Preparation method of high-performance composite nanofiltration membrane

Abstract

This invention provides a method for preparing a high-performance composite nanofiltration membrane, comprising the following steps: Step S1, dissolving an aqueous monomer in pure water, stirring thoroughly until dissolved to obtain an aqueous solution, and storing it in the dark; Step S2, adding an organic monomer to an organic solvent, stirring thoroughly until dissolved to obtain an organic solution, and storing it in the dark, and using the same organic monomer to prepare n different concentrations of organic solutions; Step S3, immersing the surface of a porous support membrane in the aqueous solution, then removing it and removing the aqueous solution until no residual droplets remain on the surface; Step S4, pouring the n different concentrations of organic solutions onto the surface of the porous support membrane in stages to carry out interfacial polymerization reactions in stages until the last interfacial polymerization reaction is completed; Step S5, thoroughly washing the surface of the porous support membrane with pure organic solvent to obtain a high-performance composite nanofiltration membrane prepared based on continuous interfacial polymerization with different acyl chloride concentrations.

Description

Technical Field

[0001] This invention belongs to the field of nanofiltration membrane separation technology, and specifically relates to a method for preparing a high-performance composite nanofiltration membrane. Background Technology

[0002] Membrane separation technology is an advanced water treatment technology currently used to address global water scarcity and pollution problems, and is widely applied in municipal water treatment, industrial water treatment, and seawater desalination. Compared with traditional water treatment processes (coagulation, sedimentation, filtration, disinfection, biological treatment, etc.), membrane separation technology has higher treatment efficiency and effectiveness, is highly adaptable to water quality, less affected by the environment, requires less land area, and does not produce secondary pollution. Based on different molecular weight cutoffs, membranes can be classified into microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO). Nanofiltration and reverse osmosis membranes have low molecular weight cutoffs and produce high-quality effluent, representing important directions for future development of membrane separation technology.

[0003] Currently, commercially available nanofiltration and reverse osmosis membranes are all polyamide membrane composites. A significant advantage of membrane composites is the ability to optimize the performance of both the membrane and the porous substrate, resulting in tunable membrane structures, high separation performance, and stability. However, nanofiltration and reverse osmosis membranes prepared using conventional methods have shortcomings in practical operation, primarily in terms of poor permeate-selectivity and fouling resistance. Researchers have made numerous improvements to membrane preparation methods and material development, such as adding nanoparticles, grafting, and modifying the membrane monomers. However, these methods are generally costly and have poor compatibility with existing membrane fabrication processes, leading to instability issues. Therefore, developing low-cost, scale-up-friendly novel membrane fabrication strategies to obtain high-performance nanofiltration membranes is a current research hotspot and challenge in the field of nanofiltration water treatment. Summary of the Invention

[0004] This invention is made to solve the above-mentioned problems, and its purpose is to provide a method for preparing a high-performance composite nanofiltration membrane.

[0005] This invention provides a method for preparing a high-performance composite nanofiltration membrane, characterized by the following steps:

[0006] Step S1: Dissolve the aqueous monomer in pure water, stir thoroughly until dissolved to obtain an aqueous solution, and store it away from light.

[0007] Step S2: Add organic phase monomer to organic solvent, stir thoroughly until dissolved to obtain organic phase solution, store in the dark, and use the same organic phase monomer to prepare n different concentrations of organic phase solution;

[0008] Step S3: Immerse the surface of the porous support membrane in the aqueous solution, then remove it and remove the aqueous solution until there are no residual droplets on the surface;

[0009] Step S4: n different concentrations of organic phase solutions are poured onto the surface of the porous support membrane in batches to carry out interfacial polymerization reactions in batches until the last interfacial polymerization reaction is completed.

[0010] Step S5: After thoroughly washing the surface of the porous support membrane with pure organic solvent, a high-performance composite nanofiltration membrane prepared by continuous interfacial polymerization with different acyl chloride concentrations is obtained.

[0011] The method for preparing the high-performance composite nanofiltration membrane provided by the present invention may also have the following features: in step S1, the aqueous monomer is a molecule in which the sum of the number of amino (-NH2) and hydroxyl (-OH) groups is greater than or equal to 2, including polyamines, polyols and polyphenols, and the aqueous solution is a solution of one aqueous monomer or a mixed solution of multiple aqueous monomers, and the concentration of the aqueous solution is 0.01%wt-10.0%wt.

[0012] The method for preparing the high-performance composite nanofiltration membrane provided by the present invention may also have the following features: in step S2, the organic phase monomer is an aromatic polyacrylamide chloride, and the organic solvent is one or more of n-hexane, cyclohexane, toluene, n-heptane or n-octane.

[0013] The method for preparing the high-performance composite nanofiltration membrane provided by the present invention may also have the following features: in step S1, a base membrane pre-wetting solution is prepared, which is obtained by dissolving an amino alcohol-containing substance in pure water and stirring it thoroughly until dissolved; in step S3, before immersing the surface of the porous support membrane in the aqueous solution, the surface of the porous support membrane is also immersed in the base membrane pre-wetting solution, and then the base membrane pre-wetting solution is removed until there are no residual droplets on the surface.

[0014] The method for preparing the high-performance composite nanofiltration membrane provided by the present invention may also have the following characteristics: wherein the amino alcohol-containing substance is a substance whose molecular formula contains both amino and hydroxyl groups, and the concentration of the base membrane pre-wetting solution is 0.01%wt-10.0%wt.

[0015] The method for preparing the high-performance composite nanofiltration membrane provided by the present invention may also have the following characteristics: wherein the porous support membrane is an ultrafiltration membrane, and the immersion time of the porous support membrane in the base membrane pre-wetting solution is ≤30min.

[0016] The method for preparing high-performance composite nanofiltration membrane provided by the present invention may also have the following feature: in step S3, the immersion time of the porous support membrane in the aqueous solution is 10s-300s.

[0017] The method for preparing the high-performance composite nanofiltration membrane provided by this invention may also have the following feature: wherein, in step S2, the concentrations of the n different organic phase solutions are 0.001% w / v to 5% w / v, n ≥ 2, and the n different organic phase solutions include organic phase solutions of concentration A, concentration B, up to concentration N.

[0018] In step S4, after each interfacial polymerization reaction, the corresponding concentration of organic phase solution is discarded, and then the next concentration of organic phase solution is added. This includes the following sub-steps:

[0019] Step S4-1: Pour the organic phase solution of concentration A onto the surface of the porous support membrane to carry out the interfacial polymerization reaction, and then remove the organic phase solution of concentration A.

[0020] Step S4-2: Pour the organic phase solution of concentration B onto the surface of the porous support membrane to carry out the interfacial polymerization reaction, and then remove the organic phase solution of concentration B.

