A method for preparing high-performance PVDF nanofiltration membrane

Abstract

The present invention belongs to the technical field of nanofiltration membranes, and specifically relates to a method for preparing a high-performance PVDF nanofiltration membrane. The present invention first polymerizes acrylic acid, methyl methacrylate, and butenyl-diquaternary ammonium salt-aminobenzenesulfonic acid to form an antibacterial polymer; then polyvinylidene fluoride, antibacterial polymer, and polyvinyl pyrrolidone are added to a solvent to form a casting solution, and after standing and degassing, an antibacterial base membrane is prepared; finally, the antibacterial base membrane is soaked in an aqueous solution, dried, and then soaked in an oil phase solution, and dried to obtain a high-performance PVDF nanofiltration membrane; the obtained high-performance PVDF nanofiltration membrane not only has a high pure water flux and salt ion interception rate, but also has good anti-pollution and antibacterial properties, can effectively prevent the nanofiltration membrane from being contaminated by organic matter and bacterial microorganisms during use, maintain a high flux recovery rate, and help to extend the service life of the PVDF nanofiltration membrane.

Description

Technical Field

[0001] The invention belongs to the technical field of nanofiltration membranes, and in particular relates to a method for preparing a high-performance PVDF nanofiltration membrane. Background Art

[0002] With the continuous expansion of cities and the acceleration of industrialization, a large amount of industrial wastewater and domestic sewage are discharged into water bodies, resulting in deterioration of water quality and water pollution, which has a huge impact on both humans and the ecological environment; membrane separation technology uses membrane materials with selective separation functions to separate, grade, purify and enrich multi-component fluid substances on the membrane through external energy effects (such as pressure difference, electric field force, temperature difference, etc.). It is widely used in the field of water pollution treatment because of its advantages such as simple operation and high effluent quality; PVDF (polyvinylidene fluoride) is one of the commonly used polymer organic membrane materials, with the advantages of good chemical resistance, high thermal stability, high mechanical strength and good film-forming properties, but PVDF has extremely strong hydrophobicity, which makes it easy for organic matter such as oils and proteins to be adsorbed and polluted on the membrane surface, causing membrane pores to be blocked, and the membrane flux decreases with long-term use, thereby shortening the service life of the membrane.

[0003] PVDF nanofiltration membrane is a pressure-driven membrane between reverse osmosis and ultrafiltration. During use, PVDF nanofiltration membrane also has problems such as membrane biofouling, membrane pore blockage, and decreased membrane flux; Chinese patent application number CN202110751739.6 discloses a high-performance hollow nanofiltration membrane based on dense hydrophobic PVDF and a preparation method thereof. A PVDF hollow fiber membrane with an outer diameter of ≤0.5mm is prepared by a dry-wet phase conversion process. The oil phase solution flows inside the PVDF hollow fiber membrane, and the water phase solution flows outside the PVDF hollow fiber membrane. The obtained PVDF hollow nanofiltration membrane has high permeability and separation The separation is much higher than that of the existing hollow fiber membrane, and the amplification repeatability and stability are good; Chinese patent application with application number CN202410810934.5 discloses a GO@MOF nanoparticle-modified PVDF nanofiltration membrane and its preparation method and application. By modifying the PVDF nanofiltration membrane with GO@MOF nanoparticles, on the one hand, the membrane pore distribution is improved, new water transfer channels are added to the nanofiltration membrane, and the water flux is increased. On the other hand, the interfacial polymerization process is affected, and the adsorption characteristics of GO@MOF on piperazine in the membrane pores are utilized to enable the polyvinylidene fluoride nanofiltration membrane to obtain a thinner polyamide layer, thereby significantly improving the water flux of the membrane.

[0004] Although the above patents have improved the membrane flux and other properties of PVDF nanofiltration membranes through different methods, the anti-pollution performance of PVDF nanofiltration membranes is still insufficient and cannot effectively prevent the deposition and contamination of microorganisms and bacteria in water on the membranes. Therefore, it is necessary to develop a high-performance PVDF nanofiltration membrane that can effectively prevent membrane contamination. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a high-performance PVDF nanofiltration membrane in view of the deficiencies in the prior art. The prepared high-performance PVDF nanofiltration membrane not only has a high pure water flux and salt ion retention rate, but also has good anti-pollution and antibacterial properties, can effectively prevent the nanofiltration membrane from being contaminated by organic matter and bacterial microorganisms during use, maintain a high flux recovery rate, and help to extend the service life of the PVDF nanofiltration membrane.

