Preparation method and application of MXene modified polytetrafluoroethylene hollow fiber composite membrane

Abstract

The invention discloses a preparation method and application of an MXene modified polytetrafluoroethylene hollow fiber composite membrane, and belongs to the technical field of membrane separation. According to the MXene modified polytetrafluoroethylene hollow fiber composite membrane prepared by the preparation method disclosed by the invention, the surface separation layer and the polytetrafluoroethylene base membrane are well combined by introducing the MXene intermediate layer transition layer, and the mechanical strength and hydrophilicity of the membrane are enhanced by utilizing an MXene lamellar structure; the base membrane prepared through a series of reactions is excellent in hydrophilic performance and antibacterial performance and good in stability; after organic-inorganic-organic compounding from inside to outside, the addition of the middle MXene layer is simple, easy to operate and easy to process, and the permeability of the membrane can be improved; therefore, the composite membrane prepared by the invention contains a three-layer membrane structure, has excellent mechanical strength, hydrophilicity and antibacterial property, is easy to process and good in permeability, and has important application value in the field of water treatment.

Description

Technical Field

[0001] The present invention belongs to the technical field of membrane separation, and specifically relates to a preparation method and application of a MXene-modified polytetrafluoroethylene hollow fiber composite membrane. Background Art

[0002] Polytetrafluoroethylene material is a highly crystalline polymer with excellent performance, which is widely used in the fields of chemical industry, machinery, petroleum, and textile. Due to the "fluorine protective layer" outside the chemical structure of polytetrafluoroethylene, it is stable under acid and alkali conditions and is one of the most widely used materials at present. Polytetrafluoroethylene material has low surface friction and good lubricity. It is a perfect anti-corrosion and anti-pollution membrane material with far-reaching application value. Currently, polytetrafluoroethylene hollow fiber membranes and polytetrafluoroethylene flat membranes have been widely used in microfiltration or ultrafiltration technology.

[0003] However, polytetrafluoroethylene has good chemical stability, and it is difficult to prepare a uniform porous structure, and the separation accuracy is difficult to control. Secondly, polytetrafluoroethylene contains a large number of CF bonds and has a high hydrophobicity, which also limits the application of polytetrafluoroethylene. Therefore, it is necessary to improve the hydrophilicity and separation performance of polytetrafluoroethylene. Develop a new type of composite polytetrafluoroethylene membrane material to meet the higher demands in the field of membrane separation technology. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide a preparation method and application of a MXene-modified polytetrafluoroethylene hollow fiber composite membrane.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for preparing a MXene-modified polytetrafluoroethylene hollow fiber composite membrane comprises the following steps:

[0007] Step 1, preparation of multilayer MXene: placing Ti3AlC2 in an etching solvent, dispersing it under ultrasonic conditions, stirring and reacting it after dispersion, and washing it with anhydrous ethanol until the surface impurities are completely removed to obtain multilayer MXene;

[0008] Step 2, preparation of MXene-modified polytetrafluoroethylene membrane: fully disperse the multilayer MXene prepared in step 1 in pure water, add a hydrophilic base membrane and a dispersant, and after fully soaking for 2-10 minutes, allow the MXene to be deposited on the surface of the base membrane to obtain a MXene-modified polytetrafluoroethylene membrane;

[0009] Step 3, preparation of MXene-modified polytetrafluoroethylene hollow fiber composite membrane: place the MXene-modified polytetrafluoroethylene membrane obtained in step 2 in the copolymer monomer spinning solution, soak it for 1-2 hours, take it out, clean the surface impurities and dry it to obtain a MXene-modified polytetrafluoroethylene hollow fiber composite membrane.

[0010] Furthermore, the etching solvent in step 1 is one of hydrofluoric acid and sodium fluoride, hydrochloric acid and lithium fluoride, and ammonium fluoride solution.

[0011] Furthermore, in step 2, the concentration of multilayer MXene in pure water is 0.5-5 g / L.

[0012] Furthermore, in step 2, the dispersant is one of ammonium perfluorooctanoate, polyethylene wax and polyvinyl alcohol 200; the monomer mass concentration of the dispersant is 1-5wt%.

[0013] Furthermore, the copolymer monomer in step 3 is one of polysulfone, polyethersulfone, polyamide, polyvinylidene fluoride and polybenzimidazole; the mass concentration of the copolymer monomer is 1-5wt%.

