A multifunctional adsorption membrane based on modified PVDF and its preparation method and application

Abstract

The present invention discloses a multifunctional adsorption membrane based on modified PVDF, and a preparation method and application thereof, and relates to the technical field of polymer modified materials. The multifunctional adsorption membrane is based on polyvinylidene fluoride, and by introducing functional materials such as zeolite powder, modifiers and polyethylene glycol, the hydrophilicity, anti-pollution ability and removal efficiency of heavy metal ion residues of the membrane are significantly improved. Specifically, the preparation of the modifier adopts the composite of β-cyclodextrin and polyvinyl alcohol, and introduces 3-aminopropyltriethoxysilane to ensure that the modification effect is durable and stable. The preparation method of the present invention includes the steps of raw material preparation, solution preparation, phase transformation membrane formation and post-treatment, which can effectively control the thickness and pore size distribution of the membrane, thereby optimizing its performance. Experimental results show that the application of the modified PVDF membrane in water treatment has the advantages of efficient removal of pollutants, increased water flux and extended service life, and is suitable for a variety of complex water quality scenarios such as municipal sewage, industrial wastewater and agricultural runoff.

Description

Technical Field

[0001] The invention relates to the technical field of polymer modified materials, in particular to a multifunctional adsorption membrane based on modified PVDF and a preparation method and application thereof. Background Art

[0002] Polyvinylidene fluoride (PVDF) is an important fluorine-containing polymer material, which is widely used in water treatment, gas separation and biomedicine due to its excellent chemical stability, thermal stability and UV resistance. The application of PVDF membrane in water treatment has attracted particular attention. However, PVDF membrane still faces many technical challenges in practical application, which limits its further development in the field of water treatment.

[0003] Main technical challenges: strong hydrophobicity, low water flux, easy to pollute: The strong hydrophobicity of PVDF membrane is a major defect in water treatment. This characteristic requires a large driving force during the separation process, which makes the water flux of the membrane relatively low. In addition, the membrane surface is easily adsorbed by organic pollutants and other impurities, causing membrane fouling. This problem not only affects the efficiency of the membrane, but also shortens its service life. For example, when treating wastewater containing high concentrations of organic matter, PVDF membranes often experience a significant decrease in flux. Conventional PVDF membranes have limited removal rates for these pollutants. Simple hydrophilic modification often cannot take into account the high selective adsorption of multiple pollutants. Therefore, it is particularly important to develop new PVDF membranes that can efficiently remove multiple complex pollutants. Modified membrane materials are easy to lose and lack stability: Some existing modification methods, such as simple surface physical coating or introduction of soluble hydrophilic polymers, may fall off, be intolerant to scouring, or have decreased membrane strength during use. This makes it difficult to maintain the modification effect for a long time. For example, a membrane that has been modified to improve its hydrophilicity by surface coating may have its hydrophilic layer fall off after repeated use, resulting in a decrease in membrane performance.

[0004] Compared with the existing technology: At present, the modification technology of PVDF membrane mainly includes surface modification and bulk modification. Although surface modification methods such as coating modification, chemical modification and plasma modification can improve the hydrophilicity and anti-fouling ability of the membrane, there are often problems such as shedding of the modified layer and decreased membrane performance. In contrast, the blending modification method has attracted widespread attention due to its simple operation and obvious modification effect. Blending modification: By blending functional materials (such as metal-organic framework materials (MOFs), graphene oxide (GO), etc.) with PVDF, the anti-fouling and water flux of the membrane can be effectively improved. For example, by introducing chelating groups such as amino and carboxyl groups into the PVDF membrane, the selective adsorption capacity of heavy metal ions can be significantly improved. Phase inversion method: Non-solvent induced phase inversion method (NIPS) and thermal induced phase inversion method (TIPS) are the main methods for preparing PVDF membranes. The NIPS method has become the most commonly used method because of its simple operation and easy control of film-forming conditions. However, this method still has some shortcomings, such as imprecise membrane pore size control and low porosity.

[0005] Although many studies have been devoted to improving the performance of PVDF membranes, the existing technology still has some shortcomings, such as the hydrophilic modification effect of the membrane is not persistent and the removal capacity of various pollutants is limited. Therefore, developing a new modified PVDF membrane to improve water flux and enhance the synergistic removal capacity of heavy metal residues will have important practical significance and application prospects. Summary of the invention

[0006] The present invention aims to break through the limitations of hydrophilic modification of PVDF membranes by introducing multiple adsorption sites and functional materials to ensure a lasting modification effect, thereby achieving efficient water treatment effects. Specifically, the present invention will: increase membrane flux and reduce membrane pollution; enhance the ability to remove residual heavy metal ions; and ensure that the functional modified components form a stable microstructure with the PVDF main body to avoid loss of the modifier during use.

[0007] In summary, polyvinylidene fluoride (PVDF), as an important polymer material, has wide application potential in the field of water treatment. However, a series of problems caused by its hydrophobic properties need to be solved. The present invention is expected to overcome the shortcomings of the prior art through innovative design and preparation methods, improve the application performance of PVDF membranes in complex environments, and contribute to future environmental protection.

[0008] To achieve the above-mentioned purpose, the present invention provides the following technical solution: a multifunctional adsorption membrane based on modified PVDF, comprising the following raw materials, in parts by weight: PVDF: 60-100 parts, zeolite powder: 5-15 parts, modifier: 1-10 parts, polyethylene glycol: 1-15 parts, N,N-dimethylformamide: 20 parts-30 parts.