[0021] In step S4-3, organic phase solutions of different concentrations are repeatedly poured onto the surface of the porous support membrane for interfacial polymerization. After each interfacial polymerization reaction, the corresponding concentration of organic phase solution is removed until the last interfacial polymerization reaction is performed using the corresponding concentration of organic phase solution. After that, the corresponding concentration of organic phase solution is removed. In step S4, the time for interfacial polymerization is ≤30 min.

[0022] The method for preparing the high-performance composite nanofiltration membrane provided by the present invention may also have the following features: In step S5, after thoroughly washing the surface of the porous support membrane with a pure organic solvent, the porous support membrane is further subjected to a heat stabilization treatment and then washed at a predetermined temperature. The predetermined temperature for the heat stabilization treatment is 25℃-50℃, and the treatment time is ≤60min. When washing after the heat stabilization treatment, the porous support membrane is thoroughly washed with pure water or a 0.1w / v~0.5%w / v ethanol solution.

[0023] The role and effect of invention

[0024] According to the method for preparing a high-performance composite nanofiltration membrane of the present invention, an aqueous solution and n organic phase solutions of different concentrations are prepared respectively. After the surface of a porous support membrane is immersed in the aqueous solution, the n organic phase solutions of different concentrations are poured onto the surface of the porous support membrane in batches to carry out interfacial polymerization reaction. After washing with organic solvent, a high-performance composite nanofiltration membrane prepared based on continuous interfacial polymerization with different acyl chloride concentrations is obtained.

[0025] The preparation method of this invention utilizes staged interfacial polymerization and adjusts the concentration of the organic phase solution involved in film formation. This allows for flexible adjustment of the pore size and thickness of the nanofiltration membrane, enabling targeted control of its permeability and selectivity, ultimately resulting in a high-performance composite nanofiltration membrane. Furthermore, the preparation method of this invention is easy to operate, can be scaled up for production, and is technologically inclusive, facilitating combination with other membrane modification methods to achieve dual performance enhancements.

[0026] Furthermore, in the preparation method of this invention, before immersing the surface of the porous support membrane in the aqueous solution, the porous support membrane is pre-wetted with a prepared base membrane pre-wetting solution. Pre-wetting enhances the base membrane's immersion properties, increases the storage of aqueous monomers, and promotes the interfacial polymerization reaction. Additionally, the preparation method of this invention performs heat treatment after the reaction and rinsing, which enhances the continuation of the interfacial polymerization reaction and makes the membrane performance more stable. Attached Figure Description

[0027] Figure 1 These are the pure water fluxes of Examples 1 and 2 and Comparative Examples 1 and 2 of the present invention;

[0028] Figure 2 These are the desalination rates of Examples 1 and 2 and Comparative Examples 1 and 2 of the present invention;

[0029] Figure 3 These are the aperture distributions of Embodiments 1 and 2 and Comparative Examples 1 and 2 of the present invention;

[0030] Figure 4 These are the molecular weight cutoffs of Examples 1 and 2 and Comparative Examples 1 and 2 of the present invention;

[0031] Figure 5 This refers to the PA layer thickness of Embodiment 1 and Comparative Examples 1 and 2 of the present invention. Detailed Implementation

[0032] To make the technical means, creative features, objectives and effects of this invention easy to understand, the following embodiments, in conjunction with the accompanying drawings, specifically illustrate the preparation method of the high-performance composite nanofiltration membrane of this invention.

[0033] <Example 1>

[0034] The method for preparing the high-performance composite nanofiltration membrane in this embodiment includes the following steps:

[0035] Step S1: Dissolve the aqueous monomer in pure water, stir thoroughly until dissolved to obtain an aqueous solution, and store it away from light. The specific process is as follows:

[0036] Dissolve piperazine in pure water and stir thoroughly until dissolved to prepare an aqueous solution with a concentration of 0.5% w / v. Store in the dark.

[0037] Step S2: Add the organic phase monomer to the organic solvent, stir thoroughly until dissolved to obtain an organic phase solution, and store it in the dark. Then, using the same organic phase monomer, prepare n different concentrations of organic phase solutions. The specific process is as follows:

[0038] Trimethylbenzene chloride was dissolved in n-hexane and stirred thoroughly to prepare organic phase solutions with concentrations of 0.02% w / v and 0.1% w / v, respectively, and stored in the dark.

[0039] Step S3 involves immersing the surface of the porous support membrane in an aqueous solution, then removing it and cleaning off the aqueous solution until no residual droplets remain on the surface. The specific process is as follows:

[0040] The surface of the polyethersulfone porous support membrane was immersed in an aqueous solution for 120 seconds, and then removed and the aqueous solution was removed until no residual droplets remained on the surface.

[0041] Step S4 involves pouring n different concentrations of organic phase solutions onto the surface of the porous support membrane in stages to carry out interfacial polymerization reactions until the final interfacial polymerization reaction is completed. The specific process includes the following sub-steps:

[0042] Step S4-1: Pour a 0.02% w / v organic phase solution onto the surface of the polyethersulfone porous support membrane for interfacial polymerization reaction for 2 seconds, and then pour off the organic phase solution.

[0043] In step S4-2, a 0.1% w / v organic phase solution is poured onto the surface of the polyethersulfone porous support membrane to continue the interfacial polymerization reaction for 68 seconds, and then the organic phase solution is poured off and removed.

[0044] Step S5: After thoroughly washing the surface of the porous support membrane with n-hexane solvent, a high-performance composite nanofiltration membrane prepared by continuous interfacial polymerization with different acyl chloride concentrations is obtained.

[0045] <Example 2>

[0046] The method for preparing the high-performance composite nanofiltration membrane in this embodiment includes the following steps:

[0047] Step S1: Dissolve the aqueous monomer in pure water, stir thoroughly until dissolved to obtain an aqueous solution, and store it away from light. The specific process is as follows:

[0048] Dissolve piperazine in pure water and stir thoroughly until dissolved to prepare an aqueous solution with a concentration of 0.5% w / v. Store in the dark.

[0049] Step S2: Add the organic phase monomer to the organic solvent, stir thoroughly until dissolved to obtain an organic phase solution, and store it in the dark. Then, using the same organic phase monomer, prepare n different concentrations of organic phase solutions. The specific process is as follows:

[0050] Trimethylbenzene chloride was dissolved in n-hexane and stirred thoroughly to prepare organic phase solutions with concentrations of 0.02% w / v and 0.1% w / v, respectively, and stored in the dark.

[0051] Step S3 involves immersing the surface of the porous support membrane in an aqueous solution, then removing it and cleaning off the aqueous solution until no residual droplets remain on the surface. The specific process is as follows:

[0052] The surface of the polyethersulfone porous support membrane was immersed in an aqueous solution for 120 seconds, and then removed and the aqueous solution was removed until no residual droplets remained on the surface.

