Microporous membrane with sterilization and heavy metal ion adsorption functions and preparation method thereof

Abstract

The application discloses a microporous membrane with functions of sterilization and adsorption of heavy metal ions and a preparation method thereof, and belongs to the technical field of water treatment. The microporous membrane is prepared by using a phase inversion method, and has low equipment requirement and simple operation. The method avoids the complicated equipment requirement and severe operation condition of a traditional high-temperature melting extrusion or solution spinning process. By introducing modified composite powder into the microporous membrane structure, the microporous membrane is endowed with good sterilization and bacteriostasis performance, and also has good heavy metal removal and hydrophilic performance.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, specifically to a microporous membrane with bactericidal and heavy metal ion adsorption functions and its preparation method. Background Technology

[0002] Water scarcity and water pollution are serious global challenges. Membrane separation technology, due to its advantages such as high efficiency, energy saving, and no secondary pollution, has become an indispensable key technology in water treatment, material separation, and biomedicine. Polyvinylidene fluoride (PVDF), as a major membrane material, has been widely used due to its excellent chemical stability and mechanical strength. However, traditional PVDF microporous membranes still face two major bottlenecks in practical applications.

[0003] PVDF itself is a hydrophobic polymer material with low surface energy. During water treatment, pollutants such as proteins, microorganisms, and organic macromolecules in the water are easily adsorbed onto the membrane surface and inside the pores through hydrophobic interactions, leading to membrane pore blockage. This phenomenon is known as "membrane fouling," which drastically reduces the membrane's water flux, shortens its lifespan, increases the frequency and cost of chemical cleaning, and may cause irreversible performance degradation.

[0004] Chinese patent document CN107670506A discloses a method for preparing an antibacterial and fouling-resistant PVDF ultrafiltration membrane for water filtration. The method primarily uses N-methylpyrrolidone as a solvent and polyethylene glycol solution to modify polyvinylidene fluoride (PVDF) material, coating it to obtain a preliminarily modified PVDF membrane. The PVDF membrane is then immersed in a silver-loaded chitosan solution to obtain a modified PVDF microporous membrane. This invention's preparation method is simple, modifying the hydrophilicity and antibacterial properties of PVDF through immersion coating. The PVDF microporous membrane prepared by this invention not only has good hydrophilicity but also kills surface microorganisms, reduces the amount of protein adhering to wastewater, and inactivates proteins, effectively extending the service life of the PVDF membrane. However, the antibacterial coating of this patent has weak bonding with PVDF, allowing silver ions to easily leak from the weak coating into the treated water, causing secondary heavy metal pollution and posing potential environmental and biosafety risks. Summary of the Invention

[0005] The main objective of this invention is to propose a microporous membrane with bactericidal and heavy metal ion adsorption functions and its preparation method. The microporous membrane has good bactericidal, bacteriostatic and hydrophilic properties.

[0006] To achieve the above objectives, this invention proposes a method for preparing a microporous membrane with bactericidal and heavy metal ion adsorption functions, comprising the following steps:

[0007] The modified composite powder was dispersed in N,N-dimethylacetamide to obtain a modified composite powder dispersion. Then, pretreated polyvinylidene fluoride and polyvinylpyrrolidone were dissolved in N,N-dimethylacetamide to obtain a casting solution. The modified composite powder dispersion and the casting solution were then mixed evenly, polyethylene glycol diglycidyl ether was added, and the mixture was heated to react. After the reaction was completed, the mixture was cooled, and the reaction solution was placed in a vacuum environment to degas and then evenly spread on a nonwoven fabric. The nonwoven fabric was then immersed in deionized water, and the resulting membrane material was cleaned to obtain a microporous membrane with bactericidal and heavy metal ion adsorption functions.

[0008] Preferably, the mass ratio of the modified composite powder, pretreated polyvinylidene fluoride, polyvinylpyrrolidone, and polyethylene glycol diglycidyl ether is 3-6:100:30-40:2-4.

[0009] Preferably, the method for preparing the modified composite powder includes the following steps:

[0010] (1) Disperse graphene oxide in water, then add copper sulfate pentahydrate and mix evenly, add NaOH aqueous solution and mix, then transfer to a high-pressure reactor for hydrothermal reaction to obtain antibacterial powder;

[0011] (2) The antibacterial powder and dopamine were added to Tris-HCl buffer solution and mixed. The mixture was ultrasonically stirred in an open container at room temperature. The reaction product was centrifuged, washed, and vacuum dried to obtain polydopamine-modified antibacterial powder.