[0009] The preparation method of the modifier is as follows: add β-cyclodextrin to polyvinyl alcohol with a mass of 5-10 times that of β-cyclodextrin, stir at 60-85°C for 2-8h using a constant temperature stirrer, then add 3-aminopropyltriethoxysilane with a mass of 10-12 times that of β-cyclodextrin dropwise, cool to 40°C and stir continuously for 30-60min, and finally treat in an ultrasonic water bath for 1-2h at a temperature of 65-80°C.

[0010] PVDF has good chemical stability and corrosion resistance, but the membrane itself is highly hydrophobic, susceptible to organic contamination, and has low water flux. By introducing hydrophilic functional groups and functional materials with adsorption / chelation properties into the PVDF matrix, the hydrophilicity and adsorption / barrier capacity for pollutants can be greatly improved while maintaining the advantages of PVDF.

[0011] Blending modification and functional composite: The present invention adopts bulk blending (uniformly mixing zeolite powder, modifier, PEG (polyethylene glycol) and PVDF in a solution) and phase transformation to form a membrane. This method can disperse multiple functional components in situ in the PVDF matrix, and construct a uniform pore structure and active sites at the microscopic level when the membrane is formed, thereby enhancing the membrane's flux, hydrophilicity and adsorption capacity for composite pollutants (heavy metal ions, etc.).

[0012] Specifically, PVDF: provides the main skeleton as the main material of the membrane, with high chemical stability and mechanical properties. PVDF (polyvinylidene fluoride) is soluble in N, N-dimethylformamide (DMF) and forms a membrane through a phase inversion process. The comprehensive performance of the hydrophobic PVDF matrix will be significantly improved after adding modifiers, zeolite powder and PEG. Modifier: β-cyclodextrin-polyvinyl alcohol-silane "ternary" modification system, β-cyclodextrin (β-CD) molecules have hydrophobic cavities and hydrophilic outer edges, which can enclose some small molecules; the hydroxyl groups of β-CD have the potential to interact with polar groups, which is also helpful for improving hydrophilicity. When polyvinyl alcohol (PVA) is compounded with β-CD, PVA can produce a synergistic effect with it through hydrogen bonds and make the modifier more stable in the aqueous phase; at the same time, PVA can also produce certain hydrogen bonds / interactions with the PVDF surface or other polar components during the film formation process, which promotes the mechanical properties and surface hydrophilicity of the membrane. 3-Aminopropyltriethoxysilane (APTES), after hydrolysis or reaction with hydroxyl groups, can form a stable silane bonding structure on the β-CD / PVA composite system, enhancing the embedding and binding of the modifier in the PVDF matrix; the amino group can further enhance the coordination / chelation with metal ions, thereby improving the adsorption effect of heavy metal ions; silane reagents can improve the interfacial compatibility between the modifier and PVDF interface to a certain extent, and reduce the loss of modified components. Zeolite powder has a porous structure and a certain ion exchange capacity, which can enhance the membrane's adsorption of pollutants such as heavy metal ions and ammonia nitrogen; its porous skeleton can also increase the internal porosity of the membrane and improve the membrane flux; it may interact with the modifier β-CD / PVA / silane through electrostatic or hydrogen bonds, allowing the zeolite to be more evenly dispersed and stably present in the membrane. PEG is often used as a porogen or hydrophilic modification component in the phase inversion method. It is easily eluted by the solvent or non-solvent part during the membrane forming process, thereby forming a pore structure in the membrane and improving the porosity and hydrophilicity of the membrane. At the same time, the PEG chain segment has a certain hydrophilicity, which can improve the water wetting properties of the membrane surface and reduce the tendency of membrane fouling. N, N-dimethylformamide (DMF) is used as a solvent to dissolve PVDF well and disperse other modified components at the same time. Under non-solvent induced phase inversion (NIPS) conditions, solvent-non-solvent exchange occurs when it comes into contact with non-solvents such as water, causing the PVDF solution to phase separate and form a porous membrane structure.

[0013] The multifunctional adsorption membrane based on modified PVDF comprises the following raw materials in parts by weight: PVDF: 70-90 parts, zeolite powder: 5-12 parts, modifier: 3-8 parts, polyethylene glycol: 5-10 parts, and N,N-dimethylformamide: 23-27 parts.

[0014] The preparation method of the modifier is as follows: add β-cyclodextrin to polyvinyl alcohol with a mass of 5-8 times that of β-cyclodextrin, stir at 70-85°C for 2-8h using a constant temperature stirrer, then add 3-aminopropyltriethoxysilane with a mass of 10-12 times that of β-cyclodextrin dropwise, cool to 40°C and stir continuously for 30-60min, and finally treat in an ultrasonic water bath for 1-2h at a temperature of 75-80°C.

[0015] The multifunctional adsorption membrane based on modified PVDF comprises the following raw materials, in parts by weight: PVDF: 80 parts, zeolite powder: 9 parts, modifier: 5 parts, polyethylene glycol: 8 parts, and N,N-dimethylformamide: 25 parts.

[0016] The preparation method of the modifier is as follows: add β-cyclodextrin to polyvinyl alcohol with a mass 7 times that of β-cyclodextrin, stir at 77°C for 5 hours using a constant temperature stirrer, then add 3-aminopropyltriethoxysilane with a mass 11 times that of β-cyclodextrin dropwise, cool to 40°C and stir continuously for 50 minutes, and finally treat in an ultrasonic water bath for 1.5 hours at a temperature of 78°C.

