CN116920638A - Novel composite micro-filtration membrane and preparation method thereof - Google Patents
Novel composite micro-filtration membrane and preparation method thereof Download PDFInfo
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- CN116920638A CN116920638A CN202311098663.7A CN202311098663A CN116920638A CN 116920638 A CN116920638 A CN 116920638A CN 202311098663 A CN202311098663 A CN 202311098663A CN 116920638 A CN116920638 A CN 116920638A
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- 239000002131 composite material Substances 0.000 title claims abstract description 45
- 238000001471 micro-filtration Methods 0.000 title claims abstract description 40
- 238000002360 preparation method Methods 0.000 title claims abstract description 12
- 229920006393 polyether sulfone Polymers 0.000 claims abstract description 64
- 239000004695 Polyether sulfone Substances 0.000 claims abstract description 62
- 239000004372 Polyvinyl alcohol Substances 0.000 claims abstract description 52
- 229920002451 polyvinyl alcohol Polymers 0.000 claims abstract description 52
- 239000002121 nanofiber Substances 0.000 claims abstract description 38
- 239000011148 porous material Substances 0.000 claims abstract description 24
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 19
- 238000010041 electrostatic spinning Methods 0.000 claims abstract description 18
- 238000005516 engineering process Methods 0.000 claims abstract description 12
- 238000002844 melting Methods 0.000 claims abstract description 6
- 238000013329 compounding Methods 0.000 claims abstract description 4
- 239000000243 solution Substances 0.000 claims description 46
- 238000005266 casting Methods 0.000 claims description 38
- 239000002904 solvent Substances 0.000 claims description 25
- 238000007790 scraping Methods 0.000 claims description 20
- 230000001112 coagulating effect Effects 0.000 claims description 19
- 238000009987 spinning Methods 0.000 claims description 17
- 239000003431 cross linking reagent Substances 0.000 claims description 14
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- 238000000034 method Methods 0.000 claims description 11
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 claims description 10
- 239000011521 glass Substances 0.000 claims description 10
- 229920000036 polyvinylpyrrolidone Polymers 0.000 claims description 8
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- 235000013855 polyvinylpyrrolidone Nutrition 0.000 claims description 8
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 6
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims description 6
- DNIAPMSPPWPWGF-UHFFFAOYSA-N Propylene glycol Chemical compound CC(O)CO DNIAPMSPPWPWGF-UHFFFAOYSA-N 0.000 claims description 6
- 239000002994 raw material Substances 0.000 claims description 6
- 239000007864 aqueous solution Substances 0.000 claims description 5
- 238000004140 cleaning Methods 0.000 claims description 5
- 238000001035 drying Methods 0.000 claims description 5
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 claims description 4
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 claims description 4
- FEWJPZIEWOKRBE-UHFFFAOYSA-N Tartaric acid Natural products [H+].[H+].[O-]C(=O)C(O)C(O)C([O-])=O FEWJPZIEWOKRBE-UHFFFAOYSA-N 0.000 claims description 4
- 239000003795 chemical substances by application Substances 0.000 claims description 4
- 238000001816 cooling Methods 0.000 claims description 4
- 239000007788 liquid Substances 0.000 claims description 4
- KDYFGRWQOYBRFD-UHFFFAOYSA-N succinic acid Chemical compound OC(=O)CCC(O)=O KDYFGRWQOYBRFD-UHFFFAOYSA-N 0.000 claims description 4
- 230000008961 swelling Effects 0.000 claims description 4
- 235000002906 tartaric acid Nutrition 0.000 claims description 4
- 239000011975 tartaric acid Substances 0.000 claims description 4
- 238000004132 cross linking Methods 0.000 claims description 3
- 238000002156 mixing Methods 0.000 claims description 3
- FEWJPZIEWOKRBE-JCYAYHJZSA-N Dextrotartaric acid Chemical compound OC(=O)[C@H](O)[C@@H](O)C(O)=O FEWJPZIEWOKRBE-JCYAYHJZSA-N 0.000 claims description 2
- 229920002125 Sokalan® Polymers 0.000 claims description 2
- 238000006243 chemical reaction Methods 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims description 2
- 238000000465 moulding Methods 0.000 claims description 2
- 239000004584 polyacrylic acid Substances 0.000 claims description 2
- 238000007711 solidification Methods 0.000 claims description 2
- 230000008023 solidification Effects 0.000 claims description 2
