Nano-filtration membrane with organic pollution resistance and antibacterial property and preparation method of nano-filtration membrane

Abstract

The embodiment of the invention discloses a nanofiltration membrane with both organic pollution resistance and antibacterial property and a preparation method thereof, and the preparation method comprises the following steps: sequentially dipping a porous ultrafiltration membrane support layer in a water phase solution containing polyamine and an organic phase solution containing polyacyl chloride, carrying out interfacial polymerization reaction on the polyamine and the polyacyl chloride to generate a polyamide separation layer of the nanofiltration membrane; the polyamide separation layer is soaked in an anti-organic-pollution antibacterial ultrathin layer preparation solution to form an anti-organic-pollution antibacterial ultrathin layer, and the porous ultrafiltration membrane supporting layer, the polyamide separation layer and the anti-organic-pollution antibacterial ultrathin layer serve as the composite nanofiltration membrane with the anti-organic-pollution and antibacterial properties.

Description

Technical Field

[0001] This invention relates to the field of nanofiltration membrane preparation technology, and in particular to a nanofiltration membrane with both resistance to organic pollution and antibacterial properties, and its preparation method. Background Technology

[0002] Polyamide composite nanofiltration membranes, as a mainstream nanofiltration membrane product, are widely used in water resource development and wastewater recycling due to their excellent separation capabilities. However, in practical applications, due to the hydrophobicity and charged nature of the polyamide material on the nanofiltration membrane surface, organic pollutants and bacteria easily deposit and adhere to the membrane surface, leading to a sharp decline in membrane performance. Physical or chemical cleaning of the membrane surface is a common method to reduce fouling, but frequent cleaning not only increases system operating costs but also damages the membrane's separation performance, resulting in a reduced service life. Therefore, improving the resistance to organic fouling and antibacterial properties of the nanofiltration membrane surface has significant theoretical and practical value for ensuring the long-term stable operation of nanofiltration membrane systems.

[0003] Nanofiltration membrane fouling primarily includes inorganic, organic, and microbial contamination. Organic and microbial contamination are common and impactful types during actual use, posing significant threats to membrane performance and lifespan. Current common methods to address these fouling issues include novel reactive monomers, membrane surface coating, and grafting. For example, adding polyvinyl alcohol (PVA) to an aqueous solution to prepare an antifouling nanofiltration membrane is problematic because PVA, being a high molecular weight, does not easily diffuse to the membrane surface during interfacial polymerization, limiting its distribution and affecting antifouling performance. Another example is loading antibacterial metal ions onto the surface of a polyamide composite nanofiltration membrane, which can achieve antibacterial properties. However, since the antibacterial metal ions are physically loaded onto the membrane surface, they are lost during use due to water erosion. Coating the membrane surface with a PVA functional layer can regulate surface charge and inhibit pollutant adsorption; however, PVA lacks antibacterial properties, and bacteria, with their strong proliferative capacity, can rapidly multiply even with small amounts adhering to the membrane surface, leading to fouling and performance degradation.

[0004] While existing technologies offer methods to improve the antifouling or antimicrobial properties of membranes, these methods still have some weaknesses. Furthermore, most methods only focus on one aspect of resistance to organic fouling or antimicrobial properties. In practical membrane applications, both types of fouling often coexist, and organic pollutants on the membrane surface can even become nutrients for bacteria, providing favorable conditions for bacterial growth and reproduction. Therefore, developing nanofiltration membranes that possess both resistance to organic fouling and antimicrobial properties is essential to synergistically promote the long-term stable and efficient operation of the membrane. Summary of the Invention

[0005] This specification provides a nanofiltration membrane with both anti-organic fouling and antibacterial properties and its preparation method to solve the following technical problems: Although some methods for improving the anti-fouling or antibacterial properties of membranes have been provided in the prior art, these methods still have some weaknesses, and most methods only focus on one aspect of anti-organic fouling or antibacterial properties. In actual membrane applications, these two types of fouling often coexist, and organic pollutants on the membrane surface can also become nutrients for bacteria, providing favorable conditions for bacterial growth and reproduction.

[0006] To solve the above-mentioned technical problems, the embodiments in this specification are implemented as follows: This specification provides a method for preparing a nanofiltration membrane that possesses both resistance to organic pollution and antibacterial properties, comprising: The porous ultrafiltration membrane support layer is sequentially immersed in an aqueous solution containing polyamine and an organic solution containing polyacryl chloride, so that the polyamine and the polyacryl chloride undergo an interfacial polymerization reaction to generate the polyamide separation layer of the nanofiltration membrane. The polyamide separation layer is immersed in an anti-organic fouling and antibacterial ultrathin layer preparation solution to form an anti-organic fouling and antibacterial ultrathin layer. The porous ultrafiltration membrane support layer, the polyamide separation layer and the anti-organic fouling and antibacterial ultrathin layer are used as a composite nanofiltration membrane that combines anti-organic fouling and antibacterial properties.

