Preparation method of polyvinylidene fluoride-based metal organic framework hybrid membrane and hybrid membrane

Abstract

This invention provides a method for preparing a polyvinylidene fluoride (PVDF) metal-organic framework (MOF) hybrid membrane and the hybrid membrane itself. The method utilizes the advantages of MOFs, such as well-developed internal pores, ease of functionalization, diverse structural morphologies, and good compatibility with polymer matrices. By introducing monodisperse UiO-66 or UiO-66-NH2 MOF materials into the PVDF membrane matrix through blending modification, the pore shape and size can be effectively adjusted, resulting in a hybrid ultrafiltration membrane with high permeability selectivity. This preparation method is simple, easy to implement, and low in cost, and is of great significance for the development of hybrid ultrafiltration membranes. The prepared PVDF MOF hybrid membrane exhibits a high rejection rate for organic matter in drinking water and good antifouling performance, making it suitable for applications in wastewater reuse and advanced drinking water treatment.

Description

Technical Field

[0001] This invention relates to the field of membrane separation, and specifically to a method for preparing a polyvinylidene fluoride metal-organic framework hybrid membrane and the hybrid membrane itself. Background Technology

[0002] Ultrafiltration technology can effectively remove microorganisms, colloids, algae, and large organic molecules from water. In advanced drinking water treatment, it offers advantages such as high treatment efficiency, stable effluent quality and quantity, small footprint, high biosafety, and environmental friendliness, making it a novel and highly efficient water treatment technology. The ultrafiltration membrane is the core of ultrafiltration technology. Most ultrafiltration membranes used in water treatment are made of organic materials, which have an upper limit to the "permeability-selectivity" balance. This limits membrane flux and rejection rate; that is, increasing membrane flux inevitably leads to a decrease in membrane selectivity, and vice versa. This affects the membrane's water production efficiency, ultimately resulting in high construction investment costs, high operating energy consumption, and high water production costs for membrane water plants, severely restricting the widespread application of ultrafiltration technology. Summary of the Invention

[0003] In view of the problems that existing ultrafiltration membranes may have, such as low permeation flux, poor hydrophilicity, instability, or serious pollution, this invention provides a method for preparing a polyvinylidene fluoride metal-organic framework hybrid membrane and the hybrid membrane itself.

[0004] This invention provides a method for preparing a polyvinylidene fluoride (PVDF) metal-organic framework hybrid membrane, characterized by the following steps: S1, preparing a monodisperse UiO-66 metal-organic framework composite material or a UiO-66-NH2 metal-organic framework composite material; S2, preparing a suspension of the monodisperse UiO-66 metal-organic framework composite material or the UiO-66-NH2 metal-organic framework composite material with a pore-forming agent powder and a solvent, and subjecting it to ultrasonic disruption; S3, fully dissolving the suspension with polyvinylidene fluoride (PVDF) powder to form a casting solution, and allowing it to stand under vacuum to remove bubbles; S4, coating the casting solution onto a glass plate to form a liquid film; S5, allowing the liquid film to stand in air for pre-evaporation, then immersing it in an aqueous solution of N,N-dimethylacetamide as a coagulation bath for phase separation, and immersing the separated PVDF blend membrane in deionized water to obtain the polyvinylidene fluoride (PVDF) metal-organic framework hybrid membrane.

[0005] The preparation method of polyvinylidene fluoride metal-organic framework hybrid membrane provided by the present invention may also have the following features: In step S1, the preparation of UiO-66 metal-organic framework composite material includes the following steps: (1) Weigh 147-152 mg zirconium chloride, 104-108 mg terephthalic acid, 8-12 mL glacial acetic acid, and 6-10 mL water, and sonicate them in 70-90 mL N,N-dimethylformamide to form a precursor solution; (2) Transfer the precursor solution to a stainless steel reactor lined with polytetrafluoroethylene, place it in an oven for full reaction, and then take out the reactor and cool it to room temperature; (3) Transfer the solution in the reactor to a centrifuge tube, and separate the precipitate with a high-speed centrifuge, then wash it with N,N-dimethylformamide and methanol respectively, and place it in a forced-air drying oven to dry the precipitate into powder; (4) Place the powder in a vacuum oven to dry further to remove the solvent, and obtain the monodisperse UiO-66 metal-organic framework composite material.