[0014] MXene is a new type of two-dimensional material with the characteristics of thermal conductivity, high surface area, excellent hydrophilicity, etc., ultra-thin interlayer structure and a large number of surface active terminals, which can regulate the spatial structure and chemical properties. The present invention deposits MXene on a porous base membrane prepared from a polytetrafluoroethylene porous base membrane, and then prepares a surface separation layer by immersion coating. The prepared membrane material contains a multilayer structure, so that MXene is used as a modified intermediate transition layer, which can not only adjust the hydrophilicity of polytetrafluoroethylene, but also stabilize its structure and improve its mechanical stability.

[0015] Further, the hydrophilic base film is prepared by the following steps:

[0016] A1. Soak the polytetrafluoroethylene hollow fiber membrane in ethanol and perform ultrasonic treatment for 1 hour to remove impurities that may be adsorbed on the membrane surface and in the pores. Take it out and dry it to obtain a pretreated polytetrafluoroethylene hollow fiber membrane.

[0017] A2, polyvinyl alcohol and polyethyleneimine are mixed with deionized water, the temperature is raised to 80°C, and the mixture is stirred continuously to dissolve the polyvinyl alcohol and polyethyleneimine to obtain a hydrophilic modified solution;

[0018] A3, diethylenetriamine and N, N-dimethylformamide (DMF) were stirred evenly, and then glutaraldehyde and piperidine (condensing agent) were added, and the mixture was stirred again. The reaction temperature was controlled to be 60° C., and the reaction was kept warm for 5 hours. After the reaction was completed, the solvent was removed by distillation under reduced pressure to obtain an intermediate product;

[0019] Under the action of the condensing agent, the aldehyde group on glutaraldehyde condenses with the amino group on diethylenetriamine to form an imine group (C=N Schiff base structure). By controlling the molar ratio of the two to be close to 2:1 and a slight excess of glutaraldehyde, an intermediate product is obtained;

[0020] A4, after the intermediate product and N, N-dimethylformamide are mixed and stirred evenly, methyl iodide is added dropwise, the reaction temperature is controlled to 55°C, and a reflux reaction is started. After the addition of methyl iodide is completed, the temperature is raised to 70°C, and the reflux reaction is continued for 8 hours. After the reaction is completed, the cross-linking agent is obtained by distillation under reduced pressure;

[0021] The intermediate product undergoes an alkylation reaction with methyl iodide to obtain a cross-linking agent;

[0022] A5. Add a crosslinking agent, methanol, sulfuric acid and acetic acid to the aqueous solution and stir to mix evenly to prepare a crosslinking solution;

[0023] A6. Pre-wet the pretreated polytetrafluoroethylene hollow fiber membrane obtained in step A1 in ethanol for 40 minutes, take it out, and then immerse it in the hydrophilic modification solution obtained in step A2. After standing for 30 minutes, take it out and dry it, then immerse it in the cross-linking solution obtained in step A5, heat it to 60°C, and cross-link it for 12 hours. After the reaction is completed, take it out and place it in deionized water for ultrasonic cleaning to remove the uncross-linked polyvinyl alcohol and polyethyleneimine, and dry it to obtain a hydrophilic base membrane.

[0024] Furthermore, in step A1, the ratio of the amount of polytetrafluoroethylene hollow fiber membrane to that of ethanol is 1 g:100 mL.

[0025] Furthermore, in step A2, the ratio of polyvinyl alcohol, polyethyleneimine and deionized water is 6.3 g:5.1 g:100 mL.

[0026] Furthermore, in step A3, the ratio of diethylenetriamine, N,N-dimethylformamide, glutaraldehyde and piperidine is 11.7 g:100 mL:22.3 g:15 mL.

[0027] Furthermore, in step A4, the ratio of the intermediate product, N,N-dimethylformamide and iodomethane is 26.7 g:150 mL:14.1 g.

[0028] Furthermore, in step A5, the ratio of the amount of aqueous solution, cross-linking agent, methanol, sulfuric acid and acetic acid is 100 mL: 9.4 g: 8 mL: 2 mL: 7 mL.