[0017] Preferably, the PVDF model is 9030, purchased from Nanjing Xinfu New Materials Co., Ltd., with a purity of 99.99%; the particle size of the zeolite powder is 200 mesh, and the specific gravity is 2.2g / cm 3 , porosity is 52%; the parameters of polyvinyl alcohol are as follows: Mw 9000-10000, 80% hydrolysis; the CAS number of N, N-dimethylformamide is 68-12-2, and the molecular weight is 73.09 g / mol.

[0018] Preferably, the CAS number of β-cyclodextrin is 7585-39-9, the refractive index is 1.59, and the molecular weight is 1134.98 g / mol, and the parameters of 3-aminopropyltriethoxysilane are as follows: CAS number is 919-30-2, and the molecular weight is 221.37 g / mol.

[0019] The method for preparing a multifunctional adsorption membrane based on modified PVDF as described above comprises the following steps: (1) raw material preparation: according to the formula requirements, weigh corresponding weight portions of PVDF, zeolite powder, modifier, polyethylene glycol and N,N-dimethylformamide.

[0020] (2) Solution preparation: In a reaction vessel, first add N,N-dimethylformamide, then slowly add PVDF into N,N-dimethylformamide and stir until completely dissolved to form a uniform PVDF solution; then, gradually add zeolite powder, modifier and polyethylene glycol into the PVDF solution and continue stirring to ensure that the components are evenly dispersed. The stirring speed is controlled at 200-500 rpm.

[0021] (3) Phase transformation film formation: Pour the obtained uniform mixed solution into the film casting tank, and use the scraper method to evenly coat it on the flat plate, and the coating thickness is controlled at 100-200um. Film casting tank: Use a dedicated film casting tank, usually made of stainless steel or plastic, to ensure corrosion resistance and easy cleaning. The interior of the film casting tank should be smooth to avoid scratches or unevenness on the film surface. Scraper: The scraper method is used for coating. The material of the scraper can be stainless steel or plastic. The width and thickness of the scraper should be selected according to the required film thickness. The angle and pressure between the scraper and the substrate should be consistent to ensure uniform coating. Flat substrate: Select a suitable flat substrate (such as glass, polyester film, etc.) to facilitate subsequent phase transformation and film removal. The substrate surface should be clean and dust-free to ensure good adhesion between the film and the substrate.

[0022] The coated film was placed in an environment at room temperature to allow phase inversion to occur.

[0023] (4) Post-treatment: After film formation, the membrane is removed from the casting tank and washed with ultrapure water to remove unreacted monomers and impurities. After washing, the membrane is placed in an oven and dried at 60-80°C for 2-4 hours.

[0024] Preferably, the parameters for stirring until complete dissolution in step (2) are: rotation speed of 60 rpm and temperature of 65°C.

[0025] Preferably, the relative humidity of the phase inversion in step (3) is 60%.

[0026] The multifunctional adsorption membrane based on modified PVDF is applied in water treatment as described.

[0027] Beneficial Effects

[0028] In the preparation process of the multifunctional adsorption membrane based on modified PVDF of the present invention, through the multi-component composite system of "PVDF+zeolite powder+modifier (β-CD / PVA / silane)+PEG+DMF", significant technical effects and performance improvements are achieved, which are specifically reflected in the following aspects: Stable modified layer and adsorption sites: Through blending modification and silane coupling reaction, β-CD, PVA and zeolite powder are firmly combined into the PVDF skeleton, forming a stable modified layer and abundant adsorption sites. This structure not only enhances the mechanical strength of the membrane, but also improves its selective adsorption capacity for pollutants.

[0029] High porosity and hydrophilicity: The pore-forming effect of PEG in the phase inversion process and its hydrophilic contribution make the membrane present higher porosity and superior surface hydrophilicity. This feature significantly improves the water flux and effectively reduces the fouling tendency of the membrane surface, thereby extending the service life of the membrane.

[0030] Synergistic removal of multiple pollutants: The synergistic effect of zeolite powder and APTES significantly improves the removal efficiency of heavy metal ions by the membrane, and achieves efficient adsorption through ion exchange and coordination chelation. At the same time, β-CD can effectively encapsulate hydrophobic pesticides or small molecular organic pollutants, achieving synergistic removal of multiple types of pollutants.

[0031] Long-lasting modification effect: Through post-processing steps (such as silane coupling, water bath ultrasound, etc.), a three-dimensional micro-network structure is formed, which effectively enhances the compatibility and stability between the modifier and PVDF, reduces the loss of modified components during use, and ensures the durability of the modification effect.

[0032] Broad application prospects: This multifunctional modified PVDF membrane has the characteristics of high flux, anti-pollution and efficient adsorption of heavy metal residues. It is suitable for the treatment of various complex water qualities such as municipal sewage, industrial wastewater and agricultural runoff, and provides an innovative and effective technical route for the efficient and coordinated removal of multiple pollutants in actual water treatment processes.

[0033] The present invention not only provides a new solution for the field of water treatment, but also has good economic benefits and environmental friendliness, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a scanning electron microscope image of the multifunctional adsorption membrane prepared in Example 7 of the present invention.

[0035] Figure 2 This is the X-ray photoelectron spectrum of the modifier prepared in Example 7 of the present invention.

