide bond, wherein the lower layer is water-soluble, protonatable and positively charged polymerAn amide dendrimer porous layer; the structure of the positively charged polyamide dendrimer consists of an aliphatic core (G0), aliphatic branching structures (G0 to Gn-1) and aromatic end-capping structures (Gn); the molecular structural general formula of the polyamide-amine dendrimer is as follows; the high-selectivity polyamide nano film prepared by the invention; the Li+ retention rate is between-15% and 15%, mg 2+ The retention rate is above 98%, the selectivity calculated by the method is between 40 and 100, and the lithium magnesium screening selectivity performance is excellent. Permeation flux at mono-salts and Li + /Mg 2+ The selectivity is superior to the ion-selective composite membrane reported at present, which shows that the membrane preparation method has obvious technical progress.
Description
Technical Field
The invention belongs to the field of high-selectivity membrane separation, and particularly relates to a high-selectivity polyamide nano composite membrane for lithium-magnesium separation and a preparation method thereof.
Background
Ion selective separation technology is a common requirement in the fields of water treatment, resource development, energy storage, conversion and the like. In particular, with the rapid development of the energy reserve field in recent years, the demand of high-purity lithium is rapidly increasing, and the extraction of lithium from salt lake brine is an important way for guaranteeing the lithium supply in China. Nanofiltration technology represented by polyamide thin-layer composite membrane (TFC) has the advantages of good ion-selective separation capability and high efficiency and energy conservation, and can be used for preparing nano-scale ion substances (such as Cl) - /SO 4 2- 、Li + /Mg 2+ Olefin/alkane, etc.) has great potential in the separation field. However, there are commercial polyamide nano-metersWhen the composite membrane is used for separating mixed liquid with high magnesium/lithium ratio, the separation layer is a single interfacial polymerization polyamide compact layer, the bottom is weak positive electricity, and lithium magnesium is difficult to screen in high selectivity, so that the energy consumption and the cost in the separation process are high. Therefore, according to the ion separation mechanism of nanomembranes, i.e., the danan effect, there is a need to design and develop polyamide nanomembranes with bottom band of strong charge positive electricity to improve Li + /Mg 2+ Selectively, to meet the rapidly growing demands of the market.
Current research generally suggests that nanofiltration membrane selective separation of mono/multivalent ions is primarily dependent on differences in hydration size and valence between different ions. For the polyamide separating layer of the prior commercial nanofiltration membrane, the structure uniformity is poor, the pore size distribution is wider, and the Mg with similar hydration radius is difficult to realize 2+ And Li (lithium) + High-precision screening of (2); and the surface and the inside of the porous membrane contain a large number of ionizable-COOH groups, so that the integral electronegativity of the separating layer is strong, and the porous membrane has strong electrostatic adsorption effect on cations, thereby reducing Li + /Mg 2+ Selectivity. Therefore, based on the separation mechanism of the nanofiltration membrane, li of the polyamide nanofiltration membrane can be improved by strengthening size sieving and charge rejection + /Mg 2+ Selectivity.
The strategy for strengthening the size screening effect is to form a polyamide compact layer with more uniform pore size distribution from the aspect of regulating and controlling the uniformity of a polyamide separation layer structure so as to improve the separation precision of the polyamide compact layer on the Emi scale. The method mainly comprises the steps of constructing an intermediate layer, regulating and controlling the diffusion rate of the aqueous phase monomer, regulating and controlling the interfacial distribution of the aqueous phase monomer and the like so as to reduce the spatial non-uniformity of the interfacial polymerization reaction, thereby realizing the narrow distribution of the aperture of the polyamide compact layer. For example, in CN113262642a and CN112755817a, a single-molecule network layer self-assembled at the water-oil interface with an anionic surfactant (such as sodium dodecyl sulfonate and a phosphodiester compound) is used to regulate the ordered diffusion of amine monomers and the spatial ordering of interfacial polymerization reaction, so as to prepare a polyamide nanofiltration membrane with uniform structure and uniform pore size distribution. The retention rate of the high-performance composite nanofiltration membrane on divalent cations is more than 98.5%, and the retention rate of the high-performance composite nanofiltration membrane on monovalent cations is greater than 98.5%The retention rate is less than 35 percent, and the pure water flux is as high as 160L m -2 h -1 The above. In practice, however, these polyamide membranes are not only susceptible to salt concentration and cross-flow shear, but are also more sensitive to chemical cleaning, and their ion selectivity may be more sensitive to changes in nanochannel size (ind. Eng. Chem. Res.2020,59,17653).