[0007] This specification provides a nanofiltration membrane that possesses both resistance to organic pollution and antibacterial properties. The composite nanofiltration membrane is prepared by the method described in the claims, and comprises: Porous ultrafiltration membrane support layer, polyamide separation layer and anti-organic fouling and antibacterial ultrathin layer; in, The porous ultrafiltration membrane support layer is located at the bottom of the composite nanofiltration membrane, and the porous ultrafiltration membrane support layer is a polysulfone ultrafiltration membrane and / or a polyethersulfone ultrafiltration membrane. The polyamide separation layer is located in the middle of the composite nanofiltration membrane, and the polyamide separation layer covers the porous ultrafiltration membrane support layer; The anti-organic pollution and antibacterial ultrathin layer is located on top of the composite nanofiltration membrane. The anti-organic pollution and antibacterial ultrathin layer is bonded to the polyamide separation layer by covalent bonds and is attached to the polyamide separation layer. The anti-organic pollution and antibacterial ultrathin layer is composed of a polymer host material, a chelating agent and antibacterial metal ions. The polymer host material and the chelating agent are connected by covalent bonds, and the chelating agent and the antibacterial metal ions are bonded by coordination bonds.

[0008] This specification provides a nanofiltration membrane with both anti-organic fouling and antibacterial properties, and its preparation method. A porous ultrafiltration membrane support layer is sequentially immersed in an aqueous solution containing polyamines and an organic solution containing polyacrylamide chlorides, causing the polyamines and polyacrylamide chlorides to undergo interfacial polymerization to generate a polyamide separation layer of the nanofiltration membrane. The polyamide separation layer is then immersed in an anti-organic fouling and antibacterial ultrathin layer preparation solution to form an anti-organic fouling and antibacterial ultrathin layer. The porous ultrafiltration membrane support layer, the polyamide separation layer, and the anti-organic fouling and antibacterial ultrathin layer constitute a composite nanofiltration membrane with both anti-organic fouling and antibacterial properties. The anti-organic fouling and antibacterial ultrathin layer is constructed using a ternary component to modify the nanofiltration membrane surface. Polyvinyl alcohol, the main polymer material, forms a hydrophilic layer on the membrane surface, and the multi-hydroxyl structure enhances the binding between the membrane surface and water molecules, preventing the adsorption and deposition of organic matter on the membrane surface. Simultaneously, polyvinyl alcohol and the polyamide separation layer are covalently bonded, and the strong chemical bonds enhance the interaction between the anti-organic fouling and antibacterial ultrathin layer and the separation layer, thereby improving the stability of the anti-organic fouling and antibacterial ultrathin layer during use. Metal ions impart antibacterial properties to the membrane surface, inactivating bacteria near the membrane surface and preventing bacterial proliferation. Chelating agents connect polyvinyl alcohol and metal ions, increasing the metal ion loading on the membrane surface while enhancing the stability of the antifouling layer. The nanofiltration membrane with both anti-organic fouling and antibacterial properties is simple to prepare and easy to industrialize. The resulting nanofiltration membrane can maintain good anti-organic fouling and antibacterial properties for a long time and can be applied in water resource development and wastewater recycling. Attached Figure Description

[0009] Figure 1 This is a schematic diagram illustrating the preparation method of a nanofiltration membrane with both resistance to organic pollution and antibacterial properties, as provided in the embodiments of this specification. Detailed Implementation

[0010] To better understand the technical solution of the present invention, the following embodiments will further illustrate the method provided by the present invention. However, the present invention is not limited to the listed embodiments, but should also include any other known modifications within the scope of the claims of the present invention.

[0011] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0012] Materials used in this invention: There are no special restrictions on the source of all raw materials in this invention and the following embodiments and comparative examples; they can be commercially available.

[0013] Figure 1 This is a schematic diagram illustrating the preparation method of a nanofiltration membrane with both resistance to organic fouling and antibacterial properties, as provided in the embodiments of this specification. Figure 1 As shown, the preparation method includes: Step 101: The porous ultrafiltration membrane support layer is sequentially immersed in an aqueous solution containing polyamine and an organic solution containing polyacrylamide chloride, so that the polyamine and the polyacrylamide chloride undergo an interfacial polymerization reaction to generate the polyamide separation layer of the nanofiltration membrane.

[0014] In the embodiments of this specification, the polyamine is piperazine, and the aqueous solution containing the polyamine comprises: an aqueous solution of 0.5-5.0 wt% piperazine, 0.3-2.0 wt% triethylamine, and 0.01-0.5 wt% sodium dodecyl sulfate; The polyacryl chloride is pyromellitic chloride, and the composition of the organic phase solution containing the polyacryl chloride includes: 0.05-0.5 wt% Isopar G solution of pyromellitic chloride.

