Hydrophilic ultrafiltration membrane, preparation method and application
By combining dopamine buffer solution and hydrophilic polymer for modification, a robust hydrophilic ultrafiltration membrane was prepared, which solved the problems of insufficient hydrophilicity and weak binding force in existing modification methods, and achieved high-efficiency separation and improved antifouling performance of the membrane.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-04
- Publication Date
- 2026-04-07
AI Technical Summary
Existing hydrophilic modification methods have limited effect on improving the hydrophilicity of ultrafiltration membranes. The binding force of the modified material on the ultrafiltration membrane is insufficient, making it easy to fall off, which leads to a shortened membrane life and increased cost.
A chloromethylated membrane was grafted with a dopamine buffer solution and then immersed in a hydrophilic polymer solution to form a chemical covalent bond between polydopamine and the chloromethylated membrane. The polydopamine was then bonded to the hydrophilic polymer through hydrogen bonding and physical adhesion, thus preparing a robust hydrophilic ultrafiltration membrane.
It significantly improves the hydrophilicity and antifouling performance of ultrafiltration membranes, extends membrane lifespan, reduces operating costs, increases membrane flux by more than 40%, reduces water contact angle to below 40°, and exhibits slow flux decay after 30 cycles of BSA solution contamination.
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Figure CN121797101A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of ultrafiltration membrane technology, and in particular to a hydrophilic ultrafiltration membrane, its preparation method, and its application. Background Technology
[0002] Ultrafiltration is a novel membrane separation technology that, due to its advantages such as simple operation, ease of scale-up, low energy consumption, and high separation efficiency, has been applied in important fields such as drinking water treatment, pharmaceuticals, food processing, the separation and purification of proteins and polysaccharides, and environmental protection. However, during use, the surface of the ultrafiltration membrane comes into contact with many contaminants, which can easily lead to membrane fouling and clogging, thus reducing membrane separation performance. This not only shortens the membrane's lifespan but also significantly increases its operating costs.
[0003] Generally, to reduce fouling and clogging of ultrafiltration membranes, hydrophilic modification is often necessary. Common hydrophilic modification methods include blending modification, surface coating modification, and grafting modification. However, 1) Blending modification requires good compatibility of the blended materials, resulting in a narrow selection of materials; furthermore, blending modification has limited effect on improving the hydrophilicity of ultrafiltration membranes, and the binding force of the blended modified materials on the ultrafiltration membrane is weak, leading to the easy washing and inactivation of the blended modified materials during long-term use. 2) While surface coating modification on the membrane surface is simple to operate, the modified coating layer is prone to peeling off from the membrane surface during long-term use and cleaning, shortening its service life. 3) Conventional grafting modification is difficult to control at a suitable grafting rate. If the grafting rate is too low, the improvement in membrane hydrophilicity will be insignificant; if the grafting rate is too high, it may damage the bulk properties of the grafted polymer, thus limiting the improvement in membrane hydrophilicity.
[0004] Therefore, it is necessary to provide a hydrophilic ultrafiltration membrane, its preparation method, and its application to solve the problems that existing hydrophilic modification methods have limited effect on improving the hydrophilicity of ultrafiltration membranes, and that the binding force of the modified material on the ultrafiltration membrane is insufficient, making it easy to fall off and fail. Summary of the Invention
[0005] The present invention aims to provide a hydrophilic ultrafiltration membrane, its preparation method, and its application. The specific technical solution is as follows: In a first aspect, the present invention provides a method for preparing a hydrophilic ultrafiltration membrane, comprising: Step S1: Immerse the prepared chloromethylated membrane in a dopamine buffer solution with a pH of 8-9. After the first immersion treatment, the grafted modified membrane is obtained. Step S2: After rinsing, the grafted modified membrane is immersed in a hydrophilic polymer solution. After a second immersion treatment, a hydrophilic ultrafiltration membrane is obtained.