The strategy for strengthening the charge repulsion is to form an integral charge positive polyamide compact layer from increasing the positive charge density on the surface and in the polyamide separation layer so as to promote the charge repulsion effect between the nano channel and cations. On one hand, more positively charged groups can be introduced into the polyamide active layer by screening water/oil phase monomers or doping positively charged organic/inorganic nano fillers so as to improve the overall positive charge of the membrane; on the other hand, molecules with positive charge groups can be grafted on the surface of the polyamide membrane through a surface modification method (such as surface coating, secondary interfacial polymerization, surface grafting, free radical reaction and the like) to increase the surface positive charge density of the separation layer. For example, patent CN113694740a prepares a polyamide membrane with high positive charge density inside the separation layer by interfacial polymerization using ionized quaternary ammonium salt as an aqueous monomer; patent CN105597577a introduces amino-functionalized MOFs by interfacial polymerization to increase the positive charge density inside the polyamide separation layer; the patent CN112844046a grafts the polyfunctional amine-based compound to the polyamide membrane surface by a secondary interfacial polymerization reaction to prepare a positive charge density that enhances the separation layer surface. These methods are limited by the paradox between diffusion rate, compatibility or layer thickness and permeability, resulting in limited positively charged enhancement of the polyamide separation layer as a whole. In addition, these methods focus on the positive charge density of the membrane surface, and there is little research attention paid to the effect of the positive charge density and structural design on the back of the polyamide separation layer on the ion selectivity and permeability of the polyamide membrane.
Disclosure of Invention
The invention aims to provide a polyamide nano-film with a separation layer lower layer of strong charge positive electricity so as to improve lithium magnesium screening selectivity. The invention is studied on the basis of our invention patent (ZL 202010754678.4), the aforesaid invention patent presents the concept of an asymmetric polyamide separating layer, namely, the separating layer is composed of two layers, the upper layer is an interfacial polymerization polyamide compact layer, the lower layer is a dendritic macromolecule porous layer, the upper layer and the lower layer are combined through amide bonds to form a structure with loose lower layer and compact upper layer, and the membrane formed by the structure has large salt water permeation flux and high desalination interception rate. However, in subsequent studies, it was found that, since the lower layer is of an aromatic dendrimer structure, it is insoluble in water, so that the peripheral end-capped amine group cannot be protonated in water, and further it is difficult to improve the charge-to-electricity of the lower layer of the separation membrane. In combination with the separation principle of charge repulsion of the nanofiltration membrane, the low-charge positive-electricity polyamide separation layer lower layer cannot realize efficient lithium magnesium screening, so that development of a high-charge positive-electricity polyamide nano-membrane with the separation layer lower layer is needed to improve lithium magnesium screening selectivity.
Aiming at the problems that the aromatic dendritic macromolecules in the lower porous layer of the asymmetric polyamide separation layer are difficult to dissolve in water, so that the peripheral end capping amine groups are difficult to proton and the charge is not strong. The invention provides a polyamide dendritic macromolecule constructed by an aliphatic inner core and a branched structure, which is used for enhancing water solubility, and the periphery is aromatic amino, so that the polyamide dendritic macromolecule has diazotization-coupling reaction activity, deprotonation capability and charge positive electricity enhancement. Because the polyamide dendritic macromolecule designed by the invention has water solubility and the peripheral end-capped amine group has protonation capability, the formed dendritic macromolecule porous layer (separating layer lower layer) has strong charge and positive electricity. And preparing a polyamide compact layer on the porous layer through interfacial polymerization, and finally forming an asymmetric polyamide nano film with an upper compact layer and a lower dendritic macromolecular porous layer with strong charge positive electricity, wherein the asymmetric polyamide nano film is used for reinforcing lithium magnesium screening.
The lower layer of the polyamide nano-film is a water-soluble, protonatable and positively charged polyamide dendritic macromolecule porous layer, and the upper layer is an interfacial polymerization polyamide compact layer.
