Composite sewage treatment membrane with high anti-pollution and anti-bacterial properties and preparation method thereof

Abstract

The present application relates to sewage treatment membrane technical field, especially to the composite sewage treatment membrane with high anti-pollution and antibacterial property and preparation method, including preparation of grafting phenyl cage silsesquioxane polyether sulfone polymer;Preparation of polydopamine powder;The polyether sulfone polymer is dissolved in N, N-dimethylformamide to prepare the base casting fluid, add the prepared polydopamine powder, after dispersion, casting film obtains the preliminary modified polyether sulfone base film;The preliminary modified polyether sulfone base film is soaked in silver nitrate solution, and the intermediate film is obtained after washing;BN and MoS2 Nanosheet are dispersed in organic solvent to form a dispersion liquid, the intermediate film is immersed in the dispersion liquid, dried at 40-60 DEG C for 1-2h, repeated 1-2 times, to obtain the composite sewage treatment membrane.The present application adopts the above-mentioned composite sewage treatment membrane with high anti-pollution and antibacterial property and preparation method, significantly improves the anti-pollution and antibacterial property of sewage treatment membrane, and the preparation process is simple, stable.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment membrane technology, and in particular to a composite wastewater treatment membrane with both high antifouling and antibacterial properties, and its preparation method. Background Technology

[0002] Membrane separation technology, as a highly efficient and energy-saving wastewater treatment method, has been widely used in the field of wastewater treatment due to its advantages such as simple operation, high separation efficiency, and no secondary pollution. Among them, polyethersulfone (PES) membranes have become one of the commonly used membrane materials in wastewater treatment because of their good chemical stability, mechanical properties, and thermal stability.

[0003] However, polyethersulfone membranes still face some unresolved issues in practical applications. On one hand, their poor hydrophilicity makes them prone to adsorbing pollutants such as proteins and organic matter from wastewater, leading to severe membrane fouling. This not only reduces the membrane's filtration performance and lifespan but also increases operating costs. On the other hand, wastewater contains a large number of bacteria, viruses, and other microorganisms. The proliferation of these microorganisms on the membrane surface further exacerbates membrane fouling and may contaminate the effluent, harming human health and the ecological environment.

[0004] To improve the antifouling and antibacterial properties of polyethersulfone (PES) membranes, researchers have conducted extensive studies. Currently, commonly used modification methods include surface grafting, coating modification, and doping with nanomaterials. For example, grafting hydrophilic groups can increase the membrane's hydrophilicity and reduce pollutant adsorption. Doping with antibacterial agents such as silver ions and zinc oxide can impart certain antibacterial properties to the membrane. However, single modification methods often cannot simultaneously meet the requirements of high antifouling and strong antibacterial properties, and some modification methods suffer from complex processes and poor stability. Summary of the Invention

[0005] The purpose of this invention is to provide a composite wastewater treatment membrane with both high antifouling and antibacterial properties and a preparation method thereof, which significantly improves the antifouling and antibacterial properties of the wastewater treatment membrane, and the preparation process is simple and has good stability.

[0006] To achieve the above objectives, the present invention provides a method for preparing a composite wastewater treatment membrane with both high antifouling and antibacterial properties, comprising the following steps:

[0007] S1. Dissolve polyethersulfone in an organic solvent to prepare a polyethersulfone solution, add phenyl cage-type silsesquioxane and catalyst, stir and react at 120-150℃ for 6-8 hours under nitrogen protection, add excess precipitant to precipitate the grafted product, filter, collect, wash and dry the precipitate to obtain the polyethersulfone polymer grafted with phenyl cage-type silsesquioxane.

[0008] S2. Preparation of polydopamine powder;

[0009] S3. Dissolve the polyethersulfone polymer of S1 in N,N-dimethylformamide to prepare a basic casting solution, add the polydopamine powder prepared in S2, disperse and cast to obtain a preliminarily modified polyethersulfone-based film.

[0010] S4. Immerse the polyethersulfone-based membrane that was initially modified in S3 in silver nitrate solution for 1-2 hours, and then rinse to obtain the intermediate membrane;

[0011] S5. Disperse BN and MoS2 nanosheets in an organic solvent to form a dispersion. Immerse the intermediate membrane from S4 in the dispersion for 10-30 min and dry it at 40-60℃ for 1-2 h. Repeat this process 1-2 times to obtain a composite wastewater treatment membrane.

[0012] Preferably, in S1, the organic solvent includes one of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone, and the concentration of the polyethersulfone solution is 10-15 wt%.

[0013] Preferably, in S1, the molar ratio of phenyl cage-type silsesquioxane to polyethersulfone is 1:10-1:50, the mass fraction of the catalyst is 0.5%-2%, the catalyst includes one of dibutyltin dilaurate, stannous octoate, bismuth neodecanoate, and zinc diacetylacetonate, the precipitant is methanol, and the volume ratio of the precipitant to the organic solvent is 3:1-5:1.

