CN116371211A - Preparation method of hydrophilic composite membrane - Google Patents
Preparation method of hydrophilic composite membrane Download PDFInfo
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- 239000012528 membrane Substances 0.000 title claims abstract description 87
- 239000002131 composite material Substances 0.000 title claims abstract description 37
- 238000002360 preparation method Methods 0.000 title claims abstract description 18
- 229920001690 polydopamine Polymers 0.000 claims abstract description 30
- 239000002105 nanoparticle Substances 0.000 claims abstract description 27
- CTENFNNZBMHDDG-UHFFFAOYSA-N Dopamine hydrochloride Chemical compound Cl.NCCC1=CC=C(O)C(O)=C1 CTENFNNZBMHDDG-UHFFFAOYSA-N 0.000 claims abstract description 17
- 229960001149 dopamine hydrochloride Drugs 0.000 claims abstract description 17
- 239000002033 PVDF binder Substances 0.000 claims description 39
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 39
- 238000005266 casting Methods 0.000 claims description 22
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 19
- 238000000034 method Methods 0.000 claims description 16
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 14
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 14
- 238000003756 stirring Methods 0.000 claims description 10
- 239000008367 deionised water Substances 0.000 claims description 8
- 229910021641 deionized water Inorganic materials 0.000 claims description 8
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 7
- 229920000620 organic polymer Polymers 0.000 claims description 7
- 239000002245 particle Substances 0.000 claims description 7
- 239000004408 titanium dioxide Substances 0.000 claims description 7
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 claims description 6
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 6
- 239000003960 organic solvent Substances 0.000 claims description 6
- 239000002861 polymer material Substances 0.000 claims description 6
- 238000001132 ultrasonic dispersion Methods 0.000 claims description 6
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 claims description 4
- 239000003495 polar organic solvent Substances 0.000 claims description 4
- 229920002239 polyacrylonitrile Polymers 0.000 claims description 4
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 3
- 229920002301 cellulose acetate Polymers 0.000 claims description 3
- 229920002492 poly(sulfone) Polymers 0.000 claims description 3
- 239000000377 silicon dioxide Substances 0.000 claims description 3
- 235000012239 silicon dioxide Nutrition 0.000 claims description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 2
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims description 2
- 229910021389 graphene Inorganic materials 0.000 claims description 2
- 239000002808 molecular sieve Substances 0.000 claims description 2
- 238000007790 scraping Methods 0.000 claims description 2
- 229910052709 silver Inorganic materials 0.000 claims description 2
- 239000004332 silver Substances 0.000 claims description 2
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 claims description 2
- 238000009987 spinning Methods 0.000 claims description 2
- 238000009210 therapy by ultrasound Methods 0.000 claims description 2
- 238000000926 separation method Methods 0.000 abstract description 35
- 230000004907 flux Effects 0.000 abstract description 20
- 239000002346 layers by function Substances 0.000 abstract description 11
- 239000010410 layer Substances 0.000 abstract description 8
- 229920000642 polymer Polymers 0.000 abstract description 5
- 239000012510 hollow fiber Substances 0.000 abstract description 3
- 238000000614 phase inversion technique Methods 0.000 abstract description 3
- 238000004140 cleaning Methods 0.000 abstract description 2
- 238000007654 immersion Methods 0.000 abstract description 2
- 238000001556 precipitation Methods 0.000 abstract description 2
- 239000007787 solid Substances 0.000 abstract description 2
- 238000002604 ultrasonography Methods 0.000 abstract 1
- 239000000243 solution Substances 0.000 description 29
- VYFYYTLLBUKUHU-UHFFFAOYSA-N dopamine Chemical compound NCCC1=CC=C(O)C(O)=C1 VYFYYTLLBUKUHU-UHFFFAOYSA-N 0.000 description 12
- 239000000463 material Substances 0.000 description 12
- 230000004048 modification Effects 0.000 description 9
- 238000012986 modification Methods 0.000 description 9
- 239000007788 liquid Substances 0.000 description 8
- 238000001471 micro-filtration Methods 0.000 description 7
- 238000000576 coating method Methods 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 6
