Polytetrafluoroethylene hollow fiber composite catalytic membrane and its preparation method and application

Abstract

The present invention discloses a polytetrafluoroethylene hollow fiber composite catalytic membrane and its preparation method and application. The polytetrafluoroethylene hollow fiber composite catalytic membrane of the present invention has both high strength and flexibility, stable catalyst loading, excellent instantaneous catalytic performance, and is suitable for industrial production and high-difficulty wastewater treatment. The present invention uses a controlled in-situ growth-low temperature calcination process to in-situ load bimetallic or multimetallic-organic framework material-derived carbon-based catalyst nanoparticles on the surface of the polytetrafluoroethylene hollow fiber base membrane and / or the polytetrafluoroethylene fiber / node interface inside. The molar ratio of singlet oxygen in the active oxygen generated by the activated persulfate can reach more than 60%, which is suitable for the efficient degradation and treatment of high-difficulty wastewater such as coal chemical industry that is difficult to degrade in a high-salt environment and emerging organic pollutant wastewater.

Description

Technical Field

[0001] The invention relates to the technical field of membrane functionalization, and in particular to a polytetrafluoroethylene hollow fiber composite catalytic membrane and a preparation method and application thereof. Background Art

[0002] Compared with short-lived reactive oxygen free radicals such as superoxide radicals, hydroxyl radicals and sulfate radicals, singlet oxygen ( 1 O 2 ) has a longer lifespan, a wider pH and higher salt concentration tolerance range. Studies have shown that singlet oxygen has strong electrophilicity and selectively attacks electron-rich substances (such as aromatic organic matter), and is particularly suitable for the treatment of complex, high-salt, and difficult-to-degrade wastewater such as emerging organic pollutants and coal chemical industry.

[0003] At present, in advanced oxidation technology, singlet oxygen is mainly generated by activating persulfate (PMS) through carbon-based derivative catalysts. The carbon-based derivative catalysts reported in the study are mainly prepared by high-temperature calcination of metal / organic composite catalyst materials. However, nanocatalyst particles have the disadvantages of being difficult to recover, easy to agglomerate and easy to lose, which limits their practical application in the field of wastewater treatment. Researchers often anchor nanocatalyst particles on porous or large particle carriers to improve their dispersibility, stability and recyclability. Among them, fixing heterogeneous catalysts on separation membranes to prepare catalytic membranes can not only solve the problems of easy loss and difficulty in recovery of catalysts, but also solve the problem of reduced catalytic sites and catalytic activity caused by secondary coating processing of traditional catalysts, and can also effectively alleviate membrane pollution. For example, the Chinese patent (CN113289666A) discloses a method for preparing a ceramic catalytic membrane, in which ZIF-67 is loaded on a ceramic membrane as a carrier, and then a ceramic composite catalytic membrane is obtained by high-temperature pyrolysis. However, ceramic membranes are generally expensive and brittle and easy to break. At the same time, ceramic membranes have low porosity, small effective membrane separation area, and often large component volume. Although traditional flexible organic separation membranes have high porosity and high component integration, they are often not able to be calcined at high temperatures due to their low thermal stability temperature, and can only load conventional native nanocatalysts for free radical activation. Carbon-based derivative nanocatalysts that have been calcined first can often only adhere to the membrane surface and are difficult to effectively load into the pores of the polymer separation membrane. The catalyst loading of the composite membrane is low and the catalytic performance is poor. Therefore, how to composite a flexible polymer separation membrane with a carbon-based derivative catalyst precursor and prepare a polymer composite catalytic membrane through a suitable calcination process to activate PMS to produce singlet oxygen for catalytic degradation of organic pollutants in wastewater is still a technical problem that needs to be solved urgently. Summary of the invention

[0004] In view of the deficiencies of the prior art, especially for the treatment of difficult-to-degrade coal chemical wastewater and emerging organic pollutant wastewater in a high-salt environment, the present invention provides a highly stable polytetrafluoroethylene hollow fiber composite catalytic membrane for efficiently generating singlet oxygen and a preparation method thereof. Through the in-situ self-assembly and low-temperature calcination technology of dual or multi-metal-organic framework nanomaterials, a high loading of carbon-based derived nanocatalysts on the flexible polytetrafluoroethylene hollow fiber membrane is achieved, the utilization rate of active catalytic sites of the polytetrafluoroethylene hollow fiber composite catalytic membrane is improved, and a high proportion of highly active singlet oxygen is dominantly generated to reduce the interference of environmental organic matter and other high-concentration anions.

[0005] To solve the above technical problems, the first aspect of the present invention provides a polytetrafluoroethylene hollow fiber composite catalytic membrane, comprising a polytetrafluoroethylene hollow fiber base membrane, and nanocatalysts distributed on the surface and / or inside of the polytetrafluoroethylene hollow fiber base membrane and / or at the nodes.