[0029] The cross-linking agent is prepared through a series of reactions. The cross-linking agent molecule contains Schiff base, quaternary ammonium salt and two aldehyde groups. The Schiff base structure can interact with bacterial proteins and enzymes to hinder the synthesis of bacterial nucleotides and amino acids, thereby improving the antibacterial property of the basement membrane. As an excellent antibacterial structure, the quaternary ammonium salt has good permeability, low toxicity and stable performance. It can penetrate the cell wall to leak intracellular substances and cause the death of bacteria. It plays a synergistic role with the Schiff base and greatly enhances the antibacterial property of the basement membrane. In addition, the cross-linking agent can reduce the swelling effect of polyvinyl alcohol in aqueous solution, improve the stability of polyvinyl alcohol, and enable polyvinyl alcohol and polyethyleneimine to greatly improve the hydrophilicity of the basement membrane.

[0030] Beneficial effects of the present invention:

[0031] 1. The MXene-modified polytetrafluoroethylene hollow fiber composite membrane prepared by the present invention has a better combination of the surface separation layer and the polytetrafluoroethylene-based membrane by introducing the MXene intermediate layer transition layer, and utilizes the MXene layer structure to enhance the mechanical strength and hydrophilicity of the membrane;

[0032] 2. The base membrane obtained through a series of reactions has excellent hydrophilicity and antibacterial properties and good stability;

[0033] 3. After the organic-inorganic-organic composite from the inside out, the addition of the middle MXene layer is simple and easy to operate, easy to process, and can also increase the permeability of the membrane;

[0034] Therefore, the composite membrane prepared by the present invention contains a three-layer membrane structure, has excellent mechanical strength, hydrophilicity and antibacterial properties, is easy to process, has good permeability, and has important application value in the field of water treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention will be further described below in conjunction with the accompanying drawings.

[0036] Figure 1 Schematic diagram of the composite membrane structure of the present invention.

[0037] Figure 2 This is a microscopic morphology of the composite film obtained in Example 2 of the present invention.

[0038] Figure 3 This is a scanning electron microscope (SEM) morphology image of the multilayer MXene in Example 2.

[0039] Figure 4 The water contact angle measurement diagrams of the composite films prepared in Comparative Example 1 and Example 2 are shown. DETAILED DESCRIPTION

[0040] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] Embodiment 1

[0042] Preparation of hydrophilic membrane:

[0043] A1. Soak 1 g of polytetrafluoroethylene hollow fiber membrane in 100 mL of ethanol and perform ultrasonic treatment for 1 h to remove impurities that may be adsorbed on the membrane surface and in the pores. Take it out and dry it to obtain a pretreated polytetrafluoroethylene hollow fiber membrane.

[0044] A2, 6.3 g of polyvinyl alcohol and 5.1 g of polyethyleneimine were mixed with 100 mL of deionized water, the temperature was raised to 80°C, and the mixture was stirred continuously to dissolve the polyvinyl alcohol and polyethyleneimine to obtain a hydrophilic modified solution;

[0045] A3, 11.7g of diethylenetriamine and 100mL of N,N-dimethylformamide were stirred evenly, and then 22.3g of glutaraldehyde and 15mL of piperidine were added, and the mixture was stirred again, and the reaction temperature was controlled to be 60°C, and the reaction was kept warm for 5h. After the reaction was completed, the solvent was removed by distillation under reduced pressure to obtain an intermediate product;

[0046] A4, after 26.7g of the intermediate product and 150mL of N,N-dimethylformamide were mixed and stirred evenly, 14.1g of methyl iodide was added dropwise, the reaction temperature was controlled to 55°C, and reflux reaction was started. After the addition of methyl iodide was completed, the temperature was raised to 70°C, and the reflux reaction was continued for 8h. After the reaction was completed, the cross-linking agent was obtained by distillation under reduced pressure;

[0047] A5. Add 9.4 g of cross-linking agent, 8 mL of methanol, 2 mL of sulfuric acid and 7 mL of acetic acid to 100 mL of aqueous solution and stir to mix well to prepare a cross-linking solution;

[0048] A6. Pre-wet the pretreated polytetrafluoroethylene hollow fiber membrane obtained in step A1 in ethanol for 40 minutes, take it out, and then immerse it in the hydrophilic modification solution obtained in step A2. After standing for 30 minutes, take it out and dry it, then immerse it in the cross-linking solution obtained in step A5, heat it to 60°C, and cross-link it for 12 hours. After the reaction is completed, take it out and place it in deionized water for ultrasonic cleaning to remove the uncross-linked polyvinyl alcohol and polyethyleneimine, and dry it to obtain a hydrophilic base membrane.

