Water treatment composite filter membrane and preparation method thereof

Abstract

The application discloses a kind of water treatment composite filter membrane and preparation method thereof, belong to membrane separation technical field, a kind of water treatment composite filter membrane described in the application, including Ag-PAN base membrane and HOFs coating, the Ag-PAN base membrane is handled grafting with 4-vinyl benzyl mercaptan, HOFs coating is modified with 5-hexene-1 alcohol olefin.The application further provides a kind of preparation method of water treatment composite filter membrane: S1.AgNPs (silver nanoparticles) synthesis;S2.Ag-PAN base membrane is grafted after preparation;S3.HOFs crystal synthesis is modified with olefin;S4.Ag-PAN-HOFs composite filter membrane synthesis.The filter membrane prepared in the application has excellent antibacterial performance and self-repairing ability, stable structure, not easy to fall off in the water treatment process, is conducive to long-term stable use in the water treatment process.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of membrane separation technology, and particularly relates to a water treatment composite filter membrane and a preparation method thereof. BACKGROUND

[0002] Membrane separation technology is a new type of separation and purification technology that has developed rapidly in the past 20 years. With the progress of science and technology and the continuous deepening of research, membrane separation technology has made great progress, with more refined classification, increasing variety, expanding application field, and gradually replacing traditional high-energy consumption separation methods. It has become one of the most sustainable green separation technologies in the 21st century. Membrane separation technology has incomparable advantages over traditional separation technology, such as significant reduction in energy consumption due to no phase change during operation, suitability for separation of heat-sensitive materials at low temperatures, simple process and easy scaling-up, easy maintenance and integration with other operation units, and environmental friendliness. Commercial low-pressure membranes are mainly prepared based on polymer materials. They are manufactured by phase inversion process, forming an asymmetric structure, and the thin layer size is based on the underlying porous support layer. Due to the physical / chemical stability of the polymer material and the typical membrane thin solid limitation--layer structure, the membrane active layer may be damaged during installation and operation. However, the key advantage of the membrane separation process over traditional processes can only be maintained if the integrity is maintained throughout the service life of the membrane. Past research reports indicate that even the smallest damage to the membrane can result in a significant reduction in its retention level, causing serious impact on its performance. During application, the decline in water quality due to damage to the separation membrane caused by stress impact, backwash cleaning, and particulate pollutants in the feed water has been widely reported. However, the current membrane integrity monitoring technology has major challenges in precisely locating the damaged part, often requiring a large amount of time and replacing the entire membrane module. Therefore, the integrity problem of the membrane is listed as a key factor limiting the development and application of membrane technology. Hydrogen-bonded organic frameworks (HOFs) are a new type of porous crystalline material connected by non-covalent bonds (hydrogen bonds, π-π stacking, electrostatic interactions, etc.) between organic molecules. As a unique bonding method, hydrogen bonds have inherent excellent reversibility, which can balance the easy processability of polymers and the orderliness of crystalline materials, and have unique advantages in the field of separation membrane materials. The unique flexible framework of HOFs materials enables them to self-repair under certain conditions after damage caused by external stress impact, thereby prolonging their service life.

[0003] On the other hand, in the face of the increasingly severe situation of global water resource shortage, the development and utilization of unconventional water resources has become an inevitable act. In recent years, the ultrafiltration membrane separation technology plays an increasingly important role in the utilization of unconventional water resources due to its excellent pollutant interception capacity, low pressure operation at room temperature, stable water quality and other advantages. However, membrane pollution is always the bottleneck restricting the popularization and application of the technology, and biological pollution is the key factor causing irreversible pollution of the ultrafiltration membrane and the most difficult to control. The essence of membrane biological pollution is that microorganisms in the influent adhere and aggregate on the membrane surface and form a biofilm. The biological colonies composed of these microorganisms and the extracellular polymeric substances secreted by them block the membrane pores, causing the permeability of the membrane to decrease. At present, the modification of the membrane for resisting biological pollution mainly improves the hydrophilicity of the membrane, reduces the deposition and adhesion of organic matters on the membrane surface, and thus reduces the growth rate of microorganisms on the membrane surface. However, the microorganisms adhered to the membrane surface usually have strong biological activity, can utilize the nutrients in the water to reproduce rapidly and form a biofilm, which is difficult to effectively control. Therefore, a water treatment composite filter membrane with self-repairing ability and strong antibacterial performance is urgently needed to improve the water quality and the durability of the filter membrane. SUMMARY

[0004] The purpose of the present application is to provide a water treatment composite filter membrane and a preparation method thereof, so as to solve the problems of poor self-repairing ability and poor antibacterial performance of the composite filter membrane in the prior art.

