CN116407959A - Hydrophilic modified polyamide pervaporation composite membrane and preparation method thereof - Google Patents
Hydrophilic modified polyamide pervaporation composite membrane and preparation method thereof Download PDFInfo
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- 239000012528 membrane Substances 0.000 title claims abstract description 100
- 239000004952 Polyamide Substances 0.000 title claims abstract description 42
- 229920002647 polyamide Polymers 0.000 title claims abstract description 42
- 238000005373 pervaporation Methods 0.000 title claims abstract description 34
- 239000002131 composite material Substances 0.000 title claims abstract description 15
- 238000002360 preparation method Methods 0.000 title claims abstract description 10
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- 239000000178 monomer Substances 0.000 claims description 25
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- 229910021641 deionized water Inorganic materials 0.000 claims description 21
- 238000002791 soaking Methods 0.000 claims description 21
- 239000000758 substrate Substances 0.000 claims description 16
- 150000001412 amines Chemical class 0.000 claims description 13
- 229920002239 polyacrylonitrile Polymers 0.000 claims description 10
- 229920002873 Polyethylenimine Polymers 0.000 claims description 8
- IXPNQXFRVYWDDI-UHFFFAOYSA-N 1-methyl-2,4-dioxo-1,3-diazinane-5-carboximidamide Chemical compound CN1CC(C(N)=N)C(=O)NC1=O IXPNQXFRVYWDDI-UHFFFAOYSA-N 0.000 claims description 7
- 235000010413 sodium alginate Nutrition 0.000 claims description 7
- 239000000661 sodium alginate Substances 0.000 claims description 7
- 229940005550 sodium alginate Drugs 0.000 claims description 7
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical group [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 claims description 6
- 238000001035 drying Methods 0.000 claims description 6
- 239000007788 liquid Substances 0.000 claims description 6
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- 239000004695 Polyether sulfone Substances 0.000 claims description 5
- 239000004372 Polyvinyl alcohol Substances 0.000 claims description 5
- 239000012535 impurity Substances 0.000 claims description 5
- 229920002492 poly(sulfone) Polymers 0.000 claims description 5
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- 239000011148 porous material Substances 0.000 claims description 5
- 230000008569 process Effects 0.000 claims description 5
- 238000009736 wetting Methods 0.000 claims description 5
- SXRSQZLOMIGNAQ-UHFFFAOYSA-N Glutaraldehyde Chemical compound O=CCCCC=O SXRSQZLOMIGNAQ-UHFFFAOYSA-N 0.000 claims description 4
- 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 4
- 239000001110 calcium chloride Substances 0.000 claims description 4
- 229910001628 calcium chloride Inorganic materials 0.000 claims description 4
- 239000003431 cross linking reagent Substances 0.000 claims description 4
- 238000005520 cutting process Methods 0.000 claims description 4
- LXEJRKJRKIFVNY-UHFFFAOYSA-N terephthaloyl chloride Chemical compound ClC(=O)C1=CC=C(C(Cl)=O)C=C1 LXEJRKJRKIFVNY-UHFFFAOYSA-N 0.000 claims description 4
- 238000005406 washing Methods 0.000 claims description 4
- WZCQRUWWHSTZEM-UHFFFAOYSA-N 1,3-phenylenediamine Chemical compound NC1=CC=CC(N)=C1 WZCQRUWWHSTZEM-UHFFFAOYSA-N 0.000 claims description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims description 3
- RPNUMPOLZDHAAY-UHFFFAOYSA-N Diethylenetriamine Chemical compound NCCNCCN RPNUMPOLZDHAAY-UHFFFAOYSA-N 0.000 claims description 3
- PIICEJLVQHRZGT-UHFFFAOYSA-N Ethylenediamine Chemical compound NCCN PIICEJLVQHRZGT-UHFFFAOYSA-N 0.000 claims description 3
- 229940018564 m-phenylenediamine Drugs 0.000 claims description 3
- VILCJCGEZXAXTO-UHFFFAOYSA-N 2,2,2-tetramine Chemical compound NCCNCCNCCN VILCJCGEZXAXTO-UHFFFAOYSA-N 0.000 claims description 2
- 238000000861 blow drying Methods 0.000 claims description 2
- 238000004140 cleaning Methods 0.000 claims description 2
- SADAOYKNIHVPHS-UHFFFAOYSA-N cyclohexane-1,1,2,2-tetracarbonyl chloride Chemical compound ClC(=O)C1(C(Cl)=O)CCCCC1(C(Cl)=O)C(Cl)=O SADAOYKNIHVPHS-UHFFFAOYSA-N 0.000 claims description 2
- 238000010438 heat treatment Methods 0.000 claims description 2
- 230000007062 hydrolysis Effects 0.000 claims description 2
- 238000006460 hydrolysis reaction Methods 0.000 claims description 2