[0006] Optionally, the method for preparing the chloromethylated base film includes: Chloromethylated polysulfone or chloromethylated polyethersulfone is added to an organic solvent, followed by a pore-forming agent. The mixture is stirred at 50-70 °C until dissolved to obtain a casting solution. Next, the casting solution is degassed under negative pressure and poured onto a substrate to form a film layer. Finally, the substrate and the film layer on it are left to stand in air and then subjected to a coagulation bath to obtain a base film. In the casting solution, the mass percentage of the chloromethylated polysulfone or the chloromethylated polyethersulfone is 15% to 20%, the mass percentage of the organic solvent is 70% to 83%, and the mass percentage of the pore-forming agent is 2% to 10%.
[0007] Optionally, the organic solvent includes at least one of dimethyl sulfoxide, dimethylformamide, dimethylacetamide, and N-methylpyrrolidone; The pore-forming agent includes at least one of polyethylene glycol, polyvinylpyrrolidone, ethylene glycol methyl ether, acetone, and lithium chloride; The substrate includes non-woven fabric or glass plate.
[0008] Optionally, the coagulation bath uses a solution comprising at least one of pure water, ethanol, and dimethylformamide; the coagulation bath is used at a processing temperature of 15-30°C for a processing time of 0.5-2 h, and the solution is replaced every 0.5-1 h. The negative pressure degassing uses a negative pressure of 0.1~0.2 MPa, a degassing temperature of 15~30 ℃, and a degassing time of 4~8 h.
[0009] Optionally, the solute used in the dopamine buffer solution is dopamine, and the solvent used is tris(hydroxymethyl)aminomethane with a molar concentration of 0.01~0.02 mol / L; in the dopamine buffer solution, the mass percentage of dopamine is 0.2%~1.0%.
[0010] Optionally, the first soaking treatment uses a soaking temperature of 30~70 ℃ and a soaking time of 6~24h.
[0011] Optionally, the solute used in the hydrophilic polymer solution is a hydrophilic polymer, and the solvent used is water; in the hydrophilic polymer solution, the mass percentage of the hydrophilic polymer is 0.5% to 3.0%; the hydrophilic polymer includes at least one of polyglutamic acid, polylysine, polyaspartic acid, polyethyleneimine, and polyvinyl alcohol.
[0012] Optionally, the second soaking treatment uses a soaking temperature of 30~70 ℃ and a soaking time of 4~12 h.
[0013] In a second aspect, the present invention provides a hydrophilic ultrafiltration membrane, which is prepared by the aforementioned method for preparing a hydrophilic ultrafiltration membrane.
[0014] In a third aspect, the present invention provides an application of a hydrophilic ultrafiltration membrane in separation and purification, wherein when the hydrophilic polymer is polyaspartic acid and / or polyglutamic acid, the hydrophilic ultrafiltration membrane carries a negative charge and is used to separate and purify negatively charged substances. When the hydrophilic polymer is polyethyleneimine and / or polylysine, the hydrophilic ultrafiltration membrane carries a positive charge and is used to separate and purify positively charged substances. When the hydrophilic polymer is polyvinyl alcohol, the hydrophilic ultrafiltration membrane is electrically neutral and is used to separate and purify electrically neutral substances.
[0015] The application of the technical solution of the present invention has at least the following beneficial effects: (1) The present invention provides a method for preparing a hydrophilic ultrafiltration membrane. By combining steps S1 and S2, an ultrafiltration membrane with significantly improved hydrophilicity and a robust structure can be prepared. This not only solves the problems of limited improvement in the hydrophilicity of ultrafiltration membranes by existing hydrophilic modification methods and insufficient binding force of modified substances on the ultrafiltration membrane, leading to easy detachment and failure, but also extends the service life of the membrane, significantly reducing the cost of membrane use. Specifically: Regarding the significant improvement in hydrophilicity, the modified hydrophilic ultrafiltration membrane exhibits a flux increase of over 40%, with water contact angles all less than 40°. This is because the dopamine buffer solution used in this invention promotes the self-polymerization of dopamine to form polydopamine, which carries a large number of amino and hydroxyl hydrophilic groups. When polyglutamic acid, polylysine, and / or polyaspartic acid are used as hydrophilic polymers, they all carry a large number of amino and carboxyl hydrophilic groups. When polyethyleneimine is used as a hydrophilic polymer, it carries a large number of amino hydrophilic groups. When polyvinyl alcohol is used as a hydrophilic polymer, it carries a large number of hydroxyl hydrophilic groups. The prepared hydrophilic ultrafiltration membrane introduces a large number of amino, hydroxyl, and carboxyl hydrophilic groups, which significantly improves the membrane's hydrophilicity, resulting in increased water flux, reduced water contact angle, and significantly improved fouling resistance in practical applications.
