Zwitterionic modified anti-fouling ultrafiltration membrane, preparation method and application thereof

Abstract

The application belongs to the field of membrane separation technology, and particularly relates to a zwitterionic modified anti-fouling ultrafiltration membrane, a preparation method and application thereof. The preparation method of the zwitterionic modified anti-fouling ultrafiltration membrane comprises the following steps: uniformly dispersing a zwitterionic polymer, a double-bond-containing urea-based pyrimidinone functional monomer and dopamine hydrochloride in a solvent, adjusting pH to obtain a modified solution; coating the modified solution on an ultrafiltration membrane, avoiding light reaction, and carrying out post-treatment after the reaction is completed to obtain the zwitterionic modified anti-fouling ultrafiltration membrane; the zwitterionic polymer is obtained by copolymerization reaction of 2-acrylamido-2-methylpropanesulfonic acid and a quaternary ammonium monomer; and the quaternary ammonium monomer is obtained by reaction of oleic acid amide propyl dimethyl tertiary amine and ethylene 2-(methacryloyloxy)ethyl phosphate. The zwitterionic modified anti-fouling ultrafiltration membrane provided by the application not only has excellent anti-fouling property, but also has good long-term stability.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation technology, specifically relating to an amphoteric ion modified antifouling ultrafiltration membrane, its preparation method, and its application. Background Technology

[0002] Ultrafiltration is a pressure membrane filtration process used to remove various macromolecules, colloids and suspended particles from solutions. It is used in various industrial processes such as domestic water treatment, wastewater treatment, chemical manufacturing and food processing.

[0003] Traditional ultrafiltration membranes, due to their high hydrophobicity, have poor antifouling properties. With prolonged use, contaminants gradually accumulate on the membrane surface, leading to decreased membrane flux, reduced retention rate, and even microbial growth. Therefore, those skilled in the art are increasingly focused on improving the antifouling properties of ultrafiltration membranes.

[0004] Amphoteric ionization of the ultrafiltration membrane surface is an effective method for improving its antifouling resistance. Since both the anions and cations in zwitterions are hydrophilic groups, zwitterionization modification of nanofiltration membranes can significantly improve their antifouling resistance.

[0005] The modification methods of zwitterionic ionization mainly include surface coating, surface grafting, and physical mixing. Surface coating utilizes hydrophobic interactions or electrostatic attraction to form a layered structure covering the membrane surface. However, this modification method significantly reduces membrane flux, and the coating is prone to peeling off due to the weak interaction between the layered structure and the membrane surface. Chinese Patent CN105727761B discloses a zwitterionic ultrafiltration membrane with protein fouling resistance and its preparation method. The zwitterionic ultrafiltration membrane is prepared by coating a gel obtained from the gelation reaction of zwitterionic chitosan and polyvinyl alcohol sol onto a support to form a film, which is then immersed in water to undergo a phase inversion reaction. This technical solution uses zwitterionic chitosan to modify polyvinyl alcohol to prepare a zwitterionic ultrafiltration membrane with good hydrophilicity and antifouling properties, as well as good antifouling selectivity, especially with a removal rate of up to 97.6% for bovine serum albumin, which can effectively resist protein fouling. However, this technical solution uses a surface coating method, but it does not address long-term stability.

[0006] Surface grafting forms covalent bonds with the membrane surface, resulting in stronger interaction between the modified material and the membrane surface. However, this modification method is difficult to graft and is prone to detachment. Chinese Patent No. CN115569536B discloses an antifouling ultrafiltration membrane, its preparation method, and its application. The preparation method of the antifouling ultrafiltration membrane includes: (1) aminated modification of polymer powder to obtain aminated modified polymer powder; (2) preparing a casting solution using the aminated modified polymer powder, casting the casting solution onto a support layer to form a membrane, then transferring it to a coagulation bath to solidify and form a wet membrane, and further washing and drying to obtain an amino-containing ultrafiltration membrane; (3) preparing an epoxy-zwitterionic copolymer by polymerization reaction using epoxy monomers, zwitterionic monomers, and initiators as raw materials; (4) grafting the epoxy-zwitterionic copolymer onto the amino-containing ultrafiltration membrane of step (2) through an epoxy ring-opening reaction to obtain the antifouling ultrafiltration membrane. However, this technical solution also does not focus on long-term stability.

