CN117065579A - Preparation method of composite nanofiltration membrane - Google Patents
Preparation method of composite nanofiltration membrane Download PDFInfo
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- CN117065579A CN117065579A CN202311240944.1A CN202311240944A CN117065579A CN 117065579 A CN117065579 A CN 117065579A CN 202311240944 A CN202311240944 A CN 202311240944A CN 117065579 A CN117065579 A CN 117065579A
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- 239000012528 membrane Substances 0.000 title claims abstract description 123
- 238000001728 nano-filtration Methods 0.000 title claims abstract description 84
- 239000002131 composite material Substances 0.000 title claims abstract description 36
- 238000002360 preparation method Methods 0.000 title claims abstract description 11
- 239000000243 solution Substances 0.000 claims abstract description 75
- 239000000178 monomer Substances 0.000 claims abstract description 61
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 58
- 239000002202 Polyethylene glycol Substances 0.000 claims abstract description 45
- 229920001223 polyethylene glycol Polymers 0.000 claims abstract description 45
- 229920000642 polymer Polymers 0.000 claims abstract description 44
- 238000000108 ultra-filtration Methods 0.000 claims abstract description 41
- 239000000758 substrate Substances 0.000 claims abstract description 31
- 150000004985 diamines Chemical class 0.000 claims abstract description 25
- 239000012074 organic phase Substances 0.000 claims abstract description 22
- 239000007864 aqueous solution Substances 0.000 claims abstract description 16
- 238000001035 drying Methods 0.000 claims abstract description 12
- -1 alkane sultone Chemical class 0.000 claims abstract description 11
- 150000008053 sultones Chemical class 0.000 claims abstract description 10
- GLUUGHFHXGJENI-UHFFFAOYSA-N Piperazine Chemical compound C1CNCCN1 GLUUGHFHXGJENI-UHFFFAOYSA-N 0.000 claims description 50
- 239000008346 aqueous phase Substances 0.000 claims description 25
- 238000000034 method Methods 0.000 claims description 25
- 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 claims description 18
- 229920002492 poly(sulfone) Polymers 0.000 claims description 14
- WZCQRUWWHSTZEM-UHFFFAOYSA-N 1,3-phenylenediamine Chemical compound NC1=CC=CC(N)=C1 WZCQRUWWHSTZEM-UHFFFAOYSA-N 0.000 claims description 13
- 229940018564 m-phenylenediamine Drugs 0.000 claims description 13
- WEVYAHXRMPXWCK-UHFFFAOYSA-N Acetonitrile Chemical compound CC#N WEVYAHXRMPXWCK-UHFFFAOYSA-N 0.000 claims description 12
- 238000000926 separation method Methods 0.000 claims description 11
- IMNFDUFMRHMDMM-UHFFFAOYSA-N N-Heptane Chemical compound CCCCCCC IMNFDUFMRHMDMM-UHFFFAOYSA-N 0.000 claims description 9
- 239000007788 liquid Substances 0.000 claims description 9
- 239000004695 Polyether sulfone Substances 0.000 claims description 8
- 239000003960 organic solvent Substances 0.000 claims description 8
- 229920006393 polyether sulfone Polymers 0.000 claims description 8
- 125000004386 diacrylate group Chemical group 0.000 claims description 7
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 claims description 7
- 230000008569 process Effects 0.000 claims description 7
- 238000009777 vacuum freeze-drying Methods 0.000 claims description 7
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 6
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 6
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 claims description 6
- 238000006243 chemical reaction Methods 0.000 claims description 6
- 238000007654 immersion Methods 0.000 claims description 6
- 238000001816 cooling Methods 0.000 claims description 5
- 238000010438 heat treatment Methods 0.000 claims description 5
- 239000011148 porous material Substances 0.000 claims description 5
- FSSPGSAQUIYDCN-UHFFFAOYSA-N 1,3-Propane sultone Chemical group O=S1(=O)CCCO1 FSSPGSAQUIYDCN-UHFFFAOYSA-N 0.000 claims description 4
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 claims description 4
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 claims description 4
- 150000001263 acyl chlorides Chemical class 0.000 claims description 4
- TVMXDCGIABBOFY-UHFFFAOYSA-N octane Chemical compound CCCCCCCC TVMXDCGIABBOFY-UHFFFAOYSA-N 0.000 claims description 4
- UENRXLSRMCSUSN-UHFFFAOYSA-N 3,5-diaminobenzoic acid Chemical compound NC1=CC(N)=CC(C(O)=O)=C1 UENRXLSRMCSUSN-UHFFFAOYSA-N 0.000 claims description 2
- XDTMQSROBMDMFD-UHFFFAOYSA-N Cyclohexane Chemical compound C1CCCCC1 XDTMQSROBMDMFD-UHFFFAOYSA-N 0.000 claims description 2
- 239000002033 PVDF binder Substances 0.000 claims description 2
- FDQSRULYDNDXQB-UHFFFAOYSA-N benzene-1,3-dicarbonyl chloride Chemical compound ClC(=O)C1=CC=CC(C(Cl)=O)=C1 FDQSRULYDNDXQB-UHFFFAOYSA-N 0.000 claims description 2
- 229920002239 polyacrylonitrile Polymers 0.000 claims description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 2
- 230000035484 reaction time Effects 0.000 claims description 2
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 claims description 2