[0016] Regarding structural robustness, the hydrophilic ultrafiltration membrane prepared in this invention exhibits slow flux decline after 30 cycles of BSA solution contamination cleaning, retaining more than 50% of its initial flux. Furthermore, the base membrane and surface skin (i.e., the incorporated polydopamine and hydrophilic polymer) of the hydrophilic ultrafiltration membrane do not detach. This is because the dopamine buffer solution used in this invention promotes the self-polymerization of dopamine to form polydopamine. Polydopamine is rich in various functional groups such as benzoquinone, amino, and hydroxyl groups. The chloromethyl groups on the surface of the chloromethylated base membrane undergo nucleophilic substitution reactions with the amino groups in the polydopamine, forming stronger covalent bonds -CH2-NH-, thus resulting in a structurally stable structure. The grafted modified membrane exhibits a strong physical electrostatic bond (i.e., physical adhesion) between the -OH group on the polydopamine and the polysulfone / chloromethyl polysulfone polymer on the chloromethylated membrane. The grafted modified membrane also exhibits a chemical covalent bond with amino-containing hydrophilic polymers (such as polyglutamic acid, polylysine, polyaspartic acid, and polyethyleneimine). Specifically, the -C=O functional group of polydopamine undergoes a Michael addition reaction with -NH2 to form the chemical covalent bond NH2-C-OH. Furthermore, the grafted modified membrane exhibits a physical adhesion with the polar polymer polyvinyl alcohol primarily through hydrogen bonds formed between -OH groups.
[0017] (2) The hydrophilic ultrafiltration membrane prepared by the present invention is used in separation and purification. The appropriate hydrophilic polymer is selected according to the charge properties of the substance to be separated and purified, which greatly improves the antifouling performance of the hydrophilic ultrafiltration membrane, extends the service life of the membrane, and significantly reduces the cost of membrane use.
[0018] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description
[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.
[0020] Figure 1 The image shown is a scanning electron microscope (SEM) image of the ultrafiltration membrane in Example 1 after the 25th cycle of regeneration.
[0021] Figure 2 The image shown is a scanning electron microscope (SEM) image of the ultrafiltration membrane in Example 1 after the 30th cycle of regeneration.
[0022] Figure 3The image shown is a scanning electron microscope (SEM) image of the ultrafiltration membrane in Comparative Example 3 after the 25th cycle of regeneration.
[0023] Figure 4 The image shown is a scanning electron microscope (SEM) image of the ultrafiltration membrane in Comparative Example 3 after the 30th cycle of regeneration. Detailed Implementation
[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0025] Example 1: A method for preparing a hydrophilic ultrafiltration membrane, comprising: Step S1: Immerse the prepared chloromethylated membrane in a dopamine buffer solution with a pH of 8.5. After the first immersion treatment, a grafted modified membrane is obtained. The grafted modified membrane can be stored in pure water for later use. Step S2: After rinsing the grafted modified membrane with pure water, immerse it in a hydrophilic polymer solution. After a second immersion treatment, rinse it with pure water again to obtain a hydrophilic ultrafiltration membrane.
[0026] The method for preparing the chloromethylated base film includes: Chloromethylated polysulfone or chloromethylated polyethersulfone is added to an organic solvent, followed by a pore-forming agent. The mixture is stirred at 60 °C until dissolved to obtain a casting solution. Next, the casting solution is degassed under negative pressure and poured onto a substrate. A film layer is formed by scraping the film with a doctor blade. Finally, the substrate and the film layer on it are left to stand in air (specifically, for 10 seconds) and then subjected to a coagulation bath to obtain a base film. After the coagulation bath treatment, the base film can be soaked in pure water for storage and later use.