- 239000001384 succinic acid Substances 0.000 claims description 2
- 230000007613 environmental effect Effects 0.000 claims 2
- 230000004907 flux Effects 0.000 abstract description 9
- 230000000694 effects Effects 0.000 abstract description 8
- 238000000614 phase inversion technique Methods 0.000 abstract description 7
- 238000001914 filtration Methods 0.000 abstract description 6
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- 108091003079 Bovine Serum Albumin Proteins 0.000 description 3
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 description 3
- 239000000853 adhesive Substances 0.000 description 3
- 230000001070 adhesive effect Effects 0.000 description 3
- 230000002238 attenuated effect Effects 0.000 description 3
- 229940098773 bovine serum albumin Drugs 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 238000001556 precipitation Methods 0.000 description 3
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- 241000588724 Escherichia coli Species 0.000 description 1
- 241000238631 Hexapoda Species 0.000 description 1
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 1
- 230000004308 accommodation Effects 0.000 description 1
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/66—Polymers having sulfur in the main chain, with or without nitrogen, oxygen or carbon only
- B01D71/68—Polysulfones; Polyethersulfones
-
- 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
-
- 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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2323/00—Details relating to membrane preparation
- B01D2323/39—Electrospinning
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2325/00—Details relating to properties of membranes
- B01D2325/02—Details relating to pores or porosity of the membranes
-
- 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
-
- 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)
- Separation Using Semi-Permeable Membranes (AREA)
Abstract
The invention provides a novel composite micro-filtration membrane and a preparation method thereof, wherein the preparation method comprises the following steps: (1) Preparing an asymmetric polyethersulfone flat membrane by adopting a phase inversion method; (2) Preparing a hydrophilic polyvinyl alcohol nanofiber layer on the surface of the asymmetric polyethersulfone membrane prepared in the step (1) by adopting an electrostatic spinning technology by taking the asymmetric polyethersulfone membrane as a receiving bottom membrane; (3) And carrying out hot micro-melting compounding to obtain the novel composite micro-filtration membrane. The composite microfiltration membrane prepared by the invention has the advantages that the surface hydrophilic nanofiber layer has large porosity, good pore channel connectivity and pore diameter distribution of 10-15 mu m, can play a role in prefiltering, has excellent biocompatibility and hydrophilicity, low protein adsorption, ensures higher filtering precision and interception effect by the asymmetric polyethersulfone flat membrane of the base layer, has good comprehensive performance, uniform pore diameter distribution and low-pressure operability of 0.5bar, greatly improves water flux and interception rate, and has important application significance in the field of life science.
Description
Technical Field
The invention relates to the technical field of membrane materials, in particular to a novel composite microfiltration membrane and a preparation method thereof.
Background
The working principle of the microfiltration membrane mainly depends on static pressure difference at two sides of the membrane as driving force, and a screening mechanism of the microfiltration membrane is utilized to allow macromolecular organic matters and soluble solids to pass through and retain suspended matters, bacteria, macromolecular colloid and other substances. The operating pressure of the microfiltration membrane is generally 0.7-7 bar, the pore diameter is 0.1-5 mu m, and the separation effect is mainly controlled by the physical structure of the membrane, namely the pore diameter size, shape, distribution and the like of the membrane. At present, the microfiltration is widely applied in the field of life science, for example, the microfiltration is used for obtaining insect cells, separating escherichia coli, preparing amidolol sterile injection and sterilizing various solutions such as tissue fluid culture, antibiotics, serum, plasma proteins and the like.