[0006] Further, the polytetrafluoroethylene hollow fiber-based membrane is a homogeneous symmetrical polytetrafluoroethylene hollow fiber membrane or a homogeneous asymmetric polytetrafluoroethylene hollow fiber membrane, and the polytetrafluoroethylene hollow fiber-based membrane is hydrophilic, and the surface water droplet complete wetting time is less than or equal to 30 seconds. It is understandable that in the process of preparing carbon-based nanocatalysts by calcining the composite membrane, the hydrophilic polytetrafluoroethylene-based membrane also needs to undergo a calcination process, which is bound to cause the membrane hydrophilicity to fail to a certain extent. The better hydrophilicity of the base membrane is conducive to the subsequent preparation of the polytetrafluoroethylene hollow fiber composite catalytic membrane to maintain good hydrophilicity. Therefore, based on the exploratory research of the development process of this patent technology, a polytetrafluoroethylene hollow fiber-based membrane with a surface water droplet complete wetting time of less than or equal to 30 seconds is preferred.

[0007] Furthermore, the polytetrafluoroethylene hollow fiber composite catalytic membrane is hydrophilic, and the surface water droplet complete wetting time is less than or equal to 60 seconds. It can be understood that in wastewater treatment projects, the better hydrophilicity of the membrane is beneficial to the transmission of water in the membrane pores and improves the membrane permeability. On the other hand, it is beneficial to the rapid wetting of the membrane to enhance the exposed catalyst sites to contact / adsorb PMS and pollutants faster, thereby improving the catalytic efficiency.

[0008] Furthermore, the nanocatalyst contains two or more metal element components. It is understandable that when bimetallic or polymetallic components exist, the catalyst activity is stronger. In the case of incomplete carbonization of the catalyst, two or more metal element components can enhance the ability of the catalyst to activate PMS and increase the proportion of singlet oxygen.

[0009] Furthermore, the mass fraction of the nanocatalyst in the polytetrafluoroethylene hollow fiber composite catalytic membrane is 1% to 10%, and the particle size of the nanocatalyst is less than or equal to 1 μm. It is understandable that although the metal-organic framework material of the present invention is based on the in-situ self-assembly synthesis of amino groups on the polytetrafluoroethylene fiber and / or the node interface grafted on the surface and / or inside of the polytetrafluoroethylene based membrane, after calcination, the anchoring effect of the nanocatalyst and the polytetrafluoroethylene based membrane is bound to be weakened. Although the smaller catalyst nanoparticle size can improve the catalytic performance of the membrane to a certain extent due to its more catalyst exposure sites, it is bound to affect the composite stability of the catalyst in the composite membrane, and there is a risk of loss; and the larger nanocatalyst particle size has a greater impact on the pore size and porosity of the composite membrane, resulting in a decrease in the membrane permeability. At the same time, it is understandable that if the nanocatalyst loading is less, the polytetrafluoroethylene hollow fiber composite catalytic membrane will have fewer active sites and its instantaneous catalytic performance will be poor. Of course, the comprehensive catalytic degradation effect of the membrane system can be improved through multiple cycles, but it is bound to increase the operating cost of the membrane system; and more nanocatalyst loading has a greater impact on the pore size and porosity of the composite membrane, resulting in a decrease in membrane permeability. The present invention is based on comprehensive experimental verification and membrane system operating cost estimation, and limits the particle size of the carbon-derived nanocatalyst and its mass fraction in the polytetrafluoroethylene hollow fiber composite catalytic membrane. Preferably, the particle size of the nanocatalyst is 30 to 300 nanometers, and the mass fraction of the nanocatalyst in the polytetrafluoroethylene hollow fiber composite catalytic membrane is 2 to 5%.

[0010] Furthermore, the polytetrafluoroethylene hollow fiber composite catalytic membrane is suitable for activating persulfate to produce singlet oxygen, and the molar proportion of the singlet oxygen produced in the total active oxygen is 60% to 90%. Based on the comprehensive test verification of the preferred process conditions of the patent of the present invention, it can be known through the active oxygen quenching test that the polytetrafluoroethylene hollow fiber composite catalytic membrane prepared by the present invention has a molar proportion of singlet oxygen in the active oxygen generated by activating PMS as high as 60% to 90%. It can be understood that in addition to the preferred conditions described in the present invention, the molar proportion of singlet oxygen can be reduced as factors such as catalyst loading and catalyst composition are regulated, and the technology of the present invention will not be described in detail.

[0011] The second aspect of the present invention provides a method for preparing the above-mentioned polytetrafluoroethylene hollow fiber composite catalytic membrane, comprising the following steps:

[0012] S1, preparing a hydrophilic polytetrafluoroethylene hollow fiber-based membrane, and performing amination modification on the surface and / or internal polytetrafluoroethylene fibers and / or node interfaces;

[0013] S2, respectively preparing a precursor A solution and a precursor B solution;

[0014] S3, placing the aminated polytetrafluoroethylene hollow fiber-based membrane in the precursor A solution, so that the surface and / or the internal pore interface are in-situ impregnated with the complex precursor A;

[0015] S4, placing the polytetrafluoroethylene hollow fiber-based membrane treated in step S3 in a precursor B solution, so that the bimetallic or multimetallic-organic framework material is synthesized in situ on the fiber and / or node interface on its surface and / or inside;

[0016] S5. Wash the ceramic membrane treated in step S4 with deionized water, dry it, and then calcine it at a low temperature to obtain a polytetrafluoroethylene hollow fiber composite catalytic membrane.