[0006] The method for preparing polyvinylidene fluoride metal-organic framework hybrid membrane provided by the present invention may also have the following features: In step S1, the preparation of UiO-66-NH2 metal-organic framework composite material includes the following steps: (1) Weigh 147-152 mg zirconium chloride, 113-118 mg p-2-aminophthalic acid, and 2-4 mL glacial acetic acid, and sonicate them in 70-90 mL N,N-dimethylformamide to form a precursor solution; (2) Transfer the precursor solution to a stainless steel reactor lined with polytetrafluoroethylene, place it in an oven for full reaction, and then remove the reactor and cool it to room temperature; (3) Transfer the solution in the reactor to a centrifuge tube, and separate the precipitate using a high-speed centrifuge, then wash it with N,N-dimethylformamide and methanol respectively, and place it in a forced-air drying oven to dry the precipitate into powder; (4) Place the powder in a vacuum oven to dry further to remove the solvent, and obtain the monodisperse UiO-66-NH2 metal-organic framework composite material.

[0007] The method for preparing polyvinylidene fluoride metal-organic framework hybrid membrane provided by the present invention may also have the following characteristics: the powder particle size of UiO-66 metal-organic framework composite material or UiO-66-NH2 metal-organic framework composite material is 50-200 nm.

[0008] In the preparation method of the polyvinylidene fluoride metal-organic framework hybrid membrane provided by the present invention, it may also have the following characteristics: the addition concentration of UiO-66 metal-organic framework composite material or UiO-66-NH2 metal-organic framework composite material in step S2 is 1-3 wt%.

[0009] The method for preparing polyvinylidene fluoride metal-organic framework hybrid membrane provided by the present invention may also have the following characteristics: the pore-forming agent powder is polyvinylpyrrolidone, polyethylene glycol or glycerol, with a concentration of 1-3 wt%.

[0010] The method for preparing the polyvinylidene fluoride metal-organic framework hybrid membrane provided by the present invention may also have the following characteristics: the solvent is N,N-dimethylformamide, dimethyl sulfoxide, or N,N-dimethylethyl amide.

[0011] The method for preparing the polyvinylidene fluoride metal-organic framework hybrid membrane provided by the present invention may also have the following characteristic: the concentration of polyvinylidene fluoride powder added is 15-25 wt%.

[0012] The method for preparing the polyvinylidene fluoride metal-organic framework hybrid membrane provided by the present invention may also have the following characteristics: the ratio of N,N-dimethylacetamide to water in the coagulation bath is 1:10, the curing temperature of the liquid film in the coagulation bath is 28±1℃, and the curing time is 10min.

[0013] The present invention also provides a polyvinylidene fluoride metal-organic framework hybrid membrane prepared by the above preparation method.

[0014] The role and effect of invention

[0015] According to the present invention, a method for preparing a polyvinylidene fluoride (PVDF) metal-organic framework (MOF) hybrid membrane and the hybrid membrane itself are disclosed. The preparation method utilizes the advantages of MOF composites, such as well-developed internal pores, ease of functionalization, diverse structural morphologies, and good compatibility with polymer matrices. By introducing monodisperse UiO-66 or UiO-66-NH2 MOF composite materials into the PVDF membrane matrix through blending modification, the pore shape and size can be effectively adjusted to prepare a hybrid ultrafiltration membrane with high permeability selectivity. This preparation method is simple, easy to implement, and low in cost, and is of great significance for the development of hybrid ultrafiltration membranes. The prepared PVDF MOF hybrid membrane exhibits a high rejection rate for organic matter in drinking water and good antifouling performance, making it suitable for applications in the reuse of domestic wastewater and advanced treatment of drinking water. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the steps in the preparation method of the polyvinylidene fluoride metal-organic framework hybrid membrane in Example 1 of the present invention;

[0017] Figure 2 This is a schematic diagram illustrating the preparation method of the polyvinylidene fluoride metal-organic framework hybrid membrane in Example 1 of the present invention;

[0018] Figure 3These are scanning electron microscope (SEM) images of the surface (a) and cross-section (b) of the polyvinylidene fluoride metal-organic framework hybrid membrane in Example 1 of the present invention.