[0036] Figure 3 This is the silicon element X-ray photoelectron spectrum of the modifier prepared in Example 7 of the present invention. DETAILED DESCRIPTION

[0037] For the embodiments of the present invention, parts by weight can be equivalently replaced with kilograms (Kg) or grams (g), which can be scaled up or down in the same proportion, with little effect on the experimental results.

[0038] Example 1

[0039] The multifunctional adsorption membrane based on modified PVDF comprises the following raw materials, in parts by weight: 60 parts of PVDF, 15 parts of zeolite powder, 1 part of modifier, 15 parts of polyethylene glycol, and 20 parts of N,N-dimethylformamide.

[0040] The preparation method of the modifier is as follows: add β-cyclodextrin to polyvinyl alcohol with a mass 5 times that of β-cyclodextrin, stir at 60°C for 8 hours using a constant temperature stirrer, then add 3-aminopropyltriethoxysilane with a mass 10 times that of β-cyclodextrin dropwise, cool to 40°C and stir continuously for 30 minutes, and finally treat in an ultrasonic water bath for 1 hour at a temperature of 80°C.

[0041] The model of PVDF is 9030, which is purchased from Nanjing Xinfu New Materials Co., Ltd. and has a purity of 99.99%.

[0042] The particle size of zeolite powder is 200 mesh and the specific gravity is 2.2g / cm 3 , the porosity is 52%.

[0043] The parameters of polyvinyl alcohol are as follows: Mw 9000-10000, 80% hydrolysis.

[0044] The CAS number of N,N-dimethylformamide is 68-12-2 and the molecular weight is 73.09 g / mol.

[0045] The CAS number of β-cyclodextrin is 7585-39-9, the refractive index is 1.59, and the molecular weight is 1134.98 g / mol.

[0046] The parameters of 3-aminopropyltriethoxysilane are as follows: CAS No. 919-30-2, molecular weight 221.37 g / mol.

[0047] The method for preparing a multifunctional adsorption membrane based on modified PVDF as described above comprises the following steps: (1) raw material preparation: according to the formula requirements, weigh corresponding weight portions of PVDF, zeolite powder, modifier, polyethylene glycol and N,N-dimethylformamide.

[0048] (2) Solution preparation: In a reaction vessel, first add N,N-dimethylformamide, then slowly add PVDF into N,N-dimethylformamide and stir until completely dissolved to form a uniform PVDF solution; the parameters for stirring until completely dissolved in step (2) are: rotation speed of 60 rpm and temperature of 65°C.

[0049] Next, zeolite powder, modifier and polyethylene glycol were gradually added to the PVDF solution, and stirring was continued to ensure that the components were evenly dispersed. The stirring speed was controlled at 200 rpm.

[0050] (3) Phase transformation film formation: The obtained uniform mixed solution is poured into a film casting tank and evenly coated on a flat plate using a scraper method, with the coating thickness controlled at 100 μm; the coated film is placed in an environment at room temperature to allow it to undergo phase transformation; the relative humidity for phase transformation in step (3) is 60%.

[0051] (4) Post-treatment: After film formation, the membrane is taken out from the film casting tank and washed with ultrapure water to remove unreacted monomers and impurities. After washing, the membrane is placed in an oven and dried at 60°C for 4 h.

[0052] Example 2

[0053] The multifunctional adsorption membrane based on modified PVDF comprises the following raw materials in parts by weight: PVDF: 100 parts, zeolite powder: 5 parts, modifier: 10 parts, polyethylene glycol: 1 part, and N,N-dimethylformamide: 30 parts.

[0054] The preparation method of the modifier is as follows: add β-cyclodextrin to polyvinyl alcohol with a mass 10 times that of β-cyclodextrin, stir at 85°C for 2 hours using a constant temperature stirrer, then add 3-aminopropyltriethoxysilane with a mass 12 times that of β-cyclodextrin dropwise, cool to 40°C and stir continuously for 60 minutes, and finally treat in an ultrasonic water bath for 2 hours at a temperature of 65°C.

[0055] The model of PVDF is 9030, which is purchased from Nanjing Xinfu New Materials Co., Ltd. and has a purity of 99.99%.

[0056] The particle size of zeolite powder is 200 mesh and the specific gravity is 2.2g / cm 3 , the porosity is 52%.

[0057] The parameters of polyvinyl alcohol are as follows: Mw 9000-10000, 80% hydrolysis.

[0058] The CAS number of N,N-dimethylformamide is 68-12-2 and the molecular weight is 73.09 g / mol.

[0059] The CAS number of β-cyclodextrin is 7585-39-9, the refractive index is 1.59, and the molecular weight is 1134.98 g / mol.

[0060] The parameters of 3-aminopropyltriethoxysilane are as follows: CAS No. 919-30-2, molecular weight 221.37 g / mol.

[0061] The method for preparing a multifunctional adsorption membrane based on modified PVDF as described above comprises the following steps: (1) raw material preparation: according to the formula requirements, weigh corresponding weight portions of PVDF, zeolite powder, modifier, polyethylene glycol and N,N-dimethylformamide.

[0062] (2) Solution preparation: In a reaction vessel, first add N,N-dimethylformamide, then slowly add PVDF into N,N-dimethylformamide and stir until completely dissolved to form a uniform PVDF solution; the parameters for stirring until completely dissolved in step (2) are: rotation speed of 60 rpm and temperature of 65°C.