[0012] (3) Thiazole-4-carboxylic acid was dissolved in dimethyl sulfoxide, and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide were added for activation. Then, polydopamine was added to modify the antibacterial powder, and the mixture was heated to obtain the modified composite powder.

[0013] Preferably, in step (1), the mass ratio of graphene oxide to copper sulfate pentahydrate is 5-10:3-5; the concentration of the NaOH aqueous solution is 1-3 mol / L; the hydrothermal reaction temperature is 180-200℃; and the reaction time is 10-12 h.

[0014] Preferably, the mass ratio of antibacterial powder to dopamine in step (2) is 1:2-4.

[0015] Preferably, in step (3), the mass ratio of thiazole-4-carboxylic acid, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide and polydopamine-modified antibacterial powder is 8-12:12-15:6-8:100.

[0016] The preparation of the modified composite powder of this invention first involves the in-situ growth of copper oxide on graphene through a hydrothermal reaction, forming a uniformly dispersed composite structure, preventing the agglomeration of copper oxide and achieving highly efficient synergistic antibacterial activity. Then, polydopamine is polymerized in-situ on the surface of the antibacterial powder, which is beneficial to improving the hydrophilicity and antifouling ability of the microporous membrane. At the same time, a large number of active hydroxyl and amino groups are introduced. Then, the carboxyl groups in the thiazole-4-carboxylic acid molecule are activated by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide. Finally, the active amino groups in the polydopamine are subjected to an amidation reaction to obtain the final product.

[0017] Preferably, the pretreated polyvinylidene fluoride is polyvinylidene fluoride treated with oxygen plasma.

[0018] Treating polyvinylidene fluoride with oxygen plasma can introduce oxygen-containing functional groups onto its surface. This can improve its hydrophilicity, and the epoxy groups in polyethylene glycol diglycidyl ether can cross-link with the hydroxyl and amino groups on the modified composite powder and the hydroxyl groups on the pretreated polyvinylidene fluoride, thereby improving the bonding strength between the modified composite powder and polyvinylidene fluoride.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1) This invention proposes a microporous membrane with sterilization and heavy metal ion adsorption functions and its preparation method. The preparation process adopts the phase inversion method, which has low equipment requirements and simple operation, avoiding the complex equipment requirements and harsh operating conditions of traditional high temperature melt extrusion or solution spinning processes. By introducing modified composite powder into the microporous membrane structure, the microporous membrane is endowed with good sterilization and bacteriostatic properties, while also having good heavy metal removal and hydrophilic properties.

[0021] 2) The preparation of the modified composite powder of the present invention firstly involves loading copper oxide with graphene oxide to prevent the aggregation of copper oxide and achieve efficient synergistic antibacterial activity. Then, polydopamine is polymerized in situ on its surface, which is beneficial to improve the hydrophilicity and antifouling ability of the microporous membrane. Then, thiazolium-4-carboxylic acid is fixed on the antibacterial powder through an acylation reaction. The thiazolium group in the thiazolium-4-carboxylic acid molecule can coordinate well with metal ions in water, thereby removing metal ions from the water. Furthermore, imine groups are introduced to further improve the removal effect of metal ions by the microporous membrane.

[0022] 3) This invention adds polyethylene glycol diglycidyl ether during the preparation of the microporous membrane. The epoxy groups in the polyethylene glycol diglycidyl ether molecule can undergo cross-linking reactions with the hydroxyl groups on polyvinylidene fluoride (PVDF) treated with oxygen plasma, as well as the hydroxyl and amino groups on the modified composite powder. This firmly binds the modified composite powder to PVDF and provides hydrophilic polyethylene glycol segments that are not easily detached during water treatment, further improving the antibacterial, heavy metal removal, and antifouling capabilities of the microporous membrane. Detailed Implementation

[0023] To avoid unnecessary details, unless otherwise specified, all items used in the following examples are commercially available products, and all methods used are conventional methods unless otherwise specified.

[0024] The sources of some of the raw materials used in this invention are as follows:

[0025] Graphene oxide, with a single-layer sheet diameter of 50-500 nm, was purchased from Shanghai Maoguo Nanotechnology Co., Ltd.