[0027] In the casting solution, the mass percentage of the chloromethylated polysulfone or the chloromethylated polyether sulfone (specifically chloromethylated polysulfone) is 15%~20% (specifically 17%), the mass percentage of the organic solvent is 70%~83% (specifically 75%), and the mass percentage of the pore-forming agent is 2%~10% (specifically 8%).
[0028] The organic solvent includes at least one of dimethyl sulfoxide, dimethylformamide, dimethylacetamide, and N-methylpyrrolidone; specifically, dimethylformamide is selected as the organic solvent.
[0029] The porogen includes at least one of polyethylene glycol, polyvinylpyrrolidone, ethylene glycol methyl ether, acetone, and lithium chloride; specifically, polyethylene glycol is selected as the porogen.
[0030] The substrate includes non-woven fabric or glass plate; specifically, non-woven fabric is selected as the substrate.
[0031] The coagulation bath uses at least one of pure water, ethanol, and dimethylformamide; specifically, the coagulation bath uses pure water; the coagulation bath is treated at a temperature of 25°C for 1 hour, and the bath solution is replaced every hour for a total of five times.
[0032] The negative pressure degassing is completed in a vacuum drying oven, with a negative pressure of 0.1 MPa, a degassing temperature of 25℃, and a degassing time of 4 h.
[0033] The chloromethylated polysulfone or the chloromethylated polyethersulfone can be prepared according to the preparation method in the existing literature, which is as follows: Modification and acidification of polysulfone as effective strategies to enhance adsorptive ability of chromium (VI) and separation properties of ultrafiltration membrane[J]. Journal of Applied Polymer Science, 2022,139(19): e52127. Specifically, the preparation steps of the chloromethylated polysulfone are as follows: 10.0 g of polysulfone and 280 mL of dichloromethane were added to a three-necked flask. After the polysulfone was completely dissolved, 30 mL of trimethylchlorosilane and 6 g of paraformaldehyde were added sequentially. Nitrogen gas was introduced for protection, and then 0.30 mL of tin tetrachloride was added dropwise. The mixture was reacted at 35 °C for 60 h. Anhydrous ethanol was then added to precipitate the polysulfone. The precipitate was filtered, washed, and dried in a vacuum drying oven at 60 °C for 4 h to obtain chloromethylated polysulfone.
[0034] The dopamine buffer solution uses dopamine as the solute and tris(hydroxymethyl)aminomethane as the solvent with a molar concentration of 0.01 mol / L. The mass percentage of dopamine in the dopamine buffer solution is 0.2% to 1.0% (specifically 0.5%). A dopamine buffer solution with a pH of 8.5 can be obtained by adjusting with dilute hydrochloric acid or dilute sulfuric acid; dilute hydrochloric acid may be used instead.
[0035] The first soaking treatment uses a soaking temperature of 30~70 ℃ (specifically 50 ℃) and a soaking time of 6~24 h (specifically 12 h).
[0036] The hydrophilic polymer solution uses a hydrophilic polymer as the solute and water as the solvent; in the hydrophilic polymer solution, the mass percentage of the hydrophilic polymer is 0.5%~3.0% (specifically 1%); the hydrophilic polymer includes at least one of polyglutamic acid, polylysine, polyaspartic acid, polyethyleneimine, and polyvinyl alcohol; specifically, polyaspartic acid is selected as the hydrophilic polymer.
[0037] The second soaking treatment uses a soaking temperature of 30~70 ℃ (specifically 50 ℃) and a soaking time of 4~12 h (specifically 6 h).
[0038] Example 2: Unlike Example 1, the hydrophilic polymer is specifically selected as polyethyleneimine.
[0039] Example 3: Unlike Example 1, the hydrophilic polymer is specifically polyvinyl alcohol.
[0040] Comparative Example 1: A common polysulfone membrane was used as the ultrafiltration membrane. The preparation method of this polysulfone membrane is as follows: 17% by mass of polysulfone was added to 75% by mass of dimethylformamide, followed by 8% by mass of polyethylene glycol. The mixture was stirred at 60 °C until dissolved to obtain a casting solution. Next, the casting solution was degassed under a negative pressure of 0.1 MPa for 4 h, then poured onto a nonwoven fabric and a film was formed by scraping with a doctor blade. Finally, the substrate and the film layer on it were left to stand in air for 10 s, then soaked in pure water at 25 °C for 1 h. The pure water was replaced every 1 h to continue the soaking treatment, which was repeated 5 times to obtain a polysulfone film.