[0053] Step S4 involves pouring n different concentrations of organic phase solutions onto the surface of the porous support membrane in stages to carry out interfacial polymerization reactions until the final interfacial polymerization reaction is completed. The specific process includes the following sub-steps:

[0054] Step S4-1: Pour a 0.02% w / v organic phase solution onto the surface of the polyethersulfone porous support membrane for interfacial polymerization reaction for 40s, and then pour off the organic phase solution.

[0055] In step S4-2, a 0.1% w / v organic phase solution is poured onto the surface of the polyethersulfone porous support membrane to continue the interfacial polymerization reaction for 30 seconds, and then the organic phase solution is poured off and removed.

[0056] Step S5: After thoroughly washing the surface of the porous support membrane with n-hexane solvent, a high-performance composite nanofiltration membrane prepared by continuous interfacial polymerization with different acyl chloride concentrations is obtained.

[0057] <Example 3>

[0058] The method for preparing the high-performance composite nanofiltration membrane in this embodiment includes the following steps:

[0059] Step S1: Dissolve the aqueous monomer in pure water, stir thoroughly until dissolved to obtain an aqueous solution, and store it away from light. The specific process is as follows:

[0060] Dissolve piperazine in pure water and stir thoroughly until dissolved to prepare an aqueous solution with a concentration of 2% w / v. Store in the dark.

[0061] Step S2: Add the organic phase monomer to the organic solvent, stir thoroughly until dissolved to obtain an organic phase solution, and store it in the dark. Then, using the same organic phase monomer, prepare n different concentrations of organic phase solutions. The specific process is as follows:

[0062] Trimethylbenzene chloride was dissolved in n-hexane and stirred thoroughly to prepare organic phase solutions with concentrations of 0.03% w / v, 0.05% w / v, and 0.1% w / v, respectively, and stored in the dark.

[0063] Step S3 involves immersing the surface of the porous support membrane in an aqueous solution, then removing it and cleaning off the aqueous solution until no residual droplets remain on the surface. The specific process is as follows:

[0064] The surface of the polyethersulfone porous support membrane was immersed in an aqueous solution for 300 seconds, and then removed and the aqueous solution was removed until no residual droplets remained on the surface.

[0065] Step S4 involves pouring n different concentrations of organic phase solutions onto the surface of the porous support membrane in stages to carry out interfacial polymerization reactions until the final interfacial polymerization reaction is completed. The specific process includes the following sub-steps:

[0066] Step S4-1: Pour a 0.03% w / v organic phase solution onto the surface of the polyethersulfone porous support membrane for interfacial polymerization reaction for 40s, and then pour off the organic phase solution.

[0067] Step S4-2: Pour a 0.05% w / v organic phase solution onto the surface of the polyethersulfone porous support membrane for interfacial polymerization reaction for 30s, and then pour off the organic phase solution.

[0068] In step S4-3, a 0.1% w / v organic phase solution is poured onto the surface of the polyethersulfone porous support membrane to continue the interfacial polymerization reaction for 30 seconds, and then the organic phase solution is poured off and removed.

[0069] Step S5: Thoroughly rinse the surface of the porous support membrane with n-hexane solvent, and then perform thermal stabilization treatment on the porous support membrane at a predetermined temperature, as follows: Place the reacted membrane in a 30°C forced-air drying oven for 10 min to stabilize it, and then thoroughly rinse the porous support membrane with pure aqueous solution to obtain a high-performance composite nanofiltration membrane prepared based on continuous interfacial polymerization with different acyl chloride concentrations.

[0070] <Example 4>

[0071] The method for preparing the high-performance composite nanofiltration membrane in this embodiment includes the following steps:

[0072] Step S1 involves dissolving the aqueous monomer in pure water, stirring thoroughly until dissolved to obtain an aqueous solution, and storing it in the dark. Simultaneously, a pre-wetting solution for the base membrane is prepared by dissolving an amino alcohol-containing substance in pure water and stirring thoroughly until dissolved. The specific process is as follows:

[0073] Piperazine was dissolved in pure water and stirred thoroughly until dissolved to prepare an aqueous solution with a concentration of 0.01% w / v. This solution was then stored away from light.

[0074] Tannic acid was dissolved in pure water and stirred thoroughly until dissolved to prepare a 2% w / v base film pre-wetting solution.

[0075] Step S2: Add the organic phase monomer to the organic solvent, stir thoroughly until dissolved to obtain an organic phase solution, and store it in the dark. Then, using the same organic phase monomer, prepare n different concentrations of organic phase solutions. The specific process is as follows:

[0076] Pyrimethanil chloride was dissolved in n-heptane and stirred thoroughly to prepare organic phase solutions with concentrations of 0.005% w / v, 0.1% w / v, 0.5% w / v and 1.0% w / v, respectively, and stored in the dark.

[0077] Step S3: Immerse the surface of the porous support membrane in the base membrane pre-wetting solution, then remove and remove the base membrane pre-wetting solution until there are no residual droplets on the surface. Then immerse the surface of the porous support membrane in the aqueous solution, then remove and remove the aqueous solution until there are no residual droplets on the surface. The specific process is as follows:

[0078] The surface of the polysulfone porous support membrane was immersed in the base membrane pre-wetting solution for 2 minutes, then removed and the base membrane pre-wetting solution was removed until no residual droplets remained on the surface.

[0079] The surface of the polysulfone porous support membrane was then immersed in the aqueous solution for 180 seconds, and then removed and the aqueous solution was removed until there were no residual droplets on the surface.

[0080] Step S4 involves pouring n different concentrations of organic phase solutions onto the surface of the porous support membrane in stages to carry out interfacial polymerization reactions until the final interfacial polymerization reaction is completed. The specific process includes the following sub-steps:

[0081] Step S4-1: Pour a 0.005% w / v organic phase solution onto the surface of the polysulfone porous support membrane for interfacial polymerization reaction for 40s, and then pour off the organic phase solution.

[0082] Step S4-2: Pour a 0.1% w / v organic phase solution onto the surface of the polysulfone porous support membrane for interfacial polymerization reaction for 30s, and then pour off the organic phase solution.

[0083] Step S4-3: Pour a 0.5% w / v organic phase solution onto the surface of the polysulfone porous support membrane for interfacial polymerization reaction for 40s, and then pour off the organic phase solution.

[0084] In step S4-4, a 1.0% w / v organic phase solution is poured onto the surface of the polysulfone porous support membrane to continue the interfacial polymerization reaction for 30 seconds, and then the organic phase solution is poured off and removed.