The microfiltration membrane has high filtration precision, but has small accommodation amount for particles, and when the microfiltration membrane is used for filtering relatively complex samples (particles with large differences and different particle diameters or processing a large amount of protein substances), the phenomenon of blocking membrane holes or hole walls is easy to occur, and in order to solve the problem, a chemical method is generally adopted for hydrophilic modification or a physical method is adopted for preparing a composite membrane. The method for preparing the common composite flat plate membrane on the market at present mainly adopts a coating method to coat the casting solution on a wet non-woven fabric substrate to obtain a supported polymer membrane, but the method has high requirements on the density, uniformity and flatness of the non-woven fabric and certain requirements on the viscosity of the casting solution.
Disclosure of Invention
The invention provides a preparation method of a novel composite microfiltration membrane, which is characterized in that an asymmetric polyethersulfone membrane is prepared by an immersion precipitation phase inversion method, then an airflow-assisted electrostatic spinning technology is adopted to spin on the surface of the polyethersulfone membrane, a hydrophilic polyvinyl alcohol nanofiber layer is prepared, and the hydrophilic polyvinyl alcohol nanofiber layer is subjected to hot micro-melting compounding to obtain the novel composite microfiltration membrane, so that the problems of pollution and blockage of large particles and impurities, protein adsorption and the like are solved.
In order to achieve the above purpose, the present invention provides a method for preparing a novel composite microfiltration membrane, comprising the following steps:
s1: preparation of asymmetric polyethersulfone plate membranes: dissolving a polyether sulfone raw material in a solvent, adding a pore-forming agent and a non-solvent additive, and uniformly mixing to obtain a casting solution; scraping the film from the film casting solution, and then placing the film casting solution in a coagulating bath for conversion to obtain the formed asymmetric polyethersulfone flat film;
s2, preparing a polyvinyl alcohol nanofiber layer on the asymmetric polyethersulfone flat membrane: adding polyvinyl alcohol and a crosslinking agent into water, and further dissolving after swelling to obtain spinning solution; forming a polyvinyl alcohol nanofiber layer on the asymmetric polyethersulfone flat membrane by using an air-flow assisted electrostatic spinning technology;
s3: and (3) further crosslinking the polyvinyl alcohol nanofiber layer through heat treatment, and carrying out hot micro-melting compounding with the asymmetric polyether sulfone flat membrane to obtain the composite micro-filtration membrane.
Preferably, step S1 is specifically: dissolving a certain amount of polyether sulfone raw material in a solvent, adding a pore-forming agent and a non-solvent additive, heating and stirring for 2-8 hours until the polyether sulfone raw material is completely dissolved, and thus obtaining uniform and clear casting film liquid; after the casting solution is kept stand and defoamed for 6-12 hours, uniformly scraping the casting solution on a glass plate by adopting an automatic film scraping machine, immediately placing the glass plate in a coagulating bath after air stays for a period of time, and cleaning and drying the glass plate by pure water after solidification molding to ensure that the solvent is completely eluted, thus obtaining the asymmetric polyether sulfone membrane;
the step S2 specifically comprises the following steps: placing polyvinyl alcohol and a crosslinking agent into pure water, stirring for 2-3 h to fully swell, heating to 95 ℃, continuously stirring until the polyvinyl alcohol and the crosslinking agent are completely dissolved, cooling and standing to obtain spinning solution, taking the asymmetric polyethersulfone flat plate film obtained in the step S1 as a receiving base film, and spinning by adopting an airflow-assisted electrostatic spinning technology to obtain a polyvinyl alcohol nanofiber layer;
the step S3 specifically comprises the following steps: and (2) carrying out heat treatment on the asymmetric polyethersulfone flat membrane carrying the polyvinyl alcohol nanofiber layer obtained in the step (S2) for 0.5-1 h at the temperature of 120-160 ℃ to obtain the composite microfiltration membrane.
Preferably, in step S1: the solvent comprises N, N-dimethylacetamide; pore formers include polyvinyl alcohol and polyvinylpyrrolidone; the non-solvent additive comprises any one or more than two of water, ethanol, ethylene glycol, propylene glycol, isopropanol and n-butanol;
in step S2: the cross-linking agent comprises any one or more than two of tartaric acid, succinic acid and polyacrylic acid.