[0026] Example 1

[0027] A method for preparing a microporous membrane with bactericidal and heavy metal ion adsorption functions includes the following steps:

[0028] (1) Disperse 7g of graphene oxide in 200mL of water, then add 4.2g of copper sulfate pentahydrate and stir until completely dissolved. Add 120mL of 2mol / L NaOH aqueous solution and mix evenly. Then transfer to a high-pressure reactor and carry out hydrothermal reaction at 200℃ for 10h. After the reaction is completed, cool, filter, centrifuge to collect the solid, wash and calcine at 500℃ for 2h and grind to obtain antibacterial powder.

[0029] (2) 7g of antibacterial powder and 21g of dopamine were added to 200mL of Tris-HCl buffer solution and mixed. The mixture was ultrasonically stirred in an open container at room temperature for 20h. The reaction product was centrifuged, washed and vacuum dried to obtain polydopamine-modified antibacterial powder.

[0030] (3) Dissolve 0.7g thiazol-4-carboxylic acid in 150mL dimethyl sulfoxide, add 0.9g 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.49g N-hydroxysuccinimide and activate at room temperature for 6h. Then add 7g polydopamine-modified antibacterial powder, heat at 70℃ for 6h, cool, filter, collect solid product, wash and dry to obtain modified composite powder;

[0031] (4) Polyvinylidene fluoride powder was treated with oxygen plasma under the following conditions: power 80W, vacuum degree 30Pa, and treatment time 4min, to obtain plasma-treated polyvinylidene fluoride.

[0032] (5) 1.8g of modified composite powder was dispersed in 50mL of N,N-dimethylacetamide to obtain a modified composite powder dispersion. Then, 40g of plasma-treated polyvinylidene fluoride and 14g of polyvinylpyrrolidone were dissolved in 500mL of N,N-dimethylacetamide to obtain a casting solution. The modified composite powder dispersion and the casting solution were mixed evenly, and 1.2g of polyethylene glycol diglycidyl ether was added. The mixture was heated at 80℃ for 3h. After the reaction was completed, the mixture was cooled and placed in a vacuum environment to degas and spread evenly on a nonwoven fabric. The mixture was left in the air for 20s. Then, the nonwoven fabric was immersed in deionized water. The obtained membrane material was cleaned to obtain a microporous membrane with bactericidal and heavy metal ion adsorption functions.

[0033] Example 2

[0034] A method for preparing a microporous membrane with bactericidal and heavy metal ion adsorption functions includes the following steps:

[0035] (1) Disperse 5g of graphene oxide in 200mL of water, then add 3g of copper sulfate pentahydrate and stir until completely dissolved. Add 140mL of 1mol / L NaOH aqueous solution and mix evenly. Then transfer to a high-pressure reactor and carry out hydrothermal reaction at 200℃ for 10h. After the reaction is completed, cool, filter, centrifuge to collect the solid, wash and calcine at 500℃ for 2h and grind to obtain antibacterial powder.

[0036] (2) Add 5g of antibacterial powder and 10g of dopamine to 200mL of Tris-HCl buffer solution and mix. Stir the mixture with ultrasound in an open container at room temperature for 20h. The reaction product is separated by centrifugation, washed and vacuum dried to obtain polydopamine modified antibacterial powder.

[0037] (3) Dissolve 0.4g thiazol-4-carboxylic acid in 150mL dimethyl sulfoxide, add 0.5g 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.3g N-hydroxysuccinimide and activate at room temperature for 6h. Then add 5g polydopamine-modified antibacterial powder, heat at 70℃ for 6h, cool, filter, collect solid product, wash and dry to obtain modified composite powder.

[0038] (4) Polyvinylidene fluoride powder was treated with oxygen plasma under the following conditions: power 80W, vacuum degree 30Pa, and treatment time 4min, to obtain plasma-treated polyvinylidene fluoride.

[0039] (5) 1.2g of modified composite powder was dispersed in 40mL of N,N-dimethylacetamide to obtain a modified composite powder dispersion. Then, 40g of plasma-treated polyvinylidene fluoride and 12g of polyvinylpyrrolidone were dissolved in 500mL of N,N-dimethylacetamide to obtain a casting solution. The modified composite powder dispersion and the casting solution were mixed evenly, and 0.8g of polyethylene glycol diglycidyl ether was added. The mixture was heated at 80℃ for 3h. After the reaction was completed, the mixture was cooled. The reaction solution was placed in a vacuum environment to degas and spread evenly on a nonwoven fabric. It was left in the air for 20s. Then, the nonwoven fabric was immersed in deionized water. The obtained membrane material was cleaned to obtain a microporous membrane with sterilization and heavy metal ion adsorption functions.