- 229960003638 dopamine Drugs 0.000 description 6
- 230000014759 maintenance of location Effects 0.000 description 6
- SOQBVABWOPYFQZ-UHFFFAOYSA-N oxygen(2-);titanium(4+) Chemical compound [O-2].[O-2].[Ti+4] SOQBVABWOPYFQZ-UHFFFAOYSA-N 0.000 description 6
- PYWVYCXTNDRMGF-UHFFFAOYSA-N rhodamine B Chemical compound [Cl-].C=12C=CC(=[N+](CC)CC)C=C2OC2=CC(N(CC)CC)=CC=C2C=1C1=CC=CC=C1C(O)=O PYWVYCXTNDRMGF-UHFFFAOYSA-N 0.000 description 6
- 229940043267 rhodamine b Drugs 0.000 description 6
- 239000006185 dispersion Substances 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- 239000004695 Polyether sulfone Substances 0.000 description 4
- 239000011248 coating agent Substances 0.000 description 4
- 229920006393 polyether sulfone Polymers 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- 229920006254 polymer film Polymers 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229920001477 hydrophilic polymer Polymers 0.000 description 2
- 239000004005 microsphere Substances 0.000 description 2
- 239000002957 persistent organic pollutant Substances 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- 239000002351 wastewater Substances 0.000 description 2
- WLWFNJKHKGIJNW-UHFFFAOYSA-N Phensuximide Chemical compound O=C1N(C)C(=O)CC1C1=CC=CC=C1 WLWFNJKHKGIJNW-UHFFFAOYSA-N 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 239000007853 buffer solution Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 229920000891 common polymer Polymers 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 229910001385 heavy metal Inorganic materials 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 229910017053 inorganic salt Inorganic materials 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 229920002521 macromolecule Polymers 0.000 description 1
- 238000002715 modification method Methods 0.000 description 1
- 108010004563 mussel adhesive protein Proteins 0.000 description 1
- 239000011664 nicotinic acid Substances 0.000 description 1
- 229920005597 polymer membrane Polymers 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 108090000623 proteins and genes Proteins 0.000 description 1
- 102000004169 proteins and genes Human genes 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 238000000108 ultra-filtration 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
- B01D67/0079—Manufacture of membranes comprising organic and inorganic components
-
- 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
- B01D69/06—Flat membranes
-
- 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
- B01D69/08—Hollow fibre membranes
-
- 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
-
- 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
-
- 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
- C02F2101/30—Organic 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
- 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)
- Inorganic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Organic Chemistry (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
Abstract
The invention belongs to the technical field of membrane separation, and discloses a preparation method of a hydrophilic composite membrane. The hydrophilic composite membrane is a flat membrane or a hollow fiber membrane and comprises a supporting layer and a separation functional layer, wherein the supporting layer is positioned below the separation functional layer; the separation functional layer is a polydopamine separation membrane containing uniformly dispersed nano particles, wherein the nano particles account for 0.01-1% of the total solid content of the separation functional layer by mass. The organic composite membrane not only has good separation and selection performance, but also has good pollution resistance. In addition, in the membrane preparation process, dopamine hydrochloride and inorganic nano particles are added into a gel bath, and are uniformly dispersed when being mixed by ultrasound, and then the nano particle modified polydopamine polymer composite membrane is prepared by adopting an immersion precipitation phase inversion method. The membrane has the advantages of simple preparation process, large permeation flux and high hydrophilicity, and can remarkably prolong the service life and prolong the cleaning period.
Description
Technical Field
The invention belongs to the technical field of membrane separation, and particularly relates to a preparation method of a composite membrane, in particular to a separation membrane suitable for treating wastewater containing organic pollutants.