Preferably, in the casting solution of step S1: the mass fraction of the polyether sulfone is 14-18%, the mass fraction of the polyvinyl alcohol is 5-20%, the mass fraction of the polyvinylpyrrolidone is 0.5-10%, and the mass fraction of the non-solvent additive is 5-20%;
in the spinning solution of step S2: the mass fraction of the polyvinyl alcohol solution is 9-11%, and the mass fraction of the cross-linking agent is 20-30% of the mass fraction of the polyvinyl alcohol.
Preferably, in the step S1, the heating and stirring temperature is 60-80 ℃, the running speed of the automatic film scraping machine is 100mm/S, the thickness of a feeler gauge of the automatic film scraping machine is 200-300 mu m, the temperature of the casting solution during film scraping is 20-40 ℃, the air residence time of the casting solution after film scraping is 5-30S and then the casting solution is placed in a coagulating bath, the ambient temperature during residence is 20-30 ℃, the ambient humidity is 60% -90%, the coagulating bath temperature is 40-70 ℃, the coagulating bath is an N, N-dimethylacetamide aqueous solution, and the concentration is 30-70%.
Preferably, in the step S2, the parameter voltage of the air-flow assisted electrostatic spinning technology is 15-20 kV, the air pressure is 0.06-0.08 MPa, the propulsion rate is 0.1-0.5 ml/h, the receiving distance is 15-20 cm, the ambient temperature is 20-30 ℃, the ambient humidity is 40-50%, and the spinning time is 2-4 h.
The invention also provides a novel composite microfiltration membrane, which is characterized by comprising an asymmetric polyethersulfone flat membrane layer and a polyvinyl alcohol nanofiber layer;
the effective aperture size of the composite microfiltration membrane is 0.15-0.30 mu m; the pore diameter of the asymmetric polyethersulfone flat membrane layer at the interface facing the polyvinyl alcohol nanofiber layer is larger than the pore diameter of the asymmetric polyethersulfone flat membrane layer at the surface of the composite microfiltration membrane, and the pore diameter of the polyvinyl alcohol nanofiber layer is 10-15 mu m.
Preferably, the composite microfiltration membrane is prepared by the preparation method.
Polyvinyl alcohol, a hydrophilic polymer organic substance which is nontoxic and has good biocompatibility, is often used as a spinning aid in electrostatic spinning due to its excellent spinnability. In the invention, the polyvinyl alcohol material is adopted to prepare the electrostatic spinning nanofiber layer, and the water solubility of the electrostatic spinning nanofiber layer is improved by adopting a method of combining chemical crosslinking and thermal crosslinking by adding a small amount of crosslinking agent in consideration of application in water environment.
Compared with the prior art, the invention has the beneficial effects that:
(1) When the composite membrane prepared by the invention is used for treating feed liquid, the feed end is firstly contacted with a hydrophilic nanofiber layer, then enters an asymmetric polyethersulfone membrane for a large Kong Yaceng and finally enters an asymmetric membrane compact layer, the high hydrophilicity of the multiple layered filtration and nanofiber layers ensures higher filtration precision, simultaneously greatly improves the flux and interception effect of the membrane, solves the problems of pollution and blockage of large particles and impurities and protein adsorption, ensures the recovery benefit of protein and enhances the durability of the membrane;
(2) The invention combines the electrostatic spinning and the phase inversion method to prepare the composite membrane, and utilizes the hot micro-melting composite, compared with a single-layer polyethersulfone membrane, the invention has the advantages that the surface layer of the composite membrane is a hydrophilic nanofiber layer, the fiber is uniformly distributed, the pore connectivity is good, the porosity is high, the pore diameter is 10-15 mu m, the prefiltration effect can be achieved, the composite membrane has hydrophilic anti-fouling property and low protein adsorption, the biocompatibility is good, and the composite membrane can operate under the low pressure of 0.5bar, thereby greatly prolonging the service life of the membrane;
(3) Compared with the density, uniformity and flatness of a base material in a non-woven fabric composite film, the invention has the advantages that polyether sulfone is adopted as the base material, a hydrophilic nanofiber layer is prepared on the surface of the base material, the film surface is smooth, meanwhile, the invention does not adopt chemical adhesive/hot-pressing ironing treatment, film holes are not obviously blocked, higher porosity can be maintained, the structure and performance of the film can be regulated and controlled more accurately, and the feasibility of the film manufacturing process is improved;
(4) The polyvinyl alcohol nanofiber layer has lower hot-melting temperature, so that the asymmetric polyether sulfone flat membrane layer can be simply hot-micro-melted and compounded under a mild condition, an adhesive is not required to be added, and the blocking of pore channels of the polyvinyl alcohol nanofiber layer by the adhesive can be avoided.