[0015] In the embodiments of this specification, the porous ultrafiltration membrane support layer is a polysulfone ultrafiltration membrane, and the pore size distribution of the porous ultrafiltration membrane support layer is 30 nm - 100 nm.

[0016] It should be noted that, in the embodiments of this specification, the pore size distribution of the porous ultrafiltration membrane support layer can be either uniform or inconsistent. Whether the pore size is uniform or inconsistent does not limit the manufacturing method of this application. In a specific embodiment, the pore size distribution of the porous ultrafiltration membrane support layer is preferably 30 nm-50 nm.

[0017] In the embodiments of this specification, the step of sequentially immersing the porous ultrafiltration membrane support layer in an aqueous solution containing a polyamine and an organic solution containing a polyacrylamide chloride, causing the polyamine and the polyacrylamide chloride to undergo an interfacial polymerization reaction to generate the polyamide separation layer of the nanofiltration membrane, specifically includes: After the porous ultrafiltration membrane support layer is contacted with the aqueous solution containing polyamine under the first contact conditions, the porous ultrafiltration membrane support layer is contacted with the organic solution containing polyacrylamide chloride under the second contact conditions, and heat treatment is performed under the heat treatment conditions to cause the polyamine and the polyacrylamide chloride to undergo an interfacial polymerization reaction to generate the polyamide separation layer of the nanofiltration membrane. in, The first contact conditions are: contact time of 20-120s and contact temperature of 15-30℃; The second contact conditions are: contact time of 20-120 seconds and contact temperature of 15-30°C; The heat treatment conditions are: a treatment temperature of 40-80℃ and a treatment time of 2-10 minutes.

[0018] The purpose of sequentially immersing the polyamine in an aqueous solution containing polyamine and an organic solution containing polyacrylamide chloride to induce interfacial polymerization of the polyamine and polyacrylamide chloride is to obtain the polyamide separation layer of the nanofiltration membrane. In the embodiments of this application, the first contact condition is preferably 25°C for 60 s, the second contact condition is preferably 25°C for 60 s, and the heat treatment condition is preferably 50°C for 5 min.

[0019] Step 103: The polyamide separation layer is immersed in the solution for preparing the anti-organic fouling and antibacterial ultrathin layer to form an anti-organic fouling and antibacterial ultrathin layer. The porous ultrafiltration membrane support layer, the polyamide separation layer and the anti-organic fouling and antibacterial ultrathin layer are used as a composite nanofiltration membrane with both anti-organic fouling and antibacterial properties.

[0020] In the embodiments of this specification, the anti-organic pollution antibacterial ultrathin layer preparation solution comprises a polymer host material, a chelating agent, and metal ions. The polymer host material is a polyhydroxy polymer, the chelating agent is an aminopolyacid, and the metal ions are copper ions or silver ions. The preparation process of the anti-organic pollution antibacterial ultrathin layer preparation solution includes: The chelating agent is dissolved in deionized water, the pH is adjusted to 8.5, and then added to a solution of soluble inorganic salts of the metal ions to generate a metal chelate solution. The metal chelate solution is added to the aqueous solution of the polymer host material, and the pH is adjusted to a preset pH to form the solution for preparing the anti-organic pollution and antibacterial ultrathin layer.

[0021] In the embodiments of this specification, the polyhydroxy polymer is polyvinyl alcohol, and the concentration of polyvinyl alcohol is 5-15 g / L; The aminopolyacid is any one of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, and triethylenetetraaminehexaacetic acid, and the concentration of the chelating agent is 5-15 mM; The concentration of soluble inorganic salts in the soluble inorganic salt solution of the metal ions is 5-15 mM.

[0022] In the embodiments of this specification, the soluble inorganic salt solution of metal ions is AgNO3 or CuSO4.

[0023] In the embodiments described in this specification, the preset pH is 8.0-9.0; The step of adding the metal chelate solution to the aqueous solution of the polymer host material and adjusting the pH to a preset pH to form the solution for preparing the anti-organic pollution and antibacterial ultrathin layer specifically includes: The metal chelate solution is added to the aqueous solution of the polymer host material, and the pH is adjusted to 8.0-9.0 with NaOH to form the solution for preparing the anti-organic pollution and antibacterial ultrathin layer.

[0024] In the embodiments of this specification, the step of immersing the polyamide separation layer in an anti-organic pollution antibacterial ultrathin layer preparation solution to form an anti-organic pollution antibacterial ultrathin layer specifically includes: The polyamide separation layer is immersed in an anti-organic pollution antibacterial thin layer preparation solution under the third contact condition and then dried to form the anti-organic pollution antibacterial ultrathin layer.