[0007] Physical mixing has the advantages of being time-efficient and simple to operate. However, during use, the hydrophilic substances blended are prone to detach from the membrane matrix, making it difficult to achieve a durable and stable modification effect. Chinese Patent CN116422163A discloses a method for modifying an ultrafiltration membrane using a zwitterionic structure and a benzimidazole structure, comprising the following steps: S1, synthesizing a polyaryl ether oxadiazole modifier containing a zwitterionic structure and a benzimidazole structure through a low-temperature polycondensation-quaternization reaction; S2, adding the above modifier, polymeric membrane matrix material, and membrane modifier to an organic solvent, stirring to obtain a uniform casting solution, and casting it into shape. This technical solution prepares an ultrafiltration membrane modified with a zwitterionic structure and a benzimidazole structure through an immersion precipitation phase inversion method. However, the antifouling properties of the modified ultrafiltration membrane prepared by this technical solution need to be improved. Summary of the Invention

[0008] The purpose of this invention is to provide an amphoteric ion-modified antifouling ultrafiltration membrane, its preparation method, and its application. The amphoteric ion-modified antifouling ultrafiltration membrane provided by this invention not only has excellent antifouling properties but also good long-term stability.

[0009] To achieve the above objectives, the present invention provides the following technical solution: The first aspect of this invention provides a method for preparing a zwitterionic modified antifouling ultrafiltration membrane, comprising the following steps: A zwitterionic polymer, a ureidopyrimidinone functional monomer containing a double bond, and dopamine hydrochloride are uniformly dispersed in a solvent, and the pH is adjusted to obtain a modified solution. The modified solution is coated on an ultrafiltration membrane and reacted in the dark. After the reaction is completed, post-treatment is performed.

[0010] Furthermore, the mass ratio of the zwitterionic polymer, the double-bonded ureidopyrimidinone functional monomer, and dopamine hydrochloride is 1:1-2:3-6.

[0011] Furthermore, the solvent is selected from at least one of dimethyl sulfoxide and tetrahydrofuran.

[0012] Furthermore, the mass ratio of dopamine hydrochloride to solvent is 1:8-12.

[0013] Furthermore, the post-processing method includes: after the reaction is complete, adding methyl tert-butyl ether for purification 2-3 times, followed by rotary evaporation to obtain the final product.

[0014] Furthermore, the amount of the modified solution coated on the ultrafiltration membrane is 40-55 g / m³. 2 .

[0015] Furthermore, the material of the ultrafiltration membrane is selected from one or more combinations of PES (polyethersulfone), PVDF (polyvinylidene fluoride), and PAN (polyacrylonitrile).

[0016] Furthermore, the pH value is adjusted to 7-8.5.

[0017] Furthermore, the conditions for the light-protected reaction include: a temperature of 70-80℃ and a time of 4-6 hours.

[0018] This invention utilizes a crosslinked polymer prepared by Michael addition reaction of a ureidopyrimidinone functional monomer containing double bonds and dopamine hydrochloride. This crosslinked polymer can not only adhere to the ultrafiltration membrane and improve the hydrophilicity of the ultrafiltration membrane, but also encapsulate the zwitterionic polymer and prevent the zwitterionic polymer from falling off. The combined effect of the crosslinked polymer and the zwitterionic polymer effectively improves the antifouling properties and long-term stability of the ultrafiltration membrane.

[0019] Furthermore, the zwitterionic polymer is obtained by copolymerization of 2-acrylamido-2-methylpropanesulfonic acid and a quaternary ammonium monomer.

[0020] Furthermore, the preparation method of the zwitterionic polymer includes: mixing 2-acrylamido-2-methylpropanesulfonic acid, quaternary ammonium monomer and water evenly, and then adding potassium persulfate under nitrogen protection to carry out a copolymerization reaction.

[0021] Furthermore, the preparation method of the zwitterionic polymer includes: mixing 2-acrylamido-2-methylpropanesulfonic acid, quaternary ammonium monomer and water evenly, adding potassium persulfate under nitrogen protection, and performing a copolymerization reaction at 70-80°C for 4-6 hours. After the reaction is completed, acetone is added, filtered, washed and dried to obtain the product.

[0022] Furthermore, the mass ratio of 2-acrylamido-2-methylpropanesulfonic acid, quaternary ammonium monomer, and water is 4-10:8-15:100.