[0014] Preferably, in S1, washing is performed 3-5 times with methanol, and drying is performed in a vacuum drying oven at a temperature of 80-100℃ for 6-8 hours.

[0015] Preferably, in step S2, dopamine is dissolved in Tris-HCl buffer solution to prepare a 1-2 mg / mL dopamine solution, and the solution is stirred and reacted at room temperature for 12-24 h to allow dopamine to undergo a self-polymerization reaction to generate polydopamine. After centrifugation, washing, and drying, polydopamine powder is obtained.

[0016] Preferably, in S3, the concentration of the base casting solution is 15-20 wt%, and the amount of polydopamine powder accounts for 1-5 wt% of the mass of the base casting solution.

[0017] Preferably, in S3, the casting process involves placing a base casting solution containing polydopamine powder in a vacuum drying oven for degassing for 3-5 hours, then using a coating machine to uniformly coat the base casting solution containing polydopamine powder onto a glass plate, quickly immersing the glass plate in a coagulation bath for phase separation and film formation, and after film formation, peeling the film off the glass plate and rinsing it with deionized water for 24 hours to obtain a preliminarily modified polyethersulfone-based film.

[0018] Preferably, in S4, the concentration of the silver nitrate solution is 0.01-0.1 mol / L.

[0019] Preferably, in S5, the organic solvent includes one of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone, the concentration of BN nanosheets in the dispersion is 0.3-1 mg / mL, and the concentration of MoS2 nanosheets in the dispersion is 0.2-1 mg / mL.

[0020] The present invention also provides a composite wastewater treatment membrane with both high antifouling and antibacterial properties, which is prepared by the above-mentioned method for preparing a composite wastewater treatment membrane with both high antifouling and antibacterial properties.

[0021] Mechanism of the invention:

[0022] The phenyl cage-like silsesquioxane in this invention possesses a unique cage-like structure. Grafting it onto the polyethersulfone molecular chain introduces a large number of phenyl and siloxy groups. The presence of phenyl groups increases the hydrophobicity of the polymer, while the steric hindrance effect of the cage structure reduces the stacking of molecular chains. Simultaneously, the siloxy groups exhibit a certain degree of polarity, which overall improves the hydrophilic-hydrophobic balance of the polymer to a certain extent, laying the foundation for subsequent modification and contributing to improved membrane antifouling performance.

[0023] Polydopamine participates in the casting reaction, exhibiting excellent hydrophilicity and adhesion. The phenolic hydroxyl and amino groups in its molecules can form hydrogen bonds with water molecules, increasing the membrane's hydrophilicity and thus reducing the adsorption of pollutants on the membrane surface. Simultaneously, polydopamine's adhesive properties enable it to form good bonds with polyethersulfone molecules and other subsequently introduced substances, enhancing membrane stability.

[0024] Silver ions in silver nitrate solution adhere to the polydopamine layer on the membrane surface and inside the membrane through electrostatic adsorption and other mechanisms. Silver ions possess broad-spectrum antibacterial properties, capable of disrupting bacterial cell membranes and inhibiting bacterial growth and reproduction, thereby endowing the membrane with antibacterial properties. BN nanosheets exhibit good chemical stability and lubricity, reducing friction between the membrane surface and contaminants and lowering the likelihood of contaminant adhesion. MoS2 nanosheets possess excellent hydrophilicity and antibacterial properties; their layered structure increases the specific surface area of ​​the membrane, improving its filtration performance, while their surface active sites inhibit bacterial activity. Through repeated immersion and drying processes, BN and MoS2 nanosheets can be uniformly deposited on the membrane surface and within the pores, forming a stable composite structure that further synergistically enhances the membrane's antifouling and antibacterial properties. The synergistic effect among the components results in a composite wastewater treatment membrane possessing both excellent antifouling and antibacterial properties.

[0025] Therefore, the present invention employs the above-mentioned composite wastewater treatment membrane with both high antifouling and antibacterial properties and its preparation method, which has the following beneficial effects:

[0026] (1) This invention preliminarily modifies polyethersulfone by grafting phenyl cage-type silsesquioxane, combining the hydrophilicity of polydopamine with the characteristics of BN nanosheets and MoS2 nanosheets, significantly improving the hydrophilicity and surface smoothness of the composite membrane. The increased hydrophilicity makes it easier for water molecules to bind to the membrane surface, forming a hydration layer and reducing the contact opportunities between pollutants and the membrane surface; the increased surface smoothness reduces the adsorption force of pollutants, thereby effectively inhibiting membrane fouling and extending the membrane's service life.

[0027] (2) In the preparation process of this invention, a silver nitrate solution treatment step is introduced, which loads silver ions with antibacterial properties on the membrane surface and inside. At the same time, MoS2 nanosheets also have certain antibacterial properties. Working synergistically with silver ions, they can effectively kill bacteria, viruses and other microorganisms in wastewater, prevent microorganisms from growing and multiplying on the membrane surface, further reduce membrane fouling, and ensure the safety of the effluent water quality.