[0040] Example 3

[0041] A method for preparing a microporous membrane with bactericidal and heavy metal ion adsorption functions includes the following steps:

[0042] (1) Disperse 10g of graphene oxide in 200mL of water, then add 5g of copper sulfate pentahydrate and stir until completely dissolved. Add 150mL of 3mol / L NaOH aqueous solution and mix evenly. Then transfer to a high-pressure reactor and carry out hydrothermal reaction at 200℃ for 10h. After the reaction is completed, cool, filter, centrifuge to collect the solid, wash and calcine at 500℃ for 2h and grind to obtain antibacterial powder.

[0043] (2) 10g of antibacterial powder and 40g of dopamine were added to 300mL of Tris-HCl buffer solution and mixed. The mixture was ultrasonically stirred in an open container at room temperature for 20h. The reaction product was centrifuged, washed and vacuum dried to obtain polydopamine-modified antibacterial powder.

[0044] (3) Dissolve 1.2g thiazol-4-carboxylic acid in 150mL dimethyl sulfoxide, add 1.5g 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.8g N-hydroxysuccinimide and activate at room temperature for 6h. Then add 10g polydopamine-modified antibacterial powder, heat at 70℃ for 6h, cool, filter, collect solid product, wash and dry to obtain modified composite powder.

[0045] (4) Polyvinylidene fluoride powder was treated with oxygen plasma under the following conditions: power 80W, vacuum degree 30Pa, and treatment time 4min, to obtain plasma-treated polyvinylidene fluoride.

[0046] (5) 2.4g of modified composite powder was dispersed in 50mL of N,N-dimethylacetamide to obtain a modified composite powder dispersion. Then, 40g of plasma-treated polyvinylidene fluoride and 16g of polyvinylpyrrolidone were dissolved in 500mL of N,N-dimethylacetamide to obtain a casting solution. The modified composite powder dispersion and the casting solution were mixed evenly, and 1.6g of polyethylene glycol diglycidyl ether was added. The mixture was heated at 80℃ for 3h. After the reaction was completed, the mixture was cooled and placed in a vacuum environment to degas and spread evenly on a nonwoven fabric. The mixture was left in the air for 20s. Then, the nonwoven fabric was immersed in deionized water. The obtained membrane material was cleaned to obtain a microporous membrane with bactericidal and heavy metal ion adsorption functions.

[0047] Comparative Example 1

[0048] A method for preparing a microporous membrane with bactericidal and heavy metal ion adsorption functions is similar to that in Example 1, except that the polyvinylidene fluoride is not treated with plasma. The method specifically includes the following steps:

[0049] (1) Disperse 7g of graphene oxide in 200mL of water, then add 4.2g of copper sulfate pentahydrate and stir until completely dissolved. Add 120mL of 2mol / L NaOH aqueous solution and mix evenly. Then transfer to a high-pressure reactor and carry out hydrothermal reaction at 200℃ for 10h. After the reaction is completed, cool, filter, centrifuge to collect the solid, wash and calcine at 500℃ for 2h and grind to obtain antibacterial powder.

[0050] (2) 7g of antibacterial powder and 21g of dopamine were added to 200mL of Tris-HCl buffer solution and mixed. The mixture was ultrasonically stirred in an open container at room temperature for 20h. The reaction product was centrifuged, washed and vacuum dried to obtain polydopamine-modified antibacterial powder.

[0051] (3) Dissolve 0.7g thiazol-4-carboxylic acid in 150mL dimethyl sulfoxide, add 0.9g 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.49g N-hydroxysuccinimide and activate at room temperature for 6h. Then add 7g polydopamine-modified antibacterial powder, heat at 70℃ for 6h, cool, filter, collect solid product, wash and dry to obtain modified composite powder;

[0052] (4) 1.8g of modified composite powder was dispersed in 50mL of N,N-dimethylacetamide to obtain a modified composite powder dispersion. Then, 40g of polyvinylidene fluoride powder and 14g of polyvinylpyrrolidone were dissolved in 500mL of N,N-dimethylacetamide to obtain a casting solution. The modified composite powder dispersion and the casting solution were mixed evenly, and 1.2g of polyethylene glycol diglycidyl ether was added. The mixture was heated at 80℃ for 3h. After the reaction was completed, the mixture was cooled. The reaction solution was placed in a vacuum environment to degas and spread evenly on a nonwoven fabric. It was left in the air for 20s. Then, the nonwoven fabric was immersed in deionized water. The obtained membrane material was cleaned to obtain a microporous membrane with bactericidal and heavy metal ion adsorption functions.