[0017] Further, in the step S1, the hydrophilic polytetrafluoroethylene hollow fiber-based membrane may be a commercially available hydrophilic polytetrafluoroethylene hollow fiber membrane that has been hydrophilically modified; or it may be a commercially available hydrophobic polytetrafluoroethylene hollow fiber membrane that has not been modified. If it is a hydrophobic polytetrafluoroethylene hollow fiber membrane, it is preferably first subjected to hydrophilic modification, because the polymer hydrophilic modification technology is relatively mature, and the present invention does not make a cumulative description. It is understandable that if the hydrophobic polytetrafluoroethylene hollow fiber membrane is not first subjected to hydrophilic modification, but is subjected to an infiltration treatment with solvents such as ethanol and isopropanol, subsequent amination modification may also be performed directly, but it is bound to affect the hydrophilicity of the subsequent composite catalytic membrane.

[0018] Furthermore, in the step S1, the fibers and / or node interfaces of the polytetrafluoroethylene hollow fiber-based membrane are subjected to amination modification, specifically by a hydrothermal self-crosslinking network reaction of a silane coupling agent, including intertwining an amino-containing silane coupling agent network with the fibers and / or node interfaces of the polytetrafluoroethylene hollow fiber-based membrane, and / or intertwining a polyethyleneimine and epoxy-containing silane coupling agent network with the fibers and / or node interfaces of the polytetrafluoroethylene hollow fiber-based membrane. Preferably, the silane coupling agent containing amino group is selected from 3-aminopropyl triethoxysilane, 3-aminopropyl trimethoxysilane, N-[3-(trimethoxysilyl)propyl]ethylenediamine, N-[3-(triethoxysilyl)propyl]ethylenediamine, and a mixture of one or more thereof; the silane coupling agent containing epoxy group is selected from a mixture of one or more thereof of glycidyloxypropyl trimethoxysilane, glycidyloxypropyl triethoxysilane, glycidyloxypropyl methyldiethoxysilane, and glycidyloxypropyl methyldimethoxysilane. It is understandable that with the advancement of chemical synthesis means and the reduction of synthesis costs, other silane coupling agents containing amino or epoxy groups can also be used for the fiber and / or node interface amination modification of the polytetrafluoroethylene hollow fiber-based membrane described in the present invention. It is understandable that the polyethyleneimine described in the present invention comprises a single molecular weight or a mixture of multiple molecular weights, and can also be ethylenediamine and oligomers of ethylenediamine, and the present invention is not described in detail. It is understandable that before the polytetrafluoroethylene hollow fiber-based membrane is aminated, the polytetrafluoroethylene hollow fiber-based membrane needs to be cleaned, and the technology of the present invention is not repeated. It is understandable that when the polytetrafluoroethylene hollow fiber-based membrane is aminated, in order to promote the hydrothermal self-crosslinking reaction of the silane coupling agent to form a network, acid catalysis or heating can be added to promote and accelerate the self-crosslinking reaction, and the technology of the present invention is not repeated.

[0019] Further, the precursor A solution is an aqueous solution composed of one or more metal salts of cobalt, iron, zinc, manganese, and copper and water; the precursor B solution is an aqueous solution composed of one or more metal salts of ferrocyanate, ferrocyanate, and cobalt cyanate and water. It is understandable that the precursor A solution is one or more metal salt solutions, and its function is to provide a metal complexing source for the polytetrafluoroethylene hollow fiber-based membrane after amination modification, to achieve the complexation of metal ions with amino groups grafted on the fiber and / or node interface of the polytetrafluoroethylene hollow fiber-based membrane, so as to achieve efficient and uniform load distribution of the first precursor of MOFs in the polytetrafluoroethylene hollow fiber-based membrane. It is understandable that the precursor B solution is the second precursor of MOFs, wherein the function is to further react with the first precursor uniformly complexed and loaded on the fiber and / or node interface of the polytetrafluoroethylene hollow fiber-based membrane to generate complete MOFs. Based on experimental verification and cost estimation, the technology of the present invention prefers the above-mentioned cheap metal ions as MOFs precursors, but other precious metal salts can also be used for the in-situ growth of MOFs described in the technology of the present invention.

[0020] Further, the step S3 specifically includes flowing the precursor A solution from one side of the polytetrafluoroethylene hollow fiber-based membrane to the other side, maintaining the time for 5-30 minutes, so that the surface and / or internal polytetrafluoroethylene fibers and / or node interfaces are in situ impregnated with the complex precursor A, and then removing the precursor A solution; the step S4 specifically includes flowing the precursor B solution from one side of the polytetrafluoroethylene hollow fiber-based membrane treated by step S3 to the other side, maintaining the time for 5-30 minutes, so that the surface and / or internal polytetrafluoroethylene fibers and / or node interfaces are in situ synthesized bimetallic or multimetallic-organic framework materials. It can be understood that by regulating the concentration of the precursor A solution or the precursor B solution, as well as the regulation of the immersion time, the loading amount of MOFs in the polytetrafluoroethylene-based membrane can be effectively regulated, and then the loading amount of the catalyst in the composite catalytic membrane can be regulated, and the present invention does not make a cumulative description of this. Preferably, after the polytetrafluoroethylene hollow fiber base membrane is impregnated with the precursor A solution, it is dried and then impregnated with the precursor B solution, which can effectively improve the uniformity and loading of the in-situ growth of MOFs and reduce the amount of precursor solution used. It is understandable that soaking and impregnation can also be selected to allow the solution to enter the polytetrafluoroethylene hollow fiber base membrane through slow free diffusion, but it is bound to require a longer soaking time to achieve sufficient infiltration and reaction of the precursor A solution or the precursor B solution in the base membrane. Therefore, the patented technology preferably uses the flow control impregnation technology, which can greatly improve production efficiency and reduce production costs.