[0028] (3) The various modification steps of the present invention are closely linked. The grafting reaction between phenyl cage-type silsesquioxane and polyethersulfone is stable. Polydopamine can enhance the binding force between the components. BN nanosheets and MoS2 nanosheets form a stable composite structure through deposition, so that the composite membrane has good chemical stability and mechanical properties and can adapt to complex sewage treatment environments.

[0029] (4) The preparation method of the present invention has clear steps, the raw materials used are easy to obtain, the reaction conditions are mild, and there is no need for complex equipment and high cost, which facilitates industrial production and application.

[0030] (5) The composite wastewater treatment membrane prepared by the present invention has both high anti-fouling and strong antibacterial properties. It can operate stably for a long time while ensuring high filtration efficiency, which reduces the operating cost and maintenance difficulty of wastewater treatment and has broad application prospects in the field of wastewater treatment.

[0031] The technical solution of the present invention will be further described in detail below through embodiments. Detailed Implementation

[0032] The present invention will be further described below with reference to embodiments. Unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art. The features mentioned above or in the specific examples mentioned in this invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the invention and are not intended to limit the scope of the invention.

[0033] Example 1

[0034] This invention provides a composite wastewater treatment membrane with both high antifouling and antibacterial properties, which is prepared by the following method, including the following steps:

[0035] S1. Polyethersulfone is dissolved in N,N-dimethylformamide to prepare a polyethersulfone solution with a concentration of 10 wt%. A phenyl cage-type silsesquioxane with a molar ratio of 1:10 to polyethersulfone and a catalyst with a mass fraction of 0.5% dibutyltin dilaurate are added. The mixture is stirred at 120°C for 6 hours under nitrogen protection to allow the phenyl cage-type silsesquioxane to undergo a grafting reaction with the polyethersulfone molecular chain.

[0036] After the reaction was complete, the reaction solution was cooled to room temperature, and excess methanol (volume ratio of precipitant to organic solvent was 3:1) was added to precipitate the grafted product. The precipitate was collected by filtration, washed three times with methanol to remove unreacted phenyl cage-like silsesquioxane and catalyst, and then placed in a vacuum drying oven and dried at 80°C for 6 hours to obtain a polyethersulfone polymer grafted with phenyl cage-like silsesquioxane.

[0037] S2. Prepare polydopamine powder by dissolving dopamine in Tris-HCl buffer solution to prepare a 1 mg / mL dopamine solution. Stir the solution at room temperature for 12 h to allow dopamine to undergo a self-polymerization reaction to generate polydopamine.

[0038] After the reaction was complete, the reaction solution was transferred to a centrifuge tube and centrifuged at 8000 r / min for 15 min to collect the precipitated polydopamine particles. The polydopamine particles were washed three times with deionized water to remove unreacted dopamine and impurities, and then placed in a vacuum drying oven and dried at 60℃ for 6 h to obtain polydopamine powder.

[0039] S3. Dissolve the polyethersulfone polymer from S1 in N,N-dimethylformamide to prepare a base casting solution with a concentration of 15wt%. Add the polydopamine powder prepared in S2 (the polydopamine powder accounts for 1wt% of the mass of the base casting solution). After dispersion, place the base casting solution with added polydopamine in a vacuum drying oven for degassing for 3 hours. Then, use a coating machine to uniformly coat the base casting solution with added polydopamine onto a glass plate. Quickly immerse the glass plate in a coagulation bath for phase separation and film formation. After film formation, peel the film off the glass plate and soak and wash it with deionized water for 24 hours to obtain a preliminarily modified polyethersulfone-based film.

[0040] S4. The polyethersulfone-based membrane initially modified in S3 was immersed in a silver nitrate solution with a concentration of 0.01 mol / L for 1 hour, and then rinsed to obtain the intermediate membrane.

[0041] S5. BN nanosheets and MoS2 nanosheets are dispersed in an organic solvent to form a dispersion. The concentration of BN nanosheets in the dispersion is 0.3 mg / mL, and the concentration of MoS2 nanosheets in the dispersion is 0.2 mg / mL. The intermediate membrane from S4 is immersed in the dispersion for 10 min and dried at 40 °C for 1 h. This process is repeated once to obtain a composite wastewater treatment membrane.

[0042] Example 2

[0043] This invention provides a composite wastewater treatment membrane with both high antifouling and antibacterial properties, which is prepared by the following method, including the following steps:

[0044] S1. Polyethersulfone was dissolved in N,N-dimethylformamide to prepare a polyethersulfone solution with a concentration of 12wt%. A phenyl cage-type silsesquioxane with a molar ratio of 1:20 to polyethersulfone and a catalyst of 0.8% by mass were added. The mixture was stirred at 130°C for 6.5 h under nitrogen protection to allow the phenyl cage-type silsesquioxane to undergo a grafting reaction with the polyethersulfone molecular chain.