[0023] Furthermore, the amount of potassium persulfate added is 0.5-1% of the total mass of 2-acrylamido-2-methylpropanesulfonic acid and quaternary ammonium monomer.

[0024] Furthermore, the quaternary ammonium monomer is obtained by reacting oleamide propyl dimethyl tertiary amine with ethylene 2-(methacryloyloxy)ethyl phosphate.

[0025] Furthermore, the preparation method of the quaternary ammonium monomer includes: adding oleamide propyl dimethyl tertiary amine to chloroform, adding ethylene 2-(methacryloyloxy)ethyl phosphate, heating under reflux reaction, rotary evaporation after the reaction is completed, and drying to obtain the product.

[0026] Furthermore, the conditions for the heating reflux reaction include: a temperature of 90-95°C and a time of 20-24 hours.

[0027] Furthermore, the mass ratio of oleamidopropyl dimethyl tertiary amine to chloroform is 1:10-20.

[0028] Furthermore, the molar ratio of oleamidopropyl dimethyl tertiary amine to ethylene 2-(methacryloyloxy)ethyl phosphate is 1:0.9-1.1.

[0029] This invention utilizes the reaction of oleamidopropyl dimethyl tertiary amine and ethylene 2-(methacryloyloxy)ethyl phosphate. The phosphate ring on ethylene 2-(methacryloyloxy)ethyl phosphate undergoes ring-opening under heating conditions and quaternization with the tertiary amine group to obtain a phosphocholine analog. This quaternary ammonium monomer is copolymerized with 2-acrylamido-2-methylpropanesulfonic acid to obtain a zwitterionic polymer. Compared with ordinary zwitterionic polymers, the zwitterionic polymer obtained by copolymerizing the quaternary ammonium monomer with 2-acrylamido-2-methylpropanesulfonic acid forms a denser and stronger hydration layer, thereby effectively preventing the adhesion of organic pollutants such as proteins for a long time.

[0030] Furthermore, the preparation method of the double-bonded ureidopyrimidinone functional monomer of the present invention refers to Chinese Patent No. CN 114621399 B, namely: 2-amino-4-hydroxy-6-methylpyrimidin is added to dimethyl sulfoxide at 150-180℃, and under nitrogen protection, isocyanate methacrylate is added, the temperature is cooled to room temperature, and the mixture is stirred thoroughly until a white precipitate appears. The purified product is then washed and dried to obtain the final product.

[0031] Furthermore, the mass ratio of 2-amino-4-hydroxy-6-methylpyrimidine to dimethyl sulfoxide is 5-15:85-95.

[0032] Furthermore, the molar ratio of 2-amino-4-hydroxy-6-methylpyrimidine to isocyanate methacrylate is 1:1-1.5.

[0033] The second aspect of the present invention provides an amphoteric ion modified antifouling ultrafiltration membrane prepared by the above-described method for preparing amphoteric ion modified antifouling ultrafiltration membrane.

[0034] The third aspect of this invention provides the application of the zwitterionic modified antifouling ultrafiltration membrane prepared by the above-described zwitterionic modified antifouling ultrafiltration membrane preparation method in the field of membrane separation.

[0035] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: 1. This invention utilizes a cross-linked polymer prepared by Michael addition reaction of a ureidopyrimidinone functional monomer containing double bonds and dopamine hydrochloride. This cross-linked polymer can not only adhere to the ultrafiltration membrane and improve the hydrophilicity of the ultrafiltration membrane, but also encapsulate the zwitterionic polymer and prevent the zwitterionic polymer from falling off. The combined effect of the cross-linked polymer and the zwitterionic polymer effectively improves the antifouling properties and long-term stability of the ultrafiltration membrane.

[0036] 2. This invention utilizes the reaction of oleamidopropyl dimethyl tertiary amine and ethylene 2-(methacryloyloxy)ethyl phosphate. The phosphate ring on ethylene 2-(methacryloyloxy)ethyl phosphate undergoes ring opening under heating conditions and quaternization with the tertiary amine group to obtain a phosphocholine analog. Compared with ordinary zwitterionic polymers, the zwitterionic polymer obtained by copolymerizing this quaternary ammonium monomer with 2-acrylamido-2-methylpropanesulfonic acid forms a denser and stronger hydration layer, thereby effectively preventing the adhesion of organic pollutants such as proteins for a long period of time.