[0006] The technical solution adopted by the present invention to achieve the above-mentioned purpose is:

[0007] A method for preparing a high-performance PVDF nanofiltration membrane comprises the following steps:

[0008] (1) Add acrylic acid, methyl methacrylate, and butylene-bisquaternary ammonium salt-aminobenzenesulfonic acid to water, raise the temperature to 75-80°C under nitrogen protection, add ammonium persulfate, react for 3-4 hours, cool, filter, dry, and crush to obtain an antibacterial polymer;

[0009] (2) adding polyvinylidene fluoride, antibacterial polymer and polyvinyl pyrrolidone to a solvent, heating to 60-70°C, stirring for 10-12 hours to obtain a casting solution, standing to degas, coating the solution on a glass plate, immersing the solution in water for phase inversion, and obtaining an antibacterial base film;

[0010] (3) The antibacterial base membrane is immersed in an aqueous solution for 250-300 seconds, dried, and then immersed in an oil solution for 30-60 seconds, dried, to obtain a high-performance PVDF nanofiltration membrane.

[0011] Furthermore, in step (1), the molar ratio of acrylic acid, methyl methacrylate and butylene-bis-quaternary ammonium salt-aminobenzenesulfonic acid is 1:0.6-0.8:0.2-0.3; and the amount of ammonium persulfate used is 0.6-0.8% of the total mass of acrylic acid, methyl methacrylate and butylene-bis-quaternary ammonium salt-aminobenzenesulfonic acid.

[0012] Furthermore, in step (2), the mass ratio of polyvinylidene fluoride, antibacterial polymer and polyvinyl pyrrolidone is 1:0.08-0.1:0.15-0.2; the amount ratio of polyvinylidene fluoride and solvent is 1g:4-5mL; and the solvent is N,N-dimethylformamide or N,N-dimethylacetamide.

[0013] Furthermore, the aqueous phase solution in step (3) is an aqueous solution containing 0.1-0.2 wt % piperazine and 0.02-0.04 wt % diquaternary ammonium salt-aminobenzenesulfonic acid.

[0014] Furthermore, the oil phase solution in step (3) is a n-hexane solution containing 0.1-0.2 wt % of trimesoyl chloride.

[0015] In the technical solution of the present invention, the preparation method of the diquaternary ammonium salt-aminobenzenesulfonic acid and the butenyl-diquaternary ammonium salt-aminobenzenesulfonic acid is:

[0016] S1. Add anhydrous dichloromethane and p-aminobenzenesulfonic acid to the reaction vessel, mix well, add epichlorohydrin dropwise, raise the temperature to 35-40°C, stir and react for 2-3h, cool, and place in an ice bath, add thionyl chloride dropwise, add dropwise, continue to react for 1-2h, and after the reaction is completed, add water for extraction, and concentrate the organic phase under reduced pressure to obtain chloro-aminobenzenesulfonic acid, the structural formula is:

[0017] ;

[0018] S2. Add ethanol, chlorinated aminobenzenesulfonic acid and dodecyldimethyl tertiary amine to the reaction vessel, mix well, heat to 80°C, stir and react for 10-12h. After the reaction is complete, remove ethanol, add water and dichloromethane for extraction, and concentrate the aqueous phase under reduced pressure to obtain diquaternary ammonium salt aminobenzenesulfonic acid, the structural formula of which is:

[0019] ;

[0020] S3, add acetonitrile, diquaternary ammonium salt-aminobenzenesulfonic acid, triethylamine and 1-bromo-3-butene-2-ol to the reaction vessel, mix well, heat to 55-60 ° C, stir and react for 3-4 hours, after the reaction is completed, remove acetonitrile, add water and dichloromethane for extraction, and concentrate the aqueous phase under reduced pressure to obtain butenyl-diquaternary ammonium salt-aminobenzenesulfonic acid, the structural formula is:

[0021] .