[0085] Step S5: Thoroughly rinse the surface of the porous support membrane with n-heptane solvent, and then perform thermal stabilization treatment on the porous support membrane at a predetermined temperature, as follows: Place the reacted membrane in a 25°C forced-air drying oven for 30 min to stabilize it, and then thoroughly rinse the porous support membrane with pure aqueous solution to obtain a high-performance composite nanofiltration membrane prepared based on continuous interfacial polymerization with different acyl chloride concentrations.

[0086] <Example 5>

[0087] The method for preparing the high-performance composite nanofiltration membrane in this embodiment includes the following steps:

[0088] Step S1 involves dissolving the aqueous monomer in pure water, stirring thoroughly until dissolved to obtain an aqueous solution, and storing it in the dark. Simultaneously, a pre-wetting solution for the base membrane is prepared by dissolving an amino alcohol-containing substance in pure water and stirring thoroughly until dissolved. The specific process is as follows:

[0089] Polyethyleneimine was dissolved in pure water and stirred thoroughly until dissolved to prepare a 2% w / v aqueous solution, which was then stored away from light.

[0090] Dissolve Tris-HCl in pure water and stir thoroughly until dissolved to prepare a 10% w / v base film pre-wetting solution.

[0091] Step S2: Add the organic phase monomer to the organic solvent, stir thoroughly until dissolved to obtain an organic phase solution, and store it in the dark. Then, using the same organic phase monomer, prepare n different concentrations of organic phase solutions. The specific process is as follows:

[0092] Trimethylbenzene chloride was dissolved in n-octane and stirred thoroughly to prepare organic phase solutions with concentrations of 0.02% w / v, 0.1% w / v, and 0.2% w / v, respectively, and stored in the dark.

[0093] Step S3: Immerse the surface of the porous support membrane in the base membrane pre-wetting solution, then remove and remove the base membrane pre-wetting solution until there are no residual droplets on the surface. Then immerse the surface of the porous support membrane in the aqueous solution, then remove and remove the aqueous solution until there are no residual droplets on the surface. The specific process is as follows:

[0094] The surface of the polyacrylonitrile porous support membrane was immersed in the base membrane pre-wetting solution for 1 minute, then removed and the base membrane pre-wetting solution was removed until no residual droplets remained on the surface.

[0095] The surface of the polyacrylonitrile porous support membrane was immersed in an aqueous solution for 120 seconds, and then removed and the aqueous solution was removed until no residual droplets remained on the surface.

[0096] Step S4 involves pouring n different concentrations of organic phase solutions onto the surface of the porous support membrane in stages to carry out interfacial polymerization reactions until the final interfacial polymerization reaction is completed. The specific process includes the following sub-steps:

[0097] Step S4-1: Pour a 0.02% w / v organic phase solution onto the surface of the polyacrylonitrile porous support membrane for interfacial polymerization reaction for 40s, and then pour off the organic phase solution.

[0098] Step S4-2: Pour a 0.1% w / v organic phase solution onto the surface of the polyacrylonitrile porous support membrane for interfacial polymerization reaction for 30s, and then pour off the organic phase solution.

[0099] Step S4-3: Pour a 0.2% w / v organic phase solution onto the surface of the polyacrylonitrile porous support membrane for interfacial polymerization reaction for 20s, and then pour off the organic phase solution.

[0100] Step S4-4: Pour a 0.1% w / v organic phase solution onto the surface of the polyacrylonitrile porous support membrane for interfacial polymerization reaction for 20s, and then pour off the organic phase solution.

[0101] In steps S4-5, a 0.02% w / v organic phase solution is poured onto the surface of the polyacrylonitrile porous support membrane to continue the interfacial polymerization reaction for 10 seconds, and then the organic phase solution is poured off and removed.

[0102] Step S5: Thoroughly rinse the surface of the porous support membrane with n-octane solvent, and then perform thermal stabilization treatment on the porous support membrane at a predetermined temperature, as follows: Place the reacted membrane in a 30°C forced-air drying oven for 10 min to stabilize it, and then thoroughly rinse the porous support membrane with pure aqueous solution to obtain a high-performance composite nanofiltration membrane prepared based on continuous interfacial polymerization with different acyl chloride concentrations.

[0103] <Example 6>

[0104] The method for preparing the high-performance composite nanofiltration membrane in this embodiment includes the following steps:

[0105] Step S1 involves dissolving the aqueous monomer in pure water, stirring thoroughly until dissolved to obtain an aqueous solution, and storing it in the dark. Simultaneously, a pre-wetting solution for the base membrane is prepared by dissolving an amino alcohol-containing substance in pure water and stirring thoroughly until dissolved. The specific process is as follows:

[0106] Piperazine was dissolved in pure water and stirred thoroughly until dissolved to prepare an aqueous solution with a concentration of 0.1% w / v. This solution was then stored away from light.

[0107] Dissolve serine in pure water and stir thoroughly until dissolved to prepare a 10% w / v base film pre-wetting solution.

[0108] Step S2: Add the organic phase monomer to the organic solvent, stir thoroughly until dissolved to obtain an organic phase solution, and store it in the dark. Then, using the same organic phase monomer, prepare n different concentrations of organic phase solutions. The specific process is as follows:

[0109] Trimethylbenzene chloride was dissolved in n-hexane and stirred thoroughly to prepare organic phase solutions with concentrations of 0.02% w / v and 0.1% w / v, respectively, and stored in the dark.

[0110] Step S3: Immerse the surface of the porous support membrane in the base membrane pre-wetting solution, then remove and remove the base membrane pre-wetting solution until there are no residual droplets on the surface. Then immerse the surface of the porous support membrane in the aqueous solution, then remove and remove the aqueous solution until there are no residual droplets on the surface. The specific process is as follows:

[0111] The surface of the polyethersulfone porous support membrane was immersed in the base membrane pre-wetting solution for 30 minutes. After that, it was removed and the base membrane pre-wetting solution was removed until there were no residual droplets on the surface.

[0112] The surface of the polyethersulfone porous support membrane is then immersed in the aqueous solution for 240 seconds, and then removed and the aqueous solution is removed until there are no residual droplets on the surface.

[0113] Step S4 involves pouring n different concentrations of organic phase solutions onto the surface of the porous support membrane in stages to carry out interfacial polymerization reactions until the final interfacial polymerization reaction is completed. The specific process includes the following sub-steps:

[0114] Step S4-1: Pour a 0.1% w / v organic phase solution onto the surface of the polyethersulfone porous support membrane for interfacial polymerization reaction for 20s, and then pour off the organic phase solution.

[0115] In step S4-2, a 0.02% w / v organic phase solution is poured onto the surface of the polyethersulfone porous support membrane to continue the interfacial polymerization reaction for 20 seconds, and then the organic phase solution is poured off and removed.

