A preparation method of MOFs-PVDF composite ultrafiltration membrane

Abstract

The present invention relates to the field of membrane separation technology, and provides a method for preparing a MOFs-PVDF composite ultrafiltration membrane with a bactericidal function. The method comprises: adding a MOFs material to an aqueous solution containing an iron source and a silver source, stirring and mixing, and obtaining a precursor solution; adding a sodium hydroxide solution to the precursor solution, stirring, passing an oxidizing gas, filtering, and drying to obtain a modified MOFs material loaded with AgO and FeOOH; adding a hydroxyl-containing PVDF, a modified MOFs material, and a porogen to an organic solvent, preparing a casting solution, coating the casting solution, and performing gel curing in a non-aqueous coagulation bath to obtain a MOFs-PVDF composite ultrafiltration membrane with a bactericidal function. The MOFs-PVDF composite ultrafiltration membrane prepared by the present invention has good hydrophilicity, strong anti-pollution ability, and at the same time has bactericidal and antibacterial functions, and can be used in the field of water treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of membrane separation, and in particular to a method for preparing a MOFs-PVDF composite ultrafiltration membrane with a bactericidal function. Background Art

[0002] Polymer separation membranes are a material used in modern high-efficiency separation, concentration, purification, and decontamination equipment. They are widely used in the chemical, environmental, food, biological, pharmaceutical, electronic, electric power, metallurgy, textile, and seawater desalination industries, playing a vital role in addressing contemporary energy, resource, and environmental pollution issues. Commonly used membrane materials include polyvinylidene fluoride, polysulfone, and polyvinyl chloride.

[0003] Metal-organic framework compounds (MOFs) are materials with supramolecular microporous network structures formed by the metal-ligand complexation between organic ligands and metal ions. Due to their special topological structure, regular internal arrangement, and pores of specific size and shape, they have the advantages of high porosity, large specific surface area, easy synthesis, and variable skeleton size. Therefore, they are widely used in adsorption, catalysis, membrane separation and other fields.

[0004] For example, CN111135733A discloses a MOFs polymer hollow fiber composite ultrafiltration membrane and its preparation method. The membrane is first prepared using a thermally induced phase separation method to form a high-strength polyvinylidene fluoride / polyacrylic acid (PVDF / PAA) ultrafiltration membrane. A chelation-assisted interfacial reaction method is then used to in situ grow an ultrathin MOFs separation layer on the outer surface of the membrane. This membrane is suitable for water treatment applications. However, this composite ultrafiltration membrane lacks bactericidal properties.

[0005] Currently, when ultrafiltration membranes are used as reverse osmosis pretreatment to produce purified water, they can only adsorb proteins and tiny microorganisms in drinking water onto the membrane surface, preventing them from passing through, but they cannot kill them. As a result, drinking water contains a large number of bacterial microorganisms, which pose a serious threat to people's drinking water health. Therefore, it is necessary to develop a method for preparing ultrafiltration membranes with bactericidal functions. Summary of the Invention

[0006] In response to the shortcomings of the existing technology, the present invention provides a method for preparing a MOFs-PVDF composite ultrafiltration membrane with a bactericidal function. The prepared MOFs-PVDF composite ultrafiltration membrane has good hydrophilicity, strong anti-pollution ability, and at the same time has bactericidal and antibacterial functions. It can be used in the field of water treatment, especially in the purification of wastewater containing a large amount of iron ions, the preparation of household drinking pure water, and the purification of circulating water.

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

[0008] In one aspect, the present invention provides a method for preparing a MOFs-PVDF composite ultrafiltration membrane, comprising:

[0009] (1) adding MOFs material to an aqueous solution containing an iron source and a silver source, stirring and mixing, and obtaining a precursor solution;

[0010] (2) adding sodium hydroxide solution to the precursor solution, stirring, introducing oxidizing gas, filtering, and drying to obtain a modified MOFs material loaded with AgO and FeOOH;

[0011] (3) adding hydroxyl-containing PVDF, modified MOFs material, and porogen to an organic solvent, stirring and mixing, standing and degassing to obtain a casting solution, coating the casting solution, and performing gel curing in a non-aqueous coagulation bath to obtain a MOFs-PVDF composite ultrafiltration membrane with a bactericidal function;

[0012] Wherein, the MOFs material is one of ZIF-8, MIL-101, and UIO-66.