The invention forms a polyamide dendritic macromolecule porous layer with strong positive charge (namely a separating layer lower layer) by carrying out self-assembly reaction on the polyamide dendritic macromolecule with water solubility and strong positive charge and anilino end capping on the surface of a porous supporting layer, and then the polyamide dendritic macromolecule porous layer is arranged on the surface of the porous supporting layerAnd performing interfacial polymerization on the dendritic macromolecule porous layer to prepare a polyamide compact layer, namely forming the polyamide membrane with the electric double layer asymmetric structure, wherein the upper layer is negatively charged compact, and the lower layer is positively charged porous. The structural description is shown in figure 1, wherein 1 is non-woven fabric, 2 is polysulfone supporting layer, 3 is high-strength positively charged polyamide dendritic macromolecule porous layer, 4 is polyamide compact layer, and 5 is polyamide separating layer. The polyamide membrane prepared by the invention has high flux and high Li + /Mg 2+ The selectivity, the preparation process is simple, and the method is easy to popularize in industry and can be used for the processes of extracting lithium from salt lake/brine, softening water, treating heavy metal wastewater and the like.
The invention is realized by the following technical scheme:
a high-selectivity polyamide nano-film for lithium-magnesium separation is composed of a lower layer and an upper layer, wherein the lower layer is a water-soluble, protonatable and positively charged polyamide dendritic macromolecular porous layer, and the upper layer is an interfacial polymerization polyamide compact layer. The polyamide dendritic macromolecule porous layer and the polyamide compact layer are called as a polyamide separation layer or an active layer in the invention, the polyamide dendritic macromolecule porous layer is formed by self-assembling dendritic macromolecules with strong positive charges, and the polyamide compact layer is prepared by interfacial polymerization of aqueous phase amine solution and oil phase acyl chloride monomer solution in the dendritic macromolecule porous layer.
The specific structure of the water-soluble, protonatable and positively charged polyamide dendritic macromolecule consists of a polyamide-amine dendritic macromolecule inner core, a branched structure and peripheral modified terminal anilino groups, wherein the peripheral modified terminal anilino groups are used for improving the positively charged property and the self-assembled reactivity of the polyamide dendritic macromolecule, and the aliphatic chain structure is used for enhancing the water solubility.
The structure of the positively charged polyamide dendritic macromolecule provided by the invention consists of an aliphatic core (G0), aliphatic branched structures (G0 to Gn-1) and an aromatic end-capping structure (Gn), wherein n is the iteration number of the dendritic macromolecule, n is 1-7, and the molecular structural general formula of the polyamide-amine dendritic macromolecule is as follows:
wherein the kernel G 0 The molecular structure and the molecular formula of the inner core are as follows:
wherein x is 2-4, y is 2-4, and z is 2-4;
(G0 to Gn-1) the branching structure is:
wherein x is 2-4, y is 2-4, and z is 2-4; k=1-7, preferably k=4, 5,6;
the capping molecule (Gn) structure is:R 3 =h, or->
The self-assembly mode of the dendritic macromolecule porous layer with high positive charge density under the separation layer is diazotization-coupling reaction.
The diazotization-coupling reaction specifically comprises:
1. preparation of dendrimer solution: the positively charged polyamide dendrimer composed of the branched structure (G0) to (Gn-1) and the end-capping structure (Gn) is prepared into an aqueous solution with pH=1-3 by adopting the core (G0);
2. preparation of a highly charged positively charged polyamide dendrimer porous layer: and respectively soaking the polysulfone base membrane in a polyamide dendritic macromolecule solution for 5-9min and a sodium nitrite solution for 30-100s, and obtaining a polyamide dendritic macromolecule porous layer with strong charge positive electricity, namely a lower layer of the polyamide nano membrane separation layer.
And respectively placing the polysulfone base membrane containing the polyamide dendritic macromolecule porous layer with strong charge positive electricity in an aqueous phase amine solution with the weight of 0.5-1.5 wt.% for 1-5min and an oil phase acyl chloride solution with the weight of 0.05-0.3w/v% for 10-180s to obtain a polyamide compact layer, namely an upper layer of the polyamide separation layer. Finally, washing with n-hexane solvent for 10-60s, and then placing at 60 ℃ for heat treatment for 5-10min. The amide bond can be formed between the residual amino group after diazotization-coupling reaction of the strong-charge positive-electricity polyamide dendritic macromolecule porous layer and acyl chloride molecules in the interfacial polymerization process, so that the polyamide separation layer with the upper layer being a polyamide compact layer and the lower layer being a double-layer asymmetric structure of the strong-charge positive-electricity polyamide dendritic macromolecule porous layer is obtained.