[0025] In the embodiments of this specification, the third contact conditions are: contact time of 1-10 min and temperature of 25-35℃; The drying process is carried out using an oven, with the oven drying conditions being 60-100℃ for 3-10 minutes.

[0026] This specification provides an embodiment of a nanofiltration membrane that combines resistance to organic fouling and antibacterial properties, comprising: Porous ultrafiltration membrane support layer, polyamide separation layer and anti-organic fouling and antibacterial ultrathin layer; in, The porous ultrafiltration membrane support layer is located at the bottom of the composite nanofiltration membrane, and the porous ultrafiltration membrane support layer is a polysulfone ultrafiltration membrane and / or a polyethersulfone ultrafiltration membrane. The polyamide separation layer is located in the middle of the composite nanofiltration membrane, and the polyamide separation layer covers the porous ultrafiltration membrane support layer; The anti-organic pollution and antibacterial ultrathin layer is located on top of the composite nanofiltration membrane. The anti-organic pollution and antibacterial ultrathin layer is bonded to the polyamide separation layer by covalent bonds and is attached to the polyamide separation layer. The anti-organic pollution and antibacterial ultrathin layer is composed of a polymer host material, a chelating agent and antibacterial metal ions. The polymer host material and the chelating agent are connected by covalent bonds, and the chelating agent and the antibacterial metal ions are bonded by coordination bonds.

[0027] The nanofiltration membranes provided in the embodiments of this specification, which have both resistance to organic fouling and antibacterial properties, can be applied to water treatment nanofiltration membranes and components.

[0028] To further understand the method provided in this embodiment, the following describes the methods used or that may be used in the embodiments or comparative examples of the present invention: 1. Evaluation of resistance to organic pollution A protein fouling test was used to calculate the flux decay rate and flux recovery rate of the membrane, characterizing the nanofiltration membrane's resistance to organic fouling. The main steps were as follows: A cross-flow membrane detection device was used, with a NaCl concentration of 2000 ppm on the feed side, an operating pressure of 0.69 MPa, and a pre-compression time of 0.5 h. Bovine serum albumin (BSA) was added to the feed at a concentration of 300 ppm, and the water flux of the nanofiltration membrane at the onset of protein fouling was recorded. J0. Continue running the membrane for 10 h and record the water flux of the nanofiltration membrane at the end of protein contamination. J 1. Replace the feed solution with pure water and rinse the nanofiltration membrane surface for 30 minutes. Then, use a mixed aqueous solution of 2000 ppm sodium chloride and 300 ppm bovine serum albumin as the feed solution and test the membrane at 0.69 MPa, recording the membrane's water flux. J 2.

[0029] Flux attenuation rate of the membrane ( FDR ): FDR = ( J 0- J 1) / J 0×100% Flux recovery rate ( FRR ): FRR = J 2 / J 0×100% 2. Evaluation of antibacterial properties The antibacterial properties of the nanofiltration membrane were characterized using a bactericidal test. The main steps were as follows: *E. coli* was incubated in a culture medium and cultured overnight at 37°C in a shaker until the bacteria reached the logarithmic growth phase. The solution was then diluted with physiological saline to a bacterial concentration of approximately 1.0 × 10⁻⁶. 6 A CFU / mL suspension was prepared. A nanofiltration membrane with a nonwoven fabric side attached to a glass slide was placed, exposing an antibacterial ultrathin layer resistant to organic contamination, measuring 2.6 × 7.6 cm. 60 μL of bacterial suspension was evenly coated onto the membrane surface and covered with a glass slide to ensure uniform bacterial dispersion and prevent evaporation. The membrane and slide were placed together in a sterile petri dish and incubated at 37°C for 3 hours. The membrane surface and the slide in contact with the membrane were then washed with 9 mL of physiological saline, and the bacteria were collected. 1 mL of this saline solution was mixed evenly with culture medium and incubated at 37°C for 48 hours. Colonies were counted, and antibacterial activity was calculated.

[0030] In the embodiments of this specification, antibacterial activity is calculated using an antibacterial rate. Antibacterial rate R The calculation is as follows: R = ( B - A ) / B ×100%, of which B This represents the number of viable bacteria on the culture medium corresponding to the comparative nanofiltration membrane. A The number of viable bacteria on the culture medium corresponding to the nanofiltration membrane in this example.