[0013] According to the preparation method of MOFs-PVDF composite ultrafiltration membrane provided by the present invention, on the one hand, the present invention modifies polyvinylidene fluoride (PVDF) to make it rich in hydroxyl groups, and the hydroxyl groups can increase the binding force between the organic metal framework material and the polymer matrix. The introduction of the organic metal framework material can enhance the hydrophilicity and anti-pollution ability of the composite ultrafiltration membrane. On the other hand, the MOFs material is modified to load AgO and iron oxyhydroxide (FeOOH). The AgO can slowly release Ag. 2+ , high-priced Ag 2+ With lower price than Ag + Stronger bactericidal effect. AgO has a certain photocatalytic effect. After being excited by light, it produces electrons and holes. The presence of FeOOH can promote the photocatalytic process of AgO, thereby giving the composite ultrafiltration membrane excellent bactericidal and antibacterial properties.

[0014] As a preferred embodiment of the present invention, the iron source is ferric nitrate; the silver source is silver nitrate.

[0015] As a preferred embodiment of the present invention, the mass fraction of the sodium hydroxide solution is 1 to 10%.

[0016] As a preferred embodiment of the present invention, the oxidizing gas is any one of O3, O2, O3 / O2 mixed gas, O3 / N2 mixed gas, and O2 / N2 mixed gas. By introducing the oxidizing gas, the iron hydroxide is oxidized to FeOOH, Ag + Oxidized to Ag 2+ .

[0017] As a preferred embodiment of the present invention, the time for introducing the oxidizing gas is 20 to 40 minutes, and the drying is vacuum drying at 40 to 80° C. for 4 to 8 hours.

[0018] As a preferred embodiment of the present invention, the mass of AgO is 5-15% of the mass of the MOFs material, for example: 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, and so on.

[0019] As a preferred embodiment of the present invention, the mass of the FeOOH is 1-10% of the mass of the MOFs material, for example: 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, and so on.

[0020] As a preferred embodiment of the present invention, the mass of the modified MOFs material is 1-10% of the total mass of the casting solution, for example: 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, and so on.

[0021] As a preferred embodiment of the present invention, the mass of the hydroxyl-containing PVDF is 10-30% of the total mass of the casting solution.

[0022] As a preferred embodiment of the present invention, based on the total mass of the casting solution as 100%, the content of the hydroxyl PVDF is 10-30%, the modified MOFs material is 1-10%, the porogen is 1-3%, and the balance is solvent.

[0023] As a preferred embodiment of the present invention, the organic solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone and dimethyl sulfoxide.

[0024] As a preferred embodiment of the present invention, the porogen is preferably polyvinyl pyrrolidone.

[0025] On the other hand, the present invention provides a MOFs-PVDF composite ultrafiltration membrane obtained by the above preparation method.

[0026] On the other hand, the present invention provides the use of MOFs-PVDF composite ultrafiltration membrane in water treatment.

[0027] Compared with the prior art, the present invention has the following technical effects:

[0028] (1) In the preparation method of the MOFs-PVDF composite ultrafiltration membrane provided by the present invention, on the one hand, the present invention modifies polyvinylidene fluoride (PVDF) to make it rich in hydroxyl groups, and the hydroxyl groups can increase the binding force between the organic metal framework material and the polymer matrix. The introduction of the organic metal framework material can enhance the hydrophilicity and anti-pollution ability of the composite ultrafiltration membrane. On the other hand, AgO can slowly release Ag. 2+ , high-priced Ag 2+ It has strong bactericidal properties, and its bactericidal effect is the best among low-cost Ag + AgO has a certain photocatalytic effect. After being excited by light, it produces electrons and holes. The presence of FeOOH (iron oxyhydroxide) can promote the photocatalytic process of AgO, thereby improving the bactericidal performance.