- 230000005660 hydrophilic surface Effects 0.000 claims description 2
- 230000007246 mechanism Effects 0.000 abstract description 3
- 238000012695 Interfacial polymerization Methods 0.000 abstract description 2
- 239000005416 organic matter Substances 0.000 abstract description 2
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- 238000001728 nano-filtration Methods 0.000 abstract 1
- 238000001223 reverse osmosis Methods 0.000 abstract 1
- 210000004379 membrane Anatomy 0.000 description 75
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 24
- 230000004907 flux Effects 0.000 description 14
- 239000012071 phase Substances 0.000 description 14
- 230000000052 comparative effect Effects 0.000 description 8
- 235000019441 ethanol Nutrition 0.000 description 7
- 238000011010 flushing procedure Methods 0.000 description 7
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
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- 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
-
- 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
- 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
- B01D71/56—Polyamides, e.g. polyester-amides
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2323/00—Details relating to membrane preparation
- B01D2323/02—Hydrophilization
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2325/00—Details relating to properties of membranes
- B01D2325/36—Hydrophilic membranes
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- 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
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
Abstract
The invention prepares the novel pervaporation dehydration composite membrane with hydrophilic membrane surface and hydrophobic membrane inside based on the adsorption and desorption mechanism of water molecules on the pervaporation membrane. Firstly, preparing a relatively hydrophobic polyamide membrane layer by using an interfacial polymerization method, then coating a hydrophilic layer on the surface of the polyamide membrane, and obtaining the high-hydrophilicity pervaporation membrane which is beneficial to water molecules to pass through and has fewer defects by changing the preparation conditions of polyamide and the types and the concentrations of the hydrophilic layer. The method adopts cheap and environment-friendly materials as the hydrophilic layer, changes the complexity of the traditional polyamide post-treatment method, and is easy to popularize. The method can reduce bacterial breeding while improving membrane separation performance, is used for pervaporation dehydration membrane, pervaporation organic matter separation membrane, pollution-resistant nanofiltration membrane and pollution-resistant reverse osmosis membrane, and opens up a new thought and a new method for preparing the membrane with high performance under severe conditions.
Description
Technical Field
The invention relates to a hydrophilic modified polyamide pervaporation composite membrane and a preparation method thereof, which are applicable to the process of industrial production of absolute ethyl alcohol.
Background
In order to solve the problem of energy shortage, the environmental pollution pressure is relieved. Fuel ethanol generally refers to absolute ethanol with a volume concentration of 99.5% or more. The traditional method for producing the absolute ethyl alcohol mainly comprises a distillation method, an extraction method and the like, and has the problems of large environmental pollution, high energy consumption, poor separation effect and the like. As an environment-friendly mixed azeotrope separation technology, the pervaporation has the advantages of energy conservation, simple operation, no secondary pollution, easy coupling with other processes and the like compared with the traditional separation technology such as distillation, extraction and absorption. The pervaporation technology has been developed rapidly in recent years, and is expected to realize industrialized application of solvent dehydration, desalination and organic matter separation. However, research on pervaporation membranes is still in the laboratory stage and has less application in industry. The development of PV membranes with simple preparation processes, high stability, low cost and high separation performance is a popular field of research.
