Preparation method and application of antibacterial and anti-pollution ZIF-8 / PVDF composite membrane

Abstract

The invention provides a preparation method and application of an antibacterial and anti-pollution zeolite imidazate framework (ZIF-8) modified polyvinylidene fluoride (PVDF) composite membrane (ZIF-8 / PVDF), and relates to the technical field of manufacturing of separation membranes for water treatment. And introducing ZIF-8 into the PVDF casting membrane solution by adopting a phase inversion method to prepare the mixed matrix composite membrane. The antibacterial and anti-pollution performance of the composite membrane is researched by adopting antibacterial experiments and dead end filtration, and the result shows that the modified composite membrane has excellent bactericidal performance and good anti-pollution behavior.

Description

Technical Field

[0001] The present invention relates to the technical field of manufacturing separation membranes used in the field of water treatment, and particularly relates to a preparation method and application of an antibacterial and antifouling ZIF-8 / PVDF composite membrane. Background Art

[0002] Due to its characteristics of high efficiency, low energy consumption, and low operating cost, membrane separation technology has become one of the mainstream technologies in the field of water treatment. Among them, membrane separation technology can effectively intercept and remove macromolecular organic matter, macromolecular colloids, particulate pollutants, and pathogenic microorganisms in water through size exclusion effect, and its treatment effect directly depends on the performance characteristics of the membrane material. Currently, most commercial membrane materials use polymer matrices, and polyvinylidene fluoride (PVDF) has become one of the widely used membrane materials due to its advantages such as easy modification and controllable cost. However, the high polarity of the C-F bond in the PVDF molecular chain results in strong hydrophobicity on the membrane surface, which easily causes the accumulation of organic matter, inorganic salts, and microorganisms on the membrane surface during actual operation, and then induces problems such as membrane pore blockage and permeation flux attenuation, not only shortening the service life of the membrane, but also greatly increasing the operation and maintenance costs. This technical bottleneck severely restricts the further development of membrane technology.

[0003] Although traditional physical cleaning and chemical modification can partially alleviate membrane fouling, they have problems such as poor stability of the modified layer and complex operation. Therefore, the development of new membrane materials with both persistent hydrophilicity and antibacterial properties has become the key to breaking through the technical bottleneck. Among them, nanocomposite technology can achieve molecular-level regulation of material properties by introducing functional nanoparticles into the polymer matrix, and has become the forefront direction of current membrane material modification.

[0004] Metal-organic frameworks (MOFs) with regular pore structures have attracted much attention due to their unique structural designability. Among the zeolitic imidazolate framework (ZIF) subclass materials, the imidazole ring of ZIF-8 can endow the membrane with hydrophilicity, and the imidazole ring can inhibit bacterial adhesion through electrostatic repulsion. At the same time, the slow-release characteristics of zinc ions can damage the integrity of the cell membrane.

[0005] When ZIF-8 nanoparticles are embedded in the PVDF matrix by the phase inversion method, its hierarchical pore structure can promote the solvent-nonsolvent exchange during the liquid-liquid phase separation of the casting solution, forming a finger-like pore structure. In view of the technical problem that it is difficult to balance hydrophilicity and antibacterial properties in the anti-fouling modification of existing PVDF membranes, the purpose of the present invention is to provide the preparation and application of an antibacterial and antifouling ZIF-8 / PVDF composite membrane, using the inherent antibacterial activity of ZIF-8 to construct a biological fouling defense system, and at the same time, the pores can achieve selective transport of substances, providing a new solution for the development of long-term anti-fouling membrane separation materials. Summary of the Invention

[0006] The object of the present invention is to provide a preparation method and application of an antibacterial and anti-pollution ZIF-8 / PVDF composite membrane.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A preparation method of an antibacterial and anti-pollution ZIF-8 / PVDF composite membrane, comprising the following steps:

[0009] Mix polyvinylidene fluoride powder (PVDF), a pore-forming agent, an organic solvent, and zeolitic imidazolate framework (ZIF-8) nanomaterials to obtain a ZIF-8 / PVDF casting solution;

[0010] Coat the ZIF-8 / PVDF casting solution onto non-woven fabric, soak it in a coagulation bath and dry it in sequence to obtain an antibacterial and anti-pollution ZIF-8 / PVDF composite membrane.