[0022] Furthermore, in step S1, the molar ratio of p-aminobenzenesulfonic acid, epichlorohydrin and dithionyl chloride is 1:1.0-1.1:1.1-1.2.

[0023] Furthermore, in step S2, the molar ratio of chloro-aminobenzenesulfonic acid to dodecyldimethyl tertiary amine is 1:2.1-2.2.

[0024] Furthermore, in step S3, the molar ratio of the diquaternary ammonium salt-aminobenzenesulfonic acid, 1-bromo-3-butene-2-ol, and triethylamine is 1:1.0-1.1:1.2-1.3.

[0025] The present invention has the following beneficial effects:

[0026] In order to improve the hydrophobicity of PVDF membrane materials and reduce membrane pollution, the present invention modifies the PVDF membrane materials. Firstly, p-aminobenzenesulfonic acid raw material is reacted with epichlorohydrin, dichlorothionyl and dodecyldimethyl tertiary amine in sequence to obtain diquaternary ammonium salt-aminobenzenesulfonic acid containing imino group, sulfonic acid group and long-chain quaternary ammonium salt in the structure; then the raw material is reacted with 1-bromo-3-butene-2-ol to obtain butenyl-diquaternary ammonium salt-aminobenzenesulfonic acid containing butenyl group, hydroxyl group, sulfonic acid group and long-chain quaternary ammonium salt in the structure; on the one hand, the present invention polymerizes butenyl-diquaternary ammonium salt-aminobenzenesulfonic acid with acrylic acid and methyl methacrylate to form an antibacterial polymer, and the antibacterial polymer is used for polyvinylidene fluoride modification, and the surface of the obtained antibacterial base membrane is introduced On the other hand, the diquaternary ammonium salt-aminobenzenesulfonic acid is added to the aqueous solution. During the interfacial polymerization of the antibacterial base membrane to form a polyamide coating, the imino group and sulfonic acid group in the diquaternary ammonium salt-aminobenzenesulfonic acid structure in the aqueous solution can also react with trimesoyl chloride, which relatively slows down the polymerization rate of piperazine and trimesoyl chloride to form a thinner polyamide coating. The hydrophilic group sulfonic acid group and the antibacterial group long-chain quaternary ammonium salt are introduced into the polyamide coating through chemical bonds, which improves the hydrophilicity and antibacterial property of the nanofiltration membrane, thereby improving the pure water flux, salt ion retention rate, anti-pollution and antibacterial properties of the nanofiltration membrane.

[0027] The high-performance PVDF nanofiltration membrane provided by the present invention not only has a high pure water flux and salt ion retention rate, but also has good anti-pollution and antibacterial properties. It can effectively prevent the nanofiltration membrane from being contaminated by organic matter and bacterial microorganisms during use, maintain a high flux recovery rate, and help to extend the service life of the PVDF nanofiltration membrane. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments; the technical features designed in different implementation modes of the present invention described below can be combined with each other as long as they do not conflict with each other; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0029] In the technical scheme of the present invention, the raw materials and reagents used in the following embodiments are all common commercial products, among which polyvinylidene fluoride CAS No. 24937-79-9; polyvinyl pyrrolidone CAS No. 9003-39-8; piperazine CAS No. 110-85-0; trimesoyl chloride CAS No. 4422-95-1; acrylic acid CAS No. 79-10-7; methyl methacrylate CAS No. 80-62-6; ammonium persulfate CAS No. 7727-54-0; p-aminobenzenesulfonic acid CAS No. 121-57-3; epichlorohydrin CAS No. 1 06-89-8; thionyl chloride CAS No. 7719-09-7; dodecyl dimethyl tertiary amine CAS No. 112-18-5; 1-bromo-3-butene-2-ol CAS No. 64341-49-7; triethylamine CAS No. 121-44-8; N,N-dimethylformamide CAS No. 68-12-2; N,N-dimethylacetamide CAS No. 127-19-5; n-hexane CAS No. 110-54-3; dichloromethane CAS No. 75-09-2; ethanol CAS No. 64-17-5; acetonitrile CAS No. 75-05-8.