[0041] Comparative Example 2: Unlike Example 1, the first soaking treatment with dopamine buffer solution and the second soaking treatment with hydrophilic polymer solution were omitted, i.e., only the chloromethylated base membrane was used as the ultrafiltration membrane.
[0042] Comparative Example 3: Unlike Example 1, only the chloromethylated base film was replaced with a common polysulfone film, which was prepared in the same way as Comparative Example 1.
[0043] Comparative Example 4: Unlike Example 1, only the second soaking treatment with the hydrophilic polymer solution was omitted.
[0044] All ultrafiltration membranes prepared in Examples 1-3 and Comparative Examples 1-4 were sampled and subjected to pure water flux experiments, water contact angle experiments, tensile mechanical property experiments, bovine serum albumin retention rate experiments, and antifouling cycle regeneration experiments; the test results are shown in Tables 1 and 2.
[0045] The pure water flux experiment method is as follows: Four ultrafiltration membranes are placed sequentially on the ultrafiltration membrane test platform. The test solution is pure water, and the temperature is controlled at 25±1 ℃. Under a pressure of 0.1 MPa, cross-flow filtration is adopted. After stable operation for 10 min, the filtrate is collected with a graduated cylinder and the volume of pure water within 8 min is read. After conversion, the average value of the four membranes is taken as the pure water flux of the membrane.
[0046] The water contact angle test method is as follows: the dehydrated and dried membrane is cut into a size of 2 cm × 10 cm, loaded onto a glass slide for testing, and measured with a contact angle measuring instrument. Five points at different positions are tested for each membrane sample, and the average value is taken to obtain the water contact angle of various ultrafiltration membranes.
[0047] The tensile mechanical properties test method is as follows: According to GB / T1040.1-2006 / ISO527-1:1993 standard, the mechanical properties are tested on a CTM4204 tensile testing machine. The tensile rate of the membrane is 5 mm / min. Under the same experimental conditions, each sample is tested 10 times. The average value is taken to calculate the tensile properties of the ultrafiltration membrane, namely tensile strength and elongation at break.
[0048] The experimental method for bovine serum albumin (BSA) retention rate is as follows: Four ultrafiltration membranes were placed sequentially on the ultrafiltration membrane test platform. The test solution was a 100 mg / L bovine serum albumin solution. The temperature was controlled at 25±1 ℃, and cross-flow filtration was performed under a pressure of 0.1 MPa. After stable operation for 30 min, the filtrate was collected using a graduated cylinder, and the filtrate volume was read over 8 min. After conversion, the average value of the four membranes was taken as the permeate flux of the membrane. At the same time, the total organic carbon content in the feed solution and the filtered permeate was measured using a total organic carbon analyzer (Shimadzu TOC-L CPH / CPN total organic carbon analyzer). The retention rate of the ultrafiltration membrane for bovine serum albumin was calculated. The calculation method for this retention rate is as follows: BSA rejection rate = 1 - TOC value of product water / TOC value of raw water.
[0049] The anti-fouling cycle regeneration experiment method is as follows: The membrane that underwent the bovine serum albumin (BSA) retention experiment was backwashed with pure water at a pressure of 0.1 MPa for 10 min. Then, BSA retention was continued according to the BSA retention rate experiment method. The permeate flux of the membrane was recorded after 30 min. This process is recorded as one cycle regeneration experiment, and a total of 30 cycles were performed. The permeate flux after each cycle regeneration was compared with the initial permeate flux, and this was recorded as the flux recovery rate. The flux recovery rate was calculated as follows: Flux recovery rate = BSA solution permeate flux after each membrane cycle regeneration / initial BSA permeate flux.
[0050] Table 1. Experimental results of pure water flux, water contact angle, tensile mechanical properties, and bovine serum albumin retention rate.