[0011] Preferably, the ZIF-8 / PVDF composite membrane comprises non-woven fabric, a PVDF substrate membrane loaded on the non-woven fabric, and ZIF-8 nanomaterials loaded on the PVDF substrate membrane.

[0012] Preferably, the soaking temperature is 20-30°C; the soaking time is 5-24 h.

[0013] Preferably, the mass ratio of the polyvinylidene fluoride powder, the pore-forming agent, and the organic solvent is 1:(1-3):(8-10); the concentration of the ZIF-8 nanomaterials in the casting solution is 0.2-5 g / L.

[0014] Preferably, the pore-forming agent comprises at least one of polyvinylpyrrolidone and polyethylene glycol.

[0015] Preferably, the organic solvent comprises at least one of dimethyl sulfoxide, N,N-dimethylacetamide, N,N-dimethylformamide, and N-methylpyrrolidone.

[0016] The present invention also provides a preparation method of the ZIF-8 nanomaterials described in the above technical solutions, comprising the following steps:

[0017] Mix an organic solvent and a metal salt, stir evenly to obtain a metal source solution; mix an organic solvent and an organic ligand, stir evenly to obtain a ligand solution, pour the ligand solution into the metal source solution, stir and mix the two, and fully react to obtain a reaction solution;

[0018] Age, wash, dry, and grind the reaction solution to obtain ZIF-8 nanomaterials.

[0019] Preferably, the organic solvent is one of methanol, ethanol, pure water, and N,N-dimethylformamide; the metal salt is one of zinc nitrate hexahydrate, zinc acetate, and zinc oxide; the stirring speed is 100 - 600 rpm; the stirring time is 0.5 - 12 h; the aging time is 12 - 24 h.

[0020] Preferably, the molar ratio of the metal salt to the organic ligand is (1 - 8):1; the washing solution is 30 - 60 mL of methanol and 30 - 60 mL of pure water, washed 2 - 3 times in sequence; the drying temperature is 60 - 80 °C, and the time is 8 - 24 h; after grinding, it is passed through a 200 - 400 mesh sieve.

[0021] The present invention provides a ZIF-8 / PVDF antibacterial and anti-fouling composite membrane obtained by the preparation method of the above technical solution.

[0022] The present invention provides the application of the ZIF-8 / PVDF antibacterial and anti-fouling composite membrane described in the above technical solution in the field of water treatment.

[0023] The present invention innovatively proposes a preparation scheme for the ZIF-8 / PVDF composite membrane, achieving through pore regulation of nanoparticles: 1) selective material transport based on molecular sieve effect; 2) constructing a biological fouling defense system by utilizing the inherent antibacterial activity of ZIF-8. Starting from the intrinsic characteristics of the material, this technical solution establishes an optimization path for the performance of membrane materials of "structural modification - functional integration", providing a new solution for the development of long-term anti-fouling membrane separation materials. Further, the ZIF-8 of the present invention is simple to prepare, enhances hydrophilicity, improves the rejection rate of BSA, and has a strong antibacterial effect, showing high anti-fouling performance, excellent antibacterial performance, a relatively simple process, which can greatly improve production efficiency, reduce production costs, and is suitable for large-scale industrial production. Description of the Drawings

[0024] Figure 1 SEM image of the ZIF-8 nanoparticles prepared in the example;

[0025] Figure 2 XRD pattern of the ZIF-8 nanoparticles prepared in the example;

[0026] Figure 3 Colony decline curve graph of the ZIF-8 nanoparticles prepared in the example;

[0027] Figure 4 Contact angle graphs of the M0 membrane in the comparative example and the MN1, MN2, and MN3 composite membranes prepared in the example;

[0028] Figure 5 Pure water flux and BSA rejection rate of the M0 membrane in the comparative example and the MN1, MN2, and MN3 composite membranes prepared in the example;

[0029] Figure 6 Analysis of the anti-pollution properties of the comparative example M0 membrane and the MN1, MN2, and MN3 composite membranes prepared in the examples;

[0030] Figure 7 Antibacterial diagram of the ZIF-8 / PVDF composite membrane prepared in the example. Detailed implementation manner

[0031] The object of the present invention is to provide a preparation method and application of an antibacterial and anti-pollution ZIF-8 / PVDF composite membrane, including the following steps:

[0032] Mix polyvinylidene fluoride nano-powder, pore-forming agent, organic solvent, and ZIF-8 nano-material to obtain a ZIF-8 / PVDF casting solution;

[0033] Coat the ZIF-8 / PVDF casting solution onto the non-woven fabric, then soak it in a coagulation bath, and obtain a ZIF-8 / PVDF composite membrane after drying.