[0037] 3. Experimental verification shows that the zwitterionic modified antifouling ultrafiltration membrane provided by this invention has a high water flux (≥75 L·m). -2 ·h -1 It exhibits excellent anti-fouling properties against bovine serum albumin (retention rate ≥98.5%, pure water flux recovery rate ≥98.2% after three cycles) and long-term stability (retention rate ≥97.5% during 72h continuous operation). Attached Figure Description

[0038] Figure 1 The image shows the infrared spectrum of the zwitterionic polymer from Example 1. Detailed Implementation

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] Example 1 A method for preparing a zwitterionic modified antifouling ultrafiltration membrane includes the following steps: Ten parts of zwitterionic polymer, 15 parts of ureidopyrimidinone functional monomer containing double bonds, and 30 parts of dopamine hydrochloride were uniformly dispersed in 300 parts of dimethyl sulfoxide, and the pH was adjusted to 8 to obtain a modified solution. The modified solution was then coated onto a PVDF ultrafiltration membrane at a coating amount of 45 g / m³. 2 The reaction was carried out at 70℃ in the dark for 5 hours. After the reaction was completed, methyl tert-butyl ether was added for purification three times, and the zwitterionic modified antifouling ultrafiltration membrane was obtained by rotary evaporation.

[0041] The zwitterionic polymer is prepared as follows: 6 parts of 2-acrylamido-2-methylpropanesulfonic acid, 12 parts of quaternary ammonium monomer, and 100 parts of water are mixed evenly. Under nitrogen protection, potassium persulfate is added, and the mixture is copolymerized at 70°C for 6 hours. After the reaction, acetone is added, and the mixture is filtered, washed, and dried to obtain the final product. The amount of potassium persulfate added is 0.8% of the total mass of 2-acrylamido-2-methylpropanesulfonic acid and quaternary ammonium monomer. The quaternary ammonium monomer is prepared as follows: 10 parts of oleamidopropyl dimethyl tertiary amine are added to 150 parts of chloroform. Ethylene 2-(methacryloyloxy)ethyl phosphate is added at a molar ratio of oleamidopropyl dimethyl tertiary amine to ethylene 2-(methacryloyloxy)ethyl phosphate at 1:1. The mixture is heated under reflux at 90°C for 24 hours. After the reaction, the mixture is rotary evaporated and dried to obtain the final product.

[0042] The infrared spectrum of the zwitterionic polymer is as follows: Figure 1 As shown, by Figure 1 It can be seen that at 1263cm -1 1112cm -1 The characteristic peak of O=S=O appears at 1225cm. -1 The presence of the characteristic peak P=O indicates that the zwitterionic polymer was successfully synthesized.

[0043] The preparation method of the ureidopyrimidinone functional monomer containing double bonds is as follows: 10 parts of 2-amino-4-hydroxy-6-methylpyrimidine are added to 90 parts of dimethyl sulfoxide at 170°C. Under nitrogen protection, isocyanate of methacrylate is added at a molar ratio of 1:1.2 of 2-amino-4-hydroxy-6-methylpyrimidine and isocyanate of methacrylate. The mixture is cooled to room temperature and stirred thoroughly until a white precipitate appears. Acetone is added to purify the product, which is then washed and dried to obtain the final product.

[0044] Example 2 A method for preparing a zwitterionic modified antifouling ultrafiltration membrane includes the following steps: Ten parts of zwitterionic polymer, ten parts of ureidopyrimidinone functional monomer containing double bonds, and 40 parts of dopamine hydrochloride were uniformly dispersed in 400 parts of dimethyl sulfoxide, and the pH was adjusted to 8 to obtain a modified solution. The modified solution was then coated onto a PVDF ultrafiltration membrane at a coating amount of 40 g / m³. 2 The reaction was carried out at 70℃ in the dark for 5 hours. After the reaction was completed, methyl tert-butyl ether was added for purification three times, and the zwitterionic modified antifouling ultrafiltration membrane was obtained by rotary evaporation.