[0021] Further, the step S5 specifically includes washing the polytetrafluoroethylene hollow fiber composite membrane treated in step S4 with deionized water, drying it, and then placing it in a tubular furnace, heating it to 250-350°C at a rate of 2-5°C / min in an inert gas environment, the heating rate is 2-5°C / min, and heat preservation treatment is 3-10h, and then naturally cooled to room temperature to obtain a polytetrafluoroethylene hollow fiber composite catalytic membrane. It can be understood that the calcination temperature and calcination time directly affect the carbonization degree of MOFs. When the temperature is low and the time is short, the carbonization degree of the catalyst is low, and the molar ratio of singlet oxygen in the active oxygen generated by the composite catalytic membrane activating PMS is low. When the temperature is high and the time is long, the carbonization degree of the catalyst is high, but the polytetrafluoroethylene based membrane is difficult to tolerate, causing the composite catalytic membrane to disintegrate and collapse. The present invention is based on a large number of experimental verifications, and the above-mentioned low-temperature calcination process is preferred.

[0022] The third aspect of the present invention provides the application of the above-mentioned polytetrafluoroethylene hollow fiber composite catalytic membrane, which is used for wastewater treatment, especially high-salt wastewater treatment in coal chemical industry, petrochemical industry, etc. The composite catalytic membrane is catalytically degraded in a high-salt environment with a salt content of more than 5000ppm in the wastewater, and can achieve a pollutant removal rate of more than 90% and / or a pollutant mineralization rate of more than 70%. It can be understood that in the treatment of wastewater in a low-salt or salt-free environment, the polytetrafluoroethylene hollow fiber composite catalytic membrane prepared by the technology of the present invention has the same catalytic degradation performance.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1) The polytetrafluoroethylene hollow fiber composite catalytic membrane of the present invention greatly improves the catalytic degradation efficiency of small organic molecule pollutants, can realize instantaneous filtration and catalytic degradation of small organic molecules in sewage, and can achieve a pollutant mineralization rate of more than 70% when used to treat high-salt coal chemical wastewater. At the same time, the composite catalytic membrane has long-term operation stability;

[0025] 2) The present invention uses a two-step controllable in-situ growth-calcination process to in-situ load carbon-based catalyst nanoparticles derived from dual or multi-metal-organic framework materials (MOFs) on the surface of the polytetrafluoroethylene hollow fiber-based membrane and / or the interface of the polytetrafluoroethylene fibers and / or nodes inside. Compared with the existing process technologies such as suction filtration membrane formation and impregnation-calcination, the present invention can greatly improve the loading amount, loading uniformity and stability of the metal-doped carbon-based nanocatalysts derived from MOFs on the surface and pore interface of the polytetrafluoroethylene hollow fiber-based membrane; at the same time, dual or multi-metal doping can greatly improve the transmission rate of the activation factor in the catalyst activation PMS process and promote the generation of active oxygen;

[0026] 3) The present invention successfully achieves in-situ high-load loading of carbon-based derivative nanocatalysts on the surface and inside the pores of the flexible polymer-based membrane through low-temperature carbonization, and realizes that the composite catalytic membrane is suitable for activating persulfate to produce singlet oxygen. The molar proportion of the singlet oxygen produced in the total active oxygen is more than 60%, which effectively makes up for the deficiency that the current flexible polymer-based composite catalytic membrane can only activate and generate free radical active oxygen or low-concentration singlet oxygen. At the same time, based on the calcination process in the low-temperature section, the native nanoparticles are semi-carbonized, rather than the full carbonization formed by traditional high-temperature calcination, which not only ensures that the nanocatalyst can activate PMS to generate singlet oxygen, but also effectively improves the good loading stability of the nanocatalyst and polytetrafluoroethylene-based membrane after calcination;

[0027] 4) The present invention can prepare flexible polytetrafluoroethylene hollow fiber composite catalytic membranes loaded with different MOFs-derived carbon-based catalysts by controlling the flow control process of the precursor solution; at the same time, the method of the present invention can prepare polytetrafluoroethylene hollow fiber composite catalytic membranes with different MOFs-derived carbon-based catalyst loadings by controlling the MOFs in-situ growth time and the precursor concentration, thereby achieving the coordinated optimization of the driving pressure, separation flux and catalytic efficiency of the composite catalytic membrane, and greatly broadening the economic designability of the composite catalytic membrane for the catalytic degradation treatment of various types of organic small molecule pollutants in sewage;

[0028] 5) The preparation method of the present invention has simple process, mild conditions, is suitable for industrial production, and has good market application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a scanning electron microscope photograph of a cross section of the polytetrafluoroethylene homogeneous symmetrical hollow fiber base membrane selected in Example 1 of the present invention.

[0030] Figure 2 This is a surface scanning electron microscope photograph of the polytetrafluoroethylene homogeneous symmetrical hollow fiber base membrane selected in Example 1 of the present invention.

[0031] Figure 3 This is a surface scanning electron microscope photograph of the polytetrafluoroethylene hollow fiber composite catalytic membrane prepared in Example 1 of the present invention.