Drawings
FIG. 1 is a flow chart of the preparation of a novel composite microfiltration membrane of the present invention;
FIG. 2 is a scanning electron microscope image of the upper surface of the composite microfiltration membrane prepared in example 1;
FIG. 3 is a scanning electron microscope image of the lower surface of the composite microfiltration membrane prepared in example 1;
FIG. 4 is a scanning electron microscope image of a cross section of the nonwoven fabric composite film prepared in comparative example 1.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described 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.
Example 1
As shown in fig. 1, this example discloses a novel preparation method of a composite microfiltration membrane,
(1) The asymmetric polyethersulfone flat membrane is prepared by adopting a phase inversion method: 48g of polyethersulfone was dissolved in 147g of N, N-dimethylacetamide solvent, followed by 48g of polyvinyl alcohol, 3g of polyvinylpyrrolidone and 54g of non-solvent additive, and heated and stirred at 80℃for 4 hours until complete dissolution, thereby obtaining a uniform and clear casting solution. After the casting solution is kept stand and defoamed for 8 hours, the casting solution is uniformly scraped and coated on a glass plate by adopting an automatic film scraping machine, the running speed of the automatic film scraping machine is 100mm/s, the thickness of a feeler gauge is 300 mu m, the casting solution temperature is 30 ℃, the ambient temperature is 20 ℃, the ambient humidity is 75%, the glass plate is immediately placed in a coagulating bath after air stays for 20 seconds, the coagulating bath temperature is 60 ℃, and the coagulating bath is 40% of N, N-dimethylacetamide aqueous solution. And (3) cleaning and drying the solidified polyethersulfone membrane by pure water to ensure that the solvent is completely eluted, thus obtaining the asymmetric polyethersulfone membrane prepared by an immersed precipitation phase inversion method.
(2) Preparing a hydrophilic polyvinyl alcohol nanofiber layer by adopting an electrostatic spinning technology: 5g of polyvinyl alcohol and 1.5g of cross-linking agent (tartaric acid is selected) are placed in 45g of pure water, and after stirring for 2-3 h and fully swelling, the temperature is raised to 95 ℃ and stirring is continued until the cross-linking agent is completely dissolved, and the spinning solution is obtained after cooling and standing. And (3) spinning by taking the polyether sulfone membrane obtained in the step (1) as a receiving base membrane and adopting an air flow assisted electrostatic spinning technology, wherein the parameter voltage of the air flow assisted electrostatic spinning is 15kV, the air pressure is 0.06MPa, the advancing speed is 0.2ml/h, the receiving distance is 17cm, the ambient temperature is 26 ℃, the ambient humidity is 50%, and the spinning time is 2h, so that the hydrophilic polyvinyl alcohol nanofiber layer is obtained.
(3) And heat-treating at 150 ℃ for 0.5h to fully heat-crosslink the polyvinyl alcohol nanofiber layer, thereby obtaining the novel composite micro-filtration membrane.
FIG. 2 is a scanning electron microscope image of the upper surface (polyvinyl alcohol nanofiber layer) of the composite microfiltration membrane prepared in example 1. FIG. 3 is a scanning electron microscope image of the lower surface (asymmetric polyethersulfone flat membrane) of the composite microfiltration membrane prepared in example 1. As can be seen from a comparison of fig. 2 and fig. 3, the pore diameter ratio of the upper and lower surfaces can reach about 50 times, and the asymmetry of the composite microfiltration membrane obtained by electrospinning is further increased, so that a multi-layer layered filtration effect is achieved. The uppermost polyvinyl alcohol nanofiber layer plays a role in resisting pollution for intercepting large-particle impurities, the pore diameter of one surface of the asymmetric polyether sulfone flat membrane layer, which is close to the polyvinyl alcohol nanofiber layer, is larger, a middle transition effect is achieved, the pore diameter of one surface of the lower surface is smaller, a final intercepting effect is achieved, and therefore high flux and intercepting effect are guaranteed. In general, the thickness of the polyvinyl alcohol nanofiber layer was lower than that of the asymmetric polyethersulfone flat plate film layer, and the asymmetric structure of the asymmetric polyethersulfone flat plate film layer can be referred to as the corresponding portion of comparative example 1 as shown in fig. 4.