[0045] After the reaction was complete, the reaction solution was cooled to room temperature, and excess methanol (volume ratio of precipitant to organic solvent was 4:1) was added to precipitate the grafted product. The precipitate was collected by filtration, washed repeatedly with methanol four times to remove unreacted phenyl cage-like silsesquioxane and catalyst, and then placed in a vacuum drying oven and dried at 90°C for 7 hours to obtain a polyethersulfone polymer grafted with phenyl cage-like silsesquioxane.

[0046] S2. Prepare polydopamine powder by dissolving dopamine in Tris-HCl buffer solution to prepare a 1.2 mg / mL dopamine solution. Stir the solution at room temperature for 14 h to allow dopamine to undergo a self-polymerization reaction to generate polydopamine.

[0047] After the reaction was complete, the reaction solution was transferred to a centrifuge tube and centrifuged at 8500 r / min for 16 min to collect the precipitated polydopamine particles. The polydopamine particles were washed repeatedly with deionized water four times to remove unreacted dopamine and impurities, and then placed in a vacuum drying oven and dried at 70℃ for 7 h to obtain polydopamine powder.

[0048] S3. Dissolve the polyethersulfone polymer from S1 in N,N-dimethylformamide to prepare a base casting solution with a concentration of 16wt%. Add the polydopamine powder prepared in S2 (the polydopamine powder accounts for 2wt% of the mass of the base casting solution). After dispersion, place the base casting solution with added polydopamine in a vacuum drying oven for degassing for 4 hours. Then, use a coating machine to uniformly coat the base casting solution with added polydopamine onto a glass plate. Quickly immerse the glass plate in a coagulation bath for phase separation and film formation. After film formation, peel the film off the glass plate and soak and wash it with deionized water for 24 hours to obtain a preliminarily modified polyethersulfone-based film.

[0049] S4. The polyethersulfone-based membrane initially modified in S3 was immersed in a silver nitrate solution with a concentration of 0.05 mol / L for 1.2 h, and then rinsed to obtain the intermediate membrane.

[0050] S5. BN nanosheets and MoS2 nanosheets are dispersed in an organic solvent to form a dispersion. The concentration of BN nanosheets in the dispersion is 0.5 mg / mL, and the concentration of MoS2 nanosheets in the dispersion is 0.4 mg / mL. The intermediate membrane from S4 is immersed in the dispersion for 15 min and dried at 45 °C for 1.5 h. This process is repeated twice to obtain a composite wastewater treatment membrane.

[0051] Example 3

[0052] This invention provides a composite wastewater treatment membrane with both high antifouling and antibacterial properties, which is prepared by the following method, including the following steps:

[0053] S1. Polyethersulfone was dissolved in N,N-dimethylformamide to prepare a polyethersulfone solution with a concentration of 13wt%. A phenyl cage-type silsesquioxane with a molar ratio of 1:30 to polyethersulfone and a catalyst with a mass fraction of 1.1% dibutyltin dilaurate were added. The mixture was stirred at 140°C for 7 hours under nitrogen protection to allow the phenyl cage-type silsesquioxane to undergo a grafting reaction with the polyethersulfone molecular chain.

[0054] After the reaction was complete, the reaction solution was cooled to room temperature, and excess methanol (volume ratio of precipitant to organic solvent was 4.5:1) was added to precipitate the grafted product. The precipitate was collected by filtration, washed repeatedly with methanol four times to remove unreacted phenyl cage-like silsesquioxane and catalyst, and then placed in a vacuum drying oven and dried at 95°C for 6.5 h to obtain a polyethersulfone polymer grafted with phenyl cage-like silsesquioxane.

[0055] S2. Prepare polydopamine powder by dissolving dopamine in Tris-HCl buffer solution to prepare a 1.5 mg / mL dopamine solution and stirring at room temperature for 18 h to allow dopamine to undergo a self-polymerization reaction to generate polydopamine.

[0056] After the reaction was complete, the reaction solution was transferred to a centrifuge tube and centrifuged at 9000 r / min for 18 min to collect the precipitated polydopamine particles. The polydopamine particles were washed repeatedly with deionized water four times to remove unreacted dopamine and impurities, and then placed in a vacuum drying oven and dried at 75℃ for 7 h to obtain polydopamine powder.

[0057] S3. Dissolve the polyethersulfone polymer of S1 in N,N-dimethylformamide to prepare a basic casting solution with a concentration of 18wt%. Add the polydopamine powder prepared in S2 (the polydopamine powder accounts for 3wt% of the mass of the basic casting solution). After dispersion, place the basic casting solution with added polydopamine in a vacuum drying oven for degassing for 4 hours. Then, use a coating machine to uniformly coat the basic casting solution with added polydopamine onto a glass plate. Quickly immerse the glass plate in a coagulation bath to perform phase separation and film formation. After film formation, peel the film off the glass plate and soak and wash it with deionized water for 24 hours to obtain a preliminarily modified polyethersulfone-based film.