[0063] Next, zeolite powder, modifier and polyethylene glycol were gradually added to the PVDF solution, and stirring was continued to ensure that the components were evenly dispersed. The stirring speed was controlled at 500 rpm.

[0064] (3) Phase transformation film formation: The obtained uniform mixed solution is poured into a film casting tank and evenly coated on a flat plate using a scraper method, with the coating thickness controlled at 200 μm; the coated film is placed in an environment at room temperature to allow it to undergo phase transformation; the relative humidity for phase transformation in step (3) is 60%.

[0065] (4) Post-treatment: After film formation, the membrane is taken out from the casting tank and washed with ultrapure water to remove unreacted monomers and impurities. After washing, the membrane is placed in an oven and dried at 80 °C for 2 h.

[0066] Example 3

[0067] The multifunctional adsorption membrane based on modified PVDF comprises the following raw materials, in parts by weight: PVDF: 70 parts, zeolite powder: 12 parts, modifier: 3 parts, polyethylene glycol: 10 parts, and N,N-dimethylformamide: 23 parts.

[0068] The preparation method of the modifier is as follows: add β-cyclodextrin to polyvinyl alcohol with a mass 5 times that of β-cyclodextrin, stir at 70°C for 2 hours using a constant temperature stirrer, then add 3-aminopropyltriethoxysilane with a mass 10 times that of β-cyclodextrin dropwise, cool to 40°C and stir continuously for 30 minutes, and finally treat in an ultrasonic water bath for 1 hour at a temperature of 75°C.

[0069] The model of PVDF is 9030, which is purchased from Nanjing Xinfu New Materials Co., Ltd. and has a purity of 99.99%.

[0070] The particle size of zeolite powder is 200 mesh and the specific gravity is 2.2g / cm 3 , the porosity is 52%.

[0071] The parameters of polyvinyl alcohol are as follows: Mw 9000-10000, 80% hydrolysis.

[0072] The CAS number of N,N-dimethylformamide is 68-12-2 and the molecular weight is 73.09 g / mol.

[0073] The CAS number of β-cyclodextrin is 7585-39-9, the refractive index is 1.59, and the molecular weight is 1134.98 g / mol.

[0074] The parameters of 3-aminopropyltriethoxysilane are as follows: CAS No. 919-30-2, molecular weight 221.37 g / mol.

[0075] The method for preparing a multifunctional adsorption membrane based on modified PVDF as described above comprises the following steps: (1) raw material preparation: according to the formula requirements, weigh corresponding weight portions of PVDF, zeolite powder, modifier, polyethylene glycol and N,N-dimethylformamide.

[0076] (2) Solution preparation: In a reaction vessel, first add N,N-dimethylformamide, then slowly add PVDF into N,N-dimethylformamide and stir until completely dissolved to form a uniform PVDF solution; the parameters for stirring until completely dissolved in step (2) are: rotation speed of 60 rpm and temperature of 65°C.

[0077] Next, zeolite powder, modifier and polyethylene glycol were gradually added to the PVDF solution, and stirring was continued to ensure that the components were evenly dispersed. The stirring speed was controlled at 200 rpm.

[0078] (3) Phase transformation film formation: The obtained uniform mixed solution is poured into a film casting tank and evenly coated on a flat plate using a scraper method, with the coating thickness controlled at 100 μm; the coated film is placed in an environment at room temperature to allow it to undergo phase transformation; the relative humidity for phase transformation in step (3) is 60%.

[0079] (4) Post-treatment: After film formation, the membrane is taken out from the casting tank and washed with ultrapure water to remove unreacted monomers and impurities. After washing, the membrane is placed in an oven and dried at 60 °C for 2 h.

[0080] Example 4

[0081] The multifunctional adsorption membrane based on modified PVDF comprises the following raw materials, in parts by weight: PVDF: 90 parts, zeolite powder: 5 parts, modifier: 8 parts, polyethylene glycol: 5 parts, and N,N-dimethylformamide: 27 parts.

[0082] The preparation method of the modifier is as follows: add β-cyclodextrin to 8 times the mass of polyvinyl alcohol, stir at 85°C for 8 hours using a constant temperature stirrer, then add 3-aminopropyltriethoxysilane at 12 times the mass of β-cyclodextrin dropwise, cool to 40°C and stir continuously for 60 minutes, and finally treat in an ultrasonic water bath for 2 hours at a temperature of 80°C.

[0083] The model of PVDF is 9030, which is purchased from Nanjing Xinfu New Materials Co., Ltd. and has a purity of 99.99%.

[0084] The particle size of zeolite powder is 200 mesh and the specific gravity is 2.2g / cm 3 , the porosity is 52%.

[0085] The parameters of polyvinyl alcohol are as follows: Mw 9000-10000, 80% hydrolysis.

[0086] The CAS number of N,N-dimethylformamide is 68-12-2 and the molecular weight is 73.09 g / mol.

[0087] The CAS number of β-cyclodextrin is 7585-39-9, the refractive index is 1.59, and the molecular weight is 1134.98 g / mol.

[0088] The parameters of 3-aminopropyltriethoxysilane are as follows: CAS No. 919-30-2, molecular weight 221.37 g / mol.

[0089] The method for preparing a multifunctional adsorption membrane based on modified PVDF as described above comprises the following steps: (1) raw material preparation: according to the formula requirements, weigh corresponding weight portions of PVDF, zeolite powder, modifier, polyethylene glycol and N,N-dimethylformamide.