[0029] (2) The MOFs-PVDF composite ultrafiltration membrane prepared by the present invention has good hydrophilicity, strong anti-pollution ability, and excellent bactericidal performance. It can kill bacterial microorganisms in drinking water and ensure the safety of residents' water use. DETAILED DESCRIPTION

[0030] Unless otherwise specified, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which this invention belongs. All patents and publications related to this invention are incorporated herein by reference in their entirety. The terms "comprising" or "including" are open-ended expressions, meaning that they include the contents specified in the present invention but do not exclude other aspects.

[0031] The following is a detailed introduction to the preparation method of the MOFs-PVDF composite ultrafiltration membrane according to the embodiment provided by the present invention.

[0032] 1. Preparation of hydroxyl-containing PVDF

[0033] The preparation method of the hydroxyl-containing PVDF can be referred to CN107626216A. The details are as follows:

[0034] The PVDF is first treated with alkali solution, and then the PVDF treated with alkali solution is reacted in an isopropanol solution of sodium borohydride. After the reaction is completed, the PVDF is filtered and dried to obtain the hydroxyl-containing PVDF.

[0035] Specifically, the alkali solution is a lithium hydroxide aqueous solution with a mass fraction of 3%; the reaction conditions of the alkali solution treatment are: stirring and reacting at 25-60° C. for 36-72 hours.

[0036] Specifically, the mass fraction of the sodium borohydride isopropanol solution is 0.1-1.5%, more preferably 0.2%; the reduction reaction conditions in the sodium borohydride isopropanol solution are: stirring the reaction at room temperature for 18-36 hours.

[0037] According to some embodiments provided by the present invention, the preparation of the hydroxyl-containing PVDF specifically includes: immersing 50g of PVDF in an aqueous solution of 200g of lithium hydroxide (mass fraction 3%), stirring at 50°C for 48h, and then rinsing with water (2000mL) and isopropanol (2000mL), respectively; then adding the rinsed PVDF to 200g of an isopropanol solution of sodium borohydride (mass fraction 0.2%), stirring the reaction at room temperature for 24h, filtering, and drying to obtain hydroxyl-containing PVDF.

[0038] 2. Preparation of modified MOFs materials

[0039] Adding MOFs material to an aqueous solution containing iron nitrate and silver nitrate, stirring and mixing to obtain a precursor solution;

[0040] Sodium hydroxide solution was added to the precursor solution, stirred, introduced into an oxidizing gas, filtered, and dried to obtain a modified MOFs material loaded with AgO and FeOOH.

[0041] Preferably, the MOFs material is one of ZIF-8, MIL-101, and UIO-66.

[0042] Examples of the MIL-101 materials include, but are not limited to, MIL-101 (Fe).

[0043] The UIO-66 may include UiO-66(Ce), UiO-66(Zr), UiO-66(Ti), etc., but is not limited thereto.

[0044] The preparation method of the MOFs material is not particularly limited and can be carried out by any method known in the art, such as a hydrothermal method.

[0045] As a preferred embodiment of the present invention, the mass fraction of the sodium hydroxide solution is 1% to 10%, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc. The amount of the sodium hydroxide solution is not particularly limited, as long as it can fully react with the iron source and the silver source.

[0046] As a preferred embodiment of the present invention, the oxidizing gas is any one of O3, O2, O3 / O2 mixed gas, O3 / N2 mixed gas, and O2 / N2 mixed gas. By introducing the oxidizing gas, the iron hydroxide is oxidized to FeOOH, Ag + Oxidized to Ag 2+ .

[0047] As a preferred embodiment of the present invention, the time for introducing the oxidizing gas is 20 to 40 minutes, and the drying is vacuum drying at 40 to 80° C. for 4 to 8 hours.

[0048] As a preferred embodiment of the present invention, the mass of AgO is 5-15% of the mass of the MOFs material, for example: 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, and so on.