[0051] From the data in Table 1, we know that: Compared to Comparative Examples 1-4, the hydrophilic ultrafiltration membranes prepared in Examples 1-3 of this invention exhibit a significantly increased pure water flux, a noticeably decreased water contact angle, and a markedly improved hydrophilicity. This is because Examples 1-3 introduced a large number of hydrophilic groups, increasing the affinity between the membrane and water. This reduces the resistance as water passes through the membrane surface during filtration, resulting in a greater pure water flux under the same filtration pressure.
[0052] A comparison of Comparative Example 2 and Example 1 shows that omitting the first immersion treatment with dopamine buffer solution and the second immersion treatment with hydrophilic polymer solution has little impact on the overall mechanical strength of the membrane. This is because both the ultrafiltration membranes prepared in Comparative Example 2 and Example 1 used nonwoven fabric, which provides basic support strength for the membrane.
[0053] Furthermore, a comparison of Comparative Example 2 and Example 1 shows that omitting the first soaking treatment with dopamine buffer solution and the second soaking treatment with hydrophilic polymer solution significantly reduced both the membrane's BSA rejection rate and the BSA solution permeation flux. This is because in Comparative Example 2, only a chloromethylated membrane was used as the ultrafiltration membrane, without the first and second soaking treatments. This meant that neither polydopamine, with its abundant amino and hydroxyl hydrophilic groups, nor polyaspartic acid, with its abundant amino and carboxyl hydrophilic groups, was incorporated. This reduced the membrane's hydrophilicity, increased its adhesion to the BSA solution, and consequently decreased the BSA solution permeation flux. Additionally, because polyaspartic acid was not used in Comparative Example 2, the membrane surface was not negatively charged, resulting in no mutual repulsion with the negatively charged BSA, thus reducing the BSA rejection rate.
[0054] Table 2 Results of Anti-pollution Recycling Experiment
[0055] From the data in Table 2, we know that: After 30 cycles of BSA solution regeneration, the ultrafiltration membranes prepared in Examples 1 and 3 showed the highest flux recovery rates, followed by Examples 2 and Comparative Example 3, while Comparative Examples 1, 2, and 4 showed relatively lower rates. The difference in flux recovery rates between Examples 1 and 3 was due to the electronegativity of the membrane surface. The negatively charged BSA solution repelled the negatively charged membrane of Example 1, reducing surface fouling. In contrast, the positively charged membrane of Example 2 attracted the BSA solution, slightly increasing fouling. The membrane surface of Example 3 tended to be neutral, and its antifouling effect was between that of the membranes in Examples 1 and 2.
[0056] Comparative Example 3 showed a significant decrease in flux recovery rate after the 30th regeneration compared to the 25th, a substantial difference from other examples and comparative examples. This is presumably due to coating peeling in Comparative Example 3, as confirmed by SEM characterization analysis. Figure 3 The SEM cross-sectional image shows obvious interfacial gaps in the membrane skin after the 25th regeneration cycle, indicating it is in a state of imminent detachment; Figure 4 Subsequently, it was observed that the membrane skin thickness was significantly thinner after the 30th cycle of regeneration, and the coating layer had completely peeled off. The main reason was that Comparative Example 3 used a common polysulfone membrane to replace the chloromethylated base membrane, resulting in the polysulfone membrane's adhesion to the coating layer being only physical adhesion (i.e., electrostatic force and hydrogen bonding). In contrast, the chloromethylated base membrane used in Example 1 underwent a nucleophilic substitution reaction between the chloromethyl groups on its surface and the amino groups in polydopamine, forming a stronger chemical bond -CH2-NH-. While possessing physical adhesion, the chloromethylated base membrane was also bonded to the hydrophilic polymer above it through chemical covalent bonds, resulting in a stronger bond under the combined effects of physical and chemical forces. Figure 1 and Figure 2 The SEM cross-sectional images show that the surface condition and thickness of the membrane in Example 1 are relatively stable, and no obvious detachment was observed during 30 cycles of contamination regeneration. Overall, the modification method of the membrane in Example 1 is more robust, and its service life is significantly increased.
[0057] The above description is only a preferred embodiment of the present invention and does not limit the scope of the present invention. All equivalent structural transformations made under the inventive concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included within the protection scope of the present invention.