[0019] Figure 4 This is a diagram showing the surface landscape water treatment performance in Embodiment 1 of the present invention. Detailed Implementation

[0020] To make the technical means, creative features, objectives and effects of this invention easier to understand, the following embodiments are described in detail with reference to the accompanying drawings.

[0021] In the following text, polyvinylidene fluoride was purchased from Arkema Fluorochemicals Ltd.; N,N-dimethylacetamide, N,N-dimethylformamide, zirconium chloride, glacial acetic acid, terephthalic acid, 2-aminophthalic acid, polyvinylpyrrolidone, bovine serum albumin, and humic acid were purchased from Aladdin Biochemical Technology Co., Ltd.; methanol, kaolin, sodium hydroxide, and hydrochloric acid were purchased from Sinopharm Chemical Reagent Co., Ltd.

[0022] Example 1

[0023] Figure 1 This is a schematic diagram illustrating the steps involved in preparing a polyvinylidene fluoride (PVDF) metal-organic framework hybrid membrane. Figure 2 This is a schematic diagram illustrating the preparation of polyvinylidene fluoride metal-organic framework hybrid membranes using a blending method.

[0024] like Figure 1 and Figure 2 As shown, this embodiment provides a method for preparing a polyvinylidene fluoride (PVDF) metal-organic framework hybrid membrane, comprising the following steps:

[0025] S1. Prepare monodisperse UiO-66 metal-organic framework composite materials or UiO-66-NH2 metal-organic framework composite materials.

[0026] The powder particle size of UiO-66 metal-organic framework composite material or UiO-66-NH2 metal-organic framework composite material is 50-200 nm.

[0027] The preparation process of monodisperse UiO-66 metal-organic framework composite materials is as follows:

[0028] (1) Weigh 147-152 mg zirconium chloride, 104-108 mg terephthalic acid, 8-12 mL glacial acetic acid, and 6-10 mL water, and sonicate them in 70-90 mL N,N-dimethylformamide (DMF) for 15-20 min at a power of 190-210 W to form a precursor solution. In this example, specifically, weigh 149.1 mg zirconium chloride, 106.3 mg terephthalic acid, 10 mL glacial acetic acid, and 8 mL water, and sonicate them in 80 mL N,N-dimethylformamide (DMF) for 15 min at a power of 200 W to form a precursor solution.

[0029] (2) Transfer the precursor liquid to a 150mL stainless steel high-temperature and high-pressure reactor lined with polytetrafluoroethylene, place it in an oven at 120℃ for 24h, and then remove the reactor and cool it to room temperature.

[0030] (3) Transfer the solution in the reaction vessel to a 50mL centrifuge tube, centrifuge at 9000rpm for 20-30min to separate the precipitate, wash it three times with N,N-dimethylformamide and methanol respectively, and then place it in an 80℃ forced-air drying oven for 5-6h to dry the precipitate into powder.

[0031] (4) The powder was placed in a vacuum oven at 120°C and dried for 20-22 hours to further remove the solvent, resulting in monodisperse UiO-66 metal-organic framework composite material.

[0032] The preparation process of the monodisperse UiO-66-NH2 metal-organic framework composite material is as follows:

[0033] (1) Weigh 147-152 mg of zirconium chloride, 113-118 mg of p-2-aminophthalic acid, and 2-4 mL of glacial acetic acid, and sonicate them in 70-90 mL of N,N-dimethylformamide for 15-20 min at a power of 190-200 W to form a precursor solution. In this example, specifically, weigh 149.1 mg of zirconium chloride, 115.9 mg of p-2-aminophthalic acid, and 2 mL of glacial acetic acid, and sonicate them in 80 mL of N,N-dimethylformamide for 15 min at a power of 200 W to form a precursor solution.