At present, the method for preparing the pervaporation membrane comprises a solution casting method and a coating method, and the composite membrane prepared by the method is often thicker in a separation layer, so that the further improvement of the permeation flux is limited; although the hollow fiber spinning method has higher flux, the method has high requirements on equipment, the preparation process is complex, and the industrial production is difficult. The interfacial polymerization can not sacrifice membrane selectivity, has higher permeation flux, is hopeful to break the trade-off effect between the conventional permeation flux and separation selectivity, and has wide application potential in the field of pervaporation due to the repeatability and expansibility. The pervaporation membrane is mainly separated based on a dissolution and diffusion mechanism, namely, a penetrating agent is adsorbed to the surface of the membrane from a feed liquid, the penetrating agent is diffused and desorbed in the membrane, and the penetrating agent is permeated from the membrane to a gas phase on a penetrating side. However, after the common aqueous phase amine monomer reacts with the oil phase monomer to generate polyamide, the hydrophilicity of the surface of the membrane is reduced, and the membrane is not resistant to pollution. Meanwhile, the thickness of the polyamide is limited, and a small amount of defects can be gradually expanded in the pervaporation process to influence the performance of the membrane, so that hydrophilic materials are coated on the surface of the polyamide, on one hand, the hydrophilicity of the surface of the membrane is increased, and on the other hand, the defects of the polyamide are reduced. The hydrophilic material increases the hydrophilicity of the membrane surface, so that the adsorption of water molecules on the surface of the pervaporation membrane is facilitated; the hydrophobicity of polyamide in the membrane helps water molecules to be quickly desorbed and diffused in the membrane, so that the aim of improving permeability and selectivity is fulfilled.
Disclosure of Invention
The invention aims to carry out hydrophilic modification on the surface of common polyamide, and obtain the membrane surface hydrophilic and internal hydrophobic pervaporation membrane through a cheap and easily available green pollution-free modified material, thereby promoting the rapid transmission of water molecules so as to improve the separation and selection performance of the membrane.
The technical scheme of the invention is summarized as follows:
the preparation method mainly comprises the steps of (1) treating a base film, combining an amine/water solution on the base film, reacting an oil phase monomer with an amine monomer to generate polyamide, carrying out heat treatment on the polyamide film, and coating a hydrophilic material on the polyamide film to form the composite film.
The specific process of steps (1) - (5) is as follows:
cutting a substrate film into a proper size, soaking in deionized water for 5-24 hours, wetting pore channels, removing surface impurities, and then removing the deionized water on the surface; step (2) fixing the substrate film on a spin coater or a self-made plate frame, uniformly distributing the amine/water solution with the mass fraction of 0.5-2.5wt% on the surface of the substrate film, standing for 5-15min, pouring out the redundant solution, and removing the amine monomer which is not combined on the surface of the film; uniformly distributing the oil phase monomer solution with the volume fraction of 0.1-0.5w/v% on the surface of the membrane in the step (2), reacting for 200-600s, pouring out the excessive oil phase/n-hexane solution, washing unreacted monomers on the surface of the membrane with n-hexane, and then removing liquid drops on the surface of the membrane; placing the polyamide membrane layer obtained in the step (4) in an oven at 40-100 ℃ for 5-20min to enable amine monomers and oil phase monomers to fully react; uniformly coating the hydrophilic material with the mass fraction of 0.5-2.5 and wt% on the surface of the film in the step (4), soaking for 10-50min, pouring off the redundant solution, removing the redundant solution on the surface of the film, enabling the surface of the film to have no liquid drops, soaking in the cross-linking agent solution with the mass fraction of 0.1-1.5wt% for 30-90min, taking out, cleaning the redundant solution on the surface of the film, and soaking in deionized water for standby.