[0034] In the present invention, the mass ratio of the polyvinylidene fluoride powder (PVDF), pore-forming agent, and organic solvent is 1:(1-3):(8-10); further preferably 1:1:8; the concentration of the ZIF-8 nano-material in the casting solution is 0.2-5 g / L. In the present invention, the particle size of the PVDF powder is preferably 100-200 μm, and further preferably 120-180 μm.

[0035] In the present invention, the pore-forming agent includes at least one of polyvinylpyrrolidone and polyethylene glycol. The pore-forming agent in the present invention is preferably polyethylene glycol, and the molecular weight is preferably 200-800 Da, and further preferably 400 Da.

[0036] In the present invention, the organic solvent includes at least one of dimethyl sulfoxide, N,N-dimethylacetamide, N,N-dimethylformamide, and N-methylpyrrolidone, and is further preferably N,N-dimethylacetamide.

[0037] In the present invention, the mixing of the PVDF powder, pore-forming agent, and organic solvent preferably includes: adding the PVDF powder to the mixed solution of the organic solvent and the pore-forming agent. In the present invention, the mixing is preferably carried out under stirring conditions; the stirring time is preferably 12-24 h, and further preferably 18-24 h. In the present invention, the stirring is preferably carried out with a glass rod. Compared with mechanical stirring, manual glass rod stirring makes the reaction of the organic solvent more sufficient and avoids the problem of PVDF powder caking.

[0038] In the present invention, the coating method is preferably coating; the equipment used for coating is preferably a film doctor. In the present invention, the thickness of the coating is preferably set to 200 - 300 μm, more preferably 250 μm; the standing time after coating is preferably 10 - 30 s, more preferably 20 - 30 s.

[0039] In the present invention, the non-woven fabric preferably comprises a polyester non-woven fabric.

[0040] In the present invention, the coagulation bath is a deionized water coagulation bath; the temperature of the immersion is 20 - 30 °C, more preferably 25 °C; the immersion time is preferably 12 - 24 h, more preferably 20 - 24 h.

[0041] In the present invention, the drying temperature is preferably 40 - 80 °C, more preferably 45 - 60 °C; the drying time is preferably 5 - 10 h, more preferably 8 - 10 h.

[0042] In the present invention, the ZIF-8 / PVDF composite membrane comprises a non-woven fabric, a PVDF substrate membrane loaded on the non-woven fabric, and ZIF-8 nanomaterials loaded on the PVDF substrate membrane. In the present invention, the thickness of the PVDF substrate membrane is preferably 200 - 250 μm.

[0043] A preparation method of ZIF-8 nanomaterials provided by the present invention is characterized in that the preparation method comprises the following steps:

[0044] Mix an organic solvent and a metal salt, and stir evenly to obtain a metal source solution; mix an organic solvent and an organic ligand, and stir evenly to obtain a ligand solution; pour the ligand solution into the metal source solution, mix the two, and fully react to obtain a reaction solution;

[0045] Age, wash, dry, and grind the reaction solution to obtain ZIF-8 nanomaterials.

[0046] In the present invention, the organic solvent is one of methanol, ethanol, pure water, and N,N-dimethylformamide, more preferably methanol; the metal salt is one of zinc nitrate hexahydrate, zinc acetate, and zinc oxide, more preferably zinc nitrate hexahydrate; the stirring time is 0.5 - 12 h; the aging time is 12 - 24 h.

[0047] In the present invention, the molar ratio of the metal salt to the organic ligand is 1:(1 - 8), more preferably (1:4); the washing solution is 30 - 60 mL of methanol and 30 - 60 mL of pure water, and wash 2 - 3 times in sequence; the drying temperature is 60 - 80 °C, and the time is 8 - 24 h; after grinding, sieve through a 200 - 400 mesh sieve.

[0048] The present invention provides an antibacterial and anti-pollution ZIF-8 / PVDF composite membrane obtained by the preparation method of the above technical solution.

[0049] The technical solutions of the present invention will be described in detail below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work fall within the protection scope of the present invention.