[0049] As a preferred embodiment of the present invention, the mass of the FeOOH is 1-10% of the mass of the MOFs material, for example: 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, and so on.

[0050] 3. Preparation of MOFs-PVDF composite ultrafiltration membrane

[0051] Hydroxyl-containing PVDF, modified MOFs material, and porogen are added to an organic solvent, stirred for 12-24 hours, and then allowed to stand for degassing to obtain a casting solution; the casting solution is coated on a substrate, allowed to remain in the air for 30-60 seconds, and then immersed in a non-aqueous coagulation bath for gel curing to obtain a MOFs-PVDF composite ultrafiltration membrane with bactericidal function.

[0052] According to the embodiment provided by the present invention, the composition of the casting solution includes: based on the total mass of the casting solution as 100%, 10-30% hydroxyl-containing PVDF, 1-10% modified MOFs material, 1-3% porogen, and the balance being organic solvent.

[0053] According to an embodiment provided by the present invention, the organic solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone and dimethyl sulfoxide.

[0054] According to an embodiment provided by the present invention, the porogen is polyvinyl pyrrolidone.

[0055] Specifically, the non-aqueous coagulation bath may be a mixed solvent of acetone and the organic solvent.

[0056] The substrate includes but is not limited to a glass plate, a PET release film, mica, and the like.

[0057] The coating method may be blade coating, slot extrusion, micro-dimpled coating, etc. In the embodiment of the present invention, the coating method is blade coating, and the blade gap can be adjusted according to the obtained film thickness.

[0058] The embodiments of the present invention will be described in detail below with reference to the examples, but it will be understood by those skilled in the art that the following examples are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. In the examples, if no specific conditions are specified, the conditions described in the specification sheets or conventional conditions or the conditions recommended by the manufacturer are followed. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0059] Example 1

[0060] The preparation method of the MOFs-PVDF composite ultrafiltration membrane provided in this embodiment comprises the following steps:

[0061] (1) Preparation of modified MOFs materials

[0062] The MOFs material is ZIF-8. In the obtained modified ZIF-8 material, the mass of AgO is 10% of the mass of ZIF-8, and the mass of FeOOH is 5% of the mass of ZIF-8.

[0063] According to the above proportions, Fe(NO3)3 and AgNO3 were weighed and dissolved in water, stirred for 30 min; then ZIF-8 was added and stirred at room temperature for 1.5 h to obtain a precursor solution;

[0064] An 8% mass fraction of NaOH solution was added to the precursor solution, and the mixture was stirred for 15 minutes. Then, an O2 / N2 mixed gas was introduced and stirred for 30 minutes. The mixture was filtered and washed, and vacuum dried at 60°C for 4 hours to obtain a modified ZIF-8 material loaded with AgO and FeOOH.

[0065] (2) Preparation of MOFs-PVDF composite ultrafiltration membrane

[0066] Taking the total mass of the casting liquid as 100%, 20% hydroxyl-containing PVDF, 5% modified ZIF-8 material, 3% polyvinyl pyrrolidone, and 72% N-methyl pyrrolidone were stirred and mixed for 12 hours, and then directly degassed to obtain a casting liquid; the casting liquid was coated on a glass plate with a coating thickness of 250 μm. After staying in the air for 40 seconds, it was immersed in a mixed solvent of acetone and N-methyl pyrrolidone for gel curing to obtain a MOFs-PVDF composite ultrafiltration membrane.

[0067] Example 2

[0068] The preparation method of the MOFs-PVDF composite ultrafiltration membrane provided in this embodiment comprises the following steps:

[0069] (1) Preparation of modified MOFs materials

[0070] The preparation method is the same as that of Example 1. In the obtained modified ZIF-8 material, the mass of AgO is 10% of the mass of ZIF-8, and the mass of FeOOH is 10% of the mass of ZIF-8.

