A method for preparing a highly antifouling polyvinylidene fluoride membrane
By constructing a PDA coating on the surface of a PVDF membrane and loading LDH nanomaterials, a PDA/LDHs composite modified structure is formed, which solves the problem of easy fouling of PVDF membranes and improves the membrane's high hydrophilicity and long-term antifouling performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- FUJIAN UNIV OF TECH
- Filing Date
- 2026-04-01
- Publication Date
- 2026-05-26
AI Technical Summary
The hydrophobicity of PVDF membrane surfaces makes them prone to fouling, and existing modification methods are insufficient to consistently improve their antifouling performance over the long term.
A PDA coating was constructed on the surface of a PVDF membrane and loaded with LDH nanomaterials to form a PDA/LDHs composite modified structure, combining the strong adhesion of PDA with the high hydrophilicity and high specific surface area of LDHs.
It significantly improves the hydrophilicity and antifouling properties of the membrane, has good stability of the modified layer, increases water flux, enhances flux recovery rate, and avoids the aggregation and shedding of LDH nanomaterials.
Smart Images
Figure CN122076241A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of membrane separation technology, specifically relating to a method for preparing a highly antifouling polyvinylidene fluoride membrane. Background Technology
[0002] In recent years, with the continuous increase in industrial wastewater discharge and the increasingly severe water shortage problem, membrane separation technology has been widely used in water treatment, industrial separation, and environmental remediation due to its advantages such as simple operation, low energy consumption, and high separation efficiency. Polyvinylidene fluoride (PVDF) membranes, with their excellent chemical stability, solvent resistance, and mechanical properties, have become one of the most widely used polymer membrane materials in the ultrafiltration field. However, the inherent hydrophobicity of the PVDF membrane surface makes it prone to adsorbing organic pollutants, proteins, and microorganisms during practical applications, leading to rapid membrane fouling. This manifests as a significant decrease in water flux, reduced separation efficiency, and shortened membrane lifespan. Therefore, improving the surface hydrophilicity and antifouling properties of PVDF membranes has become a key research focus in the field of membrane separation.
[0003] Currently, modification methods for PVDF membranes mainly include blending modification, surface coating modification, and chemical grafting modification. Among these, surface coating modification is widely used due to its simplicity and minimal impact on the membrane substrate structure. Polydopamine (PDA), as a biomimetic material, can self-polymerize and deposit on the surfaces of various materials under mild conditions to form stable coatings and significantly improve the hydrophilicity and antifouling properties of the membrane surface. However, single PDA coatings are prone to structural aging and degradation of antifouling performance during long-term operation. Layered bimetallic hydroxides (LDHs) are a class of inorganic nanomaterials with layered structures and abundant surface functional groups, possessing high specific surface area and excellent hydrophilicity, and have been used for the adsorption and removal of pollutants in water treatment. However, when LDH nanomaterials are directly loaded onto the membrane surface, they are prone to aggregation and detachment, making it difficult to form a stable structure. Therefore, how to combine the strong adhesion of PDA with the high hydrophilicity and high specific surface area of LDHs to construct a stable and efficient composite modification system and achieve long-term stable improvement of the antifouling performance of PVDF membranes is an important problem that urgently needs to be solved. Summary of the Invention
[0004] The purpose of this invention is to provide a simple, structurally stable, and long-term operating method for preparing a highly antifouling polyvinylidene fluoride (PVDF) membrane. By constructing a PDA coating on the PVDF membrane surface and loading LDH nanomaterials, a PDA / LDHs synergistic composite modified structure is formed, which significantly improves the membrane's hydrophilicity and antifouling performance while ensuring the stability and reusability of the modified layer.