[0058] S4. The polyethersulfone-based membrane initially modified in S3 was immersed in a silver nitrate solution with a concentration of 0.05 mol / L for 1.5 h, and then rinsed to obtain the intermediate membrane.

[0059] S5. BN nanosheets and MoS2 nanosheets were dispersed in an organic solvent to form a dispersion. The concentration of BN nanosheets in the dispersion was 0.7 mg / mL, and the concentration of MoS2 nanosheets in the dispersion was 0.6 mg / mL. The intermediate membrane from S4 was immersed in the dispersion for 20 min and dried at 50 °C for 2 h. This process was repeated twice to obtain a composite wastewater treatment membrane.

[0060] Example 4

[0061] This invention provides a composite wastewater treatment membrane with both high antifouling and antibacterial properties, which is prepared by the following method, including the following steps:

[0062] S1. Polyethersulfone was dissolved in N,N-dimethylformamide to prepare a polyethersulfone solution with a concentration of 14 wt%. A phenyl cage-type silsesquioxane with a molar ratio of 1:40 to polyethersulfone and a catalyst of 1.5% by mass were added. The mixture was stirred at 145°C for 7 h under nitrogen protection to allow the phenyl cage-type silsesquioxane to undergo a grafting reaction with the polyethersulfone molecular chain.

[0063] After the reaction was complete, the reaction solution was cooled to room temperature, and excess methanol (volume ratio of precipitant to organic solvent was 4:1) was added to precipitate the grafted product. The precipitate was collected by filtration, washed repeatedly with methanol four times to remove unreacted phenyl cage-like silsesquioxane and catalyst, and then placed in a vacuum drying oven and dried at 85°C for 7 hours to obtain a polyethersulfone polymer grafted with phenyl cage-like silsesquioxane.

[0064] S2. Prepare polydopamine powder by dissolving dopamine in Tris-HCl buffer solution to prepare a 1.8 mg / mL dopamine solution and stirring at room temperature for 20 h to allow dopamine to undergo a self-polymerization reaction to generate polydopamine.

[0065] After the reaction was complete, the reaction solution was transferred to a centrifuge tube and centrifuged at 9500 r / min for 20 min to collect the precipitated polydopamine particles. The polydopamine particles were washed repeatedly with deionized water 5 times to remove unreacted dopamine and impurities, and then placed in a vacuum drying oven and dried at 70℃ for 8 h to obtain polydopamine powder.

[0066] S3. Dissolve the polyethersulfone polymer from S1 in N,N-dimethylformamide to prepare a base casting solution with a concentration of 19wt%. Add the polydopamine powder prepared in S2 (the polydopamine powder accounts for 4wt% of the mass of the base casting solution). After dispersion, place the base casting solution with added polydopamine in a vacuum drying oven for degassing for 5 hours. Then, use a coating machine to uniformly coat the base casting solution with added polydopamine onto a glass plate. Quickly immerse the glass plate in a coagulation bath for phase separation and film formation. After film formation, peel the film off the glass plate and soak and wash it with deionized water for 24 hours to obtain a preliminarily modified polyethersulfone-based film.

[0067] S4. The polyethersulfone-based membrane modified in S3 was immersed in a silver nitrate solution with a concentration of 0.08 mol / L for 2 hours, and then rinsed to obtain the intermediate membrane.

[0068] S5. BN nanosheets and MoS2 nanosheets were dispersed in an organic solvent to form a dispersion. The concentration of BN nanosheets in the dispersion was 0.9 mg / mL, and the concentration of MoS2 nanosheets in the dispersion was 0.8 mg / mL. The intermediate membrane from S4 was immersed in the dispersion for 25 min and dried at 55 °C for 2 h. This process was repeated twice to obtain a composite wastewater treatment membrane.

[0069] Example 5

[0070] This invention provides a composite wastewater treatment membrane with both high antifouling and antibacterial properties, which is prepared by the following method, including the following steps:

[0071] S1. Polyethersulfone is dissolved in N,N-dimethylformamide to prepare a polyethersulfone solution with a concentration of 15wt%. A phenyl cage-type silsesquioxane with a molar ratio of 1:50 to polyethersulfone and a catalyst of 2% by mass, dibutyltin dilaurate, are added. The mixture is stirred at 150°C for 8 hours under nitrogen protection to allow the phenyl cage-type silsesquioxane to undergo a grafting reaction with the polyethersulfone molecular chain.

[0072] After the reaction was complete, the reaction solution was cooled to room temperature, and excess methanol (volume ratio of precipitant to organic solvent was 5:1) was added to precipitate the grafted product. The precipitate was collected by filtration, washed repeatedly with methanol five times to remove unreacted phenyl cage-like silsesquioxane and catalyst, and then placed in a vacuum drying oven and dried at 100°C for 8 hours to obtain a polyethersulfone polymer grafted with phenyl cage-like silsesquioxane.