- 238000010612 desalination reaction Methods 0.000 abstract description 13
- 230000035699 permeability Effects 0.000 abstract description 4
- 238000000746 purification Methods 0.000 abstract description 3
- 239000013535 sea water Substances 0.000 abstract description 3
- 239000010865 sewage Substances 0.000 abstract description 3
- 239000003651 drinking water Substances 0.000 abstract description 2
- 235000020188 drinking water Nutrition 0.000 abstract description 2
- 230000004907 flux Effects 0.000 description 17
- 230000000052 comparative effect Effects 0.000 description 16
- 239000004952 Polyamide Substances 0.000 description 10
- 229920002647 polyamide Polymers 0.000 description 10
- 238000012360 testing method Methods 0.000 description 10
- 239000012071 phase Substances 0.000 description 9
- 238000007664 blowing Methods 0.000 description 4
- 239000003344 environmental pollutant Substances 0.000 description 4
- 231100000719 pollutant Toxicity 0.000 description 4
- 150000003839 salts Chemical class 0.000 description 4
- 238000012216 screening Methods 0.000 description 4
- 238000012512 characterization method Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000012527 feed solution Substances 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- 238000012695 Interfacial polymerization Methods 0.000 description 2
- AFCARXCZXQIEQB-UHFFFAOYSA-N N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CCNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 AFCARXCZXQIEQB-UHFFFAOYSA-N 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 230000003373 anti-fouling effect Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 125000000524 functional group Chemical group 0.000 description 2
- 230000036571 hydration Effects 0.000 description 2
- 238000006703 hydration reaction Methods 0.000 description 2
- 230000003993 interaction Effects 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 238000005956 quaternization reaction Methods 0.000 description 2
- 108091003079 Bovine Serum Albumin Proteins 0.000 description 1
- 238000006845 Michael addition reaction Methods 0.000 description 1
- 150000008052 alkyl sulfonates Chemical class 0.000 description 1
- 125000003277 amino group Chemical group 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229940098773 bovine serum albumin Drugs 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 239000000084 colloidal system Substances 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 229910017053 inorganic salt Inorganic materials 0.000 description 1
- 238000009285 membrane fouling Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 150000003384 small molecules Chemical class 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- 238000011041 water permeability test Methods 0.000 description 1
- 238000003911 water pollution Methods 0.000 description 1
Classifications
-
- 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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
- B01D67/0006—Organic membrane manufacture by chemical reactions
-
- 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
- B01D71/76—Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74
- B01D71/78—Graft polymers
-
- 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
- C02F1/442—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by nanofiltration
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/08—Seawater, e.g. for desalination
-
- 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
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A20/00—Water conservation; Efficient water supply; Efficient water use
- Y02A20/124—Water desalination
- Y02A20/131—Reverse-osmosis
Abstract
The invention discloses a preparation method of a composite nanofiltration membrane, which specifically comprises the following steps: (1) preparing an aqueous monomer solution; (2) preparing an organic phase monomer solution; (3) Preparing an aqueous solution of a diamine monomer capped polyethylene glycol polymer; (4) preparing an alkane sultone organic solution; (5) immersing the surface of the porous ultrafiltration substrate by the aqueous monomer solution; (6) Immersing the surface of the porous ultrafiltration substrate by using an organic phase monomer solution; (7) Immersing the surface of the nascent nanofiltration membrane in a diamine monomer end-capped polyethylene glycol polymer aqueous solution; (8) Immersing the surface of the nanofiltration membrane grafted by the diamine monomer end-capped polyethylene glycol polymer in the sultone organic solution, drying and rinsing to obtain the nano-filtration membrane. Compared with the traditional nanofiltration membrane, the composite nanofiltration membrane has obviously improved water permeability, desalination rate and pollution resistance, can be widely applied to the fields of drinking water purification, sewage treatment, sea water desalination, brackish water desalination and the like, and has wide industrial application prospect.