[0030] Example 1

[0031] The preparation method of diquaternary ammonium salt-aminobenzenesulfonic acid and butenyl-diquaternary ammonium salt-aminobenzenesulfonic acid is as follows:

[0032] ;

[0033] S1. Add 500 mL of anhydrous dichloromethane and 17.4 g of p-aminobenzenesulfonic acid to a reaction vessel, mix well, add 9.8 g of epichlorohydrin dropwise, heat to 40 ° C, stir and react for 2 h, cool, and place in an ice bath, add 13.1 g of thionyl chloride dropwise, add dropwise, and continue to react for 2 h. After the reaction is completed, add water for extraction, and concentrate the organic phase under reduced pressure to obtain 23.5 g of chloro-aminobenzenesulfonic acid; wherein the molar ratio of p-aminobenzenesulfonic acid, epichlorohydrin, and thionyl chloride is 1:1.05:1.1;

[0034] Chloro-aminobenzenesulfonic acid: ESI (m / z): 285.2 [M+H] + , 1 H-NMR (600MHz, DMSO-d6, δppm): 8.50 (s, 1H), 7.32-7.36 (m, 3H), 7.22 (d, J=8.4Hz, 2H), 3.74-3.88 (m, 2H), 3.40-3.49 (m, 2H), 3.15-3.20 (m, 1H).

[0035] S2, add 400mL ethanol, 23.0g chlorinated-aminobenzenesulfonic acid and 36.3g dodecyldimethyl tertiary amine to the reaction vessel, mix well, warm to 80 ° C, stir and react for 12h, after the reaction is completed, remove ethanol, add water and dichloromethane for extraction, and concentrate the aqueous phase under reduced pressure to obtain 45.8g diquaternary ammonium salt-aminobenzenesulfonic acid; wherein the molar ratio of chlorinated-aminobenzenesulfonic acid to dodecyldimethyl tertiary amine is 1:2.1;

[0036] Diquaternary ammonium salt-aminobenzenesulfonic acid: ESI (m / z): 712.0 [M+H] + , 1 H-NMR (600MHz, DMSO-d6, δppm): 8.52 (s, 1H), 7.31-7.36 (m, 3H), 7.22 (d, J=8.4Hz, 2H), 4.15-4.20 (m, 1H), 3.75-3 .80 (m, 1H), 3.50-3.56 (m, 2H), 3.20-3.32 (m, 17H), 1.71-1.75 (m, 4H), 1.24-1.30 (m, 36H), 0.88 (t, J=7.2Hz, 6H).

[0037] S3, in reaction vessel, add 350mL acetonitrile, 45.0g diquaternary ammonium salt-aminobenzenesulfonic acid, 8.3g triethylamine and 10.0g 1-bromo-3-butene-2-ol, mix well, warm to 60 DEG C, stirring reaction 4h, after reaction is completed, remove acetonitrile, add water and dichloromethane to extract, aqueous phase is concentrated under reduced pressure to obtain 41.2g butenyl-diquaternary ammonium salt-aminobenzenesulfonic acid; Wherein the mol ratio of diquaternary ammonium salt-aminobenzenesulfonic acid, 1-bromo-3-butene-2-ol, triethylamine is 1:1.05:1.3;

[0038] Butenyl-bisquaternary ammonium salt-aminobenzenesulfonic acid: ESI (m / z): 782.1 [M+H] + , 1 H-NMR (600MHz, DMSO-d6, δppm): 8.50 (s, 1H), 7.26 (d, J=8.4Hz, 2H), 7.08 (d, J=8.4Hz, 2H), 6.18 (s, 1H), 5.33-5.40 (m, 3H), 4.15-4.22 (m, 2H) , 3.76-3.82 (m, 2H), 3.61-3.67 (m, 2H), 3.43-3.50 (m, 2H), 3.22-3.30 ( m, 16H), 1.71-1.74 (m, 4H), 1.24-1.32 (m, 36H), 0.88 (t, J=7.2Hz, 6H).