[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0006] A method for preparing a highly antifouling polyvinylidene fluoride membrane includes the following steps:
[0007] 1) Preparation of PVDF ultrafiltration membranes using phase inversion method
[0008] 1-1) After drying montmorillonite, pass it through a 90-110 mesh sieve, collect the undersize material and transfer it to a muffle furnace, calcine it at 400-500℃ for 5-7 hours, and cool it for later use; add the calcined montmorillonite (MMT), water and polyacrylic acid (PAA) to an Erlenmeyer flask, stir well to obtain a mixture, dry it, grind it and sieve it through a 90-110 mesh sieve to obtain the MMT-PAA mixture;
[0009] 1-2) Place PVDF powder, polyvinylpyrrolidone, MMT-PAA mixture and N,N-dimethylformamide in a flask and mechanically stir at 55-65℃ for 11-13 h to obtain casting solution;
[0010] 1-3) After removing air bubbles from the casting solution, pour it onto a clean glass plate. Use a scraper to scrape a 100-250 μm thick film of the casting solution onto the glass plate. First, pre-evaporate it in the air for 14-16 s, then immerse it in water to undergo phase inversion and form a film. Then, take it out, wash off the solvent with water, and dry it to obtain a PVDF ultrafiltration membrane.
[0011] 2) Preparation of PDA@PVDF composite membrane
[0012] After ultrasonic cleaning, the PVDF ultrafiltration membrane was pre-wetted with ethanol and then immersed in a sodium dopamine acetate buffer solution containing sodium periodate as an oxidant. The reaction was carried out at room temperature for 1-2 hours to allow dopamine to self-polymerize and deposit on the membrane surface, forming a uniform and stable PDA coating. The obtained modified membrane was then cleaned and dried to obtain a PDA@PVDF composite membrane.
[0013] 3) Preparation of ZnAl-LDHs / PDA@PVDF composite membrane
[0014] Zn(NO3)2‧6H2O, Al(NO3)3‧9H2O and urea were dissolved in water and stirred until homogeneous to obtain an LDHs solution. The LDHs solution was transferred to a polytetrafluoroethylene-lined stainless steel autoclave with a PDA@PVDF composite membrane. The autoclave was heated to 100-120 ℃ and reacted for 3-12 h to uniformly load LDHs nanoparticles onto the PDA coating surface. The obtained composite membrane was then rinsed and dried to obtain a ZnAl-LDHs / PDA@PVDF high-fouling-resistant composite membrane.
[0015] In step 1-1), the mass of water in the mixture is 10-20 times the mass of montmorillonite, and the mass of polyacrylic acid is 10-50% of the mass of montmorillonite.
[0016] In step 1-1), the montmorillonite is dried at 100-110℃ for 1.8-2.2h before calcination, and then sieved after cooling; the mixture is dried at 100-110℃ for 3.5-4.5h before grinding.
[0017] In steps 1-2), the PVDF powder, polyvinylpyrrolidone, MMT-PAA mixture and N,N-dimethylformamide account for 15-20 wt%, 2-5 wt%, 0.5-2 wt% and 70-80 wt% of the total mass of the casting solution, respectively.
[0018] In steps 1-3), the casting solution is degassed by the following method: the flask containing the casting solution is placed in a vacuum dryer, the vacuum degree is maintained at 0.1 MPa, and it is left to stand for 12-14 h.
[0019] In step 2), the ultrasonic cleaning involves cleaning the PVDF ultrafiltration membrane with ethanol and water under ultrasonic conditions for 10-15 minutes respectively.
[0020] In step 2), the dopamine sodium acetate buffer solution is prepared using a sodium acetate solution with a concentration of 50 mmol / L and pH=5.0. The concentration of dopamine in the dopamine sodium acetate buffer solution is 1-2 mg / mL, and the concentration of sodium periodate in the dopamine sodium acetate buffer solution is 2-4 mg / mL.
[0021] During the reaction in step 2), the container was shaken at 140-160 rpm and covered with aluminum foil at a constant temperature of 25 ℃ to prevent light interference. The obtained modified film was dried in an oven at 40-45 ℃ for 8-12 h.