[0034] (2) Transfer the precursor liquid to a 150mL stainless steel high-temperature and high-pressure reactor lined with polytetrafluoroethylene, place it in an oven at 120℃ for 24h, and then remove the reactor and cool it to room temperature.

[0035] (3) Transfer the solution in the reaction vessel to a 50mL centrifuge tube, centrifuge at 9000rpm for 20-30min to separate the precipitate, wash it three times with N,N-dimethylformamide and methanol respectively, and then place it in an 80℃ forced-air drying oven for 5-6h to dry the precipitate into powder.

[0036] (4) The powder was placed in a vacuum oven at 120°C and dried for 20-22 hours to further remove the solvent, resulting in a monodisperse UiO-66-NH2 metal-organic framework composite material.

[0037] S2. The above monodisperse UiO-66 or UiO-66-NH2 metal-organic framework composite material is mixed with pore-forming agent powder and solvent to form a suspension, and then subjected to ultrasonic crushing treatment.

[0038] The monodisperse UiO-66 or UiO-66-NH2 metal-organic framework composite material is added at a concentration of 1-3 wt% of the polymer, preferably 2 wt%. The porogen powder can be polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), or glycerol, at a concentration of 1-3 wt%, preferably 2 wt%. The solvent is a polar solvent, such as N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), or N,N-dimethylacetamide (DMAc).

[0039] In this embodiment, the specific process is as follows: 0.36g of monodisperse UiO-66-NH2 metal-organic framework composite material, 2g of pore-forming agent polyvinylpyrrolidone powder, and 88g of solvent N,N-dimethylacetamide are weighed and added to a 100mL beaker, and the suspension is treated with an ultrasonic cell disruptor for 10min.

[0040] S3. The above suspension is fully dissolved with a certain mass of polyvinylidene fluoride (PVDF) powder to form a casting solution, and then allowed to stand under vacuum to remove bubbles.

[0041] The concentration of polyvinylidene fluoride powder added is 15-25 wt%, preferably 18 wt%.

[0042] In this embodiment, the specific process is as follows: The above suspension is added to a 200mL tall beaker containing 18-20g of PVDF powder, and stirred magnetically for 10-14 hours to fully dissolve the PVDF powder and form a stable and uniform casting solution. The stirring temperature is set at 60±1℃ and the stirring speed is 300rpm. Then, the casting solution is allowed to stand at room temperature in a vacuum oven for 3 hours to completely remove air bubbles introduced into the casting solution during stirring.

[0043] S4. Apply the casting solution to a glass plate to form a liquid film.

[0044] In this embodiment, the specific process is as follows: using a glass plate as a substrate, setting the gap between the scraper and the glass plate to 250 μm, pouring an appropriate amount of casting liquid onto one side of the scraper, and then slowly scraping a uniform liquid film onto the glass plate using an automatic coating machine. The experimental conditions are room temperature and humidity of 40%-50%.

[0045] S5. After the liquid membrane is allowed to stand in the air for pre-evaporation, it is immersed in an aqueous solution of N,N-dimethylacetamide as a coagulation bath for phase separation. The separated PVDF blend membrane is then soaked in deionized water to obtain a polyvinylidene fluoride metal-organic framework hybrid membrane.

[0046] In this embodiment, the specific process is as follows: After the liquid film is allowed to stand in air for pre-evaporation for 30 seconds, it is immediately immersed in a solution of N,N-dimethylacetamide and water in a ratio of 1:10 for phase separation. The coagulation bath temperature is maintained at 28±1℃ by a temperature control system, and the blended membrane is completely separated from the glass plate after 10 minutes. The formed PVDF blended membrane is then removed and soaked in deionized water for 24 hours to obtain a polyvinylidene fluoride vinyl metal-organic framework hybrid membrane.

[0047] The hybrid ultrafiltration membrane prepared in this embodiment has an average pore size of 27.3 nm, a porosity of 86.05%, and a pure water flux of 158 L / m³ at 20 ± 1 °C and 0.1 MPa. 2 The retention rate of 1 g / L bovine serum albumin aqueous solution at 0.1 MPa was 99.10%.