[0116] Step S5: Thoroughly rinse the surface of the porous support membrane with n-hexane solvent, and then perform thermal stabilization treatment on the porous support membrane at a predetermined temperature, as follows: Place the reacted membrane in a 30°C forced-air drying oven for 10 min to stabilize it, and then thoroughly rinse the porous support membrane with pure aqueous solution to obtain a high-performance composite nanofiltration membrane prepared based on continuous interfacial polymerization with different acyl chloride concentrations.

[0117] <Example 7>

[0118] The method for preparing the high-performance composite nanofiltration membrane in this embodiment includes the following steps:

[0119] Step S1: Dissolve the aqueous monomer in pure water, stir thoroughly until dissolved to obtain an aqueous solution, and store it away from light. The specific process is as follows:

[0120] Lysine was dissolved in pure water and stirred thoroughly until dissolved to prepare an aqueous solution with a concentration of 5.0% w / v, which was then stored away from light.

[0121] Step S2: Add the organic phase monomer to the organic solvent, stir thoroughly until dissolved to obtain an organic phase solution, and store it in the dark. Then, using the same organic phase monomer, prepare n different concentrations of organic phase solutions. The specific process is as follows:

[0122] Trimethylbenzene chloride was dissolved in n-hexane and stirred thoroughly to prepare organic phase solutions with concentrations of 0.1% w / v, 0.5% w / v, 2.0% w / v and 5.0% w / v, respectively, and stored in the dark.

[0123] Step S3 involves immersing the surface of the porous support membrane in an aqueous solution, then removing it and cleaning off the aqueous solution until no residual droplets remain on the surface. The specific process is as follows:

[0124] The surface of the polyethersulfone porous support membrane was immersed in an aqueous solution for 20 seconds, and then removed and the aqueous solution was removed until no residual droplets remained on the surface.

[0125] Step S4 involves pouring n different concentrations of organic phase solutions onto the surface of the porous support membrane in stages to carry out interfacial polymerization reactions until the final interfacial polymerization reaction is completed. The specific process includes the following sub-steps:

[0126] Step S4-1: Pour a 5.0% w / v organic phase solution onto the surface of the polyethersulfone porous support membrane for interfacial polymerization reaction for 60s, and then pour off the organic phase solution.

[0127] Step S4-2: Pour a 2.0% w / v organic phase solution onto the surface of the polyethersulfone porous support membrane for interfacial polymerization reaction for 30s, and then pour off the organic phase solution.

[0128] Step S4-3: Pour a 0.5% w / v organic phase solution onto the surface of the polyethersulfone porous support membrane for interfacial polymerization reaction for 30s, and then pour off the organic phase solution.

[0129] In step S4-4, a 0.1% w / v organic phase solution is poured onto the surface of the polyethersulfone porous support membrane to continue the interfacial polymerization reaction for 60 seconds, and then the organic phase solution is poured off and removed.

[0130] Step S5: Thoroughly rinse the surface of the porous support membrane with n-hexane solvent, and then perform thermal stabilization treatment on the porous support membrane at a predetermined temperature, as follows: Place the reacted membrane in a 50°C forced-air drying oven for 30 min to stabilize, and then thoroughly rinse the porous support membrane with pure aqueous solution to obtain a high-performance composite nanofiltration membrane prepared based on continuous interfacial polymerization with different acyl chloride concentrations.

[0131] <Example 8>

[0132] The method for preparing the high-performance composite nanofiltration membrane in this embodiment includes the following steps:

[0133] Step S1: Dissolve the aqueous monomer in pure water, stir thoroughly until dissolved to obtain an aqueous solution, and store it away from light. The specific process is as follows:

[0134] Dissolve piperazine in pure water and stir thoroughly until dissolved to prepare an aqueous solution with a concentration of 1.0% w / v. Store in the dark.

[0135] Step S2: Add the organic phase monomer to the organic solvent, stir thoroughly until dissolved to obtain an organic phase solution, and store it in the dark. Then, using the same organic phase monomer, prepare n different concentrations of organic phase solutions. The specific process is as follows:

[0136] Trimethylbenzene chloride was dissolved in n-octane and stirred thoroughly to prepare organic phase solutions with concentrations of 0.05% w / v, 0.1% w / v, and 0.2% w / v, respectively, and stored in the dark.

[0137] Step S3 involves immersing the surface of the porous support membrane in an aqueous solution, then removing it and cleaning off the aqueous solution until no residual droplets remain on the surface. The specific process is as follows:

[0138] The surface of the polyvinylidene fluoride porous support membrane was immersed in an aqueous solution for 10 seconds, and then removed and the aqueous solution was removed until there were no residual droplets on the surface.

[0139] Step S4 involves pouring n different concentrations of organic phase solutions onto the surface of the porous support membrane in stages to carry out interfacial polymerization reactions until the final interfacial polymerization reaction is completed. The specific process includes the following sub-steps:

[0140] Step S4-1: Pour a 0.2% w / v organic phase solution onto the surface of the polyvinylidene fluoride porous support membrane for interfacial polymerization reaction for 40s, and then pour off the organic phase solution.

[0141] Step S4-2: Pour a 0.1% w / v organic phase solution onto the surface of the polyvinylidene fluoride porous support membrane for interfacial polymerization reaction for 30s, and then pour off the organic phase solution.

[0142] Step S4-3: Pour a 0.05% w / v organic phase solution onto the surface of the polyvinylidene fluoride porous support membrane for interfacial polymerization reaction for 20s, and then pour off the organic phase solution.

[0143] Step S4-4: Pour a 0.1% w / v organic phase solution onto the surface of the polyvinylidene fluoride porous support membrane for interfacial polymerization reaction for 20s, and then pour off the organic phase solution.

[0144] In steps S4-5, a 0.2% w / v organic phase solution is poured onto the surface of the polyvinylidene fluoride porous support membrane to continue the interfacial polymerization reaction for 10 seconds, and then the organic phase solution is poured off and removed.

[0145] Step S5: Thoroughly rinse the surface of the porous support membrane with n-octane solvent, and then perform thermal stabilization treatment on the porous support membrane at a predetermined temperature, as follows: Place the reacted membrane in a 40°C forced-air drying oven for 60 min to stabilize, and then thoroughly rinse the porous support membrane with pure aqueous solution to obtain a high-performance composite nanofiltration membrane prepared based on continuous interfacial polymerization with different acyl chloride concentrations.

[0146] <Example 9>

[0147] The method for preparing the high-performance composite nanofiltration membrane in this embodiment includes the following steps:

[0148] Step S1: Dissolve the aqueous monomer in pure water, stir thoroughly until dissolved to obtain an aqueous solution, and store it away from light. The specific process is as follows:

[0149] Dissolve piperazine in pure water and stir thoroughly until dissolved to prepare an aqueous solution with a concentration of 10% w / v. Store in the dark.