The separation layer performance test of the high-selectivity polyamide nano composite membrane prepared by the invention comprises the following steps: when the feed solution is a single salt, the salt tested is MgCl 2 And LiCl, single salt concentration 2000ppm, test pressure 145psi; when the feed solution is a mixed salt solution, the mixed salt solution consists of 500ppm LiCl and 10000ppm MgCl 2 Composition of Mg at this time 2+ With Li + The mass ratio of (2) was 31.2 and the temperature tested was 25 ℃.
The high-selectivity polyamide nano composite membrane for lithium-magnesium separation has the advantages that the lower layer of the polyamide separation layer is a porous layer formed by diazotizing and coupling water-soluble, protonatable and positively charged polyamide dendritic macromolecules, the positive charge is obvious, and the Zeta potential at the pH value of 7 is 10-20mV. Description of the invention
The invention has the beneficial effects that:
(1) At present, researches on increasing the charge of the lower layer of the separation layer are not reported, and the high positive charge density polyamide dendritic macromolecule porous layer in the invention is completely different from the inorganic/organic intermediate layer in the literature, can participate in interfacial polymerization reaction and stably combine with the interfacial polymerization polyamide compact layer through an amide bond, and forms the separation layer with the polyamide compact layer; therefore, the separation layer of the polyamide membrane prepared by the method has asymmetry in structure and chargeability, and is beneficial to improving permeability and selectivity.
(2) The invention starts from structural design, the charge of the lower layer of the separation layer is controllably regulated, and the polyamide dendritic macromolecule not only can provide rich positive charge groups to obviously increase the integral positive charge of the polyamide separation layer, but also can provide charged nano channels, thereby further improving the coordination effect of charge repulsion and dielectric repulsion.
(3) The polyamide membrane with high positive charge density on the lower layer of the polyamide separation layer has excellent membrane separation performance. Tested under the condition that the feed liquid is single salt (the concentration of the single salt is 2000ppm, and the single salt is MgCl respectively) 2 And LiCl, test pressure, 145 psi), mgCl 2 The retention rate is 93.0-98.3%, and the water flux is 224.8-335.9 L.m -2 ·h -1 The method comprises the steps of carrying out a first treatment on the surface of the The retention rate of LiCl is 23.6-49.6%, and the water flux is 289.6-400.7L.m -2 ·h -1 . The specific operation of the prepared high selectivity polyamide nano-film for lithium-magnesium separation is that firstly, 500ppm LiCl and 10000ppm MgCl are configured 2 The mixed brine solution simulates the salt lake composition, when Mg 2+ With Li + The mass ratio of (2) was 31.2. Continuously filtering the prepared polyamide membrane for 1h under the cross-flow condition at 25 ℃ and the operating pressure of 145psi, and respectively testing Li in the permeate liquid and the raw material liquid by adopting ion chromatography + And Mg (magnesium) 2+ Concentration according to the following formula:
ion sieving selectivity was calculated. Under the test conditions, the high-selectivity polyamide nano-film prepared by the invention has the Li+ interception rate of-15 to 15 percent and Mg 2+ The retention rate is above 98%, the selectivity calculated by the method is between 40 and 100, and the lithium magnesium screening selectivity performance is excellent. Permeation flux at mono-salts and Li + /Mg 2+ The selectivity is superior to the ion-selective composite membrane reported at present, which shows that the membrane preparation method has obvious technical progress.