[0048] Analysis of Example 1 was performed, and scanning electron microscope (SEM) images of the surface and cross-section of the polyvinylidene fluoride (PVDF) metal-organic framework (MOF) hybrid film prepared by the blending method are shown below. Figure 3 The hydrophilicity and hydrophobicity of the membrane surface were characterized using a contact angle meter (see Table 1); the separation performance using actual surface landscape water as feed liquid is shown in [Table 1]. Figure 4 The influent water quality is as follows: TN concentration is 0.94 mg / L, TOC concentration is 6.53 mg / L, UV 254 concentration is 0.154 ABS, and turbidity is 14.7 mg / L. After four consecutive cycles (8 hours per cycle), the membrane's removal rate of various organic substances remains stable, demonstrating good long-term stability.

[0049] Table 1 Hydrophilicity and hydrophobicity of membrane surfaces

[0050]

[0051] Example 2

[0052] This embodiment provides a method for preparing a polyvinylidene fluoride metal-organic framework hybrid membrane. The difference from Example 1 is that the monodisperse UiO-66-NH2 metal-organic framework composite material in step S2 of Example 1 is adjusted to a monodisperse UiO-66 metal-organic framework composite material, and the amount of nanoparticles added is adjusted to 0.18g. The other conditions are the same as in Example 1.

[0053] The hybrid ultrafiltration membrane prepared in this embodiment has an average pore size of 29.2 nm, a porosity of 76.52%, and a pure water flux of 10³ L / m³ at 20 ± 1 °C and 0.1 MPa. 2 The retention rate of 1 g / L bovine serum albumin aqueous solution at 0.1 MPa was 97.54%.

[0054] Example 3

[0055] This embodiment provides a method for preparing a polyvinylidene fluoride metal-organic framework hybrid membrane. The difference from Example 1 is that the monodisperse UiO-66-NH2 metal-organic framework composite material in step S2 of Example 1 is adjusted to a monodisperse UiO-66 metal-organic framework composite material, and the amount of nanoparticles added is adjusted to 0.27g. The other conditions are the same as in Example 1.

[0056] The hybrid ultrafiltration membrane prepared in this embodiment has an average pore size of 28.6 nm, a porosity of 79.4%, and a pure water flux of 123 L / m³ at 20 ± 1 °C and 0.1 MPa. 2 The retention rate of 1 g / L bovine serum albumin aqueous solution at 0.1 MPa was 98.56%.

[0057] Example 4

[0058] This embodiment provides a method for preparing a polyvinylidene fluoride metal-organic framework hybrid membrane. The difference from Example 1 is that the monodisperse UiO-66-NH2 metal-organic framework composite material in step S2 of Example 1 is changed to a monodisperse UiO-66 metal-organic framework composite material, while the other conditions are the same as in Example 1.

[0059] The hybrid ultrafiltration membrane prepared in this embodiment has an average pore size of 29.4 nm, a porosity of 82.44%, and a pure water flux of 120 L / m³ at 20 ± 1 °C and 0.1 MPa. 2 The retention rate of 1 g / L bovine serum albumin aqueous solution at 0.1 MPa was 98.12%.

[0060] Example 5

[0061] This embodiment provides a method for preparing a polyvinylidene fluoride metal-organic framework hybrid membrane. The difference from Example 1 is that the monodisperse UiO-66-NH2 metal-organic framework composite material in step S2 of Example 1 is changed to a monodisperse UiO-66 metal-organic framework composite material, and the amount of nanoparticles added is adjusted to 0.45g. The other conditions are the same as in Example 1.

[0062] The hybrid ultrafiltration membrane prepared in this embodiment has an average pore size of 30.2 nm, a porosity of 84.03%, and a pure water flux of 113 L / m³ at 20 ± 1 °C and 0.1 MPa. 2 The retention rate of 1 g / L bovine serum albumin aqueous solution at 0.1 MPa was 97.49%.

[0063] Example 6

[0064] This embodiment provides a method for preparing a polyvinylidene fluoride metal-organic framework hybrid membrane. The difference from Example 1 is that the monodisperse UiO-66-NH2 metal-organic framework composite material in step S2 of Example 1 is adjusted to a monodisperse UiO-66 metal-organic framework composite material, and the amount of nanoparticles added is adjusted to 0.54g. The other conditions are the same as in Example 1.