[0039] Example 2

[0040] A method for preparing a high-performance PVDF nanofiltration membrane comprises the following steps:

[0041] (1) Add acrylic acid, methyl methacrylate, and butylene-bis-quaternary ammonium salt-aminobenzenesulfonic acid into water, heat to 80°C under nitrogen protection, add ammonium persulfate, react for 3 hours, cool, filter, dry, and crush to obtain an antibacterial polymer; wherein the molar ratio of acrylic acid, methyl methacrylate, and butylene-bis-quaternary ammonium salt-aminobenzenesulfonic acid is 1:0.8:0.3; the amount of ammonium persulfate used is 0.8% of the total mass of acrylic acid, methyl methacrylate, and butylene-bis-quaternary ammonium salt-aminobenzenesulfonic acid;

[0042] (2) Add polyvinylidene fluoride, antibacterial polymer and polyvinyl pyrrolidone to a solvent, heat to 70°C, stir for 10 hours to obtain a casting solution, let it stand for degassing, then apply it on a glass plate, immerse it in water for phase inversion, and obtain an antibacterial base film; wherein the mass ratio of polyvinylidene fluoride, antibacterial polymer and polyvinyl pyrrolidone is 1:0.1:0.2; the amount ratio of polyvinylidene fluoride to solvent is 1g:5mL; the solvent is N,N-dimethylformamide;

[0043] (3) The antibacterial base membrane is immersed in an aqueous solution for 300 seconds, dried, and then immersed in an oil solution for 60 seconds and dried to obtain a high-performance PVDF nanofiltration membrane; wherein the aqueous solution is an aqueous solution containing 0.1wt% piperazine and 0.04wt% diquaternary ammonium salt-aminobenzenesulfonic acid; and the oil solution is an n-hexane solution containing 0.1wt% trimesoyl chloride.

[0044] Example 3

[0045] A method for preparing a high-performance PVDF nanofiltration membrane comprises the following steps:

[0046] (1) Add acrylic acid, methyl methacrylate, and butylene-bis-quaternary ammonium salt-aminobenzenesulfonic acid into water, heat to 75°C under nitrogen protection, add ammonium persulfate, react for 4 hours, cool, filter, dry, and crush to obtain an antibacterial polymer; wherein the molar ratio of acrylic acid, methyl methacrylate, and butylene-bis-quaternary ammonium salt-aminobenzenesulfonic acid is 1:0.7:0.2; the amount of ammonium persulfate used is 0.7% of the total mass of acrylic acid, methyl methacrylate, and butylene-bis-quaternary ammonium salt-aminobenzenesulfonic acid;

[0047] (2) Add polyvinylidene fluoride, antibacterial polymer and polyvinyl pyrrolidone to a solvent, heat to 60°C, stir for 12 hours to obtain a casting solution, let it stand for degassing, then apply it on a glass plate, immerse it in water for phase inversion, and obtain an antibacterial base film; wherein the mass ratio of polyvinylidene fluoride, antibacterial polymer and polyvinyl pyrrolidone is 1:0.08:0.15; the amount ratio of polyvinylidene fluoride to solvent is 1g:4mL; the solvent is N,N-dimethylacetamide;

[0048] (3) The antibacterial base membrane is immersed in an aqueous solution for 250 seconds, dried, and then immersed in an oil solution for 30 seconds and dried to obtain a high-performance PVDF nanofiltration membrane; wherein the aqueous solution is an aqueous solution containing 0.15wt% piperazine and 0.03wt% diquaternary ammonium salt-aminobenzenesulfonic acid; and the oil solution is an n-hexane solution containing 0.15wt% trimesoyl chloride.

[0049] Example 4

[0050] A method for preparing a high-performance PVDF nanofiltration membrane comprises the following steps:

[0051] (1) Add acrylic acid, methyl methacrylate, and butylene-bis-quaternary ammonium salt-aminobenzenesulfonic acid into water, and under nitrogen protection, heat the water to 78°C, add ammonium persulfate, react for 3.5 hours, cool, filter, dry, and crush to obtain an antibacterial polymer; wherein the molar ratio of acrylic acid, methyl methacrylate, and butylene-bis-quaternary ammonium salt-aminobenzenesulfonic acid is 1:0.6:0.25; and the amount of ammonium persulfate used is 0.6% of the total mass of acrylic acid, methyl methacrylate, and butylene-bis-quaternary ammonium salt-aminobenzenesulfonic acid;