[0150] Step S2: Add the organic phase monomer to the organic solvent, stir thoroughly until dissolved to obtain an organic phase solution, and store it in the dark. Then, using the same organic phase monomer, prepare n different concentrations of organic phase solutions. The specific process is as follows:

[0151] Tristyroyl chloride was dissolved in n-octane and stirred thoroughly to prepare organic phase solutions with concentrations of 5.0% w / v, 1.0% w / v, and 0.5% w / v, respectively, and stored in the dark.

[0152] Step S3 involves immersing the surface of the porous support membrane in an aqueous solution, then removing it and cleaning off the aqueous solution until no residual droplets remain on the surface. The specific process is as follows:

[0153] The surface of the polyvinylidene fluoride porous support membrane was immersed in an aqueous solution for 120 seconds, and then removed and the aqueous solution was removed until there were no residual droplets on the surface.

[0154] Step S4 involves pouring n different concentrations of organic phase solutions onto the surface of the porous support membrane in stages to carry out interfacial polymerization reactions until the final interfacial polymerization reaction is completed. The specific process includes the following sub-steps:

[0155] Step S4-1: Pour a 5.0% w / v organic phase solution onto the surface of the polyvinylidene fluoride porous support membrane for interfacial polymerization reaction for 40s, and then pour off the organic phase solution.

[0156] Step S4-2: Pour a 1.0% w / v organic phase solution onto the surface of the polyvinylidene fluoride porous support membrane for interfacial polymerization reaction for 30s, and then pour off the organic phase solution.

[0157] In step S4-3, a 0.5% w / v organic phase solution is poured onto the surface of the polyvinylidene fluoride porous support membrane for interfacial polymerization for 20 seconds, and then the organic phase solution is poured off.

[0158] Step S5: Thoroughly rinse the surface of the porous support membrane with n-octane solvent, and then perform thermal stabilization treatment on the porous support membrane at a predetermined temperature, as follows: Place the reacted membrane in a 30°C forced-air drying oven for 60 min to stabilize, and then thoroughly rinse the porous support membrane with pure aqueous solution to obtain a high-performance composite nanofiltration membrane prepared based on continuous interfacial polymerization with different acyl chloride concentrations.

[0159] <Example 10>

[0160] The method for preparing the high-performance composite nanofiltration membrane in this embodiment includes the following steps:

[0161] Step S1 involves dissolving the aqueous monomer in pure water, stirring thoroughly until dissolved to obtain an aqueous solution, and storing it in the dark. Simultaneously, a pre-wetting solution for the base membrane is prepared by dissolving an amino alcohol-containing substance in pure water and stirring thoroughly until dissolved. The specific process is as follows:

[0162] Piperazine was dissolved in pure water and stirred thoroughly until dissolved to prepare an aqueous solution with a concentration of 0.01% w / v. This solution was then stored away from light.

[0163] Ethanolamine was dissolved in pure water and stirred thoroughly until dissolved to prepare a base film pre-wetting solution with a concentration of 0.5% w / v.

[0164] Step S2: Add the organic phase monomer to the organic solvent, stir thoroughly until dissolved to obtain an organic phase solution, and store it in the dark. Then, using the same organic phase monomer, prepare n different concentrations of organic phase solutions. The specific process is as follows:

[0165] Trimethylbenzene chloride was dissolved in a mixed solvent of n-heptane and n-hexane, and stirred thoroughly to prepare organic phase solutions with concentrations of 0.001% w / v, 0.01% w / v, and 0.05% w / v, respectively, and stored in the dark.

[0166] Step S3: Immerse the surface of the porous support membrane in the base membrane pre-wetting solution, then remove and remove the base membrane pre-wetting solution until there are no residual droplets on the surface. Then immerse the surface of the porous support membrane in the aqueous solution, then remove and remove the aqueous solution until there are no residual droplets on the surface. The specific process is as follows:

[0167] The surface of the polyethersulfone porous support membrane was immersed in the base membrane pre-wetting solution for 2 minutes, then removed and the base membrane pre-wetting solution was removed until no residual droplets remained on the surface.

[0168] The surface of the polyethersulfone porous support membrane is then immersed in the aqueous solution for 120 seconds, and then removed and the aqueous solution is removed until there are no residual droplets on the surface.

[0169] Step S4 involves pouring n different concentrations of organic phase solutions onto the surface of the porous support membrane in stages to carry out interfacial polymerization reactions until the final interfacial polymerization reaction is completed. The specific process includes the following sub-steps:

[0170] Step S4-1: Pour a 0.001% w / v organic phase solution onto the surface of the polyethersulfone porous support membrane for interfacial polymerization reaction for 120 s, and then pour off the organic phase solution.

[0171] Step S4-2: Pour a 0.01% w / v organic phase solution onto the surface of the polyethersulfone porous support membrane for interfacial polymerization reaction for 120 s, and then pour off the organic phase solution.

[0172] In step S4-3, a 0.05% w / v organic phase solution is poured onto the surface of the polyethersulfone porous support membrane for interfacial polymerization for 120 s, and then the organic phase solution is poured off and removed.

[0173] Step S5: Thoroughly rinse the surface of the porous support membrane with a mixed solvent of n-heptane and n-hexane, and then perform a thermal stabilization treatment on the porous support membrane at a predetermined temperature, as follows: Place the reacted membrane in a 30°C forced-air drying oven for 60 min to stabilize it, and then thoroughly rinse the porous support membrane with pure aqueous solution to obtain a high-performance composite nanofiltration membrane prepared by continuous interfacial polymerization based on different acyl chloride concentrations.

[0174] <Example 11>

[0175] The method for preparing the high-performance composite nanofiltration membrane in this embodiment includes the following steps:

[0176] Step S1 involves dissolving the aqueous monomer in pure water, stirring thoroughly until dissolved to obtain an aqueous solution, and storing it in the dark. Simultaneously, a pre-wetting solution for the base membrane is prepared by dissolving an amino alcohol-containing substance in pure water and stirring thoroughly until dissolved. The specific process is as follows:

[0177] Lysine was dissolved in pure water and stirred thoroughly until dissolved to prepare an aqueous solution with a concentration of 0.01% w / v. The solution was then stored away from light.

[0178] Dissolve Tris-HCl in pure water and stir thoroughly until dissolved to prepare a base film pre-wetting solution with a concentration of 0.5% w / v.