[0032] Figure 4 This is a cross-sectional scanning electron microscope photograph (enlarged) of the polytetrafluoroethylene homogeneous symmetrical hollow fiber base membrane selected in Example 1 of the present invention.

[0033] Figure 5 This is a scanning electron microscope photograph of the cross section of the polytetrafluoroethylene hollow fiber composite catalytic membrane prepared in Example 1 of the present invention.

[0034] Figure 6 This is the TGA curve of the cobalt-iron bimetallic Prussian blue MOFs prepared in Example 1 of the present invention.

[0035] Figure 7 This is a scanning electron microscope photograph of a cross section of the polytetrafluoroethylene homogeneous asymmetric hollow fiber base membrane selected in Example 2 of the present invention.

[0036] Figure 8 This is a scanning electron microscope photograph of the cross section of the polytetrafluoroethylene hollow fiber composite catalytic membrane prepared in Example 2 of the present invention.

[0037] Fig. 9 This is a scanning electron microscope photograph of the cross section of the polytetrafluoroethylene hollow fiber composite membrane prepared in Comparative Example 1 of the present invention.

[0038] Fig.10 This is a scanning electron microscope photograph of the cross section of the polytetrafluoroethylene hollow fiber composite membrane prepared in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0039] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0040] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0041] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present application description and examples are exemplary only.

[0042] Example 1

[0043] Step 1): Add 6 grams of 3-glycidyloxypropyltriethoxysilane to 100 grams of water and stir to obtain a uniform solution; soak a commercially available hydrophilic polytetrafluoroethylene homogeneous symmetrical hollow fiber-based membrane in the solution for 1 hour; then transfer the polytetrafluoroethylene-based membrane to a 65°C pH=3 hydrochloric acid aqueous solution and let it stand for 12 hours; after taking out the polytetrafluoroethylene-based membrane, wash it with deionized water several times, and then transfer it to a 1% mass fraction PEI-10000 aqueous solution and soak it for 4 hours; after taking out the polytetrafluoroethylene-based membrane, wash it with deionized water several times and dry it.

[0044] Step 2): Add 3 grams of cobalt nitrate to 100 grams of water to obtain a precursor A solution; add 3 grams of potassium ferrocyanide to 100 grams of water to obtain a precursor B solution.

[0045] Step 3): Install the polytetrafluoroethylene hollow fiber-based membrane modified by amination in step 1) into the membrane separation system, and use a diaphragm pump to flow the precursor A solution prepared in step 2) from the inside to the outside of the polytetrafluoroethylene hollow fiber-based membrane at a low pressure of 0.01 MPa. Circulate continuously for 20 minutes, then take out the polytetrafluoroethylene hollow fiber membrane and place it in a 50°C oven for drying.

[0046] Step 4): The polytetrafluoroethylene hollow fiber membrane dried in step 3) is reinstalled into the membrane separation system, and the precursor B solution in step 2) is flowed from the inside to the outside of the polytetrafluoroethylene hollow fiber-based membrane at a low pressure of 0.01 MPa using a diaphragm pump, and circulated continuously for 20 minutes. After being taken out and dried, a polytetrafluoroethylene hollow fiber composite membrane with in-situ grown cobalt-iron bimetallic Prussian blue MOFs is obtained.

[0047] Step 5): The cobalt-iron bimetallic MOFs / polytetrafluoroethylene hollow fiber composite membrane obtained in step 4) is placed in a tubular furnace, heated to 300°C at a rate of 3.0°C / min in an argon environment, kept warm for 6 hours, and then naturally cooled to room temperature to obtain a polytetrafluoroethylene hollow fiber composite catalytic membrane with a bimetallic component carbon-based nanocatalyst composite.

[0048] like Figure 1 As shown in the figure, it is a partial enlarged photo of the cross section of a homogeneous and symmetrical polytetrafluoroethylene hollow fiber-based membrane, and it can be seen that the membrane is uniformly distributed from the inside to the outside. Figure 2 and Figure 3 By comparison, compared with the polytetrafluoroethylene-based membrane modified by amination, the polytetrafluoroethylene composite catalyst membrane has the carbon-based catalyst nanoparticles derived from the calcination of cobalt-iron bimetallic MOFs uniformly wrapped on its surface polytetrafluoroethylene fibers and node interfaces. Figure 4 and Figure 5 By comparison, compared with the polytetrafluoroethylene-based membrane modified by amination, the polytetrafluoroethylene composite catalytic membrane has carbon-based catalyst nanoparticles derived from the calcination of cobalt-iron bimetallic MOFs uniformly wrapped at the polytetrafluoroethylene fiber interface inside it, and the average size of the nanoparticles is 70 nanometers.

[0049] Through XPS scanning analysis of the cross section of the prepared polytetrafluoroethylene composite catalyst membrane, the atomic ratio of cobalt / iron in the carbon-based composite catalyst in the composite catalyst membrane is about 1: 1. Further TGA test analysis and calculation show that the mass fraction of the nanocatalyst in the composite catalyst membrane is about 5%.