[0090] (2) Solution preparation: In a reaction vessel, first add N,N-dimethylformamide, then slowly add PVDF into N,N-dimethylformamide and stir until completely dissolved to form a uniform PVDF solution; the parameters for stirring until completely dissolved in step (2) are: rotation speed of 60 rpm and temperature of 65°C.

[0091] Next, zeolite powder, modifier and polyethylene glycol were gradually added to the PVDF solution, and stirring was continued to ensure that the components were evenly dispersed. The stirring speed was controlled at 500 rpm.

[0092] (3) Phase transformation film formation: The obtained uniform mixed solution is poured into a film casting tank and evenly coated on a flat plate using a scraper method, with the coating thickness controlled at 200 μm; the coated film is placed in an environment at room temperature to allow it to undergo phase transformation; the relative humidity for phase transformation in step (3) is 60%.

[0093] (4) Post-treatment: After film formation, the membrane is taken out from the casting tank and washed with ultrapure water to remove unreacted monomers and impurities. After washing, the membrane is placed in an oven and dried at 80 °C for 4 h.

[0094] Example 5

[0095] The multifunctional adsorption membrane based on modified PVDF comprises the following raw materials, in parts by weight: PVDF: 70 parts, zeolite powder: 5 parts, modifier: 3 parts, polyethylene glycol: 5 parts, and N,N-dimethylformamide: 23 parts.

[0096] The preparation method of the modifier is as follows: add β-cyclodextrin to 8 times the mass of polyvinyl alcohol, stir at 85°C for 8 hours using a constant temperature stirrer, then add 3-aminopropyltriethoxysilane at 12 times the mass of β-cyclodextrin dropwise, cool to 40°C and stir continuously for 60 minutes, and finally treat in an ultrasonic water bath for 2 hours at a temperature of 80°C.

[0097] The model of PVDF is 9030, which is purchased from Nanjing Xinfu New Materials Co., Ltd. and has a purity of 99.99%.

[0098] The particle size of zeolite powder is 200 mesh and the specific gravity is 2.2g / cm 3 , the porosity is 52%.

[0099] The parameters of polyvinyl alcohol are as follows: Mw 9000-10000, 80% hydrolysis.

[0100] The CAS number of N,N-dimethylformamide is 68-12-2 and the molecular weight is 73.09 g / mol.

[0101] The CAS number of β-cyclodextrin is 7585-39-9, the refractive index is 1.59, and the molecular weight is 1134.98 g / mol.

[0102] The parameters of 3-aminopropyltriethoxysilane are as follows: CAS No. 919-30-2, molecular weight 221.37 g / mol.

[0103] The method for preparing a multifunctional adsorption membrane based on modified PVDF as described above comprises the following steps: (1) raw material preparation: according to the formula requirements, weigh corresponding weight portions of PVDF, zeolite powder, modifier, polyethylene glycol and N,N-dimethylformamide.

[0104] (2) Solution preparation: In a reaction vessel, first add N,N-dimethylformamide, then slowly add PVDF into N,N-dimethylformamide and stir until completely dissolved to form a uniform PVDF solution; the parameters for stirring until completely dissolved in step (2) are: rotation speed of 60 rpm and temperature of 65°C.

[0105] Next, zeolite powder, modifier and polyethylene glycol were gradually added to the PVDF solution, and stirring was continued to ensure that the components were evenly dispersed. The stirring speed was controlled at 500 rpm.

[0106] (3) Phase transformation film formation: The obtained uniform mixed solution is poured into a film casting tank and evenly coated on a flat plate using a scraper method, with the coating thickness controlled at 200 μm; the coated film is placed in an environment at room temperature to allow it to undergo phase transformation; the relative humidity for phase transformation in step (3) is 60%.

[0107] (4) Post-treatment: After film formation, the membrane is taken out from the casting tank and washed with ultrapure water to remove unreacted monomers and impurities. After washing, the membrane is placed in an oven and dried at 80 °C for 4 h.

[0108] Example 6

[0109] The multifunctional adsorption membrane based on modified PVDF comprises the following raw materials, in parts by weight: PVDF: 90 parts, zeolite powder: 12 parts, modifier: 8 parts, polyethylene glycol: 10 parts, and N,N-dimethylformamide: 27 parts.

[0110] The preparation method of the modifier is as follows: add β-cyclodextrin to polyvinyl alcohol with a mass 5 times that of β-cyclodextrin, stir at 70°C for 2 hours using a constant temperature stirrer, then add 3-aminopropyltriethoxysilane with a mass 10 times that of β-cyclodextrin dropwise, cool to 40°C and stir continuously for 30 minutes, and finally treat in an ultrasonic water bath for 1 hour at a temperature of 75°C.

[0111] The model of PVDF is 9030, which is purchased from Nanjing Xinfu New Materials Co., Ltd. and has a purity of 99.99%.

[0112] The particle size of zeolite powder is 200 mesh and the specific gravity is 2.2g / cm 3 , the porosity is 52%.

[0113] The parameters of polyvinyl alcohol are as follows: Mw 9000-10000, 80% hydrolysis.

[0114] The CAS number of N,N-dimethylformamide is 68-12-2 and the molecular weight is 73.09 g / mol.