[0179] Step S2: Add the organic phase monomer to the organic solvent, stir thoroughly until dissolved to obtain an organic phase solution, and store it in the dark. Then, using the same organic phase monomer, prepare n different concentrations of organic phase solutions. The specific process is as follows:

[0180] Trimethylbenzene chloride was dissolved in n-heptane solvent and stirred thoroughly to prepare organic phase solutions with concentrations of 0.001% w / v and 0.05% w / v, respectively, and stored in the dark.

[0181] Step S3: Immerse the surface of the porous support membrane in the base membrane pre-wetting solution, then remove and remove the base membrane pre-wetting solution until there are no residual droplets on the surface. Then immerse the surface of the porous support membrane in the aqueous solution, then remove and remove the aqueous solution until there are no residual droplets on the surface. The specific process is as follows:

[0182] The surface of the polyethersulfone porous support membrane was immersed in the base membrane pre-wetting solution for 5 minutes, then removed and the base membrane pre-wetting solution was removed until no residual droplets remained on the surface.

[0183] The surface of the polyethersulfone porous support membrane is then immersed in the aqueous solution for 120 seconds, and then removed and the aqueous solution is removed until there are no residual droplets on the surface.

[0184] Step S4 involves pouring n different concentrations of organic phase solutions onto the surface of the porous support membrane in stages to carry out interfacial polymerization reactions until the final interfacial polymerization reaction is completed. The specific process includes the following sub-steps:

[0185] Step S4-1: Pour a 0.001% w / v organic phase solution onto the surface of the polyethersulfone porous support membrane for interfacial polymerization reaction for 30 min, and then pour off the organic phase solution.

[0186] Step S4-2: Pour a 0.05% w / v organic phase solution onto the surface of the polyethersulfone porous support membrane for interfacial polymerization reaction for 120 s, and then pour off the organic phase solution.

[0187] In step S4-3, an organic phase solution with a concentration of 0.001% w / v is poured onto the surface of the polyethersulfone porous support membrane for interfacial polymerization for 120 s, and then the organic phase solution is poured off and removed.

[0188] Step S5: Thoroughly rinse the surface of the porous support membrane with n-heptane solvent, and then perform thermal stabilization treatment on the porous support membrane at a predetermined temperature, as follows: Place the reacted membrane in a 50°C forced-air drying oven for 60 min to stabilize, and then thoroughly rinse the porous support membrane with pure aqueous solution to obtain a high-performance composite nanofiltration membrane prepared based on continuous interfacial polymerization with different acyl chloride concentrations.

[0189] <Comparative Example 1>

[0190] In this comparative example, the surface of the porous support membrane was immersed in a 0.5% w / v piperazine aqueous solution, and then the aqueous solution was removed until no residual droplets remained on the surface. Then, a 0.1% w / v trimesoyl chloride / n-hexane solution was poured onto the surface of the porous support membrane. After reacting for 70 seconds, the remaining solution was poured off, and the surface was slowly rinsed with n-hexane solvent to prepare a polyamide composite nanofiltration membrane.

[0191] <Comparative Example 2>

[0192] In this comparative example, the surface of the porous support membrane was immersed in a 0.5% w / v piperazine aqueous solution, and then the aqueous solution was removed until no residual droplets remained on the surface. Then, a 0.02% w / v trimesoyl chloride / n-hexane solution was poured onto the surface of the porous support membrane. After reacting for 70 seconds, the remaining solution was poured off, and the surface was slowly rinsed with n-hexane solvent. Finally, the membrane was thoroughly rinsed with pure aqueous solution to prepare a polyamide composite nanofiltration membrane.

[0193] <Test Example>

[0194] In this test example, the high-performance composite nanofiltration membranes prepared in Examples 1 and 2, and the polyamide composite nanofiltration membranes prepared in Comparative Examples 1 and 2 were selected to test the water treatment efficiency. The operating conditions used are as follows:

[0195] When testing for inorganic salt rejection, the feed solution concentration was 10 mmol / L Na₂SO₄ solution and MgCl₂ solution; the operating pressure was 0.3 MPa, the operating temperature was 25℃, and the solution pH was 7.0. The membrane's water permeability and rejection rate were calculated using the formulas for water flux and rejection rate. Water permeability (P) refers to the volume (V) of pure water permeating through a unit membrane area (A) per unit time (t) under a unit operating pressure (S), expressed in L / (m²). 2 ·h·bar) is a parameter that measures the water permeability of a nanofiltration membrane, and its calculation formula is:

[0196] F = V / (A·t·S)

[0197] Retention rate (R) refers to the ratio of the difference between the solute concentration in the feed solution (Cf) and the solute concentration in the filtrate (Cp) of a nanofiltration membrane under a certain operating pressure to the solute concentration in the feed solution. It is a parameter for evaluating the ability of a nanofiltration membrane to remove solutes such as inorganic salt ions or organic molecules. Its calculation formula is as follows:

[0198] R(%) = (Cf - Cp) / Cf × 100%

[0199] The experimental results obtained after testing are as follows:

[0200] Comparative Example 1: Good permeability, flux of 13.65 L·m -2 ·h -1 ·bar -1 (like Figure 1 (As shown), but with poor selectivity, the rejection rate for MgCl2 is only 33.71%, while the rejection rate for Na2SO4 is 98.79% (as shown). Figure 1 (as shown);

[0201] Comparative Example 2 showed good selectivity, with rejection rates of 95.96% for Na₂SO₄ and 94.91% for MgCl₂. However, it had poor permeability, with a pure water flux of only 7.08 L·m⁻². -2 ·h -1 ·bar -1 ;

[0202] The high-performance composite nanofiltration membrane prepared in Example 1 has a permeation flux of up to 13.00 L·m⁻¹. -2 ·h -1 ·bar -1 Meanwhile, the retention rates for Na2SO4 and MgCl2 were 98.44% and 92.12%, respectively.

[0203] In addition, such as Figure 4 As shown, the molecular weight cutoff of Example 1 is 235, which is close to that of Comparative Example 2 with a molecular weight cutoff of 224, and much smaller than that of Comparative Example 1 with a molecular weight cutoff of 300.

[0204] Furthermore, in Example 2, the average pore size is smaller than that of Comparative Example 2 (e.g., ...). Figure 3 As shown, when the molecular weight cutoff is less than that of Comparative Example 2 and the salt rejection rate is higher than that of Comparative Example 2, the pure water flux of Example 2 is 40.82% higher than that of Comparative Example 2.

[0205] Figure 5 The PA layer thicknesses of Embodiment 1 and Comparative Examples 1 and 2 of the present invention are as follows. Figure 5 The thicknesses of the PA layer in the figures, from top to bottom, correspond to those of Comparative Example 1, Example 1, and Comparative Example 2.

[0206] according to Figure 5 and combined Figure 4 It can be seen that the high selectivity and high permeability of Example 1 are related to its small molecular weight cutoff and thin PA layer.