Background
The membrane separation technology is a novel energy-saving and environment-friendly separation technology, wherein the pressure-driven separation membrane can be used for heavy metal ion removal, inorganic salt separation, macromolecule separation, dye treatment and the like according to the aperture and surface charge characteristics. Common polymer separation membranes such as polyvinylidene fluoride membranes and polysulfone membranes are easy to cause membrane pollution in the use process, so that the separation capability of the membranes is greatly reduced. Thus, improving the fouling resistance of such membranes and the advanced treatment of concentrates remains an important topic of research in the field of membrane separation. The blending modification of the polymer by using hydrophilic polymer and nano particles is a relatively common method. Because the compatibility of the materials is poor, the addition amount of hydrophilic polymers and nano particles in the polymer casting solution is low, the ratio of hydrophilic materials on the surface of the separation membrane after the membrane is formed is extremely low, and the high-hydrophilicity polymer membrane is difficult to obtain. How to further improve the surface hydrophilicity and pollution resistance of the polymer film, simplify the modification process and have important research value. Inspired by mussel adhesive proteins, polydopamine (PDA) coatings have become one of the easiest and most versatile surface modification methods. The simplest surface modification mode is to soak the polymer film in alkaline aqueous solution of dopamine, and the surface of the substrate spontaneously forms a PDA coating with the thickness of usually 1-100 nm. And adding a certain amount of inorganic nano particles into the polydopamine hydrochloride solution to obtain the polydopamine composite membrane doped with the nano particles. Shao Bing and the like, wherein the poly dopamine powder and the polyvinylidene fluoride are blended to prepare a blend membrane, and when the PDA addition amount is 0.3 percent (mass fraction), the pure water flux is 59.19L/m from the PVDF control membrane 2 h is increased to 69.63L/m 2 h. Shao Bing, liu Lifen, yang Fenglin. Preparation of PVDF/PDA blend film and performance study, film science and technology, 34 volumes, 2014:57-61.CN 107486037A discloses a preparation method of a PVDF/PDA composite film with hydrophilic performance. By adding dopamine to a buffer solution, magnetic forceStirring for 24-72h, adding PVDF film, and magnetically stirring for 3-5 days; the membrane is a membrane integral hydrophilization structure which is obtained by modifying a large number of PDA microspheres generated in situ on the upper surface, the lower surface and the membrane pore walls, wherein the membrane section is a spongy structure which is formed by tiling the PDA microspheres to cover the membrane pore walls but is communicated with each other. Due to the good hydrophilicity of the dopamine and the existence of the membrane microreactor effect in the modification process, the hydrophilic performance and the anti-pollution performance of the PVDF/PDA composite membrane obtained by modification are greatly improved when the PVDF/PDA composite membrane is used as a water treatment application membrane. In order to improve the hydrophilicity and anti-pollution performance of the PVDF micro-filtration membrane, the PVDF micro-filtration membrane is prepared by an immersion precipitation phase conversion method, feng Xia and the like utilize the advantages of super-strong adhesiveness of dopamine and easy self-polymerization to form Polydopamine (PDA), and the PVDF micro-filtration membrane is subjected to surface coating modification. The results show that: PDA is successfully deposited on the surface of the PVDF micro-filtration membrane by a coating method, so that the hydrophilia and protein adsorption resistance of the surface of the PVDF micro-filtration membrane are improved, and when the modification time is 6 hours, the pure water flux is 80L/m 2 h is increased to 107L/m 2 h, the water contact angle is reduced from 95 degrees of the pure PVDF film to 44 degrees of the modified film. [ Feng Xia, xia Weiwei, ma Xiao, zhao Yiping, chen Li, preparation and performance of dopamine bionic modified PVDF microfiltration membrane, university of Tianjin university, vol.37, 2018,14-19.]
However, the method combines a phase inversion method and an interface coating two-step process, increases technical complexity, is difficult to control the process, has long coating stage time, is unfavorable for large-scale application, and has high product cost. Meanwhile, the combination of the base film and the functional layer is not tight enough, and the modification effect is poor.
Disclosure of Invention
In order to solve the technical problems, the invention provides an easily prepared polydopamine hydrophilic composite membrane modified by nano particles and a preparation method thereof. Commercial polymers such as polyvinylidene fluoride, polysulfone, polyacrylonitrile, cellulose acetate and the like are used as film forming materials, nano particles such as titanium dioxide, silicon dioxide and the like are used as gel bath inorganic additives in gel bath, dopamine hydrochloride is used as a modifying reagent, a phase inversion method is adopted to prepare a composite film, and the primary film is utilized to be in adsorption contact with polydopamine and the nano particles to realize the rapid modification of the separation film skin layer, so that the composite film with stable and high hydrophilicity is obtained, and the film pollution is remarkably reduced. The invention is helpful to greatly improve the anti-pollution performance of the organic polymer film and simplify the preparation process of the hydrophilic modified film, thereby being beneficial to realizing wider application of the polymer film.