Description
Technical Field
The invention relates to the technical field of nanofiltration membranes, in particular to a preparation method of a composite nanofiltration membrane.
Background
Most of water resources on the earth cannot be directly utilized, and inorganic/organic suspended matters, colloid, various salts and other impurities in seawater, brackish water and sewage are required to be effectively removed by adopting a proper process. Wherein the hydrodynamic size of salt and small molecule organics is close to that of water molecules, complicating the separation process based on size screening. In order to solve the problem, development of an efficient and energy-saving separation technology is urgently needed to selectively intercept ions and small molecular organic matters in water, and meanwhile, rapid transmission of the water is guaranteed, so that efficient purification of the water is realized.
Nanofiltration membrane technology is favored in the field of advanced treatment of water because of the advantages of small occupied area, no phase change in the process, environmental friendliness, simple and convenient operation, capability of effectively intercepting salt and small molecular organic matters in water and the like. According to the size, charge and chemical affinity of the pollutants, the nanofiltration membrane can realize the accurate separation of the pollutants, and provides an effective solution for alleviating the problems of increasingly serious water pollution and water shortage.
The polyamide nanofiltration membrane is the most widely applied nanofiltration membrane in the field of advanced treatment of water at present because of good stability and acceptable price. However, the conventional polyamide nanofiltration membrane has a plurality of problems in the practical use process, and the problems are mainly represented by: (1) The flux is lower, and the upper limit of balance exists between the water permeability of the membrane and the solute separation efficiency; (2) It is difficult to achieve efficient separation of multivalent cations in water; (3) The interaction between the membrane and the contaminants exacerbates membrane fouling, reduces separation efficiency and increases operating costs.
Therefore, how to develop a polyamide nanofiltration membrane with high flux, high desalination rate and strong anti-pollution capability is a problem to be solved by those skilled in the art.
Disclosure of Invention
In view of the above, the present invention aims to provide a method for preparing a composite nanofiltration membrane with a surface grafted with a zwitterionic polymer, which has high flux, high desalination rate and strong anti-pollution capability, so as to solve the defects in the prior art.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
the preparation method of the composite nanofiltration membrane specifically comprises the following steps:
(1) Dissolving an aqueous phase monomer in water to obtain an aqueous phase monomer solution for later use;
(2) Dissolving polybasic acyl chloride in an organic solvent A to obtain an organic phase monomer solution for later use;
(3) Dissolving polyethylene glycol diacrylate and excessive diamine monomer in water, heating to react, cooling, removing unreacted diamine monomer, vacuum freeze drying and dissolving in water to obtain diamine monomer end capped polyethylene glycol polymer water solution for later use;
(4) Dissolving alkane sultone in the organic solvent B to obtain alkane sultone organic solution for standby;
(5) Immersing the surface of the porous ultrafiltration substrate with the aqueous phase monomer solution, pouring out the aqueous phase monomer solution, and removing liquid drops remained on the surface of the porous ultrafiltration substrate to obtain the porous ultrafiltration substrate with the aqueous phase monomer stored in the pores;
(6) Immersing a porous ultrafiltration substrate for storing aqueous phase monomers in the holes with an organic phase monomer solution, and pouring out the redundant organic phase monomer solution to obtain a nascent nanofiltration membrane;
(7) Immersing the diamine monomer end-capped polyethylene glycol polymer aqueous solution on the surface of the nascent nanofiltration membrane, and pouring out the diamine monomer end-capped polyethylene glycol polymer aqueous solution to obtain a diamine monomer end-capped polyethylene glycol polymer grafted nanofiltration membrane;
(8) Immersing the surface of the nanofiltration membrane grafted by the diamine monomer end-capped polyethylene glycol polymer in the sultone organic solution, pouring out the redundant sultone organic solution, drying and rinsing to obtain the composite nanofiltration membrane.
Further, in the step (1), the aqueous monomer is a molecule having an amino group number of 2 or more, preferably at least one of piperazine, m-phenylenediamine and 3, 5-diaminobenzoic acid; the mass fraction of the aqueous monomer solution is 0.02% -5.0%.