[0115] The CAS number of β-cyclodextrin is 7585-39-9, the refractive index is 1.59, and the molecular weight is 1134.98 g / mol.

[0116] The parameters of 3-aminopropyltriethoxysilane are as follows: CAS No. 919-30-2, molecular weight 221.37 g / mol.

[0117] The method for preparing a multifunctional adsorption membrane based on modified PVDF as described above comprises the following steps: (1) raw material preparation: according to the formula requirements, weigh corresponding weight portions of PVDF, zeolite powder, modifier, polyethylene glycol and N,N-dimethylformamide.

[0118] (2) Solution preparation: In a reaction vessel, first add N,N-dimethylformamide, then slowly add PVDF into N,N-dimethylformamide and stir until completely dissolved to form a uniform PVDF solution; the parameters for stirring until completely dissolved in step (2) are: rotation speed of 60 rpm and temperature of 65°C.

[0119] Next, zeolite powder, modifier and polyethylene glycol were gradually added to the PVDF solution, and stirring was continued to ensure that the components were evenly dispersed. The stirring speed was controlled at 200 rpm.

[0120] (3) Phase transformation film formation: The obtained uniform mixed solution is poured into a film casting tank and evenly coated on a flat plate using a scraper method, with the coating thickness controlled at 100 μm; the coated film is placed in an environment at room temperature to allow it to undergo phase transformation; the relative humidity for phase transformation in step (3) is 60%.

[0121] (4) Post-treatment: After film formation, the membrane is taken out from the casting tank and washed with ultrapure water to remove unreacted monomers and impurities. After washing, the membrane is placed in an oven and dried at 60 °C for 2 h.

[0122] Example 7

[0123] The multifunctional adsorption membrane based on modified PVDF comprises the following raw materials in parts by weight: PVDF: 80 parts, zeolite powder: 9 parts, modifier: 5 parts, polyethylene glycol: 8 parts, and N,N-dimethylformamide: 25 parts.

[0124] The preparation method of the modifier is as follows: add β-cyclodextrin to polyvinyl alcohol with a mass 7 times that of β-cyclodextrin, stir at 77°C for 5 hours using a constant temperature stirrer, then add 3-aminopropyltriethoxysilane with a mass 11 times that of β-cyclodextrin dropwise, cool to 40°C and stir continuously for 50 minutes, and finally treat in an ultrasonic water bath for 1.5 hours at a temperature of 78°C.

[0125] The model of PVDF is 9030, which is purchased from Nanjing Xinfu New Materials Co., Ltd. and has a purity of 99.99%.

[0126] The particle size of zeolite powder is 200 mesh and the specific gravity is 2.2g / cm 3 , the porosity is 52%.

[0127] The parameters of polyvinyl alcohol are as follows: Mw 9000-10000, 80% hydrolysis.

[0128] The CAS number of N,N-dimethylformamide is 68-12-2 and the molecular weight is 73.09 g / mol.

[0129] The CAS number of β-cyclodextrin is 7585-39-9, the refractive index is 1.59, and the molecular weight is 1134.98 g / mol.

[0130] The parameters of 3-aminopropyltriethoxysilane are as follows: CAS No. 919-30-2, molecular weight 221.37 g / mol.

[0131] The method for preparing a multifunctional adsorption membrane based on modified PVDF as described above comprises the following steps: (1) raw material preparation: according to the formula requirements, weigh corresponding weight portions of PVDF, zeolite powder, modifier, polyethylene glycol and N,N-dimethylformamide.

[0132] (2) Solution preparation: In a reaction vessel, first add N,N-dimethylformamide, then slowly add PVDF into N,N-dimethylformamide and stir until completely dissolved to form a uniform PVDF solution; the parameters for stirring until completely dissolved in step (2) are: rotation speed of 60 rpm and temperature of 65°C.

[0133] Next, zeolite powder, modifier and polyethylene glycol were gradually added to the PVDF solution, and stirring was continued to ensure that the components were evenly dispersed. The stirring speed was controlled at 400 rpm.

[0134] (3) Phase transformation film formation: The obtained uniform mixed solution is poured into a film casting tank and evenly coated on a flat plate using a scraper method, with the coating thickness controlled at 150 μm; the coated film is placed in an environment at room temperature to allow it to undergo phase transformation; the relative humidity for phase transformation in step (3) is 60%.

[0135] (4) Post-treatment: After film formation, the membrane is taken out from the casting tank and washed with ultrapure water to remove unreacted monomers and impurities. After washing, the membrane is placed in an oven and dried at 70 °C for 3 h.

[0136] Comparative Example 1

[0137] Basically the same as Example 7, except that the zeolite powder is removed.

[0138] Comparative Example 2

[0139] Basically the same as Example 7, except that the polyethylene glycol is removed.

[0140] Comparative Example 3

[0141] The method is basically the same as Example 7, except that anhydrous ethanol is used in the modifier to replace polyvinyl alcohol.

[0142] Comparative Example 4

[0143] Basically the same as Example 7, except that 3-aminopropyltriethoxysilane is removed from the modifier.

[0144] Comparative Example 5

[0145] Basically the same as Example 7, except that the modifier is removed.

[0146] Test plan

[0147] Taking the products prepared in Examples 1-7 and Comparative Examples 1-5 as examples, the following tests were performed: (1) Membrane flux test: The test was performed with reference to the method of the published academic journal article (doi: 10.1016 / j.jece.2021.106730) to obtain the permeation flux LMH.