[0049] Embodiment 2

[0050] Step 1, preparation of multilayer MXene: 1g Ti3AlC2 was placed in 40mL hydrofluoric acid solution, dispersed under ultrasonic conditions for 30min, reacted at 65°C for 36h at a speed of 300 rpm, and washed with anhydrous ethanol until the surface impurities were completely removed to obtain multilayer MXene; its thickness was 80μm;

[0051] Step 2, preparation of MXene-modified polytetrafluoroethylene membrane: 0.01 g of the multilayer MXene prepared in step 1 was fully dispersed in 100 mL of pure water, and the hydrophilic base membrane prepared in Example 1 and 0.1 wt% ammonium perfluorooctanoate were added. After fully soaking for 5 minutes, MXene was deposited on the surface of the base membrane to obtain a MXene-modified polytetrafluoroethylene membrane; the membrane thickness was 0.6 mm;

[0052] Step 3, preparation of MXene-modified polytetrafluoroethylene hollow fiber composite membrane: the MXene-modified polytetrafluoroethylene membrane obtained in step 2 is placed in a 3wt% polyvinylidene fluoride spinning solution (solvent is tetrahydrofuran), immersed for 90 minutes, taken out, surface impurities are cleaned and dried to obtain a MXene-modified polytetrafluoroethylene hollow fiber composite membrane; the outermost layer is a surface separation layer, the thickness of which is 0.5mm, and the average surface pore size is 0.1μm.

[0053] The schematic diagram of the composite membrane structure of Example 2 is as follows Figure 1 As shown;

[0054] The microscopic morphology of the composite membrane of Example 2 is shown in FIG. Figure 2 As shown; from the cross-section, it is a hollow fiber, and the inner basement membrane is a cross-linked network structure.

[0055] Embodiment 3

[0056] Step 1, preparation of multilayer MXene: 1g Ti3AlC2 was placed in a 9M mixed solution of 50mL hydrochloric acid and lithium fluoride, and dispersed under ultrasonic conditions for 30min. After dispersion, the mixture was reacted at 70°C at a speed of 300 rpm for 48h. After the reaction was completed, the mixture was washed with anhydrous ethanol until the surface impurities were completely removed to obtain a multilayer MXene with a thickness of 60μm.

[0057] Step 2, preparation of MXene-modified polytetrafluoroethylene membrane: 0.01 g of the multilayer MXene prepared in step 1 was fully dispersed in 100 mL of pure water, and the hydrophilic base film prepared in Example 1 and 0.5 wt % of polyethylene wax were added. After being fully soaked for 8 min, MXene was deposited on the surface of the base film to obtain a MXene-modified polytetrafluoroethylene membrane; the membrane thickness was 0.8 mm;

[0058] Step 3, preparation of MXene-modified polytetrafluoroethylene hollow fiber composite membrane: the MXene-modified polytetrafluoroethylene membrane obtained in step 2 is placed in a 3wt% polyethersulfone spinning solution (solvent is tetrahydrofuran), immersed for 120 minutes, taken out, surface impurities are cleaned and dried to obtain a MXene-modified polytetrafluoroethylene hollow fiber composite membrane; the outermost layer is a surface separation layer, the thickness of which is 0.5mm and the average surface pore size is 0.1μm.

[0059] Embodiment 4

[0060] Step 1, preparation of multilayer MXene: 1g Ti3AlC2 was placed in 50mL ammonium fluoride solution, dispersed under ultrasonic conditions for 30min, reacted at 80°C for 36h at a speed of 350 rpm, and washed with anhydrous ethanol until the surface impurities were completely removed to obtain multilayer MXene; its thickness was 100μm;

[0061] Step 2, preparation of MXene-modified polytetrafluoroethylene membrane: 0.01 g of the multilayer MXene prepared in step 1 is fully dispersed in 100 mL of pure water, and the hydrophilic base film prepared in Example 1 and 1 wt% polyvinyl alcohol 200 are added. After being fully soaked for 10 minutes, MXene is deposited on the surface of the base film to obtain a MXene-modified polytetrafluoroethylene membrane; the membrane thickness is 1 mm;

[0062] Step 3, preparation of MXene-modified polytetrafluoroethylene hollow fiber composite membrane: the MXene-modified polytetrafluoroethylene membrane obtained in step 2 is placed in a 5wt% polyamide spinning solution (solvent is tetrahydrofuran), immersed for 120 minutes, taken out, surface impurities are cleaned and dried to obtain a MXene-modified polytetrafluoroethylene hollow fiber composite membrane; the outermost layer is a surface separation layer, the thickness of which is 0.5mm and the average surface pore size is 0.1μm.