Further, in the step (2), the polybasic acyl chloride is at least one of isophthaloyl chloride and trimesoyl chloride; the organic solvent A is at least one of n-hexane, cyclohexane, toluene, n-heptane and n-octane; the mass fraction of the organic phase monomer solution is 0.01-0.3%.
Further, in the step (3), the molecular weight of the polyethylene glycol diacrylate is 3000-20000 Da; the diamine monomer is at least one of piperazine and m-phenylenediamine; the reaction temperature is 50-80 ℃ and the reaction time is 2-8 h; the removal process adopts a membrane separation device with the molecular weight cut-off of 500-2000 Da to repeatedly screen for more than four times; the vacuum freeze drying pressure is 40-80 kPa, the temperature is-20 to-40 ℃ and the time is 1-3 hours; the mass fraction of the diamine monomer end capped polyethylene glycol polymer aqueous solution is 0.02% -5.0%.
Further, in the step (4), the alkane sultone is 1, 3-propane sultone; the organic solvent B is at least one of methanol, tetrahydrofuran, dimethylformamide, dimethyl sulfoxide and acetonitrile; the mass fraction of the alkane sultone organic solution is 0.1% -1.0%.
Further, in the step (5), the porous ultrafiltration substrate is any one of a polyvinylidene fluoride ultrafiltration membrane, a polysulfone ultrafiltration membrane, a polyethersulfone ultrafiltration membrane, a sulfonated polyethersulfone ultrafiltration membrane and a polyacrylonitrile ultrafiltration membrane; the immersion time is 0.5-30 min; removing the residual liquid drops on the surface of the porous ultrafiltration substrate.
Further, in the step (6), the immersion time is 5 to 300 seconds.
Further, in the step (7), the immersion time is 1 to 60 minutes.
Further, in the step (8), the immersing temperature is 40-60 ℃ and the immersing time is 2-8 h; the drying temperature is 30-80 ℃ and the drying time is 1-20 min.
Compared with the prior art, the invention has the following beneficial effects:
1. the composite nanofiltration membrane consists of an ultrafiltration substrate, a polyamide layer and a polymer molecule brush layer containing zwitterionic functional groups, and the preparation process comprises the following steps: firstly, preparing a diamine monomer end-capped polyethylene glycol polymer by a Michael addition method, then preparing a primary polyamide layer on an ultrafiltration substrate by an interfacial polymerization method, grafting the diamine monomer end-capped polyethylene glycol polymer on the surface of the primary polyamide layer by a secondary interfacial polymerization method, and finally forming a polymer molecular brush layer containing zwitterionic functional groups by reacting the grafted diamine monomer end-capped polyethylene glycol polymer with sultone or alkyl sulfonate, wherein one end of the polymer molecular brush layer is fixed on the polyamide layer, and the other end of the polymer molecular brush layer is in a free branched chain shape, so that the hydration layer effect and the steric hindrance effect of the zwitterionic polymer can be exerted simultaneously, and the rejection effect on pollutants in water is enhanced.
2. The composite nanofiltration membrane has strong surface hydrophilicity, and enhances the anti-pollution performance of the membrane by forming a compact hydration layer, thereby preventing non-specific interaction between pollutants and the surface of the membrane.
3. Compared with the traditional nanofiltration membrane, the composite nanofiltration membrane has obviously improved water permeability, desalination rate and pollution resistance, can be widely applied to the fields of drinking water purification, sewage treatment, sea water desalination, brackish water desalination and the like, and has wide industrial application prospect.
Drawings
FIG. 1 is a flow chart for the synthesis of diamine monomer capped polyethylene glycol polymers;
FIG. 2 is a flow chart of a synthetic composite nanofiltration membrane;
FIG. 3 is a surface SEM image of nanofiltration membranes of examples 1-2 and comparative examples 1-2;
FIG. 4 shows the surface contact angles of nanofiltration membranes of examples 1-2 and comparative examples 1-2;
FIG. 5 is the pure water flux of nanofiltration membranes of examples 1-2 and comparative examples 1-2;
FIG. 6 shows the salt rejection of nanofiltration membranes of examples 1-2 and comparative examples 1-2;
FIG. 7 is a normalized flux of nanofiltration membranes of examples 1-2 and comparative examples 1-2.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely, and it is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In the following examples, reagents used are commercially available in general, and various processes and methods not described in detail are conventional methods well known in the art, and the experimental operations and experimental conditions not noted are referred to in the art.