[0052] (2) Add polyvinylidene fluoride, antibacterial polymer and polyvinyl pyrrolidone to a solvent, heat to 65°C, stir for 11 hours to obtain a casting solution, let it stand for degassing, then apply it on a glass plate, immerse it in water for phase inversion, and obtain an antibacterial base film; wherein the mass ratio of polyvinylidene fluoride, antibacterial polymer and polyvinyl pyrrolidone is 1:0.09:0.17; the amount ratio of polyvinylidene fluoride to solvent is 1g:4.5mL; the solvent is N,N-dimethylformamide;

[0053] (3) The antibacterial base membrane is immersed in an aqueous solution for 280 seconds, dried, and then immersed in an oil solution for 50 seconds and dried to obtain a high-performance PVDF nanofiltration membrane; wherein the aqueous solution is an aqueous solution containing 0.2 wt% piperazine and 0.02 wt% diquaternary ammonium salt-aminobenzenesulfonic acid; and the oil solution is an n-hexane solution containing 0.2 wt% trimesoyl chloride.

[0054] Example 5

[0055] A method for preparing a high-performance PVDF nanofiltration membrane comprises the following steps:

[0056] (1) Add acrylic acid, methyl methacrylate, and butylene-bis-quaternary ammonium salt-aminobenzenesulfonic acid into water, heat to 75°C under nitrogen protection, add ammonium persulfate, react for 3 hours, cool, filter, dry, and crush to obtain an antibacterial polymer; wherein the molar ratio of acrylic acid, methyl methacrylate, and butylene-bis-quaternary ammonium salt-aminobenzenesulfonic acid is 1:0.6:0.3; the amount of ammonium persulfate used is 0.7% of the total mass of acrylic acid, methyl methacrylate, and butylene-bis-quaternary ammonium salt-aminobenzenesulfonic acid;

[0057] (2) Add polyvinylidene fluoride, antibacterial polymer and polyvinyl pyrrolidone to a solvent, heat to 70°C, stir for 12 hours to obtain a casting solution, let it stand for degassing, then apply it on a glass plate, immerse it in water for phase inversion, and obtain an antibacterial base film; wherein the mass ratio of polyvinylidene fluoride, antibacterial polymer and polyvinyl pyrrolidone is 1:0.08:0.2; the amount ratio of polyvinylidene fluoride and solvent is 1g:5mL; the solvent is N,N-dimethylacetamide;

[0058] (3) The antibacterial base membrane is immersed in an aqueous solution for 300 seconds, dried, and then immersed in an oil solution for 40 seconds and dried to obtain a high-performance PVDF nanofiltration membrane; wherein the aqueous solution is an aqueous solution containing 0.1wt% piperazine and 0.02wt% diquaternary ammonium salt-aminobenzenesulfonic acid; and the oil solution is an n-hexane solution containing 0.1wt% trimesoyl chloride.

[0059] Comparative Example 1

[0060] Compared with Example 2, the antibacterial polymer in this comparative example is prepared from acrylic acid and methyl methacrylate.

[0061] A method for preparing a high-performance PVDF nanofiltration membrane comprises the following steps:

[0062] (1) Add acrylic acid and methyl methacrylate to water, raise the temperature to 80°C under nitrogen protection, add ammonium persulfate, react for 3 hours, cool, filter, dry and crush to obtain an antibacterial polymer; wherein the molar ratio of acrylic acid to methyl methacrylate is 1:0.8; the amount of ammonium persulfate used is 0.8% of the total mass of acrylic acid and methyl methacrylate;

[0063] (2) Same as step (2) of Example 2;

[0064] (3) Same as step (3) of Example 2.

[0065] Comparative Example 2

[0066] Compared with Example 2, the aqueous phase solution in this comparative example is an aqueous solution containing 0.1 wt % of piperazine.