[0065] The hybrid ultrafiltration membrane prepared in this embodiment has an average pore size of 30.8 nm, a porosity of 84.46%, and a pure water flux of 110 L / m³ at 20 ± 1 °C and 0.1 MPa. 2 The retention rate of 1 g / L bovine serum albumin aqueous solution at 0.1 MPa was 97.25%.

[0066] Example 7

[0067] This embodiment provides a method for preparing a polyvinylidene fluoride metal-organic framework hybrid membrane. The difference from Example 1 is that the amount of monodisperse UiO-66-NH2 metal-organic framework composite material nanoparticles added in step S2 of Example 1 is adjusted to 0.18g, while the other conditions are the same as in Example 1.

[0068] The hybrid ultrafiltration membrane prepared in this embodiment has an average pore size of 28.9 nm, a porosity of 80.42%, and a pure water flux of 118 L / m³ at 20 ± 1 °C and 0.1 MPa. 2 The retention rate of 1 g / L bovine serum albumin aqueous solution at 0.1 MPa was 97.90%.

[0069] Example 8

[0070] This embodiment provides a method for preparing a polyvinylidene fluoride metal-organic framework hybrid membrane. The difference from Example 1 is that the amount of monodisperse UiO-66-NH2 metal-organic framework composite material nanoparticles added in step S2 of Example 1 is adjusted to 0.27g, while the other conditions are the same as in Example 1.

[0071] The hybrid ultrafiltration membrane prepared in this embodiment has an average pore size of 28.5 nm, a porosity of 84.46%, and a pure water flux of 134 L / m³ at 20 ± 1 °C and 0.1 MPa. 2 The retention rate of 1 g / L bovine serum albumin aqueous solution at 0.1 MPa was 98.93%.

[0072] Example 9

[0073] This embodiment provides a method for preparing a polyvinylidene fluoride metal-organic framework hybrid membrane. The difference from Example 1 is that the amount of monodisperse UiO-66-NH2 metal-organic framework composite material nanoparticles added in step S2 of Example 1 is adjusted to 0.45g, and the amount of solvent N,N-dimethylacetamide is adjusted to 79.55g. The other conditions are the same as in Example 1.

[0074] The hybrid ultrafiltration membrane prepared in this embodiment has an average pore size of 28.9 nm, a porosity of 87.05%, and a pure water flux of 156 L / m³ at 20 ± 1 °C and 0.1 MPa. 2 The retention rate of 1 g / L bovine serum albumin aqueous solution at 0.1 MPa was 99.04%.

[0075] Example 10

[0076] This embodiment provides a method for preparing a polyvinylidene fluoride metal-organic framework hybrid membrane. The difference from Example 1 is that the amount of monodisperse UiO-66-NH2 metal-organic framework composite material nanoparticles added in step S2 of Example 1 is adjusted to 0.54g, while the other conditions are the same as in Example 1.

[0077] The hybrid ultrafiltration membrane prepared in this embodiment has an average pore size of 31.1 nm, a porosity of 87.21%, and a pure water flux of 150 L / m³ at 20 ± 1 °C and 0.1 MPa. 2 The retention rate of 1 g / L bovine serum albumin aqueous solution at 0.1 MPa was 98.49%.

[0078] Comparative Example

[0079] This comparative example provides a method for preparing a polyvinylidene fluoride (PVDF) film, comprising the following steps:

[0080] S1. Weigh 2g of porogen polyvinylpyrrolidone powder and 88g of solvent N,N-dimethylacetamide and add them to a 100mL beaker. Treat the suspension with an ultrasonic cell disruptor for 10min.

[0081] S2. Add the above suspension to a 200mL tall beaker containing 18g of PVDF powder, and stir magnetically for 12 hours to fully dissolve the PVDF powder and form a stable and uniform casting solution. The stirring temperature was set at 60℃ and the stirring speed at 300rpm. Then, let the casting solution stand at room temperature in a vacuum oven for 3 hours to completely remove air bubbles introduced into the casting solution during stirring.