The technical scheme of the invention is as follows:
a method for preparing a hydrophilic composite membrane, comprising the steps of:
(1) Preparation of casting solution A
Adding an organic polymer material into an organic solvent, rapidly stirring, and obtaining a casting solution A after 24 hours;
(2) Preparation of gel bath B
Adding inorganic nano particles into deionized water for ultrasonic dispersion, sequentially adding hydrogen peroxide and dopamine hydrochloride, and continuing ultrasonic treatment to obtain gel bath B;
(3) Preparation of composite membranes
And uniformly scraping or spinning the casting solution A by using a scraper, immersing the casting solution A into a gel bath B, and carrying out phase inversion for a period of time to obtain the nano particle doped polydopamine composite membrane.
The mass percentage of the organic polymer material in the casting solution A in the step (1) is 12% -25%; the mass percentage of the organic solvent is 75-88%.
The organic polymer material in the step (1) is one or more than two of polyvinylidene fluoride, polyethersulfone, polyacrylonitrile and cellulose acetate;
in the step (1), the organic solvent is a strong polar organic solvent, and further, the strong polar organic solvent is one or more than two of N, N-dimethylacetamide, N, N-dimethylformamide, N-methylpyrrolidone and dimethyl sulfoxide.
The mass percentage of inorganic nano particles in the gel bath B in the step (2) is 0.001-1%, and the particle size of the inorganic nano particles is 5-50nm; the mass percentage of the dopamine hydrochloride is 0.01-1%; the mass percentage of the hydrogen peroxide is 0.001-1%.
In the step (2), the nano particles are one or more than two of titanium dioxide, silicon dioxide, silver, graphene oxide and a nano molecular sieve.
The invention has the beneficial effects that: the composite membrane prepared by the invention is a flat membrane or a hollow fiber separation membrane, the separation functional layer of the composite membrane adopts a hydrophilic polydopamine material and is doped with hydrophilic inorganic nano particles, and the prepared composite membrane not only has good separation and selection performance, but also has good anti-pollution performance due to good hydrophilicity and interface performance and extremely thin layer thickness. The membrane has the advantages of simple preparation process and large permeation flux, can obviously prolong the service life of the membrane, prolongs the cleaning period, and is very suitable for treating wastewater containing organic pollutants.
Detailed Description
The following describes the embodiments of the present invention in further detail with reference to the drawings.
Example 1
Adding a polyvinylidene fluoride material into an N, N-dimethylacetamide solution to uniformly disperse to obtain 30g of casting solution A, wherein the mass fraction of polyvinylidene fluoride is 14%, and stirring and dissolving the polyvinylidene fluoride for later use; dispersing nano titanium dioxide with the particle size of 25nm in deionized water to prepare 3000g of gel bath B, wherein the mass percentage of the titanium dioxide is 0.01%; adding 1.5g of dopamine hydrochloride and 1g of hydrogen peroxide (30%) into the mixture, and performing ultrasonic dispersion for 10min; and (3) rapidly immersing the casting film liquid scraped by a scraper into a gel bath, and carrying out phase inversion to obtain the hydrophilically modified composite film.
The prepared hydrophilic composite membrane is a flat membrane or a hollow fiber membrane and comprises a supporting layer and a separation functional layer, wherein the supporting layer is positioned below the separation functional layer; the separation functional layer is a polydopamine separation membrane containing uniformly dispersed inorganic nano particles, wherein the inorganic nano particles account for 0.01-1% of the total solid content of the separation functional layer by mass.
The thickness of the separation functional layer is 10-200nm.
The particle size of the nano particles is 5-50nm.
The supporting layer is a microfiltration or ultrafiltration membrane, the thickness is 50-500 mu m, and the aperture is 10-1000 nm.