Drawings
FIG. 1 shows a polyamide separation layer lower layer high positive charge density asymmetric polyamide nanocomposite membrane structure (wherein 1 is a nonwoven fabric, 2 is a polysulfone support layer, 3 is a high-strength positively charged polyamide dendrimer porous layer, 4 is a polyamide dense layer, 5 is a polyamide separation layer)
FIG. 2 is a schematic molecular structure of a polyamide separation layer according to example 4 of the present invention, wherein positively charged polyamide dendrimers are connected via azo bonds (-N=N-) to form a porous layer, and an amide bond (-CO-NH-) is connected to a dense interfacial polymerized polyamide layer on the porous layer to form an asymmetric structure
FIG. 3 shows the surface morphology of the polyamide separation layer of example 1 of the present invention, the surface of which shows a clear nanostripe structure
FIG. 4 shows the cross-sectional morphology of the polyamide separation layer of example 1 of the present invention, the cross-section of which shows an obvious structure of an upper layer and a lower layer, the upper layer being a polyamide dense layer and the lower layer being a positively charged porous layer
FIG. 5 shows the Zeta potential diagram of the 128-anilino-terminated polyamide dendrimer prepared in example 1 of the present invention, which shows that the surface of the macromolecular particles shows significant positively charged properties, indicating that peripheral amine groups can be protonated, and the positively charged properties
FIG. 6 shows the Zeta potential of the amine-terminated dendrimer porous layer of the polyamide resin prepared in example 1 of the present invention and the Zeta potential of the surface of the original polysulfone ultrafiltration membrane, which is shown to be-36.1 mV when pH=7, and 12.3mV when pH=7.
Detailed Description
The technical scheme of the invention is further explained and illustrated below by combining specific examples and test examples so that the technical scheme of the invention can be fully understood by those skilled in the art, but the explanation and the illustration are not further limiting of the technical scheme of the invention, and the technical scheme obtained by simple numerical replacement and conventional adjustment based on the invention belongs to the protection scope of the invention.
Example 1
Preparation of a strongly charged electropositive polyamide dendritic macromolecular porous layer: polysulfone-based membranes (PSFs) were immersed in a 0.08w/v% water-soluble, protonatable, positively charged, ph=1 polyamide dendrimer solution for 5min, followed by a 0.5w/v% sodium nitrite solution for 60s to form a strongly positively charged polyamide dendrimer porous layer. The specific structure of the water-soluble, protonatable, positively charged polyamide dendrimer is as follows:
the molecular formula of the core is:
wherein x is 2, y is 2, and z is 2;
the branching structure is as follows:
wherein x is 2, y is 2, z is 2, k=4;
the end capping molecular structure is as follows:R 3 ＝H
the water-soluble and protonatable positively charged dendritic macromolecule is a 128-anilino-terminated polyamide dendritic macromolecule, and the molecular structure is as follows:
preparation of polyamide nanocomposite membrane with separation layer lower layer having strong charge positive electricity: the polysulfone-based film having the surface assembled with the porous layer of the polyamide dendrimer was immersed in an aqueous solution containing 0.8w/v% piperazine for 2 minutes, and the excess solution was removed by a rubber roller. Then, 0.1w/v% of trimesic chloride in normal hexane reacts for 20s to form a polyamide compact layer; the asymmetric polyamide separating layer with the upper layer being a polyamide compact layer and the lower layer being a dendritic macromolecular porous layer with high positive charge density can be obtained. Washing with n-hexane solvent for 30s, and then placing at 60 ℃ for heat treatment for 5min. And finally, performing performance test on the polyamide nanocomposite film with the strong charge electropositivity on the lower layer of the polyamide separation layer. FIG. 3 shows the surface morphology of the polyamide nanocomposite film prepared in example 1 of the present invention, and the surface thereof shows a clear nanostripe structure. FIG. 4 shows the cross-sectional morphology of the polyamide nanoseparation layer obtained in example 1 of the present invention, wherein the cross section of the polyamide nanoseparation layer has an obvious structure of an upper layer and a lower layer, the upper layer is a polyamide dense layer, and the lower layer is a positively charged porous layer. FIG. 5 shows the Zeta potential map of the 128-anilino-terminated polyamide dendrimer prepared in example 1 of the present invention, wherein the surface of the macromolecular particles shows obvious charge positive electricity, which indicates that peripheral amine groups can be protonated to show charge positive electricity. FIG. 6 shows the Zeta potential of the amine-terminated dendrimer porous layer prepared in example 1 of the present invention and the Zeta potential of the surface of the original polysulfone ultrafiltration membrane, which is shown to be-36.1 mV when pH=7, and 12.3mV when pH=7.