Claims
1. A method for preparing a hydrophilic ultrafiltration membrane, characterized in that, include: Step S1: Immerse the prepared chloromethylated membrane in a dopamine buffer solution with a pH of 8-9. After the first immersion treatment, the grafted modified membrane is obtained. Step S2: After rinsing, the grafted modified membrane is immersed in a hydrophilic polymer solution. After a second immersion treatment, a hydrophilic ultrafiltration membrane is obtained.
2. The method for preparing the hydrophilic ultrafiltration membrane as described in claim 1, characterized in that, The method for preparing the chloromethylated base film includes: Chloromethylated polysulfone or chloromethylated polyethersulfone is added to an organic solvent, followed by a pore-forming agent. The mixture is stirred at 50-70 °C until dissolved to obtain a casting solution. Next, the casting solution is degassed under negative pressure and poured onto a substrate to form a film layer. Finally, the substrate and the film layer on it are left to stand in air and then subjected to a coagulation bath to obtain a base film. In the casting solution, the mass percentage of the chloromethylated polysulfone or the chloromethylated polyethersulfone is 15% to 20%, the mass percentage of the organic solvent is 70% to 83%, and the mass percentage of the pore-forming agent is 2% to 10%.
3. The method for preparing the hydrophilic ultrafiltration membrane as described in claim 2, characterized in that, The organic solvent includes at least one of dimethyl sulfoxide, dimethylformamide, dimethylacetamide, and N-methylpyrrolidone; The pore-forming agent includes at least one of polyethylene glycol, polyvinylpyrrolidone, ethylene glycol methyl ether, acetone, and lithium chloride; The substrate includes non-woven fabric or glass plate.
4. The method for preparing the hydrophilic ultrafiltration membrane as described in claim 2, characterized in that, The coagulation bath uses a solution comprising at least one of pure water, ethanol, and dimethylformamide; the coagulation bath is used at a temperature of 15-30°C for a duration of 0.5-2 hours, and the solution is replaced every 0.5-1 hours. The negative pressure degassing uses a negative pressure of 0.1~0.2 MPa, a degassing temperature of 15~30 ℃, and a degassing time of 4~8 h.
5. The method for preparing the hydrophilic ultrafiltration membrane as described in claim 1, characterized in that, The dopamine buffer solution uses dopamine as the solute and tris(hydroxymethyl)aminomethane as the solvent with a molar concentration of 0.01-0.02 mol / L; the mass percentage of dopamine in the dopamine buffer solution is 0.2%-1.0%.
6. The method for preparing the hydrophilic ultrafiltration membrane as described in claim 1, characterized in that, The first soaking treatment uses a soaking temperature of 30~70 ℃ and a soaking time of 6~24 h.
7. The method for preparing the hydrophilic ultrafiltration membrane according to any one of claims 1 to 6, characterized in that, The hydrophilic polymer solution uses a hydrophilic polymer as the solute and water as the solvent; the mass percentage of the hydrophilic polymer in the hydrophilic polymer solution is 0.5% to 3.0%; the hydrophilic polymer includes at least one of polyglutamic acid, polylysine, polyaspartic acid, polyethyleneimine, and polyvinyl alcohol.
8. The method for preparing the hydrophilic ultrafiltration membrane as described in claim 7, characterized in that, The second soaking treatment uses a soaking temperature of 30~70 ℃ and a soaking time of 4~12 h.
9. A hydrophilic ultrafiltration membrane, characterized in that, The hydrophilic ultrafiltration membrane was prepared using the method described in claim 8.
10. The application of the hydrophilic ultrafiltration membrane as described in claim 9 in separation and purification, characterized in that, When the hydrophilic polymer is polyaspartic acid and / or polyglutamic acid, the hydrophilic ultrafiltration membrane carries a negative charge and is used to separate and purify negatively charged substances. When the hydrophilic polymer is polyethyleneimine and / or polylysine, the hydrophilic ultrafiltration membrane carries a positive charge and is used to separate and purify positively charged substances. When the hydrophilic polymer is polyvinyl alcohol, the hydrophilic ultrafiltration membrane is electrically neutral and is used to separate and purify electrically neutral substances.