[0022] In step 3), the ratio of Zn(NO3)2‧6H2O, Al(NO3)3‧9H2O, urea and water in the LDHs solution is 1-3 mmol: 0.5-1.5 mmol: 5-10 mmol: 30-60 mL.
[0023] In step 3), the composite membrane is rinsed with ethanol and water, and then dried in an oven at 40°C.
[0024] This invention employs the above technical solution to obtain a ZnAl-LDHs / PDA@PVDF high-fouling-resistant composite membrane by constructing a PDA coating on the surface of a PVDF membrane and loading LDHs nanomaterials. This invention has the following beneficial effects.
[0025] 1. This invention addresses the problems of high hydrophobicity and susceptibility to organic and biological contamination of traditional PVDF membranes by introducing a PDA coating to hydrophilize the membrane surface, thereby solving the problems of low water flux and easy contamination of PVDF membranes.
[0026] 2. This invention further loads LDHs nanomaterials onto the PDA modified membrane, utilizing the high specific surface area and hydrophilic properties of LDHs to solve the problem that single modification methods are difficult to stably improve antifouling performance in the long term.
[0027] 3. This invention constructs a composite modified structure with synergistic effect of PDA / LDHs, which enables the modified material to be stably attached to the surface of PVDF membrane, significantly improving its antifouling performance and reusability while ensuring membrane separation performance.
[0028] Compared with existing single-modified PVDF membranes, the LDHs / PDA@PVDF composite membrane prepared in this invention has higher hydrophilicity and better antifouling performance, significantly reduced water contact angle, significantly increased water flux, and significantly enhanced flux recovery rate.
[0029] Compared with traditional inorganic material-supported composite membranes, this invention utilizes the strong adhesion of PDA to construct a stable intermediate layer, effectively avoiding the problems of LDH nanomaterial aggregation and shedding, making the modified layer structure more stable, and maintaining good membrane performance stability during long-term operation.
[0030] 4. This invention achieves functional modification of the membrane surface through a simple and mild chemical method. The process is simple and easy to scale up. Attached Figure Description
[0031] Figure 1 This is an electron micrograph of the surface morphology of the ZnAl-LDHs / PDA@PVDF composite film prepared in Example 1. Detailed Implementation
[0032] Example 1
[0033] A method for preparing a highly antifouling polyvinylidene fluoride membrane includes the following steps:
[0034] 1) Preparation of PVDF ultrafiltration membranes using phase inversion method
[0035] 1-1) After baking montmorillonite at 105℃ for 2 hours, remove it, cool it, and pass it through a 100-mesh sieve. Collect the sieve material and transfer it to a muffle furnace. Calcinate it at 450℃ for 6 hours and cool it for later use. Add the calcined montmorillonite (MMT) to an Erlenmeyer flask, then add 15 times the mass of montmorillonite in deionized water. Stir and mix evenly. Finally, add 30% of the mass of montmorillonite in polyacrylic acid (PPA) and continue stirring until a mud-like mixture is formed. Place it in an oven and dry it at 105℃ for 4 hours. After drying, grind it thoroughly and sieve it through a 100-mesh sieve to obtain the MMT-PAA mixture.
[0036] 1-2) PVDF powder, polyvinylpyrrolidone, MMT-PAA mixture, and N,N-dimethylformamide were placed in a 250 mL flask and mechanically stirred at 60 °C for 12 h to obtain a pale yellow, transparent, uniform casting solution; wherein, PVDF powder, polyvinylpyrrolidone, MMT-PAA mixture, and N,N-dimethylformamide accounted for 18 wt%, 3.5 wt%, 1.5 wt%, and 77 wt% of the total mass of the casting solution, respectively.