Example 2
Preparation of a strongly charged electropositive polyamide dendritic macromolecular porous layer: polysulfone-based membranes (PSFs) were immersed in a 0.08w/v% water-soluble, protonatable, positively charged, ph=2 polyamide dendrimer solution for 5min, followed by a 0.5w/v% sodium nitrite solution for 60s to form a strongly positively charged polyamide dendrimer porous layer. The specific structure of the water-soluble, protonatable, positively charged polyamide dendrimer is as follows:
the molecular formula of the core is:
the molecular formula of the core is:
wherein x is 3, y is 3, and z is 3;
the branching structure is as follows:
wherein x is 2, y is 2, z is 2, k=5;
end-capped molecular tieThe structure is as follows:R 3 ＝H
preparation of polyamide nanocomposite membrane with separation layer lower layer having strong charge positive electricity: the polysulfone-based membrane with the surface assembled with the polyamide dendrimer porous layer was immersed in an aqueous solution containing 1w/v% piperazine for 3min, and the excess solution was removed by a rubber roller. Then, 0.15w/v% of trimesic chloride in normal hexane reacts for 20s to form a polyamide compact layer; the asymmetric polyamide separating layer with the upper layer being a polyamide compact layer and the lower layer being a dendritic macromolecular porous layer with high positive charge density can be obtained. Washing with n-hexane solvent for 40s, and then placing at 60 ℃ for heat treatment for 5min. And finally, performing performance test on the polyamide nanocomposite film with the strong charge electropositivity on the lower layer of the polyamide separation layer.
Example 3
Preparation of a strongly charged electropositive polyamide dendritic macromolecular porous layer: polysulfone-based membranes (PSFs) were immersed in a 0.01w/v% water-soluble, protonatable, positively charged, ph=3 polyamide dendrimer solution for 5min, followed by a 0.5w/v% sodium nitrite solution for 90s to form a strongly positively charged polyamide dendrimer porous layer. The specific structure of the water-soluble, protonatable, positively charged polyamide dendrimer is as follows:
the molecular formula of the core is:
wherein x is 3, y is 3, and z is 3;
the branching structure is as follows:
wherein x is 2, y is 2, z is 2, k=6;
the end capping molecular structure is as follows:
preparation of polyamide nanocomposite membrane with separation layer lower layer having strong charge positive electricity: the polysulfone-based membrane with the surface assembled with the polyamide dendrimer porous layer was immersed in an aqueous solution containing 1w/v% piperazine for 3min, and the excess solution was removed by a rubber roller. Then, 0.15w/v% of trimesic chloride in normal hexane reacts for 20s to form a polyamide compact layer; the asymmetric polyamide separating layer with the upper layer being a polyamide compact layer and the lower layer being a dendritic macromolecular porous layer with high positive charge density can be obtained. Washing with n-hexane solvent for 40s, and then placing at 60 ℃ for heat treatment for 5min. And finally, performing performance test on the polyamide nanocomposite film with the strong charge electropositivity on the lower layer of the polyamide separation layer.
Example 4
Preparation of a strongly charged electropositive polyamide dendritic macromolecular porous layer: polysulfone-based membranes (PSFs) were immersed in a 0.08w/v% water-soluble, protonatable, positively charged, ph=2 polyamide dendrimer solution for 5min, followed by a 0.5w/v% sodium nitrite solution for 60s to form a strongly positively charged polyamide dendrimer porous layer. The specific structure of the water-soluble, protonatable, positively charged polyamide dendrimer is as follows:
the molecular formula of the core is:
the molecular formula of the core is:
wherein x is 2, y is 2, and z is 2;
the branching structure is as follows:
wherein x is 2, y is 2, z is 2, k=3;
the end capping molecular structure is as follows:R 3 ＝H
preparation of polyamide nanocomposite membrane with separation layer lower layer having strong charge positive electricity: the polysulfone-based membrane with the surface assembled with the polyamide dendrimer porous layer was immersed in an aqueous solution containing 1w/v% piperazine for 3min, and the excess solution was removed by a rubber roller. Then, 0.15w/v% of trimesic chloride in normal hexane reacts for 20s to form a polyamide compact layer; the asymmetric polyamide separating layer with the upper layer being a polyamide compact layer and the lower layer being a dendritic macromolecular porous layer with high positive charge density can be obtained. Washing with n-hexane solvent for 40s, and then placing at 60 ℃ for heat treatment for 5min. And finally, performing performance test on the polyamide nanocomposite film with the strong charge electropositivity on the lower layer of the polyamide separation layer. As shown in fig. 2, the positively charged polyamide dendrimer is connected with (-n=n-) through azo bond to form a loose porous layer, and the porous layer is connected with an interfacial polymerization polyamide compact layer through amide bond (-CO-NH-) to form an asymmetric structure.