[0050] Embodiment

[0051] (1) Weigh 0.595 g of zinc nitrate hexahydrate and dissolve it in 40 mL of methanol for full dissolution to form solution A; weigh 0.6568 g of dimethylimidazole and dissolve it in 40 mL of methanol for full dissolution to form solution B; then slowly pour solution B into solution A, with a stirring speed of 300 rpm; the stirring time is 2 h; after the reaction ends, age for 24 h;

[0052] (2) Centrifuge the solution obtained in step (1), with a centrifuge speed of 8000 rpm and a centrifugation time of 10 min, and repeat three times; shake and centrifuge with methanol and deionized water, pour off the supernatant, and repeat three times;

[0053] (3) Vacuum-dry the precipitate obtained in step (2) at 80 °C for 24 h to obtain ZIF-8 nanomaterials.

[0054] (4) Weigh 0.1 g, 0.3 g, and 0.5 g of the ZIF-8 nanomaterials and 10 g of PVDF powder respectively, add them to 80 mL of DMAc (and appropriately adjust the DMAC content) and 10 mL of polyethylene glycol solvent, and ultrasonically mix them evenly. Stir with a glass rod manually at 80 °C for 24 h to obtain ZIF-8 / PVDF casting solutions, numbered M1 (corresponding to 0.1 g of ZIF-8 nanomaterials), M2 (corresponding to 0.3 g of ZIF-8 nanomaterials), and M3 (corresponding to 0.5 g of ZIF-8 nanomaterials) in sequence;

[0055] (5) Place the three ZIF-8 / PVDF casting solutions in a vacuum drying oven and let them stand for defoaming at 60 °C for 2 h; use a film scraping machine, adjust the thickness to 250 μm, then coat it on the non-woven fabric, and then soak it in a deionized water coagulation bath for 12 h and dry for 8 h to obtain ZIF-8 / PVDF non-woven fabric composites, MN1 (corresponding to M1), MN2 (corresponding to M2), and MN3 (corresponding to M3);

[0056] (6) Cut MN1, MN2, and MN3 into circular membrane pieces with a radius of 4.5 cm for subsequent experiments.

[0057] Comparative Example

[0058] Using the method in step (4) of the example, 10 g of PVDF powder was added to 80 mL of DMAc and 10 mL of polyethylene glycol solvent, and ultrasonically mixed evenly without adding ZIF-8 nanomaterial. Stir with a glass rod manually at 80 °C for 24 h to obtain a PVDF casting solution, numbered M0 (corresponding to the PVDF membrane).

[0059] Structure Characterization and Performance Testing

[0060] Figure 1 SEM image of the ZIF-8 nanomaterial prepared in the example. It can be seen that the synthesized ZIF-8 presents a rhombic dodecahedron shape.

[0061] Figure 2 XRD pattern of the ZIF-8 nanomaterial prepared in the example. Strong diffraction peaks appear at 2θ values of 7.37°, 10.40°, 12.73°, 14.69°, 16.45°, 18.03°, 22.12°, 24.49° and 26.65°, revealing that the material has a sodalite (SOD)-type structure with high crystallinity. These peaks correspond to crystal planes such as (011), (002), (112), (022), (013), (222), (114), etc. The appearance of these characteristic peaks confirms the successful preparation of ZIF-8.

[0062] Test Example 1

[0063] Weigh 5 mg of the ZIF-8 material prepared in the example, add 1 mL of 0.9% sterile physiological saline for dissolution. When the ZIF-8 material is completely dissolved into a solution, through the two-fold dilution method, the concentration is diluted to 0.3125 mg / mL. Using Escherichia coli as the bacterial model, adjust the bacterial solution concentration to about 10 5 ~10 6 CFU / mL. Mix the bacteria with the material. At different time intervals of 0.5 h, 1 h, 1.5 h, 2 h, 3 h, 4 h, dilute with physiological saline and coat on a solid agar plate. After culturing in a 37 °C incubator for 24 h, count the number of colonies on the surface of the culture medium.

[0064] Figure 3 Antibacterial schematic diagram of the ZIF-8 nanomaterial prepared in the example against Escherichia coli. It can be seen that within 4 h, the antibacterial property of the material ZIF-8 reaches 99.9%.

[0065] Test Example 2

[0066] The MN1, MN2, and MN3 prepared in the examples and M0 prepared in the comparative example were each cut into a size of 2 cm × 7 cm. After being soaked in distilled water for 24 h, they were placed in an oven at 45 °C and dried for 12 h, and then adhered to a glass slide with double-sided tape. The contact angle of the membrane surface was measured with a contact angle meter. Under the conditions of constant room temperature and constant humidity, pure water was used as the liquid medium for measuring the contact angle of the membrane. The liquid droplet volume was set to 10 μL, and three different points of each sample were taken for measuring the average value.