[0071] (2) Preparation of MOFs-PVDF composite ultrafiltration membrane

[0072] Taking the total mass of the casting liquid as 100%, 20% hydroxyl-containing PVDF, 5% modified ZIF-8 material, 3% polyvinyl pyrrolidone, and 72% N-methyl pyrrolidone were stirred and mixed for 12 hours, and then directly degassed to obtain a casting liquid; the casting liquid was coated on a glass plate with a coating thickness of 250 μm. After staying in the air for 40 seconds, it was immersed in a mixed solvent of acetone and N-methyl pyrrolidone for gel curing to obtain a MOFs-PVDF composite ultrafiltration membrane.

[0073] Example 3

[0074] The preparation method of the MOFs-PVDF composite ultrafiltration membrane provided in this embodiment comprises the following steps:

[0075] (1) Preparation of modified MOFs materials

[0076] The preparation method is the same as that of Example 1. In the obtained modified ZIF-8 material, the mass of AgO is 10% of the mass of ZIF-8, and the mass of FeOOH is 1% of the mass of ZIF-8.

[0077] (2) Preparation of MOFs-PVDF composite ultrafiltration membrane

[0078] Taking the total mass of the casting liquid as 100%, 20% hydroxyl-containing PVDF, 5% modified ZIF-8 material, 3% polyvinyl pyrrolidone, and 72% N-methyl pyrrolidone were stirred and mixed for 12 hours, and then directly degassed to obtain a casting liquid; the casting liquid was coated on a glass plate with a coating thickness of 250 μm. After staying in the air for 40 seconds, it was immersed in a mixed solvent of acetone and N-methyl pyrrolidone for gel curing to obtain a MOFs-PVDF composite ultrafiltration membrane.

[0079] Example 4

[0080] The preparation method of the MOFs-PVDF composite ultrafiltration membrane provided in this embodiment comprises the following steps:

[0081] (1) Preparation of modified MOFs materials

[0082] The preparation method is the same as that of Example 1. In the obtained modified ZIF-8 material, the mass of AgO is 5% of the mass of ZIF-8, and the mass of FeOOH is 5% of the mass of ZIF-8.

[0083] (2) Preparation of MOFs-PVDF composite ultrafiltration membrane

[0084] Taking the total mass of the casting liquid as 100%, 20% hydroxyl-containing PVDF, 5% modified ZIF-8 material, 3% polyvinyl pyrrolidone, and 72% N-methyl pyrrolidone were stirred and mixed for 12 hours, and then directly degassed to obtain a casting liquid; the casting liquid was coated on a glass plate with a coating thickness of 250 μm. After staying in the air for 40 seconds, it was immersed in a mixed solvent of acetone and N-methyl pyrrolidone for gel curing to obtain a MOFs-PVDF composite ultrafiltration membrane.

[0085] Example 5

[0086] The preparation method of the MOFs-PVDF composite ultrafiltration membrane provided in this embodiment comprises the following steps:

[0087] (1) Preparation of modified MOFs materials

[0088] The preparation method is the same as that of Example 1. In the obtained modified ZIF-8 material, the mass of AgO is 15% of the mass of ZIF-8, and the mass of FeOOH is 5% of the mass of ZIF-8.

[0089] (2) Preparation of MOFs-PVDF composite ultrafiltration membrane

[0090] Taking the total mass of the casting liquid as 100%, 20% hydroxyl-containing PVDF, 5% modified ZIF-8 material, 3% polyvinyl pyrrolidone, and 72% N-methyl pyrrolidone were stirred and mixed for 12 hours, and then directly degassed to obtain a casting liquid; the casting liquid was coated on a glass plate with a coating thickness of 250 μm. After staying in the air for 40 seconds, it was immersed in a mixed solvent of acetone and N-methyl pyrrolidone for gel curing to obtain a MOFs-PVDF composite ultrafiltration membrane.

[0091] Example 6

[0092] The preparation method of the MOFs-PVDF composite ultrafiltration membrane provided in this embodiment comprises the following steps:

[0093] (1) Preparation of modified MOFs materials

[0094] The preparation method is the same as that of Example 1, except that ZIF-8 is replaced by MIL-101. In the obtained modified MIL-101 material, the mass of AgO is 10% of the mass of MIL-101, and the mass of FeOOH is 5% of the mass of MIL-101.