[0050] The obtained polytetrafluoroethylene hollow fiber composite catalytic membrane was used to test the performance of catalytic degradation and removal of emerging organic small molecules pollutants in water. The results showed that the pure water flux of the composite catalytic membrane was about 850 L / m2·hour·bar; through ultraviolet absorption spectrum comparison analysis: after one filtration, the catalytic degradation removal rate of the composite catalytic membrane for rhodamine B with a concentration of 10 ppm in the solution reached 99%; after one filtration, the catalytic degradation removal rate of the composite catalytic membrane for sulfonylmethoxazole with a concentration of 6 ppm in the solution reached 99%; after one filtration, the catalytic degradation removal rate of the composite catalytic membrane for tetracycline with a concentration of 8 ppm in the solution reached 99%; after one filtration, the catalytic degradation removal rate of the composite catalytic membrane for methylene blue with a concentration of 15 ppm in the solution reached 99%; after one filtration, the catalytic degradation removal rate of the composite catalytic membrane for bisphenol A with a concentration of 10 ppm in the solution reached 99%. The composite catalytic membrane was applied to the treatment of wastewater from a coal chemical industry with a sodium chloride concentration of up to 15,000 ppm. Through total organic carbon (TOC) analysis and testing, after one filtration, the mineralization rate of organic pollutants in the high-salt coal chemical wastewater by the composite catalytic membrane reached 78% (the inlet TOC was 280 and the outlet TOC was 61.3).

[0051] Through the active oxygen quenching test, the molar proportion of singlet oxygen in the active oxygen generated by the composite catalytic membrane activating PMS is 85%.

[0052] Cobalt-iron bimetallic Prussian blue MOFs were synthesized by free solution method and analyzed by TGA test. Figure 6 As shown, this type of MOFs nanoparticles undergo a low-temperature thermal degradation phenomenon in the temperature range of 200 to 350°C, indicating that within the temperature range of low-temperature calcination described in this patent technology, the carbonylation treatment of the nanoparticles loaded in the polytetrafluoroethylene composite membrane can be achieved, thereby improving the composite catalytic membrane to activate PMS to generate singlet oxygen.

[0053] Example 2

[0054] Step 1): Add 6 grams of 3-aminopropyltriethoxysilane to 100 grams of water and stir until the mixture is uniform to obtain an aminated modifier; soak a commercially available hydrophilic polytetrafluoroethylene homogeneous asymmetric hollow fiber base membrane in the aminated modifier for 2 hours; then transfer the base membrane to a 2% by mass citric acid aqueous solution at 70°C and let it stand for 24 hours; after taking out the base membrane, wash it several times with deionized water and dry it.

[0055] Step 2): Add 2 grams of ferric sulfate hexahydrate and 1 gram of copper sulfate to 100 grams of water to obtain a precursor A solution; add 2.5 grams of potassium cobalt cyanate to 100 grams of water to obtain a precursor B solution.

[0056] Step 3): Install the polytetrafluoroethylene hollow fiber-based membrane modified by amination in step 1) into the membrane separation system, and use a diaphragm pump to flow the precursor A solution prepared in step 2) from the inside to the outside of the polytetrafluoroethylene hollow fiber-based membrane at a low pressure of 0.015 MPa. Circulate continuously for 30 minutes, then take out the polytetrafluoroethylene hollow fiber membrane and place it in a 45°C oven for drying.

[0057] Step 4): The polytetrafluoroethylene hollow fiber membrane dried in step 3) is reinstalled into the membrane separation system, and the precursor B solution in step 2) is flowed from the inside to the outside of the polytetrafluoroethylene hollow fiber-based membrane at a low pressure of 0.015 MPa using a diaphragm pump, and circulated continuously for 30 minutes. After being taken out and dried, a polytetrafluoroethylene hollow fiber composite membrane with in-situ grown cobalt-iron-copper trimetallic MOFs is obtained.

[0058] Step 5): The cobalt-iron-copper trimetallic / polytetrafluoroethylene hollow fiber membrane obtained in step 4) is placed in a tubular furnace, heated to 250°C at a rate of 4.0°C / min in an argon environment, kept warm for 10 hours, and then naturally cooled to room temperature to obtain a polytetrafluoroethylene hollow fiber composite catalytic membrane.

[0059] like Figure 7 As shown in FIG. 1 , it is a partial magnified photo of the cross section of a homogeneous asymmetric polytetrafluoroethylene hollow fiber-based membrane. It can be seen that a polytetrafluoroethylene separation layer is compounded near the outer surface of the membrane. Figure 8 As shown, the polytetrafluoroethylene composite catalytic membrane has carbon-based catalyst nanoparticles derived from the calcination of cobalt-iron-copper trimetallic MOFs uniformly wrapped at the polytetrafluoroethylene fiber interface inside the membrane, and the average size of the nanoparticles is 40 nanometers.

[0060] Through TGA test analysis, it was calculated that the mass fraction of the carbon-based composite catalyst in its composite catalytic membrane was approximately 4%.