[0148] (2) Membrane elongation test: Refer to the method of the published academic journal article (doi: 10.1016 / j.jece.2021.106730) to perform the test and calculate the elongation.

[0149] (3) Test on the adsorption performance of heavy metals: The test was conducted according to the method in a public academic journal (doi: 10.1016 / j.colsurfa.2022.128573) to calculate the adsorption amount Q of heavy metal ions. The original concentration of heavy metal ions was 20 mg / L.

[0150] Table 1 Test results

[0151] <![CDATA[Permeation flux LMH (L / m 2 .h)]]> Elongation% Lead ion adsorption (mg / g) Cadmium ion adsorption (mg / g) Example 1 478 74.2 2.91 2.95 Example 2 484 74.4 2.92 2.98 Example 3 485 74.1 2.92 3.01 Example 4 490 74.0 2.94 3.05 Example 5 493 74.5 2.95 3.08 Example 6 495 74.8 2.97 3.16 Example 7 502 75.1 2.99 3.20 Comparative Example 1 461 66.9 2.78 2.86 Comparative Example 2 432 69.5 2.82 2.89 Comparative Example 3 428 71.3 2.87 2.91 Comparative Example 4 469 64.7 2.68 2.81 Comparative Example 5 397 62.2 2.63 2.77

[0152] In addition, taking Example 7 as an example, the scanning electron microscope image is as follows Figure 1 As shown, the X-ray photoelectron spectrum of the modifier during the preparation process is shown Figure 2 As shown, at the same time, the X-ray photoelectron spectrum of silicon is as follows Figure 3 shown.

[0153] The above describes in detail the preferred implementation of this patent, but this patent is not limited to the above implementation. Various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of this patent.

Claims

1. A multifunctional adsorption membrane based on modified PVDF, characterized in that: In parts by weight, the following raw materials are included: PVDF: 70-90 parts, Zeolite powder: 5-12 parts, Modifier: 3-8 parts, Polyethylene glycol: 5-10 parts, N,N-dimethylformamide: 23 parts to 27 parts; The preparation method of the modifier is as follows: Add β-cyclodextrin to polyvinyl alcohol with a mass of 5-8 times its mass, stir at 70-85°C for 2-8h using a thermostatic stirrer, then add 3-aminopropyltriethoxysilane with a mass of 10-12 times the mass of β-cyclodextrin dropwise, cool to 40°C and stir continuously for 30-60min, and finally treat in an ultrasonic water bath for 1-2h at a temperature of 75-80°C. The method for preparing the multifunctional adsorption membrane based on modified PVDF comprises the following steps: (1) Raw material preparation: According to the formula requirements, weigh corresponding weight portions of PVDF, zeolite powder, modifier, polyethylene glycol and N,N-dimethylformamide; (2) Solution preparation: In a reaction vessel, first add N,N-dimethylformamide, then slowly add PVDF into N,N-dimethylformamide, and stir until completely dissolved to form a uniform PVDF solution; Next, zeolite powder, modifier and polyethylene glycol were gradually added to the PVDF solution, and stirring was continued to ensure that the components were evenly dispersed. The stirring speed was controlled at 200-500 rpm; (3) Phase transformation film formation: Pour the obtained uniform mixed solution into the film casting tank and evenly coat it on the flat plate using a scraper method, with the coating thickness controlled at 100-200um; The coated film is placed in a room temperature environment to allow it to undergo phase inversion; (4) Post-processing: After the film is formed, the film is taken out from the film casting tank and washed with ultrapure water to remove unreacted impurities; After cleaning, the membrane was placed in an oven and dried at 60-80°C for 2-4h; Parameters for stirring until completely dissolved in step (2): The speed is 60 rpm and the temperature is 65°C; The relative humidity of the phase conversion in step (3) is 60%.

2. The multifunctional adsorption membrane based on modified PVDF according to claim 1, characterized in that: In parts by weight, the following raw materials are included: PVDF: 80 parts, Zeolite powder: 9 parts, Modifier: 5 parts, Polyethylene glycol: 8 parts, N,N-dimethylformamide: 25 parts; The preparation method of the modifier is as follows: Add β-cyclodextrin to polyvinyl alcohol (7 times its mass), stir at 77°C for 5 hours using a constant temperature stirrer, then add 3-aminopropyltriethoxysilane (11 times the mass of β-cyclodextrin) dropwise, cool to 40°C and stir continuously for 50 minutes, and finally treat in an ultrasonic water bath for 1.5 hours at a temperature of 78°C.

3. The multifunctional adsorption membrane based on modified PVDF according to claim 1, characterized in that: The particle size of zeolite powder is 200 mesh and the specific gravity is 2.2g / cm 3 , porosity is 52%; The parameters of polyvinyl alcohol are as follows: Mw 9000-10000, 80% hydrolysis; The CAS number of N,N-dimethylformamide is 68-12-2 and the molecular weight is 73.09 g / mol.

4. The multifunctional adsorption membrane based on modified PVDF according to claim 1, characterized in that: The CAS number of β-cyclodextrin is 7585-39-9, the refractive index is 1.59, and the molecular weight is 1134.98 g / mol. The parameters of 3-aminopropyltriethoxysilane are as follows: CAS No. 919-30-2, molecular weight 221.37 g / mol.

5. Use of the multifunctional adsorption membrane based on modified PVDF as claimed in claim 1 in water treatment.

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