[0063] Comparative Example 1

[0064] A commercially available polytetrafluoroethylene membrane was used.

[0065] The second embodiment and the first comparative embodiment were applied in the MBR process, specifically, a surface area of ​​0.02 m 2 The membrane module was used for the experiment. The membrane was immersed in the reactor and treated a municipal sewage at a pressure of -0.01Mpa. The MBR sludge concentration was 5000mg / L. The initial filtration flux and the filtration flux after one cycle were measured (one filtration cycle was one hour of operation). The flux retention rate was also measured. The flux retention rate = filtration flux after one cycle / initial filtration flux × 100%. The average COD value, turbidity and ammonia nitrogen value of the produced water after one filtration cycle were also measured. Initially, the raw water COD was 250mg / L, the turbidity was 21NTU, and the ammonia nitrogen was 25mg / L.

[0066] The measured results are shown in Table 1:

[0067] Table 1

[0068]

[0069] The third embodiment and the first comparative embodiment were applied to the MBR process, specifically, a surface area of ​​0.02 m 2 The membrane module was used for experiment. The membrane was immersed in the reactor to treat the wastewater from a hospital. Under the pressure of -0.01Mpa, the MBR sludge concentration was 8000mg / L. The initial filtration flux and the filtration flux after five cycles were measured (each operation of 1h was a filtration cycle). The flux retention rate was also measured. The flux retention rate = the filtration flux after five cycles / initial filtration flux × 100%. The average COD value, turbidity and ammonia nitrogen value of the produced water after five filtration cycles were also measured. Initially, the COD was 450mg / L, the turbidity was 32.5NTU, and the ammonia nitrogen was 45mg / L.

[0070] The measured results are shown in Table 2:

[0071] Table 2

[0072]

[0073] The fourth embodiment and the first comparative embodiment were applied in the UF process to prepare a surface area of ​​0.02 m 2 The columnar membrane assembly was used to filter river water at a pressure of 0.1 MPa, and the initial filtration flux and the filtration flux after five cycles (each 30 minutes of operation is a filtration cycle) were measured; and the flux retention rate was measured; the flux retention rate = the filtration flux after five cycles / the initial filtration flux × 100%; and the average COD value, turbidity and ammonia nitrogen value of the produced water after five filtration cycles were measured; initially: the raw water TOC was 3.8 mg / L, the turbidity was 2.1 NTU, and the ammonia nitrogen was 0.05 mg / L;

[0074] The measured results are shown in Table 3:

[0075] Table 3

[0076]

[0077]

[0078] The contact angles of Example 2 and Comparative Example 1 were measured using a contact angle meter. The results are as follows: Figure 4 As shown;

[0079] The antibacterial properties of Examples 2, 3, 4 and Comparative Example 1 were tested by the shaking bottle method. The bacterial solution and the film sample were mixed and cultured in a shaking table for 24 hours. The absorbance value was detected at an ultraviolet wavelength of 600 nm. The antibacterial rate E was calculated according to the absorbance values ​​before and after the culture. The formula is: E = (1-C1 / C0) × 100%, C0 absorbance value before culture, C1 absorbance value after culture;

[0080] The measured results are shown in Table 4:

[0081] Table 4

[0082] Test items Embodiment 2 Embodiment 3 Embodiment 4 Comparative Example 1 Antibacterial rate / % 99.8 99.9 99.9 69.6

[0083] From the above four tables and Figure 4 It can be seen that the composite membrane prepared by the present invention has excellent hydrophilicity, good permeability, strong filtration ability, excellent antibacterial performance, and has important application value in the field of water treatment.

[0084] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means 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 representation of the above terms does 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.

[0085] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A method for preparing a MXene-modified polytetrafluoroethylene hollow fiber composite membrane, characterized in that: The steps include: Step 1, preparation of multilayer MXene: placing Ti3AlC2 in an etching solvent, dispersing it under ultrasonic conditions, stirring and reacting it after dispersion, and washing it with anhydrous ethanol until the surface impurities are completely removed to obtain multilayer MXene; Step 2, preparation of MXene-modified polytetrafluoroethylene membrane: fully disperse the multilayer MXene prepared in step 1 in pure water, add a hydrophilic base membrane and a dispersant, and after fully soaking for 2-10 minutes, allow the MXene to be deposited on the surface of the base membrane to obtain a MXene-modified polytetrafluoroethylene membrane; Step 3, preparation of MXene-modified polytetrafluoroethylene hollow fiber composite membrane: place the MXene-modified polytetrafluoroethylene membrane obtained in step 2 in the copolymer monomer spinning solution, soak it for 1-2 hours, take it out, clean the surface impurities and dry it to obtain a MXene-modified polytetrafluoroethylene hollow fiber composite membrane.