[0067] A method for preparing a high-performance PVDF nanofiltration membrane comprises the following steps:

[0068] (1) Same as step (1) of Example 2;

[0069] (2) Same as step (2) of Example 2;

[0070] (3) The antibacterial base membrane is immersed in an aqueous solution for 300 seconds, dried, and then immersed in an oil solution for 60 seconds and dried to obtain a high-performance PVDF nanofiltration membrane; wherein the aqueous solution is an aqueous solution containing 0.1 wt% piperazine; and the oil solution is an n-hexane solution containing 0.1 wt% trimesoyl chloride.

[0071] Comparative Example 3

[0072] Compared with Example 2, the antibacterial polymer in this comparative example is prepared from acrylic acid and methyl methacrylate, and the aqueous phase solution is an aqueous solution containing 0.1 wt % piperazine.

[0073] A method for preparing a high-performance PVDF nanofiltration membrane comprises the following steps:

[0074] (1) Add acrylic acid and methyl methacrylate to water, raise the temperature to 80°C under nitrogen protection, add ammonium persulfate, react for 3 hours, cool, filter, dry and crush to obtain an antibacterial polymer; wherein the molar ratio of acrylic acid to methyl methacrylate is 1:0.8; the amount of ammonium persulfate used is 0.8% of the total mass of acrylic acid and methyl methacrylate;

[0075] (2) Same as step (2) of Example 2;

[0076] (3) The antibacterial base membrane is immersed in an aqueous solution for 300 seconds, dried, and then immersed in an oil solution for 60 seconds and dried to obtain a high-performance PVDF nanofiltration membrane; wherein the aqueous solution is an aqueous solution containing 0.1 wt% piperazine; and the oil solution is an n-hexane solution containing 0.1 wt% trimesoyl chloride.

[0077] Performance Testing

[0078] The high-performance PVDF nanofiltration membranes prepared in Examples 2-5 and Comparative Examples 1-3 were subjected to performance tests. At 5 bar, the pure water flux and the retention rate of 1 g / L MgSO4 and 1 g / L Na2SO4 salt solutions were tested. In addition, the PVDF nanofiltration membrane was contaminated with 500 ppm BSA solution for 2 hours, and then cleaned with 500 ppm NaClO for 30 minutes. The flux recovery rate (%) = water flux of the membrane after contamination / pure water flux of the membrane before contamination. The antibacterial rate of the membrane against Escherichia coli was tested before and after contamination. The results are shown in Table 1.

[0079] Table 1 Performance test results

[0080] As can be seen from Table 1, the high-performance PVDF nanofiltration membranes prepared in Examples 2-5 of the present invention have high pure water flux, MgSO4 retention rate, Na2SO4 retention rate, high flux recovery rate, and high antibacterial rate against Escherichia coli before and after membrane pollution, indicating that they have good anti-pollution and antibacterial properties, and can effectively prevent the nanofiltration membrane from being contaminated by organic matter and bacterial microorganisms during use, and maintain a high flux recovery rate; compared with Comparative Examples 1-3, the surface of the antibacterial base membrane in Example 2 of the present invention contains more hydrophilic groups, carboxyl groups, sulfonic acid groups, hydroxyl groups and antibacterial groups. Long-chain quaternary ammonium salts can improve the hydrophilicity and antibacterial properties of the base membrane, and the hydrophilic group sulfonic acid group and the antibacterial group long-chain quaternary ammonium salt are also introduced into the polyamide coating formed by the interfacial polymerization of the antibacterial base membrane, which can also improve the hydrophilicity and antibacterial properties of the nanofiltration membrane, thereby improving the pure water flux, salt ion retention rate, anti-pollution and antibacterial properties of the nanofiltration membrane.