[0067] Test Example 3

[0068] The circular membrane sheets of MN1, MN2, and MN3 with a radius of 4.5 cm prepared in the examples and M0 prepared in the comparative example were respectively placed in an MSC-300 ultrafiltration cup to test the pure water flux and antifouling performance. The membrane to be tested was installed in the ultrafiltration cup, and pure water was introduced from the upper solution inlet. After ensuring the airtightness of the ultrafiltration cup, the gas cylinder and gas valve were opened, and water molecules passed through the membrane pores under the action of air pressure. The filtered water flowed out from the lower outlet, and the membrane was pre-pressed for half an hour at a pressure of 0.1 MPa. First, the pure water flux (J W1 ) was measured, and then the flux of 1 g / L BSA solution (J P ) was measured to simulate protein fouling. After cleaning the fouled membrane, the pure water flux of the cleaned membrane (J W2 ) was measured again.

[0069] Prepare 0.1 g / L, 0.3 g / L, 0.5 g / L, 0.7 g / L, 0.9 g / L, and 1.0 g / L BSA standard solutions for use. Use a TU-1950 ultraviolet-visible spectrophotometer to test the above BSA solutions with different concentrations at 280 nm, and obtain the BSA standard curve according to the absorbance, y = bx.

[0070] The calculation formula for the pure water flux (J W1 ) is shown in Equation 1:

[0071]

[0072] In Equation 1, J W1 The unit of the pure water flux is L m -2 h -1 ; V represents the volume of pure water (L); A represents the effective area of the membrane to be tested (m 2 ); T represents the filtration time (h)

[0073] The calculation formula for the BSA solution flux (J P ) is shown in Equation 2:

[0074]

[0075] In Equation 2, V represents the volume of the BSA solution; A represents the effective area of the membrane to be tested (m2 ); T represents the filtration time (h)

[0076] The pure water flux (J of the membrane being cleaned W2 ) is calculated by Equation 3 as follows:

[0077]

[0078] In Equation 3, V represents the volume of pure water; A represents the effective area of the membrane to be tested (m 2 ); T represents the filtration time (h)

[0079] The calculation formula for the BSA rejection rate (R) is shown in Equation 4:

[0080]

[0081] In Equation 4, R represents the BSA rejection rate (%); C1 represents the initial BSA solution concentration (g / L); C2 represents the solution concentration after filtration (g / L)

[0082] The calculation formula for the flux recovery rate (FRR) is shown in Equation 5:

[0083]

[0084] The calculation formula for the reversible fouling rate (Rr) is shown in Equation 6:

[0085]

[0086] The calculation formula for the irreversible fouling rate (Rir) is shown in Equation 7:

[0087]

[0088] The calculation formula for the total fouling rate (Rt) is shown in Equation 8:

[0089]

[0090] Test Example 4

[0091] Using Escherichia coli as the bacterial model, a certain concentration of bacterial solution (about 10 5 ~10 6 CFU / mL) was used as the feed solution, and ultrafiltration experiments were carried out on MN1, MN2, and MN3 prepared in the examples and M0 prepared in the comparative example under an operating pressure of 30 kPa. The precipitates of various membrane samples were collected, and 100 μL of the filtrate was spread onto a solid medium with a glass spreader. The bacterial solution was spread on the solid plate with a sterilized spreader and placed in an incubator at 37 °C for 24 h, and then the number of colonies on the surface of the medium was observed. All reported values are based on at least 3 repeated measurements.

[0092] Figure 4 Contact angles of MN1, MN2, and MN3 prepared in the examples and M0 prepared in the comparative example; the contact angles of MN1, MN2, and MN3 are 85.467°, 84.074°, and 80.754° respectively, all lower than the contact angle (91.8°) of the M0 membrane, indicating that the hydrophilicity of the modified membrane has increased.