Example 1
The preparation method of the composite nanofiltration membrane specifically comprises the following steps:
(1) Dissolving 1.0g of anhydrous piperazine in 50mL of pure water to obtain a water-phase piperazine solution with the mass fraction of 2.0% for later use;
(2) Dissolving 0.05g of trimesic acid chloride in 50mL of normal hexane to obtain an organic phase trimesic acid chloride solution with the mass fraction of 0.1% for later use;
(3) Dissolving 2.0g of polyethylene glycol diacrylate with the molecular weight of 6000Da and 2.0g of anhydrous piperazine in 200mL of pure water, heating to 70 ℃, fully stirring for reaction for 6.0h, cooling to room temperature after the reaction is finished, adding the solution into a membrane separation device with the molecular weight of 2000Da, repeatedly screening for four times by adopting 200mL of pure water to remove the unreacted anhydrous piperazine, then vacuum freeze-drying the screened solution for 6.0h under the conditions of 60kPa and-30 ℃ pressure to obtain piperazine-terminated polyethylene glycol polymer (shown in figure 1), and finally dissolving 1.0g of piperazine-terminated polyethylene glycol polymer in 50mL of pure water to obtain piperazine-terminated polyethylene glycol polymer aqueous solution with the mass fraction of 2.0% for standby;
(4) Dissolving 0.1g of 1, 3-propane sultone in 50mL of acetonitrile to obtain an alkane sultone organic solution with the mass fraction of 0.2 percent for later use;
(5) Immersing the aqueous phase piperazine solution on the surface of the polysulfone ultrafiltration membrane substrate for 5min, pouring out the aqueous phase piperazine solution, and lightly blowing off liquid drops remained on the surface of the polysulfone ultrafiltration membrane substrate by using compressed air to obtain the polysulfone ultrafiltration membrane substrate with the aqueous phase monomer stored in the pores;
(6) Immersing the organic phase trimesoyl chloride solution on the surface of the polysulfone ultrafiltration membrane substrate for 1min, which stores the aqueous phase monomer in the hole, and pouring out the redundant organic phase trimesoyl chloride solution to obtain a nascent nanofiltration membrane;
(7) Immersing the surface of the nascent nanofiltration membrane in the piperazine-terminated polyethylene glycol polymer aqueous solution for 5min, and pouring out the piperazine-terminated polyethylene glycol polymer aqueous solution to obtain a piperazine-terminated polyethylene glycol polymer grafted nanofiltration membrane;
(8) Immersing the surface of the nanofiltration membrane grafted by the piperazine end-capped polyethylene glycol polymer in the sultone organic solution at 50 ℃ for 4.0h to carry out quaternization, pouring out the redundant sultone organic solution, drying for 5min at 40 ℃, and finally fully rinsing with pure water to obtain the composite nanofiltration membrane (shown in figure 2).
Example 2
The preparation method of the composite nanofiltration membrane specifically comprises the following steps:
(1) Dissolving 0.5g of anhydrous piperazine in 50mL of pure water to obtain a water-phase piperazine solution with the mass fraction of 1.0% for later use;
(2) Dissolving 0.025g of trimesic acid chloride in 50mL of n-heptane to obtain an organic phase trimesic acid chloride solution with the mass fraction of 0.05% for later use;
(3) Dissolving 2.0g of polyethylene glycol diacrylate with molecular weight of 20000Da and 2.0g of m-phenylenediamine in 200mL of pure water, heating to 60 ℃, fully stirring for reacting for 4.0h, cooling to room temperature after the reaction is finished, adding the mixture into a membrane separation device with molecular weight of 2000Da, repeatedly screening for four times by adopting 200mL of pure water to remove unreacted m-phenylenediamine, then vacuum freeze-drying the screened solution for 12.0h under the conditions of 60kPa and-20 ℃ to obtain m-phenylenediamine end-capped polyethylene glycol polymer (shown in figure 1), and finally dissolving 0.5g of m-phenylenediamine end-capped polyethylene glycol polymer in 50mL of pure water to obtain m-phenylenediamine end-capped polyethylene glycol polymer water solution with mass fraction of 1.0% for later use;
(4) 0.25g of 1, 3-propane sultone is dissolved in 50mL of acetonitrile to obtain an alkane sultone organic solution with the mass fraction of 0.5 percent for standby;
(5) Immersing the surface of a polyethersulfone ultrafiltration membrane substrate in a water-phase piperazine solution for 10min, pouring out the water-phase piperazine solution, and lightly blowing off liquid drops remained on the surface of the polyethersulfone ultrafiltration membrane substrate by using compressed air to obtain the polyethersulfone ultrafiltration membrane substrate with water-phase monomers stored in holes;
(6) Immersing the surface of a polyethersulfone ultrafiltration membrane substrate storing water phase monomers in holes for 2min by using an organic phase trimesoyl chloride solution, and pouring out the redundant organic phase trimesoyl chloride solution to obtain a nascent nanofiltration membrane;
(7) Immersing the surface of the nascent nanofiltration membrane in an aqueous solution of m-phenylenediamine end-capped polyethylene glycol polymer for 10min, and pouring out the aqueous solution of m-phenylenediamine end-capped polyethylene glycol polymer to obtain a m-phenylenediamine end-capped polyethylene glycol polymer grafted nanofiltration membrane;
(8) Immersing the surface of the nano-filtration membrane grafted by m-phenylenediamine end-capped polyethylene glycol polymer in a sultone organic solution at 50 ℃ for 2.0h to carry out quaternization, pouring out the redundant sultone organic solution, drying for 2min at 60 ℃, and finally fully rinsing with pure water to obtain the composite nano-filtration membrane (shown in figure 2).