[0031] Comparative Example 1 Using a nanofiltration membrane with an antibacterial ultrathin layer free from organic pollution as Comparative Example 1, its preparation method is as follows: An aqueous solution containing 1.5 wt% piperazine, 1.0 wt% triethylamine, and 0.1 wt% sodium dodecyl sulfate was prepared; an Isopar G organic solution containing 0.1 wt% trimesoyl chloride was prepared; a porous ultrafiltration support membrane was soaked in deionized water and its surface was purged with nitrogen until no droplets remained; the surface of the porous ultrafiltration support membrane was immersed in the aqueous solution for 60 s, and then purged with nitrogen until no droplets remained; the surface of the support membrane containing the aqueous monomer was immersed in the organic solution for 60 s to obtain the nanofiltration membrane; the nanofiltration membrane was heat-treated in a 50℃ oven for 5 min to further crosslink the polyamide separation layer; the surface was washed with deionized water and stored in deionized water for later use.

[0032] The nanofiltration membrane obtained in Comparative Example 1 was evaluated for its resistance to organic fouling and its antibacterial properties. The evaluation results are detailed in Table 1. Example 1

[0033] A nanofiltration membrane containing only polyvinyl alcohol in an ultrathin layer was used as Comparative Example 2. The preparation method was as follows: the nanofiltration membrane was prepared using the method of Comparative Example 1; polyvinyl alcohol was dissolved in deionized water at a concentration of 10 g / L, stirred at 90 °C until dissolved, and allowed to stand and cool; the surface of the nanofiltration membrane was immersed in the polyvinyl alcohol solution and contacted at 25 °C for 2 min, excess solution was removed, and the membrane was treated in an oven at 80 °C for 10 min; the surface was washed with deionized water and stored in deionized water for later use.

[0034] The nanofiltration membrane obtained in Example 1 was evaluated for its resistance to organic fouling and its antibacterial properties. The evaluation results are detailed in Table 1. Example 2

[0035] A nanofiltration membrane containing only polyvinyl alcohol and diethylenetriaminepentaacetic acid (DTA) in its ultrathin layer was used as Comparative Example 2. The preparation method was as follows: The nanofiltration membrane was prepared using the method described in Comparative Example 1; polyvinyl alcohol was dissolved in deionized water and stirred at 90 °C until dissolved, then allowed to cool; DTA was dissolved in deionized water and stirred thoroughly; the DTA solution was poured into the polyvinyl alcohol solution to achieve a final polyvinyl alcohol concentration of 10 g / L and a DTA concentration of 10 mM; the surface of the nanofiltration membrane was immersed in the solution and contacted at 25 °C for 2 min, excess solution was removed, and the membrane was treated in an oven at 80 °C for 5 min; the surface was washed with deionized water and stored in deionized water for later use.

[0036] The nanofiltration membrane obtained in Example 2 was evaluated for its resistance to organic fouling and its antibacterial properties. The evaluation results are detailed in Table 1. Example 3

[0037] A nanofiltration membrane containing polyvinyl alcohol, diethylenetriaminepentaacetic acid (DTA), and copper ions in an ultrathin layer was used as Comparative Example 1. The preparation method was as follows: The nanofiltration membrane was prepared using the method described in Comparative Example 1; polyvinyl alcohol was dissolved in deionized water and stirred at 90°C until dissolved, then allowed to cool; DTA was dissolved in deionized water, and CuSO4 was added and stirred thoroughly; the mixed solution of DTA and CuSO4 was poured into the polyvinyl alcohol solution, so that the final solution contained 10 g / L polyvinyl alcohol, 10 mM DTA, and 10 mM CuSO4; the surface of the nanofiltration membrane was immersed in the solution and contacted at 25°C for 2 min; excess solution was removed, and the membrane was treated in an oven at 80°C for 5 min; the surface was washed with deionized water and stored in deionized water for later use.

[0038] The nanofiltration membrane obtained in Example 3 was evaluated for its resistance to organic fouling and its antibacterial properties. The evaluation results are detailed in Table 1. Example 4

[0039] Nanofiltration membranes were prepared using the method described in Comparative Example 1. Polyvinyl alcohol was dissolved in deionized water and stirred at 90 °C until dissolved, then allowed to cool. Diethylenetriaminepentaacetic acid (DTA) was dissolved in deionized water, and AgNO3 was added and stirred thoroughly. The mixed solution of DTA and AgNO3 was poured into the DTA solution to make the final solution have a concentration of 10 g / L for DTA, 10 mM for DTA, and 10 mM for AgNO3. The surface of the nanofiltration membrane was immersed in the solution and contacted at 25 °C for 2 min. Excess solution was removed, and the membrane was dried in an oven at 80 °C for 5 min. The surface was then washed with deionized water and stored in deionized water for later use.

[0040] The nanofiltration membrane obtained in Example 4 was evaluated for its resistance to organic fouling and its antibacterial properties. The evaluation results are detailed in Table 1.