[0005] The purpose of the present application can be realized by the following technical solutions.

[0006] A water treatment composite filter membrane, characterized in that it comprises an Ag-PAN base membrane and a HOFs coating layer, wherein the Ag-PAN base membrane is subjected to grafting treatment with 4-vinylbenzyl mercaptan, and the HOFs coating layer is subjected to olefin modification with 5-hexene-1-ol.

[0007] The preparation method of the water treatment composite filter membrane comprises the following steps:

[0008] S1. Synthesis of AgNPs (silver nanoparticles)

[0009] Under oil bath heating conditions, glycerol and AgNO3 solution are added to a flask, stirred and refluxed, gradually heated to 95℃, and then sodium citrate solution and polyvinylpyrrolidone (PVP) solution are quickly added, the heat source is removed, and stirring is carried out at room temperature (25-30℃) until cooling. Centrifugal separation is performed to obtain AgNPs.

[0010] S2. Post-grafting of Ag-PAN base membrane

[0011] The Ag-PAN base film is prepared by non-solvent induced phase inversion method. The PAN (polyacrylonitrile) powder is dried in an oven at 60°C for 12h to remove moisture. The dried PAN powder and PEG 800 (polyethylene glycol 800) are dissolved in NMP (1-methyl-2-pyrrolidone), 0.5mL AgNPs are added, stirred at 75°C for 15h, and then placed at 50°C for 8h to remove bubbles. After cooling to room temperature, the coating solution is poured onto a clean glass plate and cast with a 200um doctor blade. Then, immediately place the glass plate with the cast film into a deionized water bath at 25°C. After phase inversion, replace the deionized water to remove residual solvent and save for the next step modification. The prepared Ag-PAN base film is soaked in 4-vinylbenzyl mercaptan for 24h, washed with deionized water to remove excess reagent on the surface of the film, and the modified Ag-PAN base film is obtained.

[0012] S3. Olefin modification after HOFs crystal synthesis

[0013] 40-50mg tetra-(4-carboxyphenyl)-porphyrin (H2TCPP) is dissolved in dimethyl sulfoxide (DMSO) solution, 40% tetrapropylammonium hydroxide (TPA) is added to MeOH, and the temperature is uniformly increased from room temperature to 100°C, and then kept at 100°C for 2h. After the reaction is completed, the product is naturally cooled to room temperature, filtered and dried to obtain HOFs crystals. The prepared HOFs crystals are ultrasonically pulverized into powder, and HOFs, EDC and 5-hexen-1-ol are added to a mixed solution of tetrahydrofuran (THF) and deionized water, stirred at room temperature for 12h, centrifuged and washed with acetone and THF.

[0014] S4. Synthesis of Ag-PAN-HOFs composite filter membrane

[0015] The olefin-modified HOFs obtained in S3 are dissolved in DMSO, and the grafted Ag-PAN base film obtained in S2 is soaked in the solution after ultrasonic dispersion. A crosslinking agent is added and uniformly dispersed, and HOFs and Ag-PAN are copolymerized and crosslinked to form a dense and soft coating on the surface of the Ag-PAN base film, i.e. an Ag-PAN-HOFs composite filter membrane with a double membrane structure.

[0016] Further, the volume ratio of glycerol, AgNO3 solution, sodium citrate solution and PVP solution in S1 is 100mL:10mL:2mL:10mL.

[0017] Further, the concentrations of AgNO3 solution and sodium citrate solution in S1 are 0.1M and 1M, respectively.

[0018] Further, the heating rate in S1 is 2.5-3°C / min.

[0019] Further, the ratio of the amount of PAN powder and PEG 800 in S2 is 20 g:1-1.5 g.

[0020] Further, the volume ratio of NMP and AgNPs in S2 is 100 mL:0.5 mL.

[0021] Further, the concentration of 4-vinylbenzenethiol in S2 is 100 μM, and the volume is 10 mL.

[0022] Further, the volume ratio of DMSO, TPA and MeOH in S3 is 8 mL:70 μL:5 mL.

[0023] Further, the heating rate in S3 is 8 ℃ / h.

[0024] Further, the ratio of the amount of HOFs, EDC and 5-hexen-1-ol in S4 is 45 mg:3 mg:50-65 μL.