[0073] S2. Prepare polydopamine powder by dissolving dopamine in Tris-HCl buffer solution to prepare a 2 mg / mL dopamine solution. Stir the solution at room temperature for 24 h to allow dopamine to undergo a self-polymerization reaction to generate polydopamine.

[0074] After the reaction was complete, the reaction solution was transferred to a centrifuge tube and centrifuged at 10,000 rpm for 20 minutes to collect the precipitated polydopamine particles. The polydopamine particles were washed repeatedly with deionized water five times to remove unreacted dopamine and impurities, and then placed in a vacuum drying oven and dried at 80°C for 8 hours to obtain polydopamine powder.

[0075] S3. Dissolve the polyethersulfone polymer from S1 in N,N-dimethylformamide to prepare a base casting solution with a concentration of 20wt%. Add the polydopamine powder prepared in S2 (the polydopamine powder accounts for 5wt% of the mass of the base casting solution). After dispersion, place the base casting solution with added polydopamine in a vacuum drying oven for degassing for 5 hours. Then, use a coating machine to uniformly coat the base casting solution with added polydopamine onto a glass plate. Quickly immerse the glass plate in a coagulation bath for phase separation and film formation. After film formation, peel the film off the glass plate and soak and wash it with deionized water for 24 hours to obtain a preliminarily modified polyethersulfone-based film.

[0076] S4. The polyethersulfone-based membrane modified in S3 was immersed in a silver nitrate solution with a concentration of 0.1 mol / L for 2 hours, and then rinsed to obtain the intermediate membrane.

[0077] S5. BN nanosheets and MoS2 nanosheets are dispersed in an organic solvent to form a dispersion. The concentration of BN nanosheets in the dispersion is 1 mg / mL, and the concentration of MoS2 nanosheets in the dispersion is 1 mg / mL. The intermediate membrane from S4 is immersed in the dispersion for 30 min and dried at 60 °C for 2 h. This process is repeated twice to obtain a composite wastewater treatment membrane.

[0078] Comparative Example 1

[0079] Based on Example 2, the difference from Example 2 is that the grafted phenyl cage-type silsesquioxane in step S1 was not performed, and polyethersulfone was used directly; otherwise, it was the same as Example 2.

[0080] Comparative Example 2

[0081] Based on Example 2, the difference from Example 2 is that step S2 was not performed, and polydopamine powder was not added during the casting process in step S3. All other aspects are the same as in Example 2.

[0082] Comparative Example 3

[0083] Based on Example 2, the difference from Example 2 is that step S4 was not performed, but everything else is the same as Example 2.

[0084] Comparative Example 4

[0085] Based on Example 2, the difference from Example 2 is that only BN nanosheets are added in step S5, and MoS2 nanosheets are not added. All other aspects are the same as in Example 2.

[0086] Comparative Example 5

[0087] Based on Example 2, the difference from Example 2 is that only MoS2 nanosheets are added in step S5, and BN nanosheets are not added. All other aspects are the same as in Example 2.

[0088] Comparative Example 6

[0089] Unmodified polyethersulfone ultrafiltration membranes purchased from the market were used as wastewater treatment membranes.

[0090] Performance testing

[0091] Contact angle and pure water flux test

[0092] Contact angle: The deionized water droplet (5 μL) was dropped onto the membrane surface using the seat drop method, and the contact angle was measured at 25°C using a contact angle meter. The average value of 5 different positions was taken for each sample.

[0093] Pure water flux: Under operating pressure of 0.1 MPa and temperature of 25°C, the membrane was installed in the membrane filtration device, and the volume of water permeated within 60 minutes was measured. The flux was calculated using the formula (flux = volume / (membrane area × time × pressure)). The results are shown in Table 1.

[0094] Table 1. Contact angle and pure water flux of different wastewater treatment membranes

[0095] Contact angle (°) <![CDATA[Pure water flux (L / m 2 ·h·MPa)]]> Example 1 46.2 245 Example 2 45.6 263 Example 3 42.3 287 Example 4 43.1 279 Example 5 44.7 268 Comparative Example 1 72.5 186 Comparative Example 2 65.2 201 Comparative Example 3 47.8 231 Comparative Example 4 48.7 224 Comparative Example 5 48.1 229 Comparative Example 6 78.3 165

[0096] As shown in Table 1, the contact angles of the wastewater treatment membranes prepared in Examples 1-5 of this invention are significantly lower than those in Comparative Examples 1-6, indicating that the hydrophilicity of the composite membranes prepared by the method of this invention is significantly improved. Among them, Example 3 has the lowest contact angle (42.3°) and the best hydrophilicity. This is because the synergistic effect of phenyl cage-type silsesquioxane, polydopamine, and BN / MoS2 nanosheets effectively improves the wettability of the membrane surface.

[0097] The wastewater treatment membranes prepared in Examples 1-5 of this invention exhibit significantly higher pure water flux than those in Comparative Examples 1-6, indicating that the multi-step modification of this invention did not clog the membrane pores; instead, it improved water transport efficiency by optimizing the membrane structure. Example 3 showed the highest pure water flux, demonstrating that the proportions of each component achieved optimal synergistic effects under these conditions.