[0045] The preparation method of the zwitterionic polymer is as follows: 4 parts of 2-acrylamido-2-methylpropanesulfonic acid, 8 parts of quaternary ammonium monomer, and 100 parts of water are mixed evenly. Under nitrogen protection, potassium persulfate is added and copolymerized at 70°C for 6 hours. After the reaction, acetone is added, filtered, washed, and dried to obtain the final product. The amount of potassium persulfate added is 0.8% of the total mass of 2-acrylamido-2-methylpropanesulfonic acid and quaternary ammonium monomer. The preparation method of the quaternary ammonium monomer is as follows: 10 parts of oleamidopropyl dimethyl tertiary amine are added to 150 parts of chloroform. Ethylene 2-(methacryloyloxy)ethyl phosphate is added at a molar ratio of oleamidopropyl dimethyl tertiary amine to ethylene 2-(methacryloyloxy)ethyl phosphate at 1:1. The mixture is heated under reflux at 90°C for 24 hours. After the reaction, it is rotary evaporated and dried to obtain the final product.

[0046] The preparation method of the ureidopyrimidinone functional monomer containing double bonds is as follows: 10 parts of 2-amino-4-hydroxy-6-methylpyrimidine are added to 90 parts of dimethyl sulfoxide at 170°C. Under nitrogen protection, isocyanate of methacrylate is added at a molar ratio of 1:1.2 of 2-amino-4-hydroxy-6-methylpyrimidine and isocyanate of methacrylate. The mixture is cooled to room temperature and stirred thoroughly until a white precipitate appears. Acetone is added to purify the product, which is then washed and dried to obtain the final product.

[0047] Example 3 A method for preparing a zwitterionic modified antifouling ultrafiltration membrane includes the following steps: Ten parts of zwitterionic polymer, 20 parts of ureidopyrimidinone functional monomer containing double bonds, and 60 parts of dopamine hydrochloride were uniformly dispersed in 600 parts of dimethyl sulfoxide, and the pH was adjusted to 8 to obtain a modified solution. The modified solution was then coated onto a PVDF ultrafiltration membrane at a coating amount of 55 g / m³. 2 The reaction was carried out at 70℃ in the dark for 5 hours. After the reaction was completed, methyl tert-butyl ether was added for purification three times, and the zwitterionic modified antifouling ultrafiltration membrane was obtained by rotary evaporation.

[0048] The preparation method of the zwitterionic polymer is as follows: 10 parts of 2-acrylamido-2-methylpropanesulfonic acid, 15 parts of quaternary ammonium monomer, and 100 parts of water are mixed evenly. Under nitrogen protection, potassium persulfate is added and copolymerized at 70°C for 6 hours. After the reaction, acetone is added, filtered, washed, and dried to obtain the final product. The amount of potassium persulfate added is 0.8% of the total mass of 2-acrylamido-2-methylpropanesulfonic acid and quaternary ammonium monomer. The preparation method of the quaternary ammonium monomer is as follows: 10 parts of oleamidopropyl dimethyl tertiary amine are added to 150 parts of chloroform. Ethylene 2-(methacryloyloxy)ethyl phosphate is added at a molar ratio of oleamidopropyl dimethyl tertiary amine to ethylene 2-(methacryloyloxy)ethyl phosphate at 1:1. The mixture is heated under reflux at 90°C for 24 hours. After the reaction, it is rotary evaporated and dried to obtain the final product.

[0049] The preparation method of the ureidopyrimidinone functional monomer containing double bonds is as follows: 10 parts of 2-amino-4-hydroxy-6-methylpyrimidine are added to 90 parts of dimethyl sulfoxide at 170°C. Under nitrogen protection, isocyanate of methacrylate is added at a molar ratio of 1:1.2 of 2-amino-4-hydroxy-6-methylpyrimidine and isocyanate of methacrylate. The mixture is cooled to room temperature and stirred thoroughly until a white precipitate appears. Acetone is added to purify the product, which is then washed and dried to obtain the final product.

[0050] Comparative Example 1 The only difference between this comparative example and Example 1 is that the zwitterionic polymer is replaced with 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propionate, and all other aspects are the same.

[0051] Comparative Example 2 The only difference between this comparative example and Example 1 is that the zwitterionic polymer is replaced with 2-methacryloyloxyethyl phosphocholine; all other aspects are the same.

[0052] Comparative Example 3 The only difference between this comparative example and Example 1 is the preparation method of the zwitterionic polymer: 10 parts of 2-acrylamido-2-methylpropanesulfonic acid, 15 parts of methacryloyloxyethyltrimethylammonium chloride and 100 parts of water are mixed evenly, potassium persulfate is added under nitrogen protection and copolymerization reaction is carried out at 70°C for 6 hours. After the reaction is completed, acetone is added, filtered, washed and dried to obtain the polymer.