[0025] Further, the volume ratio of THF and deionized water in S3 is 4:1.

[0026] Further, the crosslinking agent in S4 is any one of ethylene glycol dimethacrylate (EGDMA) or glycerol diglycidyl ether.

[0027] Further, the ratio of the amount of olefin-modified HOFs, DMSO and crosslinking agent in S4 is 40 mg:200 mL:3 mg.

[0028] The beneficial effects of the present application are:

[0029] 1. The present application utilizes olefin-modified HOFs to co-polymerize and cross-link a self-assembly layer on the surface of the Ag-PAN base film grafted with 4-vinylbenzenethiol, to prepare a water treatment composite filter membrane with a double-membrane structure.

[0030] 2. In the preparation method of the water treatment composite filter membrane provided by the present application, the AgNPs in the PAN base film form stable Ag-S bonds with the mercapto groups in the 4-vinylbenzenethiol, so that the 4-vinylbenzenethiol is grafted to the surface of the base film, realizing co-polymerization and cross-linking of the vinyl group and the olefin-modified HOFs, and enhancing the binding force between the HOFs and the base film.

[0031] 3. The hydrogen-bonded organic framework (HOFs) synthesized in the present application has a rich hydrogen-bonded network, and the reversibility of the hydrogen bonds enables the HOFs to have excellent self-repairing ability; at the same time, the free quaternary ammonium in the HOFs has a synergistic antibacterial effect with the AgNPs in the Ag-PAN base film, making the antibacterial performance more persistent and efficient.

[0032] 4. The water treatment composite filter membrane prepared by the present invention has a modified functional layer that is chemically bonded to the base membrane, resulting in a stable structure that is not easily detached during water treatment, thus extending the service life of the composite filter membrane and facilitating its long-term stable use in water treatment. Attached Figure Description

[0033] The invention will now be further described with reference to the accompanying drawings.

[0034] Figure 1 This is a schematic diagram of the antibacterial properties in Embodiment 5 of the present invention. Detailed Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1

[0037] A method for preparing a water treatment composite filter membrane includes the following steps:

[0038] Synthesis of S1.AgNPs (silver nanoparticles)

[0039] Under oil bath heating conditions, 100 mL of glycerol and 10 mL of 0.1 M AgNO3 solution were added to a flask, stirred and refluxed, and the temperature was gradually increased at a rate of 2.5 °C / min to 95 °C. 2 mL of 1 M sodium citrate solution and 10 mL of PVP solution were quickly added, the heat source was removed, and the mixture was stirred at room temperature until cooled. The mixture was then centrifuged to obtain AgNPs.

[0040] Grafting after preparation of S2.Ag-PAN base film

[0041] Ag-PAN base membranes were prepared using a solvent-inducible phase inversion method. PAN powder was dried in a 60°C oven for 12 hours to remove moisture. 20 g of dried PAN powder and 1 g of PEG 800 were dissolved in 100 g of NMP, and 0.5 mL of AgNPs were added. The mixture was stirred at 75°C for 15 hours. The solution was then allowed to stand at 50°C for 8 hours to remove air bubbles. After cooling to room temperature, the coating solution was poured onto a clean glass plate and cast using a 200 μm doctor blade. The glass plate and the cast membrane were then immediately placed in a 25°C deionized water bath. After phase inversion, the deionized water was replaced to remove any residual solvent, and the membrane was stored for further modification. The Ag-PAN base membrane was immersed in 10 mL of 100 μM 4-vinylbenzyl mercaptan for 24 hours, and then washed with deionized water to remove excess reagent from the membrane surface, yielding the modified Ag-PAN base membrane.

[0042] After synthesis of S3.HOFs crystals, olefin modification was performed.

[0043] 50 mg H2TCPP was dissolved in 8 mL DMSO solution, and 5 mL MeOH was added. The temperature was increased from room temperature to 100 °C at a rate of 8 °C / h, and held at this temperature for 2 h. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The product was collected by filtration and dried to obtain HOF crystals. The prepared HOF crystals were ultrasonically pulverized into powder. 45 mg HOF, 3 mg EDC, and 50 μL 5-hexen-1 alcohol were added to 10 mL THF / H2O (v / v = 4:1) mixed solvent. The mixture was stirred at room temperature for 12 h, centrifuged, and washed with acetone and THF (tetrahydrofuran).