[0098] Antifouling performance test (BSA solution filtration)

[0099] Prepare a 1 g / L bovine serum albumin (BSA) solution (pH = 7.0), filter it at 0.1 MPa pressure for 2 h, and record the initial flux (J0) and the flux after 2 h (J1). The flux decay rate is calculated as (J0 - J1) / J0 × 100%.

[0100] The membrane was backwashed with deionized water for 30 min, and the flux after recovery (J2) was measured. The recovery rate was calculated as J2 / J0 × 100%. The results are shown in Table 2.

[0101] Table 2. Antifouling performance of different wastewater treatment membranes

[0102]

[0103]

[0104] As shown in Table 2, the flux decay rate of the wastewater treatment membranes prepared in Examples 1-5 of this invention is significantly lower than that in Comparative Examples 1-6, and the recovery rate after cleaning is also higher, indicating that the composite membranes of this invention have excellent antifouling capabilities. Among them, Example 3 has the lowest flux decay rate and the highest recovery rate, indicating that the phenyl cage-type silsesquioxane grafting, the introduction of polydopamine, and the BN / MoS2 composite layer work together to reduce pollutant adsorption and enhance the membrane's washability.

[0105] Comparing Comparative Example 1 (without grafted phenyl cage silsesquioxane) and Example 2, the flux decay rate decreased from 45.2% to 22.3%, demonstrating that grafting phenyl cage silsesquioxane can effectively suppress fouling; the recovery rate of Comparative Example 2 (without polydopamine) (78.4%) was lower than that of Example 2 (91.5%), indicating that the adhesion of polydopamine improved the fouling resistance of the membrane.

[0106] Plate count was used to analyze the bacterial suspensions of Escherichia coli and Staphylococcus aureus (10⁻⁶ oz). 6 The CFU / mL samples were contacted with the membrane samples for 24 hours, diluted, and then spread onto nutrient agar plates. The samples were incubated at 37°C for 24 hours, and the colony counts were performed.

[0107] Antibacterial rate = (number of colonies in control group - number of colonies in experimental group) / number of colonies in control group × 100% (control group is bacterial solution that has not been in contact with the membrane). The results are shown in Table 3.

[0108] Table 3 Antibacterial properties of different wastewater treatment membranes

[0109]

[0110]

[0111] As shown in Table 3, the wastewater treatment membranes prepared in Examples 1-5 of this invention all achieved an antibacterial rate of over 94% against Escherichia coli and Staphylococcus aureus. Among them, Example 4 showed the highest antibacterial rate, indicating that silver ions and MoS2 nanosheets produced a significant synergistic antibacterial effect, which can effectively kill microorganisms in wastewater.

[0112] Comparative Example 3 (without silver nitrate treatment) showed an antibacterial rate of only about 30%, proving that silver ions are the core source of antibacterial performance. Comparative Examples 4-5 (single nanosheets) showed lower antibacterial rates than Example 2, indicating that the combined use of BN and MoS2 can enhance the antibacterial effect, and that the two have a synergistic effect. Comparative Example 6 (commercial membrane) showed an antibacterial rate of less than 30%, highlighting the breakthrough advantage of the composite membrane of this invention in antibacterial performance.

[0113] Long-term stability test

[0114] Continuous filtration of simulated wastewater (containing 0.5 g / L LBSA + 10 g / L) 5 (CFU / mL mixed bacteria) for 100h, record the initial flux and the flux after 100h, and the flux decrease rate = (initial flux - 100h flux) / initial flux × 100%.

[0115] The content of Si, Ag, B, and Mo elements in the filtrate was detected by ICP-MS, and the antifouling layer peeling rate was calculated as (dissolution amount / initial loading amount) × 100%. The results are shown in Table 4.

[0116] Table 4. Long-term operational stability of different wastewater treatment membranes

[0117] Flux decline rate (%) Anti-fouling layer peeling rate (%) Example 1 16.8 3.8 Example 2 14.7 3.1 Example 3 12.4 2.3 Example 4 13.5 2.7 Example 5 15.2 3.3 Comparative Example 1 35.6 12.7 Comparative Example 2 31.2 10.5 Comparative Example 3 28.7 9.2 Comparative Example 4 25.4 7.8 Comparative Example 5 26.3 8.1 Comparative Example 6 42.8 15.6

[0118] As shown in Table 4, the flux decline rate and antifouling layer shedding rate of the wastewater treatment membranes prepared in Examples 1-5 of this invention are much lower than those in the comparative examples, indicating that the composite membranes have excellent long-term operational stability. Example 1 has the lowest flux decline rate and the smallest shedding rate, indicating that the components form a stable structure through chemical bonding and physical deposition, effectively resisting scouring and leaching during long-term filtration.