[0081] It should be noted that, in this article, terms such as "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0082] Although the embodiments of the present application have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a high-performance PVDF nanofiltration membrane, characterized in that: The steps include: (1) Add acrylic acid, methyl methacrylate, and butylene-bisquaternary ammonium salt-aminobenzenesulfonic acid to water, raise the temperature to 75-80°C under nitrogen protection, add ammonium persulfate, react for 3-4 hours, cool, filter, dry, and crush to obtain an antibacterial polymer; (2) adding polyvinylidene fluoride, antibacterial polymer and polyvinyl pyrrolidone to a solvent, heating to 60-70°C, stirring for 10-12 hours to obtain a casting solution, standing to degas, coating the solution on a glass plate, immersing the solution in water for phase inversion, and obtaining an antibacterial base film; (3) soaking the antibacterial base membrane in an aqueous solution for 250-300 seconds, drying it, and then soaking it in an oil solution for 30-60 seconds, drying it, to obtain a high-performance PVDF nanofiltration membrane; The preparation method of the butenyl-bis-quaternary ammonium salt-aminobenzenesulfonic acid in step (1) is: S1. Add anhydrous dichloromethane and p-aminobenzenesulfonic acid to a reaction vessel, mix well, add epichlorohydrin dropwise, raise the temperature to 35-40°C, stir and react for 2-3h, cool, place in an ice bath, add thionyl chloride dropwise, add dropwise, continue to react for 1-2h, add water for extraction after the reaction is completed, and concentrate the organic phase under reduced pressure to obtain chloro-aminobenzenesulfonic acid; S2, add ethanol, chlorinated-aminobenzenesulfonic acid and dodecyldimethyl tertiary amine to the reaction vessel, mix well, heat to 80 ° C, stir and react for 10-12 hours, after the reaction is completed, remove ethanol, add water and dichloromethane for extraction, and concentrate the aqueous phase under reduced pressure to obtain diquaternary ammonium salt-aminobenzenesulfonic acid; S3. Add acetonitrile, diquaternary ammonium salt-aminobenzenesulfonic acid, triethylamine and 1-bromo-3-butene-2-ol into the reaction vessel, mix well, heat to 55-60°C, stir and react for 3-4 hours. After the reaction is completed, remove acetonitrile, add water and dichloromethane for extraction, and concentrate the aqueous phase under reduced pressure to obtain butenyl-diquaternary ammonium salt-aminobenzenesulfonic acid.

2. The method for preparing a high-performance PVDF nanofiltration membrane according to claim 1, characterized in that: The molar ratio of p-aminobenzenesulfonic acid, epichlorohydrin and dithionyl chloride in step S1 is 1:1.0-1.1:1.1-1.

2.

3. The method for preparing a high-performance PVDF nanofiltration membrane according to claim 1, characterized in that: The molar ratio of chloro-aminobenzenesulfonic acid to dodecyldimethyl tertiary amine in step S2 is 1:2.1-2.

2.

4. The method for preparing a high-performance PVDF nanofiltration membrane according to claim 1, characterized in that: The molar ratio of the diquaternary ammonium salt-aminobenzenesulfonic acid, 1-bromo-3-butene-2-ol and triethylamine in step S3 is 1:1.0-1.1:1.2-1.

3.

5. The method for preparing a high-performance PVDF nanofiltration membrane according to claim 1, characterized in that: The molar ratio of acrylic acid, methyl methacrylate and butylene-bis-quaternary ammonium salt-aminobenzenesulfonic acid in step (1) is 1:0.6-0.8:0.2-0.3; the amount of ammonium persulfate used is 0.6-0.8% of the total mass of acrylic acid, methyl methacrylate and butylene-bis-quaternary ammonium salt-aminobenzenesulfonic acid.

6. The method for preparing a high-performance PVDF nanofiltration membrane according to claim 1, characterized in that: The mass ratio of the polyvinylidene fluoride, the antibacterial polymer and the polyvinyl pyrrolidone in step (2) is 1:0.08-0.1:0.15-0.2; the dosage ratio of the polyvinylidene fluoride and the solvent is 1g:4-5mL.

7. The method for preparing a high-performance PVDF nanofiltration membrane according to claim 6, characterized in that: The solvent is N,N-dimethylformamide or N,N-dimethylacetamide.

8. The method for preparing a high-performance PVDF nanofiltration membrane according to claim 1, characterized in that: The aqueous phase solution in step (3) is an aqueous solution containing 0.1-0.2 wt % piperazine and 0.02-0.04 wt % diquaternary ammonium salt-aminobenzenesulfonic acid.

9. The method for preparing a high-performance PVDF nanofiltration membrane according to claim 1, characterized in that: The oil phase solution in step (3) is a n-hexane solution containing 0.1-0.2 wt % of trimesoyl chloride.

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