[0044] Synthesis of S4.Ag-PAN-HOFs composite filter membrane

[0045] 40 mg of olefin-modified HOFs were dissolved in 200 mL of DMSO and ultrasonically dispersed. The grafted Ag-PAN base membrane obtained in S2 was then immersed in the solution. 3 mg of EGDMA was added and ultrasonicated for 5 min. The HOFs and Ag-PAN copolymerized and crosslinked to form a dense and soft coating on the surface of the Ag-PAN base membrane, which is the Ag-PAN-HOFs composite filter membrane with a dual membrane structure.

[0046] Example 2

[0047] A method for preparing a water treatment composite filter membrane includes the following steps:

[0048] Synthesis of S1.AgNPs (silver nanoparticles)

[0049] Under oil bath heating conditions, 100 mL of glycerol and 10 mL of 0.1 M AgNO3 solution were added to a flask, stirred and refluxed, and the temperature was gradually increased at a rate of 3 °C / min to 95 °C. 2 mL of 1 M sodium citrate solution and 10 mL of PVP solution were quickly added, the heat source was removed, and the mixture was stirred at room temperature until cooled. The mixture was then centrifuged to obtain AgNPs.

[0050] Grafting after preparation of S2.Ag-PAN base film

[0051] Ag-PAN base films were prepared using a solvent-inducible phase inversion method. PAN powder was dried in a 60°C oven for 12 hours to remove moisture. 20 g of dried PAN powder and 1.3 g of PEG 800 were dissolved in 100 g of NMP, and 0.5 mL of AgNPs were added. The mixture was stirred at 75°C for 15 hours. The solution was then allowed to stand at 50°C for 8 hours to remove air bubbles. After cooling to room temperature, the coating solution was poured onto a clean glass plate and cast using a 200 μm doctor blade. The glass plate and the cast film were then immediately placed in a 25°C deionized water bath. After phase inversion, the deionized water was replaced to remove any residual solvent, and the film was stored for further modification. The Ag-PAN base film was immersed in 10 mL of 100 μM 4-vinylbenzyl mercaptan for 24 hours, and then washed with deionized water to remove excess reagent from the film surface, yielding the modified Ag-PAN base film.

[0052] After synthesis of S3.HOFs crystals, olefin modification was performed.

[0053] 42 mg H2TCPP was dissolved in 8 mL DMSO solution, and 5 mL MeOH was added. The temperature was increased from room temperature to 100 °C at a rate of 8 °C / h, and held at this temperature for 2 h. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The product was collected by filtration and dried to obtain HOF crystals. The prepared HOF crystals were ultrasonically pulverized into powder. 45 mg HOF, 3 mg EDC, and 60 μL 5-hexen-1 alcohol were added to 10 mL THF / H2O (v / v = 4:1) mixed solvent, stirred at room temperature for 12 h, centrifuged, and washed with acetone and THF (tetrahydrofuran).

[0054] Synthesis of S4.Ag-PAN-HOFs composite filter membrane

[0055] 40 mg of olefin-modified HOFs were dissolved in 200 mL of DMSO and ultrasonically dispersed. The grafted Ag-PAN base membrane obtained in S2 was then immersed in the solution. 3 mg of glycerol diglycidyl ether was added and ultrasonicated for 5 min. The HOFs and Ag-PAN copolymerized and crosslinked to form a dense and soft coating on the surface of the Ag-PAN base membrane, which is the Ag-PAN-HOFs composite filter membrane with a dual membrane structure.

[0056] Comparative Example 1

[0057] PAN powder was dried in a 60°C oven for 12 hours to remove moisture. 20g of the dried PAN powder and 1g of PEG 800 were dissolved in 100g of NMP and stirred at 75°C for 15 hours. The solution was then allowed to stand at 50°C for 8 hours to remove air bubbles. After cooling to room temperature, the coating solution was poured onto a clean glass plate and cast using a 200µm scraper. The glass plate and the cast membrane were then immediately placed in a deionized water bath at 25°C. After phase inversion, the deionized water was replaced to remove any residual solvent, yielding the PAN filter membrane.

[0058] Comparative Example 2

[0059] Synthesis of S1.AgNPs (silver nanoparticles)

[0060] Under oil bath heating conditions, 100 mL of glycerol and 10 mL of 0.1 M AgNO3 solution were added to a flask, stirred and refluxed, and the temperature was gradually increased at a rate of 2.5 °C / min to 95 °C. 2 mL of 1 M sodium citrate solution and 10 mL of PVP solution were quickly added, the heat source was removed, and the mixture was stirred at room temperature until cooled. The mixture was then centrifuged to obtain AgNPs.