[0037] 1-3) Place the flask containing the casting solution in a vacuum desiccator, maintain a vacuum of 0.1 MPa, and let it stand for 12 h to fully remove air bubbles from the casting solution. Then pour the casting solution onto a clean glass plate and use a scraper to scrape out a 180 μm thick film of the casting solution onto the glass plate covered with non-woven fabric. First, pre-evaporate it in the air for 15 s, then immerse it in deionized water to undergo phase inversion and form a membrane. Then remove it, wash off the solvent with deionized water, and let it air dry to obtain a PVDF ultrafiltration membrane.
[0038] 2) Preparation of PDA@PVDF composite membrane
[0039] 2-1) The PVDF ultrafiltration membrane was first cleaned with ethanol and deionized water under ultrasonic conditions for 12 min each. After cleaning, the PVDF ultrafiltration membrane was pre-wetted with ethanol and then immersed in a 1.5 mg / mL dopamine acetate sodium buffer solution (50 mmol / L, pH=5.0) containing 3 mg / mL sodium periodate (NaIO4) as an oxidant. The reaction was carried out at room temperature for 1.5 h to allow dopamine to self-polymerize and deposit on the membrane surface, forming a uniform and stable PDA coating. During the reaction, the container was shaken at 150 rpm and covered with aluminum foil at a constant temperature of 25 ℃ to prevent light interference. After the oxidant-induced polymerization, the modified membrane was thoroughly cleaned with deionized water and dried in an oven at 40 ℃ for 10 h to obtain the PDA@PVDF composite membrane.
[0040] 3) Preparation of ZnAl-LDHs / PDA@PVDF composite membrane
[0041] 2 mmol of Zn(NO3)2‧6H2O, 1.0 mmol of Al(NO3)3‧9H2O, and 7.50 mmol of urea were dissolved in 45 mL of deionized water and stirred for 15 min to obtain an LDHs solution. The LDHs solution was transferred to a polytetrafluoroethylene-lined stainless steel autoclave with a PDA@PVDF composite membrane. The autoclave was heated to 105 °C and reacted for 8 h to uniformly load LDHs nanoparticles onto the PDA coating surface. The composite membrane was then rinsed several times with ethanol and deionized water and dried in an oven at 40 °C to obtain a ZnAl-LDHs / PDA@PVDF high-fouling-resistant composite membrane.
[0042] Example 2
[0043] A method for preparing a highly antifouling polyvinylidene fluoride membrane includes the following steps:
[0044] 1) Preparation of PVDF ultrafiltration membranes using phase inversion method
[0045] 1-1) After baking montmorillonite at 105℃ for 2 hours, remove it, cool it, and pass it through a 100-mesh sieve. Collect the sieve material and transfer it to a muffle furnace. Calcinate it at 500℃ for 5.5 hours and cool it for later use. Add the calcined montmorillonite (MMT) to an Erlenmeyer flask, then add 10 times the mass of montmorillonite in deionized water. Stir and mix evenly. Finally, add 10% of the mass of montmorillonite in polyacrylic acid (PPA) and continue stirring until it forms a mud-like mixture. Place it in an oven and dry it at 100℃ for 4.5 hours. After drying, grind it thoroughly and sieve it through a 100-mesh sieve to obtain the MMT-PAA mixture.
[0046] 1-2) PVDF powder, polyvinylpyrrolidone, MMT-PAA mixture, and N,N-dimethylformamide were placed in a 250 mL flask and mechanically stirred at 55 °C for 13 h to obtain a pale yellow, transparent, uniform casting solution; wherein, PVDF powder, polyvinylpyrrolidone, MMT-PAA mixture, and N,N-dimethylformamide accounted for 15 wt%, 5 wt%, 1 wt%, and 79 wt% of the total mass of the casting solution, respectively.
[0047] 1-3) Place the flask containing the casting solution in a vacuum desiccator, maintain a vacuum of 0.1 MPa, and let it stand for 14 h to fully remove air bubbles from the casting solution. Then pour the casting solution onto a clean glass plate and use a scraper to scrape a 100 μm thick film of the casting solution onto the glass plate covered with non-woven fabric. First, pre-evaporate it in the air for 14 s, then immerse it in deionized water to undergo phase inversion and form a membrane. Then take it out, wash the solvent with deionized water, and let it air dry to obtain a PVDF ultrafiltration membrane.