[0053] The amount of potassium persulfate added is 0.8% of the total mass of 2-acrylamido-2-methylpropanesulfonic acid and methacryloyloxyethyltrimethylammonium chloride, and all other amounts are the same.

[0054] Comparative Example 4 The only difference between this comparative example and Example 1 is that it does not contain a ureidopyrimidinone functional monomer with a double bond; all other aspects are the same.

[0055] Comparative Example 5 The only difference between this comparative example and Example 1 is that the double-bonded ureidopyrimidinone functional monomer is replaced with polyvinylpyrrolidone; all other aspects are the same.

[0056] Comparative Example 6 The difference between this comparative example and Example 1 is that the double-bonded ureidopyrimidinone functional monomer is replaced with polyethyleneimine; all other aspects are the same.

[0057] Comparative Example 7 The only difference between this comparative example and Example 1 is that the preparation method of the zwitterionic modified antifouling ultrafiltration membrane includes the following steps: 40 parts of dopamine hydrochloride were uniformly dispersed in 400 parts of dimethyl sulfoxide, and the pH was adjusted to 8 to obtain modified solution A. The PVDF ultrafiltration membrane was placed in modified solution A and reacted at 50°C in the dark for 4 hours. After the reaction was completed, the membrane was washed to obtain the polydopamine-coated PVDF ultrafiltration membrane. Ten parts of zwitterionic polymer and ten parts of ureidopyrimidinone functional monomer containing double bonds were uniformly dispersed in 200 parts of dimethyl sulfoxide to obtain modified solution B. The polydopamine-coated PVDF ultrafiltration membrane was placed in modified solution B and reacted at 50°C in the dark for 16 hours. After the reaction was completed, the membrane was dried. Finally, the PVDF ultrafiltration membrane was placed in an ethanol solution with a mass percentage concentration of 2 wt% glutaraldehyde at 50°C for 20 minutes for crosslinking, and then removed and dried to obtain the final product. All other steps were the same.

[0058] Performance testing 1. Pure water flux: Under an operating pressure of 0.1 MPa, record the volume of filtrate obtained within a certain time. The calculation formula is: Pure water flux = V / (A × Δt), where V represents the volume of filtrate, A represents the effective filtration area, and Δt represents the time. 2. Retention performance: Under an operating pressure of 0.1 MPa, a 1 g / L bovine serum albumin solution was used as the feed solution for separation. The separation performance of the ultrafiltration membrane was evaluated, and the calculation formula was: Retention rate = (1 - ρ p / ρ f )×100%; ρ p ρ is the mass concentration of the permeate. f =1g / L; 3. Resistance to protein fouling: Using a 1 g / L bovine serum albumin solution to simulate contaminants, under an operating pressure of 0.1 MPa, the flux change of filtering the 1 g / L bovine serum albumin solution was measured (cycle: pure water 30 min - bovine serum albumin solution 60 min - washing 30 min - pure water 30 min). After 3 cycles, the pure water flux recovery rate of the membrane was measured. The calculation formula is: Pure water flux recovery rate = water flux recovered after washing step / initial pure water flux × 100%; 4. Long-term stability: Under an operating pressure of 0.1 MPa, a 1 g / L bovine serum albumin solution was used as the feed solution for separation. The rejection rate was calculated after 72 hours of continuous operation.

[0059] Table 1

[0060] Note: The water flux of the blank membrane is 66 L·m. -2 ·h -1 .

[0061] As can be seen from Table 1, the ultrafiltration membranes provided in Examples 1-3 have high water flux (≥75 L·m). -2 ·h -1 It exhibits excellent anti-fouling properties against bovine serum albumin (retention rate ≥98.5%, pure water flux recovery rate ≥98.2% after three cycles) and long-term stability (retention rate ≥97.5% during 72h continuous operation).

[0062] In Comparative Examples 1-3, after replacing the zwitterionic polymers with conventional zwitterionic polymers, the antifouling performance and long-term stability of the resulting ultrafiltration membranes against bovine serum albumin all decreased. Comparative Examples 1-3 show that the zwitterionic polymers of the present invention can effectively improve the antifouling properties and long-term stability of the ultrafiltration membranes.