Comparative example 1
The preparation method of the unmodified nanofiltration membrane specifically comprises the following steps:
(1) Dissolving 1.0g of anhydrous piperazine in 50mL of pure water to obtain a water-phase piperazine solution with the mass fraction of 2.0% for later use;
(2) Dissolving 0.05g of trimesic acid chloride in 50mL of normal hexane to obtain an organic phase trimesic acid chloride solution with the mass fraction of 0.1% for later use;
(3) Immersing the aqueous phase piperazine solution on the surface of the polysulfone ultrafiltration membrane substrate for 5min, pouring out the aqueous phase piperazine solution, and lightly blowing off liquid drops remained on the surface of the polysulfone ultrafiltration membrane substrate by using compressed air to obtain the polysulfone ultrafiltration membrane substrate with the aqueous phase monomer stored in the pores;
(4) Immersing the organic phase trimesoyl chloride solution in the polysulfone ultrafiltration membrane substrate surface storing the aqueous phase monomer in the hole for 1min, pouring out the redundant organic phase trimesoyl chloride solution, drying for 5min at 40 ℃, and finally fully rinsing with pure water to obtain the unmodified nanofiltration membrane.
Comparative example 2
The preparation method of the non-quaternized grafted nanofiltration membrane specifically comprises the following steps:
(1) Dissolving 1.0g of anhydrous piperazine in 50mL of pure water to obtain a water-phase piperazine solution with the mass fraction of 2.0% for later use;
(2) Dissolving 0.05g of trimesic acid chloride in 50mL of normal hexane to obtain an organic phase trimesic acid chloride solution with the mass fraction of 0.1% for later use;
(3) Dissolving 2.0g of polyethylene glycol diacrylate with the molecular weight of 6000Da and 2.0g of anhydrous piperazine in 200mL of pure water, heating to 70 ℃, fully stirring and reacting for 6.0h, cooling to room temperature after the reaction is finished, adding the solution into a membrane separation device with the molecular weight of 2000Da, repeatedly screening for four times by adopting 200mL of pure water to remove the unreacted anhydrous piperazine, then vacuum freeze-drying the screened solution for 6.0h under the conditions of 60kPa and-30 ℃ of pressure to obtain piperazine-terminated polyethylene glycol polymer, and finally dissolving 1.0g of piperazine-terminated polyethylene glycol polymer in 50mL of pure water to obtain piperazine-terminated polyethylene glycol polymer aqueous solution with the mass fraction of 2.0% for later use;
(4) Immersing the aqueous phase piperazine solution on the surface of the polysulfone ultrafiltration membrane substrate for 5min, pouring out the aqueous phase piperazine solution, and lightly blowing off liquid drops remained on the surface of the polysulfone ultrafiltration membrane substrate by using compressed air to obtain the polysulfone ultrafiltration membrane substrate with the aqueous phase monomer stored in the pores;
(5) Immersing the organic phase trimesoyl chloride solution on the surface of the polysulfone ultrafiltration membrane substrate for 1min, which stores the aqueous phase monomer in the hole, and pouring out the redundant organic phase trimesoyl chloride solution to obtain a nascent nanofiltration membrane;
(6) Immersing the surface of the nascent nanofiltration membrane in the piperazine-terminated polyethylene glycol polymer aqueous solution for 5min, pouring out the piperazine-terminated polyethylene glycol polymer aqueous solution, drying for 5min at 40 ℃, and finally fully rinsing with pure water to obtain the non-quaternized grafted nanofiltration membrane.