[0048] 2) Preparation of PDA@PVDF composite membrane
[0049] The PVDF ultrafiltration membrane was first cleaned with ethanol and deionized water under ultrasonic conditions for 10 min each. After cleaning, the PVDF ultrafiltration membrane was pre-wetted with ethanol and then immersed in a 1 mg / mL sodium dopamine acetate buffer solution (50 mmol / L, pH=5.0) containing 2 mg / mL sodium periodate (NaIO4) as an oxidant. The reaction was carried out at room temperature for 1 h to allow dopamine to self-polymerize and deposit on the membrane surface, forming a uniform and stable PDA coating. During the reaction, the container was shaken at 140 rpm and covered with aluminum foil at a constant temperature of 25 ℃ to prevent light interference. After the oxidant-induced polymerization, the modified membrane was thoroughly cleaned with deionized water and dried in an oven at 45 ℃ for 8 h to obtain the PDA@PVDF composite membrane.
[0050] 3) Preparation of ZnAl-LDHs / PDA@PVDF composite membrane
[0051] 1 mmol of Zn(NO3)2‧6H2O, 0.5 mmol of Al(NO3)3‧9H2O, and 5 mmol of urea were dissolved in 35 mL of deionized water and stirred for 10 min to obtain an LDHs solution. The LDHs solution was transferred to a polytetrafluoroethylene-lined stainless steel autoclave with a PDA@PVDF composite membrane. The autoclave was heated to 100 °C and reacted for 10 h to uniformly load LDHs nanoparticles onto the PDA coating surface. The composite membrane was then rinsed several times with ethanol and deionized water and dried in an oven at 40 °C to obtain the ZnAl-LDHs / PDA@PVDF high-fouling-resistant composite membrane.
[0052] Example 3
[0053] A method for preparing a highly antifouling polyvinylidene fluoride membrane includes the following steps:
[0054] 1) Preparation of PVDF ultrafiltration membranes using phase inversion method
[0055] 1-1) After baking montmorillonite at 100℃ for 12 hours, remove it, cool it, and pass it through a 100-mesh sieve. Collect the sieve material and transfer it to a muffle furnace. Calcinate it at 500℃ for 5 hours and cool it for later use. Add the calcined montmorillonite (MMT) to an Erlenmeyer flask, then add 20 times the mass of montmorillonite in deionized water. Stir and mix evenly. Finally, add 50% of the mass of montmorillonite in polyacrylic acid (PPA) and continue stirring until it becomes a mud-like mixture. Place it in an oven and dry it at 110℃ for 3.5 hours. After drying, grind it thoroughly and sieve it using a 90-110 mesh sieve to obtain the MMT-PAA mixture.
[0056] 1-2) PVDF powder, polyvinylpyrrolidone, MMT-PAA mixture, and N,N-dimethylformamide were placed in a 250 mL flask and mechanically stirred at 65 °C for 11 h to obtain a pale yellow, transparent, and uniform casting solution; wherein, PVDF powder, polyvinylpyrrolidone, MMT-PAA mixture, and N,N-dimethylformamide accounted for 20 wt%, 5 wt%, 2 wt%, and 73% of the total mass of the casting solution, respectively;
[0057] 1-3) Place the flask containing the casting solution in a vacuum desiccator, maintain a vacuum of 0.1 MPa, and let it stand for 13 h to fully remove air bubbles from the casting solution. Then pour the casting solution onto a clean glass plate and use a scraper to scrape a 250 μm thick film of the casting solution onto the glass plate covered with non-woven fabric. First, pre-evaporate it in the air for 16 s, then immerse it in deionized water to undergo phase inversion and form a membrane. Then take it out, wash the solvent with deionized water, and let it air dry to obtain a PVDF ultrafiltration membrane.