[0061] The obtained polytetrafluoroethylene hollow fiber composite catalytic membrane was used to test the performance of catalytic degradation and removal of emerging organic small molecules in water pollutants. The results showed that the pure water flux of the composite catalytic membrane was about 630 L / m2·hour·bar; through ultraviolet absorption spectrum comparison analysis: after one filtration, the catalytic degradation removal rate of the composite catalytic membrane for rhodamine B with a concentration of 15 ppm in the solution reached 99%; after one filtration, the catalytic degradation removal rate of the composite catalytic membrane for sulfonylmethoxazole with a concentration of 8 ppm in the solution reached 99%; after one filtration, the catalytic degradation removal rate of the composite catalytic membrane for tetracycline with a concentration of 10 ppm in the solution reached 99%; after one filtration, the catalytic degradation removal rate of the composite catalytic membrane for methylene blue with a concentration of 20 ppm in the solution reached 99%; after one filtration, the catalytic degradation removal rate of the composite catalytic membrane for bisphenol A with a concentration of 12 ppm in the solution reached 99%. The composite catalytic membrane was applied to the treatment of wastewater from a coal chemical industry with a sodium chloride concentration of up to 16,000 ppm. Through total organic carbon (TOC) analysis and testing, after one filtration, the mineralization rate of organic pollutants in the high-salt coal chemical wastewater by the composite catalytic membrane reached 78.3% (the inlet TOC was 300 and the outlet TOC was 65.1).

[0062] Through the active oxygen quenching test, the molar proportion of singlet oxygen in the active oxygen generated by the composite catalytic membrane activating PMS was 89%.

[0063] Example 3

[0064] Step 1): Add 6 grams of glycidyloxypropyltriethoxysilane and 4 grams of glycidyloxypropylmethyldiethoxysilane to 100 grams of water and stir to obtain a uniform solution; soak a commercially available hydrophilic polytetrafluoroethylene homogeneous symmetrical hollow fiber base membrane in the solution for 4 hours; then transfer the base membrane to a 55°C pH=2 nitric acid aqueous solution and let it stand for 20 hours; after removing the base membrane, wash it with deionized water several times, and then transfer it to a 2% by mass PEI-600 aqueous solution and soak it for 4 hours; after removing the base membrane, wash it with deionized water several times and dry it.

[0065] Step 2): Add 1 gram of manganese nitrate and 1 gram of zinc nitrate to 100 grams of water to obtain a precursor A solution; add 1 gram of sodium ferrocyanide and 1 gram of sodium cobalt cyanide to 100 grams of water to obtain a precursor B solution.

[0066] Step 3): Install the polytetrafluoroethylene hollow fiber-based membrane modified by amination in step 1) into the membrane separation system, and use a diaphragm pump to flow the precursor A solution prepared in step 2) from the inside to the outside of the polytetrafluoroethylene hollow fiber-based membrane at a low pressure of 0.005 MPa. Circulate continuously for 5 minutes, then take out the polytetrafluoroethylene hollow fiber membrane and place it in a 50°C oven for drying.

[0067] Step 4): The polytetrafluoroethylene hollow fiber membrane dried in step 3) is reinstalled into the membrane separation system, and the precursor B solution in step 2) is flowed from the inside to the outside of the polytetrafluoroethylene hollow fiber-based membrane at a low pressure of 0.005 MPa using a diaphragm pump. The solution is circulated continuously for 5 minutes, taken out and dried to obtain a polytetrafluoroethylene hollow fiber composite membrane with in-situ growth of four metal MOFs.

[0068] Step 5): The four-metal MOFs / polytetrafluoroethylene hollow fiber composite membrane obtained in step 4) is placed in a tubular furnace, heated to 350°C at a rate of 5.0°C / min in a nitrogen environment, kept warm for 3 hours, and then naturally cooled to room temperature to obtain a polytetrafluoroethylene hollow fiber composite catalytic membrane.

[0069] Scanning electron microscopy observations and measurements showed that the average size of the catalyst nanoparticles in the prepared catalytic membrane was 120 nanometers.

[0070] Through TGA test analysis, it was calculated that the mass fraction of the carbon-based composite catalyst in the composite catalytic membrane was approximately 2%.

[0071] The obtained composite catalytic membrane was used to test the performance of catalytic degradation and removal of emerging organic small molecules pollutants in water. The results showed that the pure water flux of the composite catalytic membrane was about 1050 L / m2·hour·bar; through comparative analysis of ultraviolet absorption spectra: after one filtration, the catalytic degradation removal rate of the composite membrane for rhodamine B with a concentration of 10 ppm in the solution reached 95%; after one filtration, the catalytic degradation removal rate of the composite membrane for sulfonylmethoxazole with a concentration of 5 ppm in the solution reached 93%; after one filtration, the catalytic degradation removal rate of the composite membrane for tetracycline with a concentration of 5 ppm in the solution reached 95%; after one filtration, the catalytic degradation removal rate of the composite membrane for methylene blue with a concentration of 15 ppm in the solution reached 97%; after one filtration, the catalytic degradation removal rate of bisphenol A with a concentration of 6 ppm in the solution reached 95%. The composite membrane was applied to the treatment of wastewater from a coal chemical industry with a sodium chloride concentration of up to 10,000 ppm. Through total organic carbon (TOC) analysis and testing, after one filtration, the mineralization rate of organic pollutants in the high-salt coal chemical wastewater by the composite catalytic membrane reached 71% (the inlet TOC was 260 and the outlet TOC was 75).

[0072] Example 4

[0073] Step 1): Add 5 grams of N-[3-(trimethoxysilyl)propyl]ethylenediamine and 5 grams of 3-aminopropyltrimethoxysilane to 100 grams of water, stir until mixed evenly, and obtain an aminated modifier; soak a commercially available hydrophilic polytetrafluoroethylene homogeneous asymmetric hollow fiber base membrane in the aminated modifier for 2 hours; then transfer the base membrane to a 65°C pH=5 sulfuric acid aqueous solution and let it stand for 30 hours; after taking out the base membrane, wash it with deionized water several times and dry it.