[0061] Grafting after preparation of S2.Ag-PAN base film

[0062] Ag-PAN membranes were prepared using a solvent-inducible phase inversion method. PAN powder was dried in a 60°C oven for 12 hours to remove moisture. 20 g of dried PAN powder and 1 g of PEG 800 were dissolved in 100 g of NMP, and 0.5 mL of AgNPs were added. The mixture was stirred at 75°C for 15 hours. The solution was then allowed to stand at 50°C for 8 hours to remove air bubbles. After cooling to room temperature, the coating solution was poured onto a clean glass plate and cast using a 200 μm doctor blade. The glass plate and the cast membrane were then immediately placed in a 25°C deionized water bath. After phase inversion, the deionized water was replaced to remove any residual solvent, yielding an Ag-PAN filter membrane.

[0063] Comparative Example 3

[0064] Grafting after preparation of S1.PAN base film

[0065] PAN powder was dried in a 60℃ oven for 12 hours to remove moisture. 20g of dried PAN powder and 1g of PEG 800 were dissolved in 100g of NMP and stirred at 75℃ for 15 hours. The solution was then allowed to stand at 50℃ for 8 hours to remove air bubbles. After cooling to room temperature, the coating solution was poured onto a clean glass plate and cast using a 200µm scraper. The glass plate and the cast film were then immediately placed in a 25℃ deionized water bath. After phase inversion, the deionized water was replaced to remove any residual solvent, and the film was stored. The PAN-based film was then immersed in 10mL of 100µM 4-vinylbenzyl mercaptan for 24 hours, followed by washing with deionized water to remove excess reagent from the film surface, yielding the modified PAN-based film.

[0066] After synthesis of S2.HOFs crystals, olefin modification was performed.

[0067] 50 mg H2TCPP was dissolved in 8 mL DMSO solution, and 5 mL MeOH was added. The temperature was increased from room temperature to 100 °C at a rate of 8 °C / h, and held at this temperature for 2 h. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The product was collected by filtration and dried to obtain HOF crystals. The prepared HOF crystals were ultrasonically pulverized into powder. 45 mg HOF, 3 mg EDC, and 50 μL 5-hexen-1 alcohol were added to 10 mL THF / H2O (v / v = 4:1) mixed solvent. The mixture was stirred at room temperature for 12 h, centrifuged, and washed with acetone and THF (tetrahydrofuran).

[0068] S3. PAN-HOFs composite filter membrane synthesis

[0069] 40 mg of olefin-modified HOFs were dissolved in 200 mL of DMSO and ultrasonically dispersed. The grafted PAN-based membrane obtained in S2 was then immersed in the solution. 3 mg of EGDMA was added and ultrasonicated for 5 min. The HOFs and PAN copolymerized and crosslinked, forming a dense and soft coating on the surface of the PAN-based membrane, which is the PAN-HOFs composite filter membrane with a dual membrane structure.

[0070] Example 3

[0071] Hydrophilicity and antifouling performance tests

[0072] The water contact angle of the membrane surface was measured using a contact angle meter. The antifouling performance of the membrane was measured using a cross-flow MBR with sludge mixed liquor (sludge concentration of 3800-5200 mg / L) from the aerobic tank of the sewage treatment plant as the feed liquid. The performance of the Ag-PAN-HOFs composite filter membrane prepared in Example 1 and the PAN membrane prepared in Comparative Example 1 were tested, and the test results are shown in Table 1.

[0073] Table 1

[0074]

[0075]

[0076] As shown in the table, the water treatment ultrafiltration membrane prepared by the present invention has 75% better resistance to biofouling and 66% better resistance to organic fouling than the PAN membrane.

[0077] Example 4

[0078] Self-repair performance test

[0079] The Ag-PAN-HOFs composite filter membrane prepared in Example 1 was scratched with a sharp knife. The membrane was then divided in half, with the scratch present on both halves. One half was heat-treated at 50°C for 18 minutes, while the other half was left untreated as a control. The results showed that the filter membrane was morphologically completely repaired, and the reversibility of hydrogen bonds endowed the Ag-PAN-HOFs composite filter membrane with self-healing ability.

[0080] The self-healing performance of Example 2 and Comparative Examples 1-3 were tested in the same manner. The test results showed that Example 2 was completely repaired, Comparative Example 1 and Comparative Example 2 were not repaired, and Comparative Example 3 was completely repaired.