2. The method for preparing a MXene-modified polytetrafluoroethylene hollow fiber composite membrane according to claim 1, characterized in that: In step 1, the etching solvent is one of hydrofluoric acid and sodium fluoride, hydrochloric acid and lithium fluoride, and ammonium fluoride solution.

3. The method for preparing a MXene-modified polytetrafluoroethylene hollow fiber composite membrane according to claim 1, characterized in that: The concentration of multilayer MXene in pure water in step 2 is 0.5-5 g / L.

4. The method for preparing a MXene-modified polytetrafluoroethylene hollow fiber composite membrane according to claim 1, characterized in that: In step 2, the dispersant is one of ammonium perfluorooctanoate, polyethylene wax and polyvinyl alcohol 200; the monomer mass concentration of the dispersant is 1-5wt%.

5. The method for preparing a MXene-modified polytetrafluoroethylene hollow fiber composite membrane according to claim 1, characterized in that: The copolymer monomer in step 3 is one of polysulfone, polyethersulfone, polyamide, polyvinylidene fluoride and polybenzimidazole; the mass concentration of the copolymer monomer is 1-5wt%.

6. The method for preparing a MXene-modified polytetrafluoroethylene hollow fiber composite membrane according to claim 1, characterized in that: The hydrophilic base film is prepared by the following steps: A1. Soak the polytetrafluoroethylene hollow fiber membrane in ethanol and perform ultrasonic treatment for 1 hour to remove impurities that may be adsorbed on the membrane surface and in the pores. Take it out and dry it to obtain a pretreated polytetrafluoroethylene hollow fiber membrane. A2, polyvinyl alcohol and polyethyleneimine are mixed with deionized water, the temperature is raised to 80°C, and the mixture is stirred continuously to dissolve the polyvinyl alcohol and polyethyleneimine to obtain a hydrophilic modified solution; A3, diethylenetriamine and N, N-dimethylformamide were stirred evenly, and then glutaraldehyde and piperidine were added, and the mixture was stirred again, and the mixture was kept at 60° C. for 5 h. After the reaction was completed, the mixture was distilled under reduced pressure to obtain an intermediate product; A4, after the intermediate product and N, N-dimethylformamide are mixed and stirred evenly, methyl iodide is added dropwise, and reflux reaction is carried out at 55°C until the addition of methyl iodide is completed, the temperature is raised to 70°C, and the reflux reaction is continued for 8 hours. After the reaction is completed, the cross-linking agent is obtained by distillation under reduced pressure; A5. Add a crosslinking agent, methanol, sulfuric acid and acetic acid to the aqueous solution and stir to mix evenly to prepare a crosslinking solution; A6. Pre-wet the pretreated polytetrafluoroethylene hollow fiber membrane obtained in step A1 in ethanol for 40 minutes, take it out, and then immerse it in the hydrophilic modification solution obtained in step A2. After standing for 30 minutes, take it out and dry it, and then immerse it in the cross-linking solution obtained in step A5. Heat it to 60°C and perform the cross-linking reaction for 12 hours. After the reaction is completed, ultrasonically clean it and dry it to obtain a hydrophilic base membrane.

7. The method for preparing a MXene-modified polytetrafluoroethylene hollow fiber composite membrane according to claim 6, characterized in that: In step A3, the ratio of diethylenetriamine, N,N-dimethylformamide, glutaraldehyde and piperidine is 11.7 g:100 mL:22.3 g:15 mL.

8. The method for preparing a MXene-modified polytetrafluoroethylene hollow fiber composite membrane according to claim 6, characterized in that: In step A4, the ratio of the intermediate product, N,N-dimethylformamide and iodomethane is 26.7 g:150 mL:14.1 g.

9. Application of the MXene-modified polytetrafluoroethylene hollow fiber composite membrane prepared by the method according to any one of claims 1 to 8 in the field of water treatment.

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