[0082] S3. Using a glass plate as the substrate, with the gap between the doctor blade and the glass plate set to 250 μm, an appropriate amount of casting solution was poured onto one side of the doctor blade, and then a uniform liquid film was slowly scraped onto the glass plate using an automatic coating machine. The experimental conditions were room temperature and humidity of 40%-50%.

[0083] S4. After pre-evaporating the liquid film in air for 30 seconds, immediately immerse it in a solution of N,N-dimethylacetamide and water at a ratio of 1:10 for phase separation. The coagulation bath temperature is maintained at 28±1℃ using a temperature control system. After 10 minutes, the membrane is completely separated from the glass plate. Remove the formed PVDF membrane and soak it in deionized water for 24 hours to obtain the polyvinylidene fluoride membrane.

[0084] This comparative example is a polyvinylidene fluoride membrane without the addition of monodisperse UiO-66 or UiO-66-NH2 metal-organic framework composite nanoparticles. It has an average pore size of 31.0 nm, a porosity of 72.34%, and a pure water flux of 78 L / m³ at 20 ± 1 °C and 0.1 MPa. 2 The retention rate of 1 g / L bovine serum albumin aqueous solution at 0.1 MPa was 96.34%.

[0085] Comparing the separation performance of Example 1 and the comparative example, it can be seen that when monodisperse UiO-66 or UiO-66-NH2 metal-organic framework composite materials are added to the casting solution as a blending modifier, the surface of the membrane becomes denser, the porosity increases, the pore size decreases, and the flux of pure water increases while the retention rate of organic matter also increases.

[0086] In addition, it should be noted that the concepts and formulas for permeation flux and rejection rate mentioned above are as follows:

[0087] Let A(m²) represent the area of ​​the membrane flowing through it during time t(h). 2 The volume of pure water V (L) of the composite membrane.

[0088] In the formula C fThe concentration (mol / L) of bovine serum albumin aqueous solution in the raw material solution is C. p The concentration of bovine serum albumin aqueous solution in the permeate is expressed in mol / L.

[0089] The role and effect of the embodiments

[0090] According to the preparation method and hybrid membrane of polyvinylidene fluoride metal-organic framework (PVDF) involved in the above embodiments, PVDF as an ultrafiltration membrane material has good film-forming properties, good acid and alkali resistance and chlorine resistance, excellent mechanical strength, chemical stability and thermal stability, and good plasticity. PVDF membranes prepared with it have been widely used in many fields. Meanwhile, metal-organic framework composites have the characteristics of well-developed internal pores, high specific surface area, easy functionalization, numerous structural morphologies, and good compatibility with polymer matrices. The preparation method involves adding glacial acetic acid and water as regulators to a mother liquor containing metal ions and organic ligands during a solvothermal reaction to obtain monodisperse UiO-66 or UiO-66-NH2 metal-organic framework composite materials. These materials are then added to a PVDF casting solution to adjust the pore size and structure of the hybrid membrane. Finally, through a solvent-free phase inversion process, a polyvinylidene fluoride metal-organic framework hybrid membrane with high permeability selectivity can be prepared. This preparation method is simple, easy to implement, and low in cost, and is of great significance for the development of hybrid ultrafiltration membranes. The prepared polyvinylidene fluoride metal-organic framework hybrid membrane has a high rejection rate for organic matter in drinking water and good anti-fouling performance. It can be applied to the reuse of domestic sewage and the advanced treatment of drinking water.

[0091] The above embodiments are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention.