Performance testing
1. Membrane characterization
The nanofiltration membranes prepared in examples 1-2 and comparative examples 1-2 were subjected to SEM characterization and contact angle characterization, respectively, and the results are shown in FIGS. 3-4.
As can be seen from FIG. 3, the surface nodules of the unmodified nanofiltration membrane prepared in comparative example 1 are relatively small, the surface nodules of the non-quaternized grafted nanofiltration membrane prepared in comparative example 2 are increased, and the surface nodules of the composite nanofiltration membranes prepared in examples 1 and 2 are further increased, so that the effective filtration area of the nanofiltration membrane surface can be increased.
As can be seen from FIG. 4, the surface contact angle of the composite nanofiltration membrane of example 2 is 18 ° Compared with the polyamide composite nanofiltration membrane of comparative example 1, the method has the advantages that the method is reduced by 30 percent ° 。
2. Water treatment efficacy test
The nanofiltration membranes prepared in examples 1-2 and comparative examples 1-2 were respectively subjected to water treatment efficacy tests, specifically including water permeability tests, desalination rate tests and anti-pollution performance tests.
The test conditions for the water treatment efficiency test are as follows:
(1) The operating pressure was 0.6MPa when water permeability (pure water flux) test was performed; the cross-flow velocity is 10cm/s; the water temperature was 25 ℃.
(2) The Pure Water Flux (PWF) is the volume (V) of pure water passing through the unit membrane area (A) per unit time (t) at the unit operating pressure (S), in L.m -2 ·h -1 ·bar -1 The method is used for measuring the water passing capacity of the nanofiltration membrane, and the calculation formula is as follows: pwf=v/(a·t·s). When the desalination rate test is performed, the concentration of the feed solution is as follows: 1000mg/LNaCl solution, 1000mg/LNa 2 SO 4 Solution, 1000mg/LMgCl 2 Solution and 1000mg/LMgSO 4 A solution; the operating pressure is 0.6MPa; the cross-flow velocity is 10cm/s; the pH value of the solution is 7.0; the water temperature was 25 ℃.
Desalination rate (R) refers to the concentration of the solute (C) in the feed solution at a given operating pressure f ) Concentration of solute with permeate (C p ) The ratio of the difference to the concentration of the solute in the feed liquid is used for evaluating the removal capacity of the nanofiltration membrane on inorganic salt ions, and the calculation formula is as follows: r (%) = (C f -C p )/C f ×100％。
(3) When anti-pollution performance (normalized flux) tests were performed, feed solution concentration: bovine serum albumin concentration 50mg/L and sodium chloride concentration 1000mg/L; initial flux of 70 L.m -2 ·h -1 The method comprises the steps of carrying out a first treatment on the surface of the The cross-flow velocity is 10cm/s; the pH value of the solution is 7.0; the water temperature was 25 ℃. Hydraulic cleaning conditions: the cross-flow velocity is 20cm/s; the water temperature is 25 ℃; the duration was 10min.
Normalized flux (N) f ) Refers to the flux of the membrane during the fouling process (J f ) With initial membrane flux (J 0 ) For evaluating the anti-fouling properties of the film, the calculation formula is: n (N) f ＝J f /J 0 。
The test results are shown in FIGS. 5-7. As can be seen from FIG. 5, the pure water flux of the composite nanofiltration membrane of example 2 was 15.6L.m -2 ·h -1 ·bar -1 The polyamide composite nanofiltration membrane is improved by 35.7 percent compared with the polyamide composite nanofiltration membrane of comparative example 1.
As can be seen from FIG. 6, the composite nanofiltration membrane of example 2 achieved 99.2% Na 2 SO 4 Desalination rate and 95.2% MgCl 2 Desalination rate.