[0207] The role and effect of the embodiments

[0208] As can be seen from Examples 1-11, the high-performance composite nanofiltration membrane preparation method of the present invention can successfully obtain high-performance composite nanofiltration membranes prepared by continuous interfacial polymerization with different acyl chloride concentrations under different preparation conditions.

[0209] Furthermore, based on the test results of the preparation products of Examples 1 and 2 and Comparative Examples 1 and 2 in the test examples, it can be seen that the preparation method of the present invention can perform staged interfacial polymerization by adjusting the concentration of the organic phase solution participating in the film formation, thereby flexibly adjusting the pore size and thickness of the nanofiltration membrane, and directionally controlling the permeability and selectivity of the nanofiltration membrane. Moreover, the high-performance composite nanofiltration membrane prepared has high selectivity and high permeability.

[0210] Furthermore, a comparison of Examples 1 and 2 with Examples 3, 7, 8, and 9 shows that the preparation method of the present invention also performs heat treatment after the reaction is completed and the membrane is rinsed, which can enhance the continuation of the interfacial polymerization reaction and make the membrane performance more stable.

[0211] Meanwhile, according to the comparison between Examples 3, 7, 8, and 9 and Examples 4, 5, 6, 10, and 11, in the preparation method of the present invention, before immersing the surface of the porous support membrane in the aqueous phase solution, the porous support membrane is also wetted with a prepared base membrane pre-wetting solution. Pre-wetting can improve the water-tightness of the base membrane, increase the storage of aqueous phase monomers, and promote the interfacial polymerization reaction.

[0212] Therefore, according to the preparation method of a high-performance composite nanofiltration membrane of the present invention, after immersing the surface of a porous support membrane in a base membrane pre-wetting solution and an aqueous solution in sequence, n organic phase solutions of different concentrations are poured onto the surface of the porous support membrane in stages to carry out interfacial polymerization reaction. After washing with organic solution and heat stabilization treatment, a high-performance composite nanofiltration membrane is obtained. This high-performance composite nanofiltration membrane has excellent performance of high selectivity and high permeability, and the pore size and thickness of the nanofiltration membrane are flexibly adjustable, which can be used to directionally control the permeability and selectivity of the nanofiltration membrane based on different application scenarios.

[0213] The above embodiments are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention.

Claims

1. A method for preparing a high performance composite nanofiltration membrane, characterized by, The method comprises the following steps: Step S1, dissolving water phase monomers in pure water, fully stirring until dissolved to obtain a water phase solution and storing in the dark; Step S2, adding organic phase monomers to an organic solvent, fully stirring until dissolved to obtain an organic phase solution and storing in the dark, and using the same organic phase monomers to prepare n kinds of organic phase solutions with different concentrations; Step S3, immersing the surface of a porous support membrane in the water phase solution, then taking it out and removing the water phase solution until no liquid droplets are left on the surface; Step S4, pouring the n kinds of organic phase solutions with different concentrations on the surface of the porous support membrane in batches to perform interface polymerization in batches until the last interface polymerization is completed; Step S5, fully rinsing the surface of the porous support membrane with pure organic solvent to obtain a high-performance composite nanofiltration membrane prepared by continuous interface polymerization based on different acyl chloride concentrations, In step S1, a base membrane pre-wetting solution is also prepared by dissolving an amine-containing alcohol substance in pure water, fully stirring until dissolved to obtain the base membrane pre-wetting solution, In step S3, before immersing the surface of the porous support membrane in the water phase solution, the surface of the porous support membrane is also immersed in the base membrane pre-wetting solution, then the base membrane pre-wetting solution is taken out and removed until no liquid droplets are left on the surface, In step S2, the concentrations of the n kinds of organic phase solutions with different concentrations are 0.001% w / v-5% w / v, n>2, and the n kinds of organic phase solutions with different concentrations include an organic phase solution with A concentration, an organic phase solution with B concentration, and an organic phase solution with N concentration, In step S4, after each interface polymerization, the organic phase solution with the corresponding concentration is poured out, and the next concentration of the organic phase solution is poured in, including the following sub-steps: Step S4-1, pouring the organic phase solution with A concentration on the surface of the porous support membrane to perform interface polymerization, then removing the organic phase solution with A concentration; Step S4-2, pouring the organic phase solution with B concentration on the surface of the porous support membrane to perform interface polymerization, then removing the organic phase solution with B concentration; Step S4-3, continuing to pour the organic phase solutions with different concentrations on the surface of the porous support membrane to perform interface polymerization, and removing the organic phase solution with the corresponding concentration after each interface polymerization until the last interface polymerization is performed using the organic phase solution with the corresponding concentration, and then removing the organic phase solution with the corresponding concentration, In step S4, the time for interface polymerization is ≤30 min.

2. The method for preparing a high-performance composite nanofiltration membrane according to claim 1, characterized in that: wherein In step S1, the water phase monomers are molecules with the sum of the number of amino groups and hydroxyl groups in the molecules being greater than or equal to 2, including polyamines, polyols, and polyphenols, The water phase solution is a solution of one kind of water phase monomer or a mixed solution of multiple water phase monomers, The concentration of the water phase solution is 0.01% wt-10.0% wt.

3. The method for preparing a high-performance composite nanofiltration membrane according to claim 1, characterized in that: wherein In step S2, the organic phase monomer is an aromatic polyacyl chloride, and the organic solvent is one or more of n-hexane, cyclohexane, toluene, n-heptane, or n-octane.

4. The method of claim 1, wherein the concentration of the base membrane pre- infiltration solution is 0.01 wt% to 10.0 wt%. wherein, The amine-containing alcohol is a substance containing both an amino group and a hydroxyl group in its molecular formula. The concentration of the base membrane pre-infiltration solution is 0.01 wt% to 10.0 wt%.

5. The method of claim 1, wherein the porous support membrane is an ultrafiltration membrane, and the immersion time of the porous support membrane in the base membrane pre-infiltration solution is less than or equal to 30 minutes. wherein 6. The method of claim 1, wherein the immersion time of the porous support membrane in the aqueous solution in step S3 is 10 seconds to 300 seconds.

7. The method of claim 1, wherein, after the surface of the porous support membrane is sufficiently rinsed with a pure organic solvent in step S5, the porous support membrane is further subjected to a heat stabilization treatment at a predetermined temperature and rinsed. wherein, The predetermined temperature for the heat stabilization treatment is 25°C to 50°C, and the treatment time is less than or equal to 60 minutes. After the heat stabilization treatment, the porous support membrane is rinsed with pure water or an ethanol solution with a concentration of 0.1% w / v to 0.5% w / v. wherein ​ ​ ​

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