[0041] Table 1. Data on the anti-organic fouling and antibacterial properties of composite nanofiltration membranes

[0042] As can be seen from the experimental results in Table 1, compared with Comparative Example 1, the flux decline rate after contamination in Examples 1-4 was significantly reduced, and the flux recovery rate after cleaning was significantly improved. This indicates that the construction of the anti-organic fouling and antibacterial ultrathin layer can reduce the binding force between the membrane surface and organic pollutants, prevent the adsorption and accumulation of organic matter on the membrane surface, and improve the anti-organic fouling performance of the nanofiltration membrane. Compared with Comparative Example 1, the antibacterial rate of Examples 3 and 4 was significantly improved. The anti-fouling and antibacterial ultrathin layers of Examples 3 and 4 introduced copper ions and silver ions, respectively, which can kill more than 99% of the bacteria that fall on the membrane surface, prevent bacterial proliferation on the membrane surface, and improve the antibacterial performance of the nanofiltration membrane.

[0043] Taking into account the results in Table 1, when polyvinyl alcohol, chelating agents and antibacterial metal ions are used to construct an anti-organic fouling and antibacterial ultrathin layer, a nanofiltration membrane with both anti-organic fouling and antibacterial properties can be obtained.

[0044] In addition, to further verify the preparation method of the nanofiltration membrane with both anti-organic pollution and antibacterial properties in the embodiments of this specification, the preparation method was verified below. Example 5

[0045] Nanofiltration membranes were prepared using the method described in Comparative Example 1. Polyvinyl alcohol was dissolved in deionized water and stirred at 90 °C until dissolved, then allowed to cool. Diethylenetriaminepentaacetic acid (DTA) was dissolved in deionized water, and AgNO3 / CuSO4 was added and stirred thoroughly. The mixed solution of DTA and AgNO3 / CuSO4 was poured into the polyvinyl alcohol solution to make the final solution have a polyvinyl alcohol concentration of 10 g / L, a DTA concentration of 10 mM, and an AgNO3 / CuSO4 concentration of 10 mM. The surface of the nanofiltration membrane was immersed in the solution and contacted at 30 °C for 2 min. Excess solution was removed, and the membrane was treated in an oven at 80 °C for 5 min. The surface was washed with deionized water and stored in deionized water for later use. Example 6

[0046] Nanofiltration membranes were prepared using the method described in Comparative Example 1. Polyvinyl alcohol was dissolved in deionized water and stirred at 90 °C until dissolved, then allowed to cool. Diethylenetriaminepentaacetic acid (DTA) was dissolved in deionized water, and AgNO3 / CuSO4 was added and stirred thoroughly. The mixed solution of DTA and AgNO3 / CuSO4 was poured into the polyvinyl alcohol solution to make the final solution have a polyvinyl alcohol concentration of 10 g / L, a DTA concentration of 10 mM, and an AgNO3 / CuSO4 concentration of 10 mM. The surface of the nanofiltration membrane was immersed in the solution and contacted at 35 °C for 2 min. Excess solution was removed, and the membrane was treated in an oven at 80 °C for 5 min. The surface was washed with deionized water and stored in deionized water for later use. Example 7

[0047] Nanofiltration membranes were prepared using the method described in Comparative Example 1. Polyvinyl alcohol was dissolved in deionized water and stirred at 90 °C until dissolved, then allowed to cool. Diethylenetriaminepentaacetic acid (DTA) was dissolved in deionized water, and AgNO3 / CuSO4 was added and stirred thoroughly. The mixed solution of DTA and AgNO3 / CuSO4 was poured into the polyvinyl alcohol solution to make the final solution have a polyvinyl alcohol concentration of 10 g / L, a DTA concentration of 10 mM, and an AgNO3 / CuSO4 concentration of 10 mM. The surface of the nanofiltration membrane was immersed in the solution and contacted at 25 °C for 3 min. Excess solution was removed, and the membrane was treated in an oven at 80 °C for 5 min. The surface was then washed with deionized water and stored in deionized water for later use. Example 8

[0048] Nanofiltration membranes were prepared using the method described in Comparative Example 1. Polyvinyl alcohol was dissolved in deionized water and stirred at 90 °C until dissolved, then allowed to cool. Diethylenetriaminepentaacetic acid (DTA) was dissolved in deionized water, and AgNO3 was added and stirred thoroughly. A mixed solution of DTA and AgNO3 / CuSO4 was poured into the DTA solution to make the final solution have a DTA concentration of 10 g / L, a DTA concentration of 10 mM, and an AgNO3 / CuSO4 concentration of 10 mM. The surface of the nanofiltration membrane was immersed in the solution and contacted at 25 °C for 4 min. Excess solution was removed, and the membrane was dried in an oven at 80 °C for 5 min. The surface was then washed with deionized water and stored in deionized water for later use. Example 9