2. The method of claim 1, wherein the base membrane in step (1) is a base membrane material such as polysulfone, polyethersulfone, polyacrylonitrile, polytetrafluoroethylene, and polyacrylonitrile after hydrolysis.
3. The method according to claim 1, wherein the method for removing the surface residual solution is spin drying by using a rotating centrifugal force or blow drying by using an air knife.
4. The method according to claim 1, wherein the amine in step (2) is polyethyleneimine, diethylenetriamine, m-phenylenediamine, triethylenetetramine, ethylenediamine.
5. The method according to claim 1, wherein the oil phase monomer in the step (3) is trimesoyl chloride, terephthaloyl chloride, 1,3, 5-hexane tricarboxyl chloride, cyclohexane tetracarboxylic acid chloride.
6. The method of claim 1, wherein the hydrophilic material in step (5) is sodium alginate, polyvinyl alcohol, or dextran solution, and the corresponding cross-linking agent is calcium chloride, glutaraldehyde, or polyethyleneimine solution, respectively.
7. The polyamide pervaporation composite membrane with the hydrophilic layer prepared by the method of claim 1 can solve the problems of poor hydrophilicity, pollution resistance and more defects of a polyamide membrane layer, and can be used for preparing a pervaporation dehydration membrane with hydrophilic surface and hydrophobic inside, so as to promote rapid adsorption and desorption of water molecules on the membrane and improve the separation performance of the membrane.
The invention has the advantages that:
1. the invention solves the problems of poor surface hydrophilicity, pollution resistance and defects of common polyamide membranes, is suitable for various substrate membrane materials such as polyacrylonitrile, polyethersulfone, polysulfone and the like, is simultaneously suitable for various hydrophilic materials such as sodium alginate, polyvinyl alcohol, dextran and the like, and has simple operation and easy popularization.
2. Based on the adsorption and desorption mechanism of water molecules on the pervaporation membrane, the pervaporation composite membrane prepared by the invention has the characteristics of hydrophobic surface and hydrophilic property in the membrane, and the separation performance of the membrane is obviously improved.
Drawings
FIG. 1 is an infrared spectrum of a modified polyamide pervaporation membrane with or without hydrophilicity in the practice of the present invention.
FIG. 2 shows the surface water contact angle of a hydrophilically modified polyamide pervaporation membrane in the practice of the present invention.
FIG. 3 is a scanning electron microscope image of a pervaporation membrane of a hydrophilically modified polyamide in the practice of the present invention.
Detailed Description
The used base film is a commodity film.
The invention will be further illustrated with reference to specific examples.
Comparative examples
(1) Shearing a polyacrylonitrile substrate film into a proper size, soaking the proper size in a 1.5mol/L sodium hydroxide solution at 55 ℃ for 2 hours, increasing the hydrophilicity of the surface of the film, then soaking the film in deionized water for 24 hours, fixing the film on a spin coater, and removing the water on the surface of the film by utilizing a rotary centrifugal force;
(2) Uniformly soaking the surface of the substrate film obtained in the step (1) by using polyethyleneimine/water solution with the mass fraction of 1.5wt%, standing for 5min, pouring out excess solution, and removing unbound water phase monomer on the surface of the film by using rotary centrifugal force;
(3) Uniformly distributing 0.2w/v% of trimesic acid chloride/n-hexane solution on the surface of the material obtained in the step (2), reacting for 120s, pouring out excessive solution, washing n-hexane, and removing unreacted oil phase monomer on the surface of the membrane by using rotary centrifugal force;
(4) And (3) standing the material obtained in the step (3) at 60 ℃ for 7min to obtain a uniform and compact polyamide separation layer.