Claims

1. A method for preparing a polyvinylidene fluoride (PVDF) metal-organic framework hybrid membrane, characterized in that, Includes the following steps: S1. Prepare monodisperse UiO-66 metal-organic framework composite materials or UiO-66-NH2 metal-organic framework composite materials; S2. The monodisperse UiO-66 metal-organic framework composite material or the UiO-66-NH2 metal-organic framework composite material is mixed with pore-forming agent powder and solvent to form a suspension, and then subjected to ultrasonic crushing treatment. S3. The suspension is fully dissolved with polyvinylidene fluoride powder to form a casting solution, and then allowed to stand under vacuum to remove bubbles. S4. The casting liquid is coated onto a glass plate to form a liquid film. S5. After pre-evaporating the liquid membrane in air, it is immersed in an aqueous solution of N,N-dimethylacetamide as a coagulation bath for phase separation. The separated PVDF blend membrane is then soaked in deionized water to obtain the polyvinylidene fluoride metal-organic framework hybrid membrane. In step S1, the preparation of the UiO-66 metal-organic framework composite material includes the following steps: (1) Weigh 147-152 mg zirconium chloride, 104-108 mg terephthalic acid, 8-12 mL glacial acetic acid, and 6-8 mL water, and sonicate them in 70-90 mL N,N-dimethylformamide to form a precursor solution; (2) The precursor liquid is transferred to a stainless steel reactor lined with polytetrafluoroethylene, and after being fully reacted in an oven, the reactor is removed and cooled to room temperature. (3) Transfer the solution in the reaction vessel to a centrifuge tube and separate the precipitate using a high-speed centrifuge. Then wash the precipitate with N,N-dimethylformamide and methanol respectively and place it in a forced-air drying oven to dry the precipitate into powder. (4) The powder is placed in a vacuum oven to dry further to remove the solvent, thereby obtaining the monodisperse UiO-66 metal-organic framework composite material. In step S1, the preparation of the UiO-66-NH2 metal-organic framework composite material includes the following steps: (1) Weigh 147-152 mg zirconium chloride, 113-118 mg p-2-aminophthalic acid, and 2-4 mL glacial acetic acid, and sonicate them in 70-90 mL N,N-dimethylformamide to form a precursor solution; (2) The precursor liquid is transferred to a stainless steel reactor lined with polytetrafluoroethylene, and after being fully reacted in an oven, the reactor is removed and cooled to room temperature. (3) Transfer the solution in the reaction vessel to a centrifuge tube and separate the precipitate using a high-speed centrifuge. Then wash the precipitate with N,N-dimethylformamide and methanol respectively and place it in a forced-air drying oven to dry the precipitate into powder. (4) The powder is placed in a vacuum oven to dry and further remove the solvent, so as to obtain the monodisperse UiO-66-NH2 metal-organic framework composite material.

2. The method for preparing the polyvinylidene fluoride metal-organic framework hybrid membrane according to claim 1, characterized in that: in, The powder particle size of the UiO-66 metal-organic framework composite material or the UiO-66-NH2 metal-organic framework composite material is 50-200 nm.

3. The method for preparing the polyvinylidene fluoride metal-organic framework hybrid membrane according to claim 1, characterized in that: in, The concentration of the UiO-66 metal-organic framework composite material or the UiO-66-NH2 metal-organic framework composite material added in step S2 is 1-3 wt%.

4. The method for preparing the polyvinylidene fluoride metal-organic framework hybrid membrane according to claim 1, characterized in that: in, The pore-forming agent powder is polyvinylpyrrolidone, polyethylene glycol, or glycerin, with a concentration of 1-3 wt%.

5. The method for preparing the polyvinylidene fluoride metal-organic framework hybrid membrane according to claim 1, characterized in that: in, The solvent is N,N-dimethylformamide, dimethyl sulfoxide, or N,N-dimethylethyl amide.

6. The method for preparing the polyvinylidene fluoride metal-organic framework hybrid membrane according to claim 1, characterized in that: in, The concentration of the added polyvinylidene fluoride powder is 15-25 wt%.

7. The method for preparing the polyvinylidene fluoride metal-organic framework hybrid membrane according to claim 1, characterized in that: in, The ratio of N,N-dimethylacetamide to water in the coagulation bath is 1:10, and the curing temperature of the liquid film in the coagulation bath is 28±1℃, with a curing time of 10min.

8. A polyvinylidene fluoride metal-organic framework hybrid membrane, characterized in that, It is prepared by the method for preparing polyvinylidene fluoride metal-organic framework hybrid membrane according to any one of claims 1 to 7.

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