The pure water flux of the prepared composite membrane is 290L/m under 0.1MPa 2 h，The retention rate of rhodamine B with the concentration of 50mg/L is 99 percent, and the dye solution flux reaches 260L/m after 1h of operation 2 h。
Example 2
Adding a polyethersulfone material into an N-methyl pyrrolidone solution for uniform dispersion to obtain 30g of casting solution A, wherein the mass fraction of polyethersulfone is 15%, and stirring uniformly for later use; dispersing nano titanium dioxide with the particle size of 25nm in deionized water to prepare 3000g of gel bath B, wherein the mass percentage of the titanium dioxide is 0.01%; adding 1.5g of dopamine hydrochloride and 1g of hydrogen peroxide (30%) into the mixture, and performing ultrasonic dispersion for 10min; and (3) rapidly immersing the casting film liquid scraped by a scraper into a gel bath, and carrying out phase inversion to obtain the hydrophilically modified composite film.
The pure water flux of the prepared composite membrane is 278L/m under 0.1MPa 2 h, the retention rate of rhodamine B with the concentration of 50mg/L is 97%, and the dye solution flux reaches 260L/m after 1h of operation 2 h。
Example 3
Adding a polyacrylonitrile material into an N, N-dimethylformamide solution for uniform dispersion to obtain 30g of casting solution A, wherein the mass fraction of polyethersulfone is 15%, and stirring uniformly for later use; dispersing nano titanium dioxide with the particle size of 25nm in deionized water to prepare 3000g of gel bath B, wherein the mass percentage of the titanium dioxide is 0.01%; adding 3g of dopamine hydrochloride and 1g of hydrogen peroxide (30%) into the mixture, and performing ultrasonic dispersion for 10min; and (3) rapidly immersing the casting film liquid scraped by a scraper into a gel bath, and carrying out phase inversion to obtain the hydrophilically modified composite film.
The pure water flux of the prepared composite membrane is 230L/m under 0.1MPa 2 h, the retention rate of rhodamine B with the concentration of 50mg/L is 97%, and the dye solution flux reaches 204L/m after 1h of operation 2 h。
Comparative example 1
Adding polyvinylidene fluoride material, dopamine hydrochloride and 25nm nano titanium dioxide into N, N-dimethylacetamide solution to perform uniform dispersion to obtain 30g of dispersion liquid A, wherein the mass percent of polyvinylidene fluoride is 14%, the mass percent of dopamine hydrochloride is 0.5%, and the mass percent of nano titanium dioxide is 0.5%, and uniformly stirring for later use; 3000g of deionized water as gel bath B; and (3) rapidly immersing the casting film liquid scraped by a scraper into a gel bath, and carrying out phase inversion to obtain the separation film.
The pure water flux of the prepared separation membrane at 0.1MPa is 187L/m 2 h, the retention rate of rhodamine B with the concentration of 50mg/L is 98%, and the dye solution flux reaches 138L/m after 1h of operation 2 h。
Comparative example 2
Adding hydrogen peroxide into the dopamine hydrochloride solution, stirring for 24 hours at room temperature, filtering, drying, grinding and collecting dopamine powder;
adding polyvinylidene fluoride material and polydopamine into N, N-dimethylacetamide solution to uniformly disperse to obtain 30g of dispersion liquid A, wherein the mass fraction of polyvinylidene fluoride is 14%, the mass fraction of polydopamine is 1%, and uniformly stirring for later use; 3000g of deionized water as gel bath B; and (3) rapidly immersing the casting film liquid scraped by a scraper into a gel bath, and carrying out phase inversion to obtain the separation film.
The pure water flux of the prepared separation membrane is 166L/m under 0.1MPa 2 h, the retention rate of rhodamine B with the concentration of 50mg/L is 98%, and the dye solution flux reaches 134L/m after 1h of operation 2 h。
Comparative example 3
Adding a polyvinylidene fluoride material into an N, N-dimethylacetamide solution to uniformly disperse to obtain 30g of casting solution A, wherein the mass fraction of polyvinylidene fluoride is 14%, and stirring and dissolving the polyvinylidene fluoride for later use; preparing 3000g of gel bath B by deionized water; and (3) rapidly immersing the casting film liquid scraped by a scraper into a gel bath, and carrying out phase inversion to obtain the polyvinylidene fluoride separation film.