The unmodified polyamide pervaporation composite membrane was tested, at 70 ℃, for a separation factor of 125.1 for an 85wt% ethanol/water solution, permeation flux of 2574.1 g.m -2 ·h -1 。
Example 1
(1) Soaking polyacrylonitrile base film cut into proper size in deionized water for 5 hr to eliminate surface impurity, wetting pore canal, fixing on a spin coater and eliminating water from the surface of the film;
(2) Uniformly infiltrating the surface of the substrate film obtained in the step (1) with m-phenylenediamine/water solution with the mass fraction of 1.5wt%, standing for 5min, pouring out excess solution, and removing unbound water phase monomer on the surface of the film by using rotary centrifugal force;
(3) Uniformly distributing 0.3w/v% of terephthaloyl chloride/n-hexane solution on the surface of the material obtained in the step (2), standing for 120s, pouring off excessive solution, flushing with n-hexane, and removing unreacted oil phase monomer on the surface of the membrane by using rotary centrifugal force;
(4) And (3) standing the material obtained in the step (3) at 60 ℃ for 5min to obtain a uniform and compact polyamide separation layer.
(5) Fixing the film in the step (4) by using a self-made plate frame, clamping the peripheral frame by using a clamp to prevent the reaction solution from leaking and overflowing, uniformly coating the sodium alginate solution with the mass fraction of 1.5wt% on the surface of the film, standing for 30min, pouring out the redundant solution, flushing the surface of the film by using deionized water, removing the redundant solution, and drying by using an air knife. Then the membrane material is soaked in a calcium chloride solution with the mass fraction of 1.25wt% for 30min, taken out, and the superfluous calcium ions on the surface of the membrane are cleaned and soaked in deionized water for standby.
The sodium alginate and calcium chloride modified polyamide pervaporation composite membranes were tested on unhydrolyzed polyacrylonitrile base membranes as compared to the comparative examples. At 70 ℃, the separation factor for 85wt% ethanol/water solution is 363.8, the permeation flux is 1986.2 g.m -2 ·h -1 . Compared with an unmodified polyamide pervaporation membrane, the membrane surface hydrophilicity is improved, so that the separation selectivity of the membrane is remarkably improved, and the membrane thickness is increased, so that the permeation flux is reduced.
Example 2
(1) Shearing a polyacrylonitrile substrate film into a proper size, soaking the proper size in a 1.5mol/L sodium hydroxide solution at 55 ℃ for 2 hours to increase the hydrophilicity of the surface of the film, then soaking the film in deionized water for 24 hours, fixing the film on a spin coater, and removing the moisture on the surface of the film by utilizing a rotary centrifugal force;
(2) Uniformly soaking the surface of the substrate film obtained in the step (1) by using polyethyleneimine/water solution with the mass fraction of 1.5wt%, standing for 5min, pouring out excess solution, and removing unbound water phase monomers on the surface of the film by using rotary centrifugal force;
(3) Uniformly distributing 0.2w/v% of trimesic acid chloride/n-hexane solution on the surface of the substrate film obtained in the step (2), reacting for 120s, pouring out excessive solution, flushing n-hexane, and removing unreacted oil phase monomer on the surface of the film by using rotary centrifugal force;
(4) And (3) standing the material obtained in the step (3) at 60 ℃ for 7min to obtain a uniform and compact polyamide separation layer.
(5) Fixing the film in the step (4) by using a self-made plate frame, clamping the peripheral frame by using a clamp to prevent the reaction solution from leaking and overflowing, uniformly coating the sodium alginate solution with the mass fraction of 1.5wt% on the surface of the film, standing for 30min, pouring out the redundant solution, flushing the surface of the film by using deionized water, removing the redundant solution, and drying by using an air knife. Then the membrane material is soaked in a calcium chloride solution with the mass fraction of 1.25wt% for 30min, taken out, and the superfluous calcium ions on the surface of the membrane are cleaned and soaked in deionized water for standby.
The sodium alginate and calcium chloride modified polyamide pervaporation composite membranes were tested on hydrolyzed polyacrylonitrile base membranes as compared to the comparative examples. At 70 ℃, the separation factor for 85wt% ethanol/water solution is 525.1, the permeation flux is 2087.9 g.m -2 ·h -1 . Compared with an unmodified polyamide pervaporation membrane, the membrane separation selectivity is improved by 4 times, and the membrane thickness is increased so that the permeation flux is reduced.