[0053] Comparative Example 2

[0054] A method for preparing a microporous membrane with bactericidal and heavy metal ion adsorption functions is similar to that in Example 1, except that thiazolium-4-carboxylic acid is not added to the modified composite powder. The method specifically includes the following steps:

[0055] (1) Disperse 7g of graphene oxide in 200mL of water, then add 4.2g of copper sulfate pentahydrate and stir until completely dissolved. Add 120mL of 2mol / L NaOH aqueous solution and mix evenly. Then transfer to a high-pressure reactor and carry out hydrothermal reaction at 200℃ for 10h. After the reaction is completed, cool, filter, centrifuge to collect the solid, wash and calcine at 500℃ for 2h and grind to obtain antibacterial powder.

[0056] (2) 7g of antibacterial powder and 21g of dopamine were added to 200mL of Tris-HCl buffer solution and mixed. The mixture was ultrasonically stirred in an open container at room temperature for 20h. The reaction product was centrifuged, washed and vacuum dried to obtain the modified composite powder.

[0057] (3) Polyvinylidene fluoride powder was treated with oxygen plasma under the following conditions: power 80W, vacuum degree 30Pa, and treatment time 4min to obtain plasma-treated polyvinylidene fluoride.

[0058] (4) 1.8g of modified composite powder was dispersed in 50mL of N,N-dimethylacetamide to obtain a modified composite powder dispersion. Then, 40g of plasma-treated polyvinylidene fluoride and 14g of polyvinylpyrrolidone were dissolved in 500mL of N,N-dimethylacetamide to obtain a casting solution. The modified composite powder dispersion and the casting solution were mixed evenly, and 1.2g of polyethylene glycol diglycidyl ether was added. The mixture was heated at 80℃ for 3h. After the reaction was completed, the mixture was cooled and placed in a vacuum environment to degas and spread evenly on a nonwoven fabric. The mixture was left in the air for 20s. Then, the nonwoven fabric was immersed in deionized water. The obtained membrane material was cleaned to obtain a microporous membrane with bactericidal and heavy metal ion adsorption functions.

[0059] Comparative Example 3

[0060] A method for preparing a microporous membrane with bactericidal and heavy metal ion adsorption functions is similar to that in Example 1, except that polyethylene glycol diglycidyl ether is not added. The method specifically includes the following steps:

[0061] (1) Disperse 7g of graphene oxide in 200mL of water, then add 4.2g of copper sulfate pentahydrate and stir until completely dissolved. Add 120mL of 2mol / L NaOH aqueous solution and mix evenly. Then transfer to a high-pressure reactor and carry out hydrothermal reaction at 200℃ for 10h. After the reaction is completed, cool, filter, centrifuge to collect the solid, wash and calcine at 500℃ for 2h and grind to obtain antibacterial powder.

[0062] (2) 7g of antibacterial powder and 21g of dopamine were added to 200mL of Tris-HCl buffer solution and mixed. The mixture was ultrasonically stirred in an open container at room temperature for 20h. The reaction product was centrifuged, washed and vacuum dried to obtain polydopamine-modified antibacterial powder.

[0063] (3) Dissolve 0.7g thiazol-4-carboxylic acid in 150mL dimethyl sulfoxide, add 0.9g 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.49g N-hydroxysuccinimide and activate at room temperature for 6h. Then add 7g polydopamine-modified antibacterial powder, heat at 70℃ for 6h, cool, filter, collect solid product, wash and dry to obtain modified composite powder;

[0064] (4) Polyvinylidene fluoride powder was treated with oxygen plasma under the following conditions: power 80W, vacuum degree 30Pa, and treatment time 4min, to obtain plasma-treated polyvinylidene fluoride.

[0065] (5) 1.8g of modified composite powder was dispersed in 50mL of N,N-dimethylacetamide to obtain a modified composite powder dispersion. Then, 40g of plasma-treated polyvinylidene fluoride and 14g of polyvinylpyrrolidone were dissolved in 500mL of N,N-dimethylacetamide to obtain a casting solution. The modified composite powder dispersion and the casting solution were mixed evenly and heated at 80℃ for 3h. After the reaction was completed, the mixture was cooled and placed in a vacuum environment to degas and spread evenly on a nonwoven fabric. The mixture was left in the air for 20s and then the nonwoven fabric was immersed in deionized water. The obtained membrane material was cleaned to obtain a microporous membrane with sterilization and heavy metal ion adsorption functions.