Preparing 3000g of a solution C of the bazamine hydrochloride, adding 1.5g of dopamine hydrochloride, 1g of hydrogen peroxide (30%) and 25nm of titanium dioxide, and performing ultrasonic dispersion for 10min;
immersing the polyvinylidene fluoride separation membrane into a dopamine hydrochloride solution for 10min, taking out and airing to obtain a polyvinylidene fluoride/polydopamine composite membrane;
the pure water flux of the prepared composite membrane is 97L/m under 0.1MPa 2 h, the retention rate of rhodamine B with the concentration of 50mg/L is 99%, and the dye solution flux reaches 85L/m after 1h of operation 2 h。
As shown in comparative example 1, the separation membrane obtained by adding the inorganic nano particles and the dopamine hydrochloride into the polyvinylidene fluoride casting membrane solution is an organic-inorganic hybrid membrane, and the dopamine hydrochloride and the nano titanium dioxide have stronger hydrophilicity and poorer compatibility with the polyvinylidene fluoride material, so that compared with the composite membrane prepared by the invention, the prepared membrane is compact and has smaller flux. Meanwhile, the hydrophilic material is wrapped by polyvinylidene fluoride, so that the pollution resistance is poor.
As can be seen from comparative example 2, the membrane is prepared by directly blending polydopamine and polyvinylidene fluoride, and the obtained membrane pure water flux and dye solution flux are smaller than those of the polyvinylidene fluoride membrane, and the polydopamine nanoparticles are wrapped by the polyvinylidene fluoride when the membrane is prepared by blending, so that the polydopamine is less left on the surface of the membrane, and the membrane performance is improved less.
As is clear from comparative example 3, the composite membrane was obtained by immersing the polyvinylidene fluoride membrane in the dopamine hydrochloride solution, but two steps were required, and the flux of the obtained composite membrane was remarkably decreased due to the thicker skin layer. According to the invention, the polydopamine composite membrane with excellent anti-pollution performance can be obtained by adopting a one-step method, the polydopamine cortex is positioned on the surface of the polyvinylidene fluoride composite membrane, hydrophilic particles are prevented from being wrapped by polymers, and the method is simple and feasible.
Claims (5)
1. A method for preparing a hydrophilic composite membrane, comprising the steps of:
(1) Preparation of casting solution A
Adding an organic polymer material into an organic solvent, rapidly stirring, and obtaining a casting solution A after 24 hours;
(2) Preparation of gel bath B
Adding inorganic nano particles into deionized water for ultrasonic dispersion, sequentially adding hydrogen peroxide and dopamine hydrochloride, and continuing ultrasonic treatment to obtain gel bath B;
(3) Preparation of composite membranes
And uniformly scraping or spinning the casting solution A by using a scraper, immersing the casting solution A into a gel bath B, and carrying out phase inversion for a period of time to obtain the nano particle doped polydopamine composite membrane.
2. The method according to claim 1, wherein,
the mass percentage of the organic polymer material in the casting solution A in the step (1) is 12% -25%; the mass percentage of the organic solvent is 75-88%;
the organic polymer material in the step (1) is one or more than two of polyvinylidene fluoride, polysulfone, polyacrylonitrile and cellulose acetate;
the organic solvent in the step (1) is a strong polar organic solvent.
3. The method according to claim 2, wherein the strongly polar organic solvent is one or a combination of two or more of N, N-dimethylacetamide, N-dimethylformamide, N-methylpyrrolidone and dimethylsulfoxide.
4. A process according to any one of claims 1 to 3, wherein,
the mass percentage of inorganic nano particles in the gel bath B in the step (2) is 0.001-1%, and the particle size of the inorganic nano particles is 5-50nm; the mass percentage of the dopamine hydrochloride is 0.01-1%; the mass percentage of the hydrogen peroxide is 0.001-1%.
5. The method according to claim 4, wherein,
in the step (2), the nano particles are one or more than two of titanium dioxide, silicon dioxide, silver, graphene oxide and a nano molecular sieve.
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| CN117643806B (en) * | 2024-01-30 | 2024-04-19 | 中国科学院合肥物质科学研究院 | Double-channel composite membrane and preparation method and application thereof |
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