[0119] The shedding rate of Comparative Example 1 (without grafted phenyl cage silsesquioxane) was significantly higher than that of Example 2, proving that the grafting of phenyl cage silsesquioxane enhanced the structural stability of the membrane; the flux reduction rate of Comparative Example 2 (without polydopamine) was higher than that of Example 2, indicating that polydopamine can strengthen the bonding force between layers and reduce coating shedding.

[0120] Therefore, this invention employs the aforementioned composite wastewater treatment membrane and preparation method that combines high antifouling and antibacterial properties. Through multi-step synergistic modification involving phenyl cage-type silsesquioxane grafting, polydopamine doping, silver ion loading, and BN / MoS2 composite modification, a composite wastewater treatment membrane with high hydrophilicity, high antifouling, strong antibacterial properties, and long-term stability is successfully prepared. All performance characteristics are significantly superior to those of unmodified membranes and single-component modified membranes, fully demonstrating the synergistic effect of each technical feature.

[0121] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a composite wastewater treatment membrane with both high antifouling and antibacterial properties, characterized in that, Includes the following steps: S1. Dissolve polyethersulfone in an organic solvent to prepare a polyethersulfone solution, add phenyl cage-type silsesquioxane and catalyst, stir and react at 120-150℃ for 6-8 hours under nitrogen protection, add excess precipitant to precipitate the grafted product, filter, collect, wash and dry the precipitate to obtain the polyethersulfone polymer grafted with phenyl cage-type silsesquioxane. The molar ratio of phenyl cage-type silsesquioxane to polyethersulfone is 1:10-1:50, the mass fraction of the catalyst is 0.5%-2%, the catalyst includes one of dibutyltin dilaurate, stannous octoate, bismuth neodecanoate, and zinc diacetylacetonate, the precipitant is methanol, and the volume ratio of precipitant to organic solvent is 3:1-5:

1. S2. Preparation of polydopamine powder; S3. Dissolve the polyethersulfone polymer of S1 in N,N-dimethylformamide to prepare a basic casting solution, add the polydopamine powder prepared in S2, disperse and cast to obtain a preliminarily modified polyethersulfone-based film. The casting process involves placing a base casting solution containing polydopamine powder in a vacuum drying oven for degassing for 3-5 hours, then using a coating machine to uniformly coat the base casting solution containing polydopamine powder onto a glass plate, and quickly immersing the glass plate in a coagulation bath for phase separation and film formation. After film formation, the film is peeled off from the glass plate and soaked and washed with deionized water for 24 hours to obtain a preliminarily modified polyethersulfone-based film. S4. Immerse the polyethersulfone-based membrane that was initially modified in S3 in silver nitrate solution for 1-2 hours, and then rinse to obtain the intermediate membrane; S5. Disperse BN nanosheets and MoS2 nanosheets in an organic solvent to form a dispersion. Immerse the intermediate membrane from S4 in the dispersion for 10-30 min and dry it at 40-60℃ for 1-2 h. Repeat this process 1-2 times to obtain a composite wastewater treatment membrane.

2. The method for preparing a composite wastewater treatment membrane with both high antifouling and antibacterial properties according to claim 1, characterized in that: In S1, the organic solvent includes one of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone, and the concentration of the polyethersulfone solution is 10-15 wt%.

3. The method for preparing a composite wastewater treatment membrane with both high antifouling and antibacterial properties according to claim 1, characterized in that: In S1, washing is performed 3-5 times with methanol, and drying is performed in a vacuum drying oven at a temperature of 80-100℃ for 6-8 hours.

4. The method for preparing a composite wastewater treatment membrane with both high antifouling and antibacterial properties according to claim 1, characterized in that: In S2, dopamine is dissolved in Tris-HCl buffer solution to prepare a 1-2 mg / mL dopamine solution. The solution is stirred and reacted at room temperature for 12-24 h to allow dopamine to undergo a self-polymerization reaction to generate polydopamine. After centrifugation, washing, and drying, polydopamine powder is obtained.

5. The method for preparing a composite wastewater treatment membrane with both high antifouling and antibacterial properties according to claim 1, characterized in that: In S3, the concentration of the base casting solution is 15-20 wt%, and the amount of polydopamine powder accounts for 1-5 wt% of the mass of the base casting solution.

6. The method for preparing a composite wastewater treatment membrane with both high antifouling and antibacterial properties according to claim 1, characterized in that: In S4, the concentration of silver nitrate solution is 0.01-0.1 mol / L.

7. The method for preparing a composite wastewater treatment membrane with both high antifouling and antibacterial properties according to claim 1, characterized in that: In S5, the organic solvent includes one of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone. The concentration of BN nanosheets in the dispersion is 0.3-1 mg / mL, and the concentration of MoS2 nanosheets in the dispersion is 0.2-1 mg / mL.

8. A composite wastewater treatment membrane possessing both high antifouling and antibacterial properties, characterized in that: The composite wastewater treatment membrane with high anti-fouling and antibacterial properties is prepared by the method described in any one of claims 1-7.

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