Example 3
(1) Cutting a polysulfone basement membrane into a proper size, soaking in deionized water for 5 hours, wetting pore channels, removing surface impurities, fixing by a self-made plate frame, and blowing off water on the surface of the membrane by an air knife;
(2) Uniformly soaking the surface of the substrate film obtained in the step (1) by using a diethylenetriamine/water solution with the mass fraction of 1.5wt%, standing for 5min, pouring out the redundant solution, and blowing off the unbound water phase monomer on the surface of the film by using an air knife;
(3) Uniformly distributing 0.2w/v% of 1,3, 5-cyclohexane triacyl chloride/n-hexane solution on the surface of the material obtained in the step (2), standing for 120s, pouring off the redundant solution, and blowing off the redundant solution on the surface of the film by using an air knife;
(4) And (3) standing the material obtained in the step (3) at 50 ℃ for 7min to obtain a uniform and compact polyamide separation layer.
(5) Fixing the film in the step (4) by using the plate frame, uniformly coating the dextran solution with the mass fraction of 1.0wt% on the surface of the film in the step (4), standing for 10min, pouring off the redundant solution, flushing the surface of the film by using deionized water, removing the redundant solution, and drying by using an air knife. Then, the membrane material is soaked in polyethyleneimine solution with the mass fraction of 1.5wt% for 1 hour, and then the membrane material is taken out, a large amount of deionized water is used for washing the unreacted solution on the surface, and the membrane material is soaked in deionized water for standby.
The test was performed on dextran and polyethyleneimine modified polyamide pervaporation composite membranes on polysulfone substrate membranes, in contrast to the comparative examples. At 70 ℃, the separation factor for 85wt% ethanol/water solution is 249.5, the permeation flux is 2413.8 g.m -2 ·h -1 The separation selectivity of the membrane is improved by 1 time, and the permeation flux is slightly reduced.
Example 4
(1) Cutting a polyethersulfone basement membrane into a proper size, soaking in deionized water for 5 hours, wetting pore channels, removing surface impurities, fixing by a self-made plate frame, and blowing off water on the surface of the membrane by an air knife;
(2) Uniformly soaking the surface of the material obtained in the step (1) by using an ethylenediamine/water solution with the mass fraction of 1.5wt%, standing for 5min, pouring off the redundant solution, and blowing off the redundant solution on the surface of the film by using an air knife to ensure that no liquid drops exist on the surface of the film;
(3) Uniformly distributing 0.3w/v% of terephthaloyl chloride/n-hexane solution on the surface of the material obtained in the step (2), standing for 150s, pouring off redundant solution, and blowing off redundant solution on the surface of the film by using an air knife;
(4) And (3) standing the material obtained in the step (3) at 60 ℃ for 5min to obtain a uniform and compact polyamide separation layer.
(5) Fixing the membrane in the step (4) by using a polymethyl methacrylate frame and a rubber sealing ring, clamping the peripheral frame by using a clamp to prevent the reaction solution from leaking and overflowing, uniformly coating the polyvinyl alcohol solution with the mass fraction of 1.0wt% on the surface of the membrane in the step (4), standing for 30min, pouring off the redundant solution, flushing the surface of the membrane by using deionized water, removing the redundant solution, drying by using an air knife, then soaking in glutaraldehyde solution with the mass fraction of 1.5wt% at 70 ℃ for 1h, taking out, flushing the solution with a large amount of deionized water, and soaking in deionized water for standby.
The test was performed on a polyvinyl alcohol and glutaraldehyde modified polyamide pervaporation composite membrane on a polyethersulfone substrate membrane, in comparison with the comparative example. At 70 ℃, the separation factor for 85wt% ethanol/water solution is 396.3, the permeation flux is 1956.8 g.m -2 ·h -1 。
Table 1 shows the main differences between the conditions for the preparation of films of comparative examples and examples 1-4, and Table 2 shows the dehydration properties of pervaporated ethanol for the preparation of film materials of comparative examples and examples 1-4.