As can be seen from FIG. 7, the anti-fouling performance of the composite nanofiltration membranes of examples 1-2 is significantly improved compared with that of comparative examples 1-2, the final normalized fluxes of the composite nanofiltration membranes of examples 1-2 are 85.7% and 90.0%, respectively, while the final normalized fluxes of the nanofiltration membranes of comparative examples 1-2 are only 50.0% and 61.0%. In addition, the normalized flux of the composite nanofiltration membrane of example 1-2 was almost completely recovered after simple hydraulic washing, while the normalized flux of the nanofiltration membrane of comparative example 1-2 was recovered to only 57.6% and 71.0%.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. The preparation method of the composite nanofiltration membrane is characterized by comprising the following steps of:
(1) Dissolving an aqueous phase monomer in water to obtain an aqueous phase monomer solution for later use;
(2) Dissolving polybasic acyl chloride in an organic solvent A to obtain an organic phase monomer solution for later use;
(3) Dissolving polyethylene glycol diacrylate and excessive diamine monomer in water, heating to react, cooling, removing unreacted diamine monomer, vacuum freeze drying and dissolving in water to obtain diamine monomer end capped polyethylene glycol polymer water solution for later use;
(4) Dissolving alkane sultone in the organic solvent B to obtain alkane sultone organic solution for standby;
(5) Immersing the surface of the porous ultrafiltration substrate with the aqueous phase monomer solution, pouring out the aqueous phase monomer solution, and removing liquid drops remained on the surface of the porous ultrafiltration substrate to obtain the porous ultrafiltration substrate with the aqueous phase monomer stored in the pores;
(6) Immersing the surface of a porous ultrafiltration substrate storing aqueous phase monomers in the holes with an organic phase monomer solution, and pouring out redundant organic phase monomer solution to obtain a nascent nanofiltration membrane;
(7) Immersing the diamine monomer end-capped polyethylene glycol polymer aqueous solution on the surface of the nascent nanofiltration membrane, and pouring out the diamine monomer end-capped polyethylene glycol polymer aqueous solution to obtain a diamine monomer end-capped polyethylene glycol polymer grafted nanofiltration membrane;
(8) Immersing the surface of the nanofiltration membrane grafted by the diamine monomer end-capped polyethylene glycol polymer in the sultone organic solution, pouring out the redundant sultone organic solution, drying and rinsing to obtain the composite nanofiltration membrane.
2. The method for preparing a composite nanofiltration membrane according to claim 1, wherein in the step (1), the aqueous phase monomer is at least one of piperazine, m-phenylenediamine and 3, 5-diaminobenzoic acid; the mass fraction of the aqueous monomer solution is 0.02% -5.0%.
3. The method for preparing a composite nanofiltration membrane according to claim 1, wherein in the step (2), the polybasic acyl chloride is at least one of isophthaloyl chloride and trimesoyl chloride; the organic solvent A is at least one of n-hexane, cyclohexane, toluene, n-heptane and n-octane; the mass fraction of the organic phase monomer solution is 0.01% -0.3%.
4. The method for preparing a composite nanofiltration membrane according to claim 1, wherein in the step (3), the molecular weight of the polyethylene glycol diacrylate is 3000-20000 Da; the diamine monomer is at least one of piperazine and m-phenylenediamine; the reaction temperature is 50-80 ℃ and the reaction time is 2-8 h; the removing process adopts a membrane separation device with the molecular weight cut-off of 500-2000 Da to repeatedly screen for more than four times; the vacuum freeze drying pressure is 40-80 kPa, the temperature is-20 to-40 ℃ and the time is 1-3 hours; the mass fraction of the diamine monomer end capped polyethylene glycol polymer aqueous solution is 0.02% -5.0%.
5. The method for preparing a composite nanofiltration membrane according to claim 1, wherein in the step (4), the alkane sultone is 1, 3-propane sultone; the organic solvent B is at least one of methanol, tetrahydrofuran, dimethylformamide, dimethyl sulfoxide and acetonitrile; the mass fraction of the alkane sultone organic solution is 0.1% -1.0%.
6. The method for preparing a composite nanofiltration membrane according to claim 1, wherein in the step (5), the porous ultrafiltration substrate is any one of polyvinylidene fluoride ultrafiltration membrane, polysulfone ultrafiltration membrane, polyethersulfone ultrafiltration membrane, sulfonated polyethersulfone ultrafiltration membrane and polyacrylonitrile ultrafiltration membrane; the immersion time is 0.5-30 min; the drying is carried out until no liquid drops are on the surface.
7. The method of claim 1, wherein in step (6), the immersion time is 5 to 300 seconds.
8. The method for preparing a composite nanofiltration membrane according to claim 1, wherein in the step (7), the immersion time is 1 to 60min.
9. The method for preparing a composite nanofiltration membrane according to claim 1, wherein in the step (8), the immersing temperature is 40-60 ℃ and the immersing time is 2-8 hours.
10. The method for preparing a composite nanofiltration membrane according to claim 1, wherein in the step (8), the drying temperature is 30-80 ℃ and the drying time is 1-20 min.
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