[0049] Nanofiltration membranes were prepared using the method described in Comparative Example 1. Polyvinyl alcohol was dissolved in deionized water and stirred at 90 °C until dissolved, then allowed to cool. Diethylenetriaminepentaacetic acid (DTA) was dissolved in deionized water, and AgNO3 / CuSO4 was added and stirred thoroughly. The mixed solution of DTA and AgNO3 / CuSO4 was poured into the polyvinyl alcohol solution to make the final solution have a polyvinyl alcohol concentration of 10 g / L, a DTA concentration of 10 mM, and an AgNO3 / CuSO4 concentration of 10 mM. The surface of the nanofiltration membrane was immersed in the solution and contacted at 25 °C for 5 min. Excess solution was removed, and the membrane was treated in an oven at 80 °C for 5 min. The surface was then washed with deionized water and stored in deionized water for later use. Example 10

[0050] Nanofiltration membranes were prepared using the method described in Comparative Example 1. Polyvinyl alcohol was dissolved in deionized water and stirred at 90 °C until dissolved, then allowed to cool. Diethylenetriaminepentaacetic acid (DTA) was dissolved in deionized water, and AgNO3 / CuSO4 was added and stirred thoroughly. The mixed solution of DTA and AgNO3 / CuSO4 was poured into the polyvinyl alcohol solution to make the final solution have a polyvinyl alcohol concentration of 10 g / L, a DTA concentration of 10 mM, and an AgNO3 / CuSO4 concentration of 10 mM. The surface of the nanofiltration membrane was immersed in the solution and contacted at 25 °C for 7 min. Excess solution was removed, and the membrane was treated in an oven at 80 °C for 5 min. The surface was then washed with deionized water and stored in deionized water for later use. Example 11

[0051] Nanofiltration membranes were prepared using the method described in Comparative Example 1. Polyvinyl alcohol was dissolved in deionized water and stirred at 90 °C until dissolved, then allowed to cool. Diethylenetriaminepentaacetic acid (DTA) was dissolved in deionized water, and AgNO3 / CuSO4 was added and stirred thoroughly. The mixed solution of DTA and AgNO3 / CuSO4 was poured into the polyvinyl alcohol solution to make the final solution have a polyvinyl alcohol concentration of 10 g / L, a DTA concentration of 10 mM, and an AgNO3 / CuSO4 concentration of 10 mM. The surface of the nanofiltration membrane was immersed in the solution and contacted at 25 °C for 10 min. Excess solution was removed, and the membrane was treated in an oven at 80 °C for 5 min. The surface was then washed with deionized water and stored in deionized water for later use.

[0052] The nanofiltration membranes obtained in Examples 5-11 were evaluated for their resistance to organic fouling and antibacterial properties. The evaluation results are detailed in Table 2.

[0053] Table 2. Data on the anti-organic fouling and antibacterial properties of composite nanofiltration membranes

[0054] Taking into account the results in Table 2, the preparation method of the nanofiltration membrane with both anti-organic pollution and antibacterial properties provided in this specification is adopted. The contact time of the third contact condition is 2-10 min, preferably 2-5 min. Meanwhile, the contact temperature of the third contact condition has no significant effect on the preparation method of this application.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the implementation. It should be noted that those skilled in the art can make other variations or modifications without departing from the principles of the present invention, and any obvious variations or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for preparing a composite nanofiltration membrane with both anti-organic pollution and antibacterial properties, characterized in that, The preparation method includes: The porous ultrafiltration membrane support layer is sequentially immersed in an aqueous solution containing polyamine and an organic solution containing polyacryl chloride, so that the polyamine and the polyacryl chloride undergo an interfacial polymerization reaction to generate the polyamide separation layer of the nanofiltration membrane. The polyamide separation layer is immersed in an anti-organic fouling and antibacterial ultrathin layer preparation solution to form an anti-organic fouling and antibacterial ultrathin layer. The porous ultrafiltration membrane support layer, the polyamide separation layer and the anti-organic fouling and antibacterial ultrathin layer are used as a composite nanofiltration membrane that combines anti-organic fouling and antibacterial properties.

2. The preparation method according to claim 1, characterized in that, The polyamine is piperazine, and the aqueous solution containing the polyamine comprises: an aqueous solution of 0.5-5.0 wt% piperazine, 0.3-2.0 wt% triethylamine, and 0.01-0.5 wt% sodium dodecyl sulfate; The polyacryl chloride is pyromellitic chloride, and the composition of the organic phase solution containing the polyacryl chloride includes: 0.05-0.5 wt% Isopar G solution of pyromellitic chloride.

3. The preparation method according to claim 1, characterized in that, The porous ultrafiltration membrane support layer is a polysulfone ultrafiltration membrane, and the pore size distribution of the porous ultrafiltration membrane support layer is 30 nm - 100 nm.