TABLE 1
TABLE 2
| Flux (J, g.m) -2 ·h -1 ) | Separation factor (alpha) | PSI(＝J·(α-1),×10 5 ,g·m -2 ·h -1 ) | |
| Comparative examples | 125.1 | 2574.1 | 3.2 |
| Example 1 | 363.8 | 1986.2 | 7.2 |
| Example 2 | 525.1 | 2087.9 | 10.9 |
| Example 3 | 249.5 | 2413.8 | 6.0 |
| Example 4 | 396.3 | 1956.8 | 7.7 |
It can be seen that the separation factor of the hydrophilically modified polyamide pervaporation membrane is remarkably improved due to the improvement of the hydrophilicity of the active layer, and meanwhile, the mass transfer resistance of water molecules is increased and the flux is reduced due to the increase of the thickness of the membrane layer.
Claims (7)
1. The preparation method mainly comprises the steps of (1) treating a base film, combining an amine/water solution on the base film, reacting an oil phase monomer with an amine monomer to generate polyamide, carrying out heat treatment on the polyamide film, and coating a hydrophilic material on the polyamide film to form the composite film.
The specific process of steps (1) - (5) is as follows:
cutting a substrate film into a proper size, soaking in deionized water for 5-24 hours, wetting pore channels, removing surface impurities, and then removing the deionized water on the surface; step (2) fixing the substrate film on a spin coater or a self-made plate frame, uniformly distributing the amine/water solution with the mass fraction of 0.5-2.5wt% on the surface of the substrate film, standing for 5-15min, pouring out the redundant solution, and removing the amine monomer which is not combined on the surface of the film; uniformly distributing the oil phase monomer solution with the volume fraction of 0.1-0.5w/v% on the surface of the membrane in the step (2), reacting for 200-600s, pouring out the excessive oil phase/n-hexane solution, washing unreacted monomers on the surface of the membrane with n-hexane, and then removing liquid drops on the surface of the membrane; placing the polyamide membrane layer obtained in the step (4) in an oven at 40-100 ℃ for 5-20min to enable amine monomers and oil phase monomers to fully react; uniformly coating 0.5-2.5wt% of hydrophilic material on the surface of the film in the step (4), soaking for 10-50min, pouring off redundant solution, removing redundant solution on the surface of the film, enabling the surface of the film to have no liquid drops, soaking in 0.1-1.5wt% of cross-linking agent solution for 30-90min, taking out, cleaning redundant solution on the surface of the film, and soaking in deionized water for standby.
2. The method of claim 1, wherein the base membrane in step (1) is a base membrane material such as polysulfone, polyethersulfone, polyacrylonitrile, and polyacrylonitrile after hydrolysis.
3. The method according to claim 1, wherein the method for removing the surface residual solution is spin drying by using a rotating centrifugal force or blow drying by using an air knife.
4. The method according to claim 1, wherein the amine in step (2) is polyethyleneimine, diethylenetriamine, m-phenylenediamine, triethylenetetramine, ethylenediamine.
5. The method according to claim 1, wherein the oil phase monomer in the step (3) is trimesoyl chloride, terephthaloyl chloride, 1,3, 5-hexane tricarboxyl chloride, cyclohexane tetracarboxylic acid chloride.
6. The method of claim 1, wherein the hydrophilic material in step (5) is sodium alginate, polyvinyl alcohol, or dextran solution, and the corresponding cross-linking agent is calcium chloride, glutaraldehyde, or polyethyleneimine solution, respectively.
7. The polyamide pervaporation composite membrane with the hydrophilic layer prepared by the method of claim 1 can solve the problems of poor hydrophilicity, pollution resistance and more defects of a polyamide membrane layer, and can prepare a pervaporation dehydration membrane with hydrophilic surface and hydrophobic inside, so that rapid adsorption and desorption of water molecules on the membrane are promoted, and the separation performance of the membrane is improved.
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