The test shows that the composite microfiltration membrane prepared in the embodiment has a membrane thickness of 175 μm, a pore size of 0.22 μm and can operate under a pressure of 0.5bar, a test effective area of 3.14cm < 2 >, a pure water flux of 47.5ml/min/cm < 2 >/bar and a bovine serum albumin rejection rate of 98.1%, and the flux is not attenuated within 5 minutes.
Example 2
The asymmetric polyethersulfone flat membrane is prepared by adopting a phase inversion method: 42g of polyethersulfone is dissolved in 172.5g of N, N-dimethylacetamide solvent, 60g of polyvinyl alcohol, 7.5g of polyvinylpyrrolidone and 18g of non-solvent additive are added, and the mixture is heated and stirred at 80 ℃ for 4 hours until the mixture is completely dissolved, so that a uniform and clear casting solution is obtained. After the casting solution is kept stand and defoamed for 8 hours, the casting solution is uniformly scraped and coated on a glass plate by adopting an automatic film scraping machine, the running speed of the automatic film scraping machine is 100mm/s, the thickness of a feeler gauge is 300 mu m, the casting solution temperature is 23 ℃, the ambient temperature is 20 ℃, the ambient humidity is 75%, the glass plate is immediately placed in a coagulating bath after air stays for 50 seconds, the coagulating bath temperature is 60 ℃, and the coagulating bath is 40% of N, N-dimethylacetamide aqueous solution. And (3) cleaning and drying the solidified polyethersulfone membrane by pure water to ensure that the solvent is completely eluted, thus obtaining the asymmetric polyethersulfone membrane prepared by an immersed precipitation phase inversion method.
Preparing a hydrophilic polyvinyl alcohol nanofiber layer by adopting an electrostatic spinning technology: 4.5g of polyvinyl alcohol and 1g of cross-linking agent (tartaric acid is selected) are placed in 45.5g of pure water, and after stirring for 2-3 h for full swelling, the temperature is raised to 95 ℃ and stirring is continued until complete dissolution, and the spinning solution is obtained after cooling and standing. And (3) spinning by taking the polyether sulfone membrane obtained in the step (1) as a receiving base membrane and adopting an air flow assisted electrostatic spinning technology, wherein the parameter voltage of the air flow assisted electrostatic spinning is 20kV, the air pressure is 0.06MPa, the advancing speed is 0.2ml/h, the receiving distance is 17cm, the ambient temperature is 26 ℃, the ambient humidity is 50%, and the spinning time is 2h, so that the hydrophilic polyvinyl alcohol nanofiber layer is obtained.
And (3) carrying out heat treatment for 0.5h at 160 ℃ to fully thermally crosslink the polyvinyl alcohol nanofiber layer, thereby obtaining the novel composite microfiltration membrane.
The test shows that the composite microfiltration membrane prepared in the embodiment has a membrane thickness of 182 μm, a pore size of 0.30 μm, a test effective area of 3.14cm < 2 >, a pure water flux of 50.2ml/min/cm < 2 >/bar and a bovine serum albumin retention of 97.7%, and can be operated under a pressure of 0.5bar, and the flux is not attenuated within 5 minutes.