[0063] Comparative Example 4 did not contain a ureidinone functional monomer with a double bond. Comparative Example 5 replaced the ureidinone functional monomer with a double bond with polyvinylpyrrolidone. Comparative Example 6 replaced the ureidinone functional monomer with a double bond with polyethyleneimine. The ultrafiltration membranes obtained in Comparative Examples 4-6 showed a decrease in antifouling performance against bovine serum albumin and a decrease in long-term stability. Comparative Examples 4-6 indicate that the ureidinone functional monomer with a double bond added in this invention can effectively improve the antifouling performance and long-term stability of the ultrafiltration membrane.

[0064] The ultrafiltration membrane prepared by the conventional method in Comparative Example 7 showed a decrease in antifouling properties and long-term stability, indicating that the preparation method of the present invention can effectively improve the stability of the ultrafiltration membrane.

[0065] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a zwitterionic modified antifouling ultrafiltration membrane, characterized in that, The preparation method includes the following steps: uniformly dispersing the zwitterionic polymer, the ureidopyrimidinone functional monomer containing double bonds, and dopamine hydrochloride in a solvent, adjusting the pH value to obtain a modified solution; coating the modified solution onto an ultrafiltration membrane, reacting in the dark, and performing post-treatment after the reaction is completed; The zwitterionic polymer was obtained by copolymerization of 2-acrylamido-2-methylpropanesulfonic acid and a quaternary ammonium monomer. The quaternary ammonium monomer is obtained by reacting oleamide propyl dimethyl tertiary amine with ethylene 2-(methacryloyloxy)ethyl phosphate. The preparation method of the ureidopyrimidinone functional monomer containing double bonds is as follows: 2-amino-4-hydroxy-6-methylpyrimidine is added to dimethyl sulfoxide at 150-180℃, and under nitrogen protection, isocyanate methacrylate is added. The mixture is cooled to room temperature and stirred thoroughly until a white precipitate appears. The purified product is washed and dried to obtain the final product.

2. The method for preparing the zwitterionic modified antifouling ultrafiltration membrane according to claim 1, characterized in that, The mass ratio of the zwitterionic polymer, the double-bonded ureidopyrimidinone functional monomer, and the dopamine hydrochloride is 1:1-2:3-6.

3. The method for preparing the zwitterionic modified antifouling ultrafiltration membrane according to claim 1 or 2, characterized in that, The pH value is adjusted to 7-8.5; the conditions for the light-protected reaction include: a temperature of 70-80℃ and a time of 4-6 hours.

4. The method for preparing the zwitterionic modified antifouling ultrafiltration membrane according to claim 3, characterized in that, The preparation method of the zwitterionic polymer includes: mixing 2-acrylamido-2-methylpropanesulfonic acid, quaternary ammonium monomer and water evenly, adding potassium persulfate under nitrogen protection, and performing a copolymerization reaction at 70-80℃ for 4-6 hours. After the reaction is completed, acetone is added, filtered, washed and dried to obtain the product.

5. The method for preparing the zwitterionic modified antifouling ultrafiltration membrane according to claim 4, characterized in that, The mass ratio of 2-acrylamido-2-methylpropanesulfonic acid, quaternary ammonium monomer, and water is 4-10:8-15:

100.

6. The method for preparing the zwitterionic modified antifouling ultrafiltration membrane according to claim 5, characterized in that, The method for preparing the quaternary ammonium monomer includes: adding oleamidopropyl dimethyl tertiary amine to chloroform, adding ethylene 2-(methacryloyloxy)ethyl phosphate, heating under reflux, and after the reaction is completed, rotary evaporating and drying to obtain the product.

7. The method for preparing the zwitterionic modified antifouling ultrafiltration membrane according to claim 6, characterized in that, The conditions for the heating reflux reaction include: a temperature of 90-95℃ and a time of 20-24h.

8. The method for preparing the zwitterionic modified antifouling ultrafiltration membrane according to claim 7, characterized in that, The molar ratio of oleamidopropyl dimethyl tertiary amine and ethylene 2-(methacryloyloxy)ethyl phosphate is 1:0.9-1.

1.

9. The zwitterionic modified antifouling ultrafiltration membrane prepared by the method of any one of claims 1-8.

10. The application of the zwitterionic modified antifouling ultrafiltration membrane prepared by the method of any one of claims 1-8 in the field of membrane separation.

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