[0081] Example 5

[0082] Antibacterial performance test

[0083] Escherichia coli was used as an indicator bacterium to test the antibacterial properties of the filter membranes prepared in Examples 1, 2, and 1-3. Escherichia coli was cultured in the filter membranes prepared in Examples 1, 2, and 1-3 at 37°C for 4 hours, and then diluted 10... 4 Then, the E. coli suspension was plated onto solid LB agar plates and incubated at 37°C for another 12 hours. The results were as follows. Figure 1 As shown, the PAN filter membrane prepared in Comparative Example 1 has almost no antibacterial properties. The water treatment composite filter membranes prepared in Examples 1 and 2 have stronger antibacterial properties than those in Comparative Examples 2 and 3. This is mainly due to the synergistic antibacterial effect of quaternary ammonium and AgNPs.

[0084] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0085] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A water treatment composite filter membrane, characterized in that, It includes an Ag-PAN base film and an HOFs coating, wherein the Ag-PAN base film is grafted with 4-vinylbenzylthiol and the HOFs coating is olefin-modified with 5-hexen-1 alcohol.

2. The method for preparing a water treatment composite filter membrane according to claim 1, characterized in that, Includes the following steps: S1. Glycerol and AgNO3 solution were stirred and heated to 90-95℃ at a constant rate. Sodium citrate solution and PVP solution were added. AgNPs were obtained by cooling at room temperature. S2. Dissolve dry PAN powder and PEG 800 in NMP, add AgNPs, stir at 70-75℃ for 12-16h, let stand at 40-55℃ for 6-9h to remove bubbles, cool to room temperature, pour the solution onto a glass plate, cast with a scraper, and then put the glass plate and the cast film together into deionized water. After phase inversion, wash with deionized water, immerse the obtained Ag-PAN base film in 4-vinylbenzyl mercaptan for 20-26h, and wash with deionized water to obtain the grafted Ag-PAN base film. S3.H2TCPP was dissolved in DMSO solution, and then 40% TPA and MeOH were added. The temperature was raised to 100℃ at a constant rate from room temperature and kept at this temperature for 2 hours. After the reaction was completed, the mixture was naturally cooled to room temperature, filtered to collect the product, and dried to obtain HOFs. HOFs, EDC and 5-hexen-1 alcohol were added to a mixed solution of THF and deionized water, stirred at room temperature for 12 hours, centrifuged and analyzed, and washed with acetone and THF to obtain olefin-modified HOFs. S4. Olefin-modified HOFs are dissolved in DMSO, ultrasonically dispersed, and then the grafted Ag-PAN base membrane is immersed in the solution. A crosslinking agent is added to copolymerize and crosslink on the Ag-PAN surface to form an HOF coating, thus synthesizing an Ag-PAN-HOFs composite filter membrane.

3. The method for preparing a water treatment composite filter membrane according to claim 2, characterized in that, The concentrations of AgNO3 solution and sodium citrate solution in S1 are 0.1M and 1M, respectively, and the concentration of 4-vinylbenzyl mercaptan in S2 is 100μM.

4. The method for preparing a water treatment composite filter membrane according to claim 2, characterized in that, In S1, the volume ratio of glycerol, AgNO3 solution, sodium citrate solution and PVP solution is 100mL:10mL:2mL:10mL; in S2, the volume ratio of NMP and AgNPs is 100mL:0.5mL; and in S3, the volume ratio of THF and deionized water is 4:

1.

5. The method for preparing a water treatment composite filter membrane according to claim 2, characterized in that, The heating rate in S1 is 2.5-3℃ / min, and the heating rate in S3 is 8℃ / h.

6. The method for preparing a water treatment composite filter membrane according to claim 2, characterized in that, In S2, the ratio of PAN powder to PEG 800 is 20g:1-1.5g, and in S3, the ratio of HOFs, EDC, and 5-hexen-1 alcohol is 45mg:3mg:50-65μL.

7. The method for preparing a water treatment composite filter membrane according to claim 2, characterized in that, The ratio of H2TCPP, DMSO, TPA, and MeOH in S3 is 40-50 mg: 8 mL: 70 μL: 5 mL.

8. The method for preparing a water treatment composite filter membrane according to claim 2, characterized in that, The crosslinking agent in S4 is either EGDMA or glycerol diglycidyl ether.

9. The method for preparing a water treatment composite filter membrane according to claim 2, characterized in that, Furthermore, the ratio of olefin-modified HOFs, DMSO, and crosslinking agent in S4 is 40 mg: 200 mL: 3 mg.

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