[0095] (2) Preparation of MOFs-PVDF composite ultrafiltration membrane

[0096] Taking the total mass of the casting liquid as 100%, 20% hydroxyl-containing PVDF, 5% modified MIL-101 material, 3% polyvinyl pyrrolidone, and 72% N-methyl pyrrolidone were stirred and mixed for 12 hours, and then directly degassed to obtain a casting liquid; the casting liquid was coated on a glass plate with a coating thickness of 250 μm. After staying in the air for 40 seconds, it was immersed in a mixed solvent of acetone and N-methyl pyrrolidone for gel curing to obtain a MOFs-PVDF composite ultrafiltration membrane.

[0097] Example 7

[0098] The preparation method of the MOFs-PVDF composite ultrafiltration membrane provided in this embodiment comprises the following steps:

[0099] (1) Preparation of modified MOFs materials

[0100] The preparation method is the same as that of Example 1, except that ZIF-8 is replaced by UIO-66. In the obtained modified UIO-66 material, the mass of AgO is 10% of the mass of UIO-66, and the mass of FeOOH is 5% of the mass of UIO-66.

[0101] (2) Preparation of MOFs-PVDF composite ultrafiltration membrane

[0102] Taking the total mass of the casting liquid as 100%, 20% hydroxyl-containing PVDF, 5% modified UIO-66 material, 3% polyvinyl pyrrolidone, and 72% N-methyl pyrrolidone were stirred and mixed for 12 hours, and then directly degassed to obtain a casting liquid; the casting liquid was coated on a glass plate with a coating thickness of 250 μm. After staying in the air for 40 seconds, it was immersed in a mixed solvent of acetone and N-methyl pyrrolidone for gel curing to obtain a MOFs-PVDF composite ultrafiltration membrane.

[0103] Comparative Example 1

[0104] The preparation method of the MOFs-PVDF composite ultrafiltration membrane provided in this comparative example comprises the following steps:

[0105] Taking the total mass of the casting liquid as 100%, 20% hydroxyl-containing PVDF, 5% unmodified ZIF-8 material, 3% polyvinyl pyrrolidone, and 72% N-methyl pyrrolidone were stirred and mixed for 12 hours, and then directly degassed to obtain a casting liquid; the casting liquid was coated on a glass plate with a coating thickness of 250 μm. After staying in the air for 40 seconds, it was immersed in a mixed solvent of acetone and N-methyl pyrrolidone for gel curing to obtain a MOFs-PVDF composite ultrafiltration membrane.

[0106] Comparative Example 2

[0107] This comparative example provides a method for preparing a MOFs-PVDF composite ultrafiltration membrane, which differs from Example 1 in that: in step (2), PVDF does not contain hydroxyl groups.

[0108] Performance Testing

[0109] 1. Water flux test

[0110] After the prepared composite ultrafiltration membrane was placed in deionized water for a period of time, a circular membrane piece with a diameter of 7.5 cm was cut and placed in a YL-300 ultrafiltration cup. It was pre-pressed at a pressure of 0.1 MPa for 40 minutes until the water flux was basically stable, and then measured at a pressure of 0.1 MPa. The test results are shown in Table 1.

[0111] 2. Anti-pollution performance test

[0112] At 0.1 MPa, 1 g / L of bovine serum albumin with a molecular weight of 80,000 was used as the test object. The retention rate of the ultrafiltration membrane was determined by measuring the residual amount of bovine serum albumin on the membrane. Among them C p is the concentration of bovine serum albumin in the influent, C f is the concentration of bovine serum albumin in purified water. The test results are shown in Table 1.

[0113] 3. Hydrophilic performance test

[0114] The contact angle between the prepared ultrafiltration membrane and water was tested using a contact angle tester. The test results are shown in Table 1.