[0058] 2) Preparation of PDA@PVDF composite membrane
[0059] The PVDF ultrafiltration membrane was first cleaned with ethanol and deionized water under ultrasonic conditions for 15 min each. After cleaning, the PVDF ultrafiltration membrane was pre-wetted with ethanol and then immersed in a 2 mg / mL sodium dopamine acetate buffer solution (50 mmol / L, pH=5.0) containing 4 mg / mL sodium periodate (NaIO4) as an oxidant. The reaction was carried out at room temperature for 2 h to allow dopamine to self-polymerize and deposit on the membrane surface, forming a uniform and stable PDA coating. During the reaction, the container was shaken at 160 rpm and covered with aluminum foil at a constant temperature of 25 ℃ to prevent light interference. After the oxidant-induced polymerization, the modified membrane was thoroughly cleaned with deionized water and dried in an oven at 40 ℃ for 12 h to obtain the PDA@PVDF composite membrane.
[0060] 3) Preparation of ZnAl-LDHs / PDA@PVDF composite membrane
[0061] 3 mmol of Zn(NO3)2‧6H2O, 1.5 mmol of Al(NO3)3‧9H2O, and 10 mmol of urea were dissolved in 60 mL of deionized water and stirred for 20 min to obtain an LDHs solution. The LDHs solution was transferred to a polytetrafluoroethylene-lined stainless steel autoclave with a PDA@PVDF composite membrane. The autoclave was heated to 120 °C and reacted for 3 h to uniformly load LDHs nanoparticles onto the PDA coating surface. The composite membrane was then rinsed several times with ethanol and deionized water and dried in an oven at 40 °C to obtain the ZnAl-LDHs / PDA@PVDF high-fouling-resistant composite membrane.
[0062] Table 1 Performance of the high antifouling membranes prepared in Examples 1-3
[0063] Serial Number Antifouling membrane <![CDATA[Pure water flux (L·m –2 ·h –1 ), test pressure 0.1 MPa]]> Tensile strength (N) Contact angle (°) Bovine serum albumin retention rate (%) Water flux recovery rate (%) 1 PVDF ultrafiltration membrane 2000-2500 400-420 45-50 90-97 93-98 2 PDA@PVDF composite membrane 1000-1500 410-425 36-42 92-98 94-99 3 ZnAl-LDHs / PDA@PVDF composite membrane 500-800 415-430 25-35 95-99 95-99
[0064] Compared with single modified PVDF ultrafiltration membranes, the ZnAl-LDHs / PDA@PVDF composite membrane prepared in this invention has higher hydrophilicity and better antifouling performance, significantly reduced water contact angle, significantly increased water flux, and significantly enhanced flux recovery rate.
Claims
1. A method for preparing a highly stain-resistant polyvinylidene fluoride film, characterized by, The method comprises the following steps: 1) preparing a PVDF ultrafiltration membrane by a phase inversion method 1-1) drying the montmorillonite, then passing it through a 90-110 mesh sieve, collecting the undersize and transferring it to a muffle furnace, calcining at 400-500℃ for 5-7h, then adding the calcined montmorillonite, water and polyacrylic acid into a conical flask, stirring to obtain a mixture, drying, grinding and sieving with a 90-110 mesh sieve to obtain an MMT-PAA mixture; 1-2) placing PVDF powder, polyvinylpyrrolidone, the MMT-PAA mixture and N,N-dimethylformamide into a flask, mechanically stirring at 55-65℃ for 11-13h to obtain a casting solution; 1-3) after removing bubbles from the casting solution, pouring it onto a clean glass plate, using a doctor blade to scrape a 100-250μm thick casting solution film on the glass plate, pre-evaporating in air for 14-16s, then immersing it in water to undergo phase inversion to form a membrane, taking it out, washing it with water to remove the solvent, and air-drying to obtain a PVDF ultrafiltration membrane; 2) preparing a PDA@PVDF composite membrane ultrasonically cleaning the PVDF ultrafiltration membrane, then pre-wetting it with ethanol, then immersing it in a dopamine sodium acetate buffer solution containing sodium periodate as an oxidizing agent, reacting at room temperature for 1-2h to allow dopamine to self-polymerize and deposit on the membrane surface to form a uniform and stable PDA coating, then washing and drying the obtained modified membrane to obtain a PDA@PVDF composite membrane; 3) preparing a ZnAl-LDHs / PDA@PVDF composite membrane dissolving Zn(NO3)2‧6H2O, Al(NO3)3‧9H2O and urea in water, stirring to obtain an LDHs solution, transferring the LDHs solution into a polytetrafluoroethylene-lined stainless steel high-pressure kettle with the PDA@PVDF composite membrane, heating the reaction kettle to 100-120℃, and reacting for 3-12h to allow LDHs nanoparticles to be uniformly loaded on the surface of the PDA coating, then rinsing and drying the obtained composite membrane to obtain a ZnAl-LDHs / PDA@PVDF high-anti-pollution composite membrane.