[0066] Performance testing

[0067] The test subjects were the microporous membranes with bactericidal and heavy metal ion adsorption functions obtained in each embodiment and comparative example.

[0068] Antibacterial properties: The antibacterial properties of the microporous membrane samples were determined according to GB / T37206-2018 "Test Method for Antibacterial Properties of Organic Separation Membranes";

[0069] Contact angle test experiment: Place the microporous membrane on the test stage of the water contact angle tester, drop 4μL of water onto the surface of the microporous membrane at room temperature, take a picture and measure the angle between the water droplet cross-section and the membrane surface. Each microporous membrane is tested 5 times at different water droplet positions and the average value is calculated.

[0070] Heavy metal ion removal rate: Equal masses of microporous membrane material were added to 500 mL of 50 mg / L Cd solution. 2+ Neutralize 500 mL of Pb solution 2+ In the solution, the mixture was stirred and adsorbed at room temperature for 1.5 h. The concentration of Cd in the solution was then determined by atomic absorption spectrophotometry. 2+ and Pb 2+ Calculate the removal rate based on the concentration before adsorption. Removal rate = (Concentration before adsorption - Concentration after adsorption) ÷ Concentration before adsorption × 100%.

[0071] Table 1 Performance test results of microporous membranes with bactericidal and heavy metal ion adsorption functions

[0072]

[0073] As can be seen from the experimental results in Table 1, the microporous membrane prepared in this application has good bactericidal and bacteriostatic properties, hydrophilicity, and heavy metal removal performance.

[0074] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the patent protection scope of the present invention.

Claims

1. A method for preparing a microporous membrane with bactericidal and heavy metal ion adsorption functions, characterized in that, Includes the following steps: The modified composite powder was dispersed in N,N-dimethylacetamide to obtain a modified composite powder dispersion. Then, pretreated polyvinylidene fluoride and polyvinylpyrrolidone were dissolved in N,N-dimethylacetamide to obtain a casting solution. The modified composite powder dispersion and the casting solution were then mixed evenly, polyethylene glycol diglycidyl ether was added, and the mixture was heated to react. After the reaction was completed, the mixture was cooled, and the reaction solution was placed in a vacuum environment to degas and then evenly spread on a nonwoven fabric. The nonwoven fabric was then immersed in deionized water, and the resulting membrane material was cleaned to obtain a microporous membrane with bactericidal and bacteriostatic functions. The method for preparing the modified composite powder includes the following steps: (1) Disperse graphene oxide in water, then add copper sulfate pentahydrate and mix evenly, add NaOH aqueous solution and mix, then transfer to a high-pressure reactor for hydrothermal reaction to obtain antibacterial powder; (2) The antibacterial powder and dopamine were added to Tris-HCl buffer solution and mixed. The mixture was ultrasonically stirred in an open container at room temperature. The reaction product was centrifuged, washed, and vacuum dried to obtain polydopamine-modified antibacterial powder. (3) Thiazole-4-carboxylic acid was dissolved in dimethyl sulfoxide, and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide were added for activation. Then, polydopamine was added to modify the antibacterial powder, and the reaction was heated to obtain the modified composite powder. The pretreated polyvinylidene fluoride is polyvinylidene fluoride treated with oxygen plasma.

2. The preparation method according to claim 1, characterized in that: The mass ratio of the modified composite powder, pretreated polyvinylidene fluoride, polyvinylpyrrolidone, and polyethylene glycol diglycidyl ether is 3-6:100:30-40:2-4.

3. The preparation method according to claim 1, characterized in that: In step (1), the mass ratio of graphene oxide to copper sulfate pentahydrate is 5-10:3-5; the concentration of the NaOH aqueous solution is 1-3 mol / L.

4. The preparation method according to claim 1, characterized in that: The hydrothermal reaction temperature in step (1) is 180-200℃, and the reaction time is 10-12h.

5. The preparation method according to claim 1, characterized in that: In step (2), the mass ratio of antibacterial powder to dopamine is 1:2-4.

6. The preparation method according to claim 1, characterized in that: In step (3), the mass ratio of thiazole-4-carboxylic acid, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide and polydopamine-modified antibacterial powder is 8-12:12-15:6-8:

100.

7. A microporous membrane with bactericidal and heavy metal ion adsorption functions, characterized in that: It is prepared by any one of the preparation methods of claims 1-6.

8. The application of the microporous membrane with bactericidal and heavy metal ion adsorption functions as described in claim 7 in water treatment.

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