Comparative example 1
The polyether sulfone casting solution of example 1 was used to knife-coat a PET nonwoven fabric (thickness 78 μm, density 0.51 g/cm) 3 ) The steps are as follows: 48g of polyethersulfone is dissolved in 147g of N, N-dimethylacetamide solvent, 48g of polyvinyl alcohol, 3g of polyvinylpyrrolidone and 54g of non-solvent additive are added, and the mixture is heated and stirred at 80 ℃ for 4 hours until the mixture is completely dissolved, so that a uniform and clear casting solution is obtained. After the casting solution is kept stand and defoamed for 8 hours, the casting solution is uniformly scraped on a non-woven fabric substrate by adopting an automatic film scraping machine, the running speed of the automatic film scraping machine is 100mm/s, the thickness of a feeler gauge is 300 mu m, the casting solution temperature is 30 ℃, the ambient temperature is 20 ℃, the ambient humidity is 75%, and after air stays for 10 seconds, the casting solution is immediately placed in a coagulating bath, the coagulating bath temperature is 60 ℃, and the coagulating bath is 40% of N, N-dimethylacetamide aqueous solution. And (3) cleaning and drying the solidified polyethersulfone membrane by pure water to ensure that the solvent is completely eluted, thus obtaining the asymmetric polyethersulfone membrane supported by the non-woven fabric.
FIG. 4 is a scanning electron microscope image of a cross section of a non-woven fabric composite membrane prepared in comparative example 1, and the scanning electron microscope image can observe that a casting membrane liquid almost completely permeates into the lower layer of a substrate to seriously block membrane holes, and meanwhile, the surface of the membrane has more flaws and a small number of hidden holes, and the non-woven fabric composite membrane prepared in comparative example has 168 μm of thickness, 1.23-3.43 μm of pore size and uneven pore size distribution.
Comparative example 2
A single-layer asymmetric polyethersulfone membrane is prepared by the method of the step (1) in the example 1, and is used as a comparative example 2, polyethersulfone is subjected to hydrophilic modification by blending a small amount of polyvinylpyrrolidone, the static contact angle of the prepared polyethersulfone membrane is 52 degrees, the static contact angle of the surface layer of the example 1 is 15 degrees, and according to tests, the prepared polyethersulfone membrane in the comparative example has a thickness of 155 mu m, a pore size of 0.23 mu m and a low-pressure non-operation performance of 0.5bar, the effective test area is 3.14cm < 2 >, the pure water flux is 48.3ml/min/cm < 2 >/bar, the bovine serum albumin rejection rate is 97.8%, and the flux is obviously attenuated within 5 minutes.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. For example, hydrophilic additives including polyethers, sulfonated polyethersulfones, hydroxylated polyethersulfones, or celluloses, etc., may be added to the membrane substrate; other high boiling point organic solvents such as N, N-dimethylformamide and N-methylpyrrolidone can be selected/added to the casting solution and the coagulation bath.
The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Furthermore, it should be understood that although the present disclosure describes embodiments, not every embodiment is provided with a separate embodiment, and that this description is provided for clarity only, and that the disclosure is not limited to the embodiments described in detail below, and that the embodiments described in the examples may be combined as appropriate to form other embodiments that will be apparent to those skilled in the art.
Claims (8)
1. The preparation method of the novel composite micro-filtration membrane is characterized by comprising the following steps:
s1: preparation of asymmetric polyethersulfone plate membranes: dissolving a polyether sulfone raw material in a solvent, adding a pore-forming agent and a non-solvent additive, and uniformly mixing to obtain a casting solution; scraping the film from the film casting solution, and then placing the film casting solution in a coagulating bath for conversion to obtain the formed asymmetric polyethersulfone flat film;
s2, preparing a polyvinyl alcohol nanofiber layer on the asymmetric polyethersulfone flat membrane: adding polyvinyl alcohol and a crosslinking agent into water, and further dissolving after swelling to obtain spinning solution; forming a polyvinyl alcohol nanofiber layer on the asymmetric polyethersulfone flat membrane by using an air-flow assisted electrostatic spinning technology;
s3: and (3) further crosslinking the polyvinyl alcohol nanofiber layer through heat treatment, and carrying out hot micro-melting compounding with the asymmetric polyether sulfone flat membrane to obtain the composite micro-filtration membrane.