Example 5
Preparation of a strongly charged electropositive polyamide dendritic macromolecular porous layer: polysulfone-based membranes (PSFs) were immersed in a 0.08w/v% water-soluble, protonatable, positively charged, ph=2 polyamide dendrimer solution for 5min, followed by a 0.5w/v% sodium nitrite solution for 60s to form a strongly positively charged polyamide dendrimer porous layer. The specific structure of the water-soluble, protonatable, positively charged polyamide dendrimer is as follows:
the molecular formula of the core is:
the molecular formula of the core is:
wherein x is 2, y is 2, and z is 2;
the branching structure is as follows:
wherein x is 2, y is 2, z is 2, k=5;
the end capping molecular structure is as follows:R 3 ＝H
preparation of polyamide nanocomposite membrane with separation layer lower layer having strong charge positive electricity: the polysulfone-based membrane with the surface assembled with the polyamide dendrimer porous layer was immersed in an aqueous solution containing 1w/v% of tris (2-aminoethyl) amine for 3min, and the excess solution was removed by a rubber roller. Then, 0.15w/v% of trimesic chloride in normal hexane reacts for 20s to form a polyamide compact layer; the asymmetric polyamide separating layer with the upper layer being a polyamide compact layer and the lower layer being a dendritic macromolecular porous layer with high positive charge density can be obtained. Washing with n-hexane solvent for 40s, and then placing at 60 ℃ for heat treatment for 5min. And finally, performing performance test on the polyamide nanocomposite film with the strong charge electropositivity on the lower layer of the polyamide separation layer.
Example 6
Preparation of a strongly charged electropositive polyamide dendritic macromolecular porous layer: polysulfone-based membranes (PSFs) were immersed in a 0.08w/v% water-soluble, protonatable, positively charged, ph=2 polyamide dendrimer solution for 5min, followed by a 0.5w/v% sodium nitrite solution for 60s to form a strongly positively charged polyamide dendrimer porous layer. The specific structure of the water-soluble, protonatable, positively charged polyamide dendrimer is as follows:
the molecular formula of the core is:
the molecular formula of the core is:
wherein x is 2, y is 2, and z is 2;
the branching structure is as follows:
wherein x is 2, y is 2, z is 2, k=5;
end-capped molecular tieThe structure is as follows:R 3 ＝H
preparation of polyamide nanocomposite membrane with separation layer lower layer having strong charge positive electricity: the polysulfone-based membrane with the surface assembled with the polyamide dendrimer porous layer was immersed in an aqueous solution containing 1w/v% piperazine for 3min, and the excess solution was removed by a rubber roller. Then, 0.09w/v% of 1,2,3, 4-cyclobutanetetra-formyl chloride in n-hexane was reacted for 20s to form a polyamide compact layer; the asymmetric polyamide separating layer with the upper layer being a polyamide compact layer and the lower layer being a dendritic macromolecular porous layer with high positive charge density can be obtained. Washing with n-hexane solvent for 40s, and then placing at 60 ℃ for heat treatment for 5min. And finally, performing performance test on the polyamide nanocomposite film with the strong charge electropositivity on the lower layer of the polyamide separation layer.
Example 7
Preparation of a strongly charged electropositive polyamide dendritic macromolecular porous layer: polysulfone-based membranes (PSFs) were immersed in a 0.08w/v% water-soluble, protonatable, positively charged, ph=2 polyamide dendrimer solution for 5min, followed by a 0.5w/v% sodium nitrite solution for 60s to form a strongly positively charged polyamide dendrimer porous layer. The specific structure of the water-soluble, protonatable, positively charged polyamide dendrimer is as follows:
the molecular formula of the core is:
the molecular formula of the core is:
wherein x is 2, y is 2, and z is 2;
the branching structure is as follows:
wherein x is 2, y is 2, z is 2, k=4;
the end capping molecular structure is as follows:R 3 ＝H
preparation of polyamide nanocomposite membrane with separation layer lower layer having strong charge positive electricity: the polysulfone-based membrane with the surface assembled with the polyamide dendrimer porous layer was immersed in an aqueous solution containing 1w/v% piperazine for 3min, and the excess solution was removed by a rubber roller. Then, 0.12w/v% of 1,2,3, 4-cyclopentatetraoyl chloride in n-hexane was reacted for 20s to form a polyamide dense layer; the asymmetric polyamide separating layer with the upper layer being a polyamide compact layer and the lower layer being a dendritic macromolecular porous layer with high positive charge density can be obtained. Washing with n-hexane solvent for 40s, and then placing at 60 ℃ for heat treatment for 5min. And finally, performing performance test on the polyamide nanocomposite film with the strong charge electropositivity on the lower layer of the polyamide separation layer.