[0093] Figure 5 Pure water fluxes and BSA rejection rates of MN1, MN2, and MN3 prepared in the examples and M0 prepared in the comparative example; Figure 6 Analysis of flux recovery rate and anti-fouling performance of MN1, MN2, and MN3 prepared in the examples and M0 prepared in the comparative example. Combining Figures 5 - 6 with the results, the contact angle of M0 is 91.8°, the pure water flux is 21.83 L / m 2 h, the BSA rejection rate is 37.2%, and the flux recovery rate after physical cleaning after filtering BSA is 59.78%, and the irreversible fouling rate is 40.22%. The reason is that M0 has strong hydrophobicity due to C-F bonds, making the membrane surface vulnerable to contamination by substances such as proteins. The pure water fluxes of MN1, MN2, and MN3 prepared in the examples are significantly improved compared to M0, and MN1, MN2, and MN3 have good flux recovery. The pure water fluxes are 37.3 L / m 2 h, 50.55 L / m 2 h, 42.37 L / m 2 h, respectively, which are improved compared to the M0 membrane (21.83 L / m 2 h); the BSA rejection rates are 59%, 77.1%, and 68.3%; the flux recovery rates are 70.54%, 94.32%, and 75.69% respectively, and the irreversible fouling rates are 29.46%, 5.68%, and 24.31% respectively; indicating that after modification with ZIF-8 material, the hydrophilicity and anti-fouling performance of MN2 are improved, and the irreversible fouling rate is reduced, indicating that the pollutants on the membrane surface can be removed by physical cleaning. The reason for the decrease in the flux and rejection rate of MN3 may be that too many doped ZIF-8 nanoparticles are doped, thus blocking some surface pores.

[0094] Figure 7 Original bacterial liquid concentration and colony growth conditions after filtering the bacterial liquid with MN2 prepared in the examples and M0 membrane prepared in the comparative example; it can be seen that the MN2 membrane has good retention and inhibition rate for Escherichia coli.

[0095] The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of an antibacterial and anti-pollution ZIF-8 / PVDF composite membrane, comprising the following steps: Mix polyvinylidene fluoride powder, a pore-forming agent, an organic solvent, and ZIF-8 nanomaterials to obtain a ZIF-8 / PVDF casting solution; Coat the ZIF-8 / PVDF casting solution onto non-woven fabric, soak it in a coagulation bath in sequence and dry it to obtain an antibacterial and anti-fouling ZIF-8 / PVDF composite membrane.

2. The preparation method according to claim 1, characterized in that, The ZIF-8 / PVDF composite membrane comprises non-woven fabric, a PVDF base membrane loaded on the non-woven fabric, and ZIF-8 nanomaterials loaded on the PVDF base membrane.

3. The preparation method according to claim 1, characterized in that, The soaking temperature is 20-30°C; the soaking time is 5-24 h.

4. The preparation method according to claim 1, wherein The mass ratio of the polyvinylidene fluoride powder, the pore-forming agent, and the organic solvent is 1:(1-3):(8-10); the concentration of the ZIF-8 nanomaterials in the casting solution is 0.2-5 g / L.

5. The preparation method according to claim 1, characterized in that, The pore-forming agent comprises at least one of polyvinylpyrrolidone and polyethylene glycol.

6. The preparation method according to claim 1, wherein The organic solvent comprises at least one of dimethyl sulfoxide, N,N-dimethylacetamide, N,N-dimethylformamide, and N-methylpyrrolidone.

7. A preparation method of ZIF-8 nanomaterial, characterized in that, The preparation method comprises the following steps: Mix an organic solvent and a metal salt, stir evenly to obtain a metal source solution; mix an organic solvent and an organic ligand, stir evenly to obtain a ligand solution; pour the ligand solution into the metal source solution, mix the two, and fully react to obtain a reaction solution; Age, wash, dry, and grind the reaction solution to obtain ZIF-8 nanomaterials.

8. The preparation method according to claim 7, characterized in that, The organic solvent is one of methanol, ethanol, pure water, and N,N-dimethylformamide; the metal salt is one of zinc nitrate hexahydrate, zinc acetate, and zinc oxide; the stirring time is 0.5-12 h; the aging time is 12-24 h.

9. The preparation method according to claim 7, wherein The molar ratio of the metal salt to the organic ligand is (1-8):1; the washing solution is 30-60 mL of methanol and 30-60 mL of pure water, wash 2-3 times in sequence; the drying temperature is 60-80°C, and the time is 8-24 h; pass through a 200-400 mesh sieve after grinding.

10. An antibacterial and anti-pollution ZIF-8 / PVDF composite membrane obtained by using the preparation method according to claims 1-6.

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