2. The method according to claim 1, wherein,
the step S1 specifically comprises the following steps: dissolving a certain amount of polyether sulfone raw material in a solvent, adding a pore-forming agent and a non-solvent additive, heating and stirring for 2-8 hours until the polyether sulfone raw material is completely dissolved, and thus obtaining uniform and clear casting film liquid; after the casting solution is kept stand and defoamed for 6-12 hours, uniformly scraping the casting solution on a glass plate by adopting an automatic film scraping machine, immediately placing the glass plate in a coagulating bath after air stays for a period of time, and cleaning and drying the glass plate by pure water after solidification molding to ensure that the solvent is completely eluted, thus obtaining the asymmetric polyether sulfone membrane;
the step S2 specifically comprises the following steps: placing polyvinyl alcohol and a crosslinking agent into pure water, stirring for 2-3 h to fully swell, heating to 95 ℃, continuously stirring until the polyvinyl alcohol and the crosslinking agent are completely dissolved, cooling and standing to obtain spinning solution, taking the asymmetric polyethersulfone flat plate film obtained in the step S1 as a receiving base film, and spinning by adopting an airflow-assisted electrostatic spinning technology to obtain a polyvinyl alcohol nanofiber layer;
the step S3 specifically comprises the following steps: and (2) carrying out heat treatment on the asymmetric polyethersulfone flat membrane carrying the polyvinyl alcohol nanofiber layer obtained in the step (S2) for 0.5-1 h at the temperature of 120-160 ℃ to obtain the composite microfiltration membrane.
3. The method according to claim 1, wherein,
in step S1: the solvent comprises N, N-dimethylacetamide; pore formers include polyvinyl alcohol and polyvinylpyrrolidone; the non-solvent additive comprises any one or more than two of water, ethanol, ethylene glycol, propylene glycol, isopropanol and n-butanol;
in step S2: the cross-linking agent comprises any one or more than two of tartaric acid, succinic acid and polyacrylic acid.
4. A process according to claim 3, wherein,
in the casting solution of step S1: the mass fraction of the polyether sulfone is 14-18%, the mass fraction of the polyvinyl alcohol is 5-20%, the mass fraction of the polyvinylpyrrolidone is 0.5-10%, and the mass fraction of the non-solvent additive is 5-20%;
in the spinning solution of step S2: the mass fraction of the polyvinyl alcohol solution is 9-11%, and the mass fraction of the cross-linking agent is 20-30% of the mass fraction of the polyvinyl alcohol.
5. The method according to claim 2, wherein,
in the step S1, the heating and stirring temperature is 60-80 ℃, the running speed of the automatic film scraping machine is 100mm/S, the thickness of a feeler gauge of the automatic film scraping machine is 200-300 mu m, the temperature of the casting solution during film scraping is 20-40 ℃, the residence time of the casting solution after film scraping is 5-30S, the casting solution is placed in a coagulating bath, the environmental temperature is 20-30 ℃ during residence, the environmental humidity is 60-90%, the coagulating bath temperature is 40-70 ℃, the coagulating bath is N, N-dimethylacetamide aqueous solution, and the concentration is 30-70%.
6. The method according to claim 2, wherein,
in the step S2, the parameter voltage of the air-flow auxiliary electrostatic spinning technology is 15-20 kV, the air pressure is 0.06-0.08 MPa, the propulsion rate is 0.1-0.5 ml/h, the receiving distance is 15-20 cm, the ambient temperature is 20-30 ℃, the ambient humidity is 40-50%, and the spinning time is 2-4 h.
7. The novel composite microfiltration membrane is characterized by comprising an asymmetric polyethersulfone flat membrane layer and a polyvinyl alcohol nanofiber layer;
the effective aperture size of the composite microfiltration membrane is 0.15-0.30 mu m; the pore diameter of the asymmetric polyethersulfone flat membrane layer at the interface facing the polyvinyl alcohol nanofiber layer is larger than the pore diameter of the asymmetric polyethersulfone flat membrane layer at the surface of the composite microfiltration membrane, and the pore diameter of the polyvinyl alcohol nanofiber layer is 10-15 mu m.
8. The composite microfiltration membrane according to claim 7, produced by the production method according to any one of claims 1 to 6.
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