The separation properties of the polyamide membranes prepared according to the invention are shown in Table 1
a Test conditions: 2000ppm MgCl 2 Or LiCl water solution is used as a test solution, and the prepared polyamide membrane is continuously filtered for 1h under 145psi operation pressure and 25 ℃ to test performance;
b test conditions: 500ppm LiCl and 10000ppm MgCl 2 The prepared polyamide membrane was continuously filtered for 1 hour at 25℃under 145psi operating pressure with a mixed brine solution as a test solution to test Li + And Mg (magnesium) 2+ The retention rate is calculated, and the ion screening selection performance is calculated; as can be seen from Table 1, the prepared high-selectivity polyamide nanomembrane for lithium-magnesium separation has high Mg under the test condition of mixed salt solution 2+ Rejection rate (98% or more) and lower Li + Rejection rate, li of Polyamide nanomembrane prepared in examples 2,4,6 and 7 + The rejection was negative, and the selectivity (Li + /Mg 2+ ) 44.72-97.13 shows that the nano film obtained by the invention has application potential in the aspect of lithium-magnesium separationCan realize high-selectivity screening of lithium and magnesium.
The technical scheme disclosed and proposed by the invention can be realized by a person skilled in the art by appropriately changing the condition route and other links in consideration of the content of the present invention, although the method and the preparation technology of the invention have been described by the preferred embodiment examples, the related person can obviously modify or recombine the method and the technical route described herein to realize the final preparation technology without departing from the content, spirit and scope of the invention. It is expressly intended that all such similar substitutes and modifications apparent to those skilled in the art are deemed to be included within the spirit, scope and content of the invention.
Claims (5)
1. A high-selectivity polyamide nano-film for lithium-magnesium separation is characterized by comprising a lower layer and an upper layer which are combined through an amide bond, wherein the lower layer is a dendritic macromolecular porous layer which has water solubility and can be protonated and positively charged, and the upper layer is an interfacial polymerization polyamide compact layer.
2. The high selectivity polyamide nanomembrane for lithium magnesium separation according to claim 1, wherein the specific structure of the water-soluble, protonatable, positively charged polyamide dendrimer consists of an aliphatic core (G0), an aliphatic branched structure (G0 to Gn-1), and an aromatic end-capping structure (Gn), and the molecular structure of the polyamide-amine dendrimer has the following general formula:
wherein n is the iteration number of the dendritic macromolecule, and n is 1-7.
3. The high selectivity polyamide nanomembrane for lithium magnesium separation according to claim 2, wherein the core G 0 The molecular structure and the molecular formula of the inner core are as follows:
wherein x is 2-4, y is 2-4, and z is 2-4;
(G0 to Gn-1) the branching structure is:
wherein x is 2-4, y is 2-4, and z is 2-4; k=1-7, preferably k=4, 5,6;
the capping molecule (Gn) structure is:R 3 =h, or->
4. The method for preparing a high selectivity polyamide nano-membrane for lithium-magnesium separation according to claim 2, wherein the self-assembly mode of the dendritic macromolecule porous layer with high positive charge density under the separation layer is diazotization-coupling reaction.
5. The method for preparing the high-selectivity polyamide nano-membrane for lithium-magnesium separation according to claim 4, which is characterized by comprising the following steps:
1) Preparation of dendrimer solution: the positively charged polyamide dendrimer composed of the aliphatic core (G0), the aliphatic branched structures (G0 to Gn-1) and the aromatic end-capping structure (Gn) is prepared into an aqueous solution with pH=1-3;
2) Preparation of a highly charged positively charged polyamide dendrimer porous layer: and respectively soaking the polysulfone base membrane in a polyamide dendritic macromolecule solution for 5-9min and a sodium nitrite solution for 30-100s, and then obtaining the polyamide dendritic macromolecule porous layer with strong charge positive electricity.
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