2. The method for preparing a highly antifouling polyvinylidene fluoride membrane according to claim 1, characterized in that, In step 1-1), in the mixture, the mass of water is 10-20 times the mass of the montmorillonite, and the mass of the polyacrylic acid is 10-50% of the mass of the montmorillonite.
3. The method of claim 1, wherein the polyvinylidene fluoride membrane has a contact angle of 90° or more. In step 1-1), the montmorillonite is dried at 100-110℃ for 1.8-2.2h before calcination, and then sieved after cooling; the mixture is dried at 100-110℃ for 3.5-4.5h before grinding.
4. The method of claim 1, wherein the polyvinylidene fluoride membrane has a contact angle of 90° or more. In step 1-2), the PVDF powder, polyvinylpyrrolidone, MMT-PAA mixture and N,N-dimethylformamide account for 15-20wt%, 2-5wt%, 0.5-2wt% and 70-80wt% of the total mass of the casting solution, respectively.
5. The method of claim 1, wherein the polyvinylidene fluoride membrane has a contact angle of 90° or more. In step 1-3), the casting solution is degassed by placing the flask containing the casting solution in a vacuum dryer, maintaining a vacuum degree of 0.1MPa, and standing for 12-14h.
6. The method of claim 1, wherein the polyvinylidene fluoride membrane has a high pollution resistance. In step 2), the ultrasonic cleaning involves cleaning the PVDF ultrafiltration membrane with ethanol and water under ultrasonic conditions for 10-15 minutes respectively.
7. The method for preparing a highly antifouling polyvinylidene fluoride membrane according to claim 1, characterized in that, In step 2), the dopamine sodium acetate buffer solution is prepared using a sodium acetate solution with a concentration of 50 mmol / L and pH=5.
0. The concentration of dopamine in the dopamine sodium acetate buffer solution is 1-2 mg / mL, and the concentration of sodium periodate in the dopamine sodium acetate buffer solution is 2-4 mg / mL.
8. The method of claim 1, wherein the polyvinylidene fluoride membrane has a high pollution resistance. During the reaction in step 2), the container was shaken at 140-160 rpm and covered with aluminum foil at a constant temperature of 25 ℃ to prevent light interference. The obtained modified film was dried in an oven at 40-45 ℃ for 8-12 h.
9. The method of claim 1, wherein the polyvinylidene fluoride membrane has a high pollution resistance. In step 3), the ratio of Zn(NO3)2‧6H2O, Al(NO3)3‧9H2O, urea and water in the LDHs solution is 1-3 mmol: 0.5-1.5 mmol: 5-10 mmol: 30-60 mL.
10. The method of claim 1, wherein the polyvinylidene fluoride membrane has a high pollution resistance. In step 3), the composite membrane is rinsed with ethanol and water, and then dried in an oven at 40°C.