4. The preparation method according to claim 1, characterized in that, The process of sequentially immersing the porous ultrafiltration membrane support layer in an aqueous solution containing polyamines and an organic solution containing polyacrylamide chlorides, causing the polyamines and polyacrylamide chlorides to undergo an interfacial polymerization reaction to generate the polyamide separation layer of the nanofiltration membrane, specifically includes: After the porous ultrafiltration membrane support layer is contacted with the aqueous solution containing polyamine under the first contact conditions, the porous ultrafiltration membrane support layer is contacted with the organic solution containing polyacrylamide chloride under the second contact conditions, and heat treatment is performed under the heat treatment conditions to cause the polyamine and the polyacrylamide chloride to undergo an interfacial polymerization reaction to generate the polyamide separation layer of the nanofiltration membrane. in, The first contact conditions are: contact time of 20-120s and contact temperature of 15-30℃; The second contact conditions are: contact time of 20-120 seconds and contact temperature of 15-30°C; The heat treatment conditions are: a treatment temperature of 40-80℃ and a treatment time of 2-10 min.

5. The preparation method according to claim 1, characterized in that, The anti-organic pollution and antibacterial ultrathin layer preparation solution comprises a polymer host material, a chelating agent, and metal ions. The polymer host material is a polyhydroxy polymer, the chelating agent is an amino polyacid, and the metal ions are copper ions or silver ions. The preparation process of the anti-organic pollution and antibacterial ultrathin layer preparation solution includes: The chelating agent is dissolved in deionized water, the pH is adjusted to 8.5, and then added to a solution of soluble inorganic salts of the metal ions to generate a metal chelate solution. The metal chelate solution is added to the aqueous solution of the polymer host material, and the pH is adjusted to a preset pH to form the solution for preparing the anti-organic pollution and antibacterial ultrathin layer.

6. The preparation method according to claim 5, characterized in that, The polyhydroxy polymer is polyvinyl alcohol, and the concentration of polyvinyl alcohol is 5-15 g / L; The aminopolyacid is any one of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, and triethylenetetraaminehexaacetic acid, and the concentration of the chelating agent is 5-15 mM; The concentration of soluble inorganic salts in the soluble inorganic salt solution of the metal ions is 5-15 mM.

7. The preparation method according to claim 5, characterized in that, The preset pH is 8.0-9.0; The step of adding the metal chelate solution to the aqueous solution of the polymer host material and adjusting the pH to a preset pH to form the solution for preparing the anti-organic pollution and antibacterial ultrathin layer specifically includes: The metal chelate solution is added to the aqueous solution of the polymer host material, and the pH is adjusted to 8.0-9.0 with NaOH to form the solution for preparing the anti-organic pollution and antibacterial ultrathin layer.

8. The preparation method according to claim 1, characterized in that, The step of immersing the polyamide separation layer in an anti-organic pollution and antibacterial ultrathin layer preparation solution to form an anti-organic pollution and antibacterial ultrathin layer specifically includes: The polyamide separation layer is immersed in an anti-organic pollution antibacterial thin layer preparation solution under the third contact condition and then dried to form the anti-organic pollution antibacterial ultrathin layer.

9. The preparation method according to claim 8, characterized in that, The third contact condition is: contact time of 1-10 min and temperature of 25-35 ℃; The drying process is carried out by oven drying, and the oven drying conditions are: 60-100 ℃, 3-10 min.

10. A composite nanofiltration membrane possessing both resistance to organic pollution and antibacterial properties, characterized in that, The composite nanofiltration membrane is prepared by the preparation method according to any one of claims 1 to 9, and the composite nanofiltration membrane comprises: Porous ultrafiltration membrane support layer, polyamide separation layer and anti-organic fouling and antibacterial ultrathin layer; in, The porous ultrafiltration membrane support layer is located at the bottom of the composite nanofiltration membrane, and the porous ultrafiltration membrane support layer is a polysulfone ultrafiltration membrane and / or a polyethersulfone ultrafiltration membrane. The polyamide separation layer is located in the middle of the composite nanofiltration membrane, and the polyamide separation layer covers the porous ultrafiltration membrane support layer; The anti-organic pollution and antibacterial ultrathin layer is located on top of the composite nanofiltration membrane. The anti-organic pollution and antibacterial ultrathin layer is covalently bonded to the polyamide separation layer and attached to the polyamide separation layer. The anti-organic pollution and antibacterial ultrathin layer is composed of a polymer host material, a chelating agent and antibacterial metal ions. The polymer host material and the chelating agent are connected by covalent bonds, and the chelating agent and the antibacterial metal ions are combined by coordination bonds.

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