[0115] 4. Tensile strength

[0116] The tensile strength of the prepared ultrafiltration membrane was tested using a universal material tensile testing machine. The test results are shown in Table 1.

[0117] 5. Antibacterial performance test

[0118] Escherichia coli was used as an indicator bacteria to culture the filtrate of the prepared membrane. The number of Escherichia coli in the filtrate was calculated by the plate count method, and the antibacterial rate was calculated. The test results are shown in Table 1.

[0119] Table 1

[0120]

[0121]

[0122] The data in Table 1 show that the MOFs-PVDF composite ultrafiltration membranes obtained in the examples of the present invention exhibit good hydrophilicity, high water flux, high rejection rate, good anti-fouling properties, and excellent antibacterial and mechanical properties. However, Comparative Example 1 lacks antibacterial properties due to the absence of AgO and FeOOH. In Comparative Example 2, the hydrophilicity and mechanical properties of the resulting ultrafiltration membranes are somewhat reduced due to the lack of hydroxyl groups in PVDF and its poor binding to the MOFs material.

[0123] In the description of this specification, the reference terms "some embodiments", "other embodiments", "embodiments", "examples", etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0124] Although the embodiments and examples of the present invention have been shown and described above, it will be understood that the above embodiments and examples are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments and examples within the scope of the present invention.

Claims

1. A method for preparing a MOFs-PVDF composite ultrafiltration membrane, characterized in that: include: (1) adding MOFs material to an aqueous solution containing an iron source and a silver source, stirring and mixing, and obtaining a precursor solution; (2) adding sodium hydroxide solution to the precursor solution, stirring, introducing oxidizing gas, filtering, and drying to obtain a modified MOFs material loaded with AgO and FeOOH; (3) adding hydroxyl-containing PVDF, modified MOFs material, and porogen into an organic solvent, stirring and mixing, standing and degassing to obtain a casting solution, coating the casting solution, and gel-curing in a non-aqueous coagulation bath to obtain a MOFs-PVDF composite ultrafiltration membrane with a bactericidal function; Wherein, the MOFs material is one of ZIF-8, MIL-101, and UIO-66.

2. The method for preparing a MOFs-PVDF composite ultrafiltration membrane according to claim 1, wherein: The iron source is ferric nitrate; the silver source is silver nitrate; and the mass fraction of the sodium hydroxide solution is 1-10%.

3. The method for preparing the MOFs-PVDF composite ultrafiltration membrane according to claim 1, wherein: The oxidizing gas is any one of O3, O2, O3 / O2 mixed gas, O3 / N2 mixed gas, and O2 / N2 mixed gas.

4. The method for preparing the MOFs-PVDF composite ultrafiltration membrane according to claim 1, characterized in that: The time for introducing the oxidizing gas is 20 to 40 minutes, and the drying is vacuum drying at 40 to 80° C. for 4 to 8 hours.

5. The method for preparing the MOFs-PVDF composite ultrafiltration membrane according to claim 1, characterized in that: The mass of the AgO is 5-15% of the mass of the MOFs material, and the mass of the FeOOH is 1-10% of the mass of the MOFs material.

6. The method for preparing a MOFs-PVDF composite ultrafiltration membrane according to claim 1, wherein: The mass of the modified MOFs material is 1-10% of the total mass of the casting solution.

7. The method for preparing the MOFs-PVDF composite ultrafiltration membrane according to claim 6, characterized in that: The composition of the casting solution includes: based on the total mass of the casting solution as 100%, 10-30% of hydroxyl-containing PVDF, 1-10% of modified MOFs material, 1-3% of porogen, and the balance being organic solvent.

8. The method for preparing a MOFs-PVDF composite ultrafiltration membrane according to claim 1, wherein: The organic solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone and dimethyl sulfoxide; and the porogen is polyvinyl pyrrolidone.

9. The MOFs-PVDF composite ultrafiltration membrane obtained according to the preparation method according to any one of claims 1 to 8.

10. Use of the MOFs-PVDF composite ultrafiltration membrane according to claim 9 in water treatment.

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