[0074] Step 2): Add 3 grams of cobalt sulfate and 3 grams of copper sulfate to 100 grams of water to obtain a precursor A solution; add 6 grams of sodium ferrocyanide to 100 grams of water to obtain a precursor B solution.

[0075] Step 3): Install the polytetrafluoroethylene hollow fiber-based membrane modified by amination in step 1) into the membrane separation system, and use a diaphragm pump to flow the precursor A solution prepared in step 2) from the inside to the outside of the polytetrafluoroethylene hollow fiber-based membrane at a low pressure of 0.02 MPa, and circulate continuously for 100 minutes. Then, take out the polytetrafluoroethylene hollow fiber membrane and place it in a 60°C oven for drying.

[0076] Step 4): The polytetrafluoroethylene hollow fiber membrane dried in step 3) is reinstalled into the membrane separation system, and the precursor B solution in step 2) is flowed from the inside to the outside of the polytetrafluoroethylene hollow fiber-based membrane at a low pressure of 0.02 MPa using a diaphragm pump. The solution is circulated continuously for 10 minutes, taken out and dried to obtain a polytetrafluoroethylene hollow fiber composite membrane with in-situ growth of cobalt-iron-copper trimetallic MOFs.

[0077] Step 5): The cobalt-iron-copper trimetallic MOFs / polytetrafluoroethylene hollow fiber composite membrane obtained in step 4) is placed in a tubular furnace, heated to 250°C at a rate of 5.0°C / min in an argon environment, kept warm for 3 hours, and then naturally cooled to room temperature to obtain a polytetrafluoroethylene hollow fiber composite catalytic membrane.

[0078] Through TGA test analysis, it was calculated that the mass fraction of the carbon-based composite catalyst in the composite catalytic membrane was approximately 3%.

[0079] The obtained polytetrafluoroethylene hollow fiber composite catalytic membrane was used to test the performance of catalytic degradation and removal of emerging pollutants such as small organic molecules in water. The results showed that the pure water flux of the composite catalytic membrane was about 910 L / m2·hour·bar. Through comparative analysis of ultraviolet absorption spectra, after one filtration, the catalytic degradation removal rate of the composite catalytic membrane for rhodamine B with a concentration of 10 ppm in the solution reached 95%; after one filtration, the catalytic degradation removal rate of the composite catalytic membrane for sulfonylmethoxazole with a concentration of 6 ppm in the solution reached 92%; after one filtration, the catalytic degradation removal rate of the composite catalytic membrane for tetracycline with a concentration of 10 ppm in the solution reached 91%; after one filtration, the catalytic degradation removal rate of the composite catalytic membrane for methylene blue with a concentration of 20 ppm in the solution reached 94%; after one filtration, the catalytic degradation removal rate of the composite catalytic membrane for bisphenol A with a concentration of 10 ppm in the solution reached 94%. The composite catalytic membrane was applied to the treatment of wastewater from a coal chemical industry with a sodium chloride concentration of up to 8000 ppm. Through total organic carbon (TOC) analysis and testing, after one filtration, the mineralization rate of organic pollutants in the high-salt coal chemical wastewater by the composite catalytic membrane reached 71.5% (the inlet TOC was 300 and the outlet TOC was 85.3).

[0080] Through the active oxygen quenching test, the molar proportion of singlet oxygen in the active oxygen generated by the composite catalytic membrane activating PMS is 67%.

[0081] Comparative Example 1

[0082] Keeping other steps of Example 1 unchanged, step 5) is adjusted as follows: placing the cobalt-iron bimetallic MOFs / polytetrafluoroethylene hollow fiber composite membrane obtained in step 4) in a tubular furnace, heating to 100°C at a rate of 3.0°C / min in an argon environment, keeping the temperature for 6 hours, and then naturally cooling to room temperature to obtain a polytetrafluoroethylene hollow fiber composite membrane.

[0083] like Fig. 9 The figure is a partial enlarged photograph of the cross section of the polytetrafluoroethylene hollow fiber composite membrane obtained in this comparative example. Figure 5 By comparison, it can be seen that after drying at 100°C, the morphology of the nanoparticles loaded on the interface of the internal polytetrafluoroethylene fibers is similar.

[0084] The obtained polytetrafluoroethylene hollow fiber composite membrane was used for catalytic degradation and removal of organic small molecules, which are emerging pollutants in water. The results showed that the pure water flux of the composite catalytic membrane was about 850 L / m2·hour·bar. Through comparative analysis of ultraviolet absorption spectra, after one filtration, the catalytic degradation removal rate of the composite membrane for rhodamine B with a concentration of 10 ppm in the solution reached 97%; after one filtration, the catalytic degradation removal rate of the composite membrane for sulfonylmethoxazole with a concentration of 6 ppm in the solution reached 93%; after one filtration, the catalytic degradation removal rate of the composite membrane for tetracycline with a concentration of 8 ppm in the solution reached 95%; after one filtration, the catalytic degradation removal rate of the composite membrane for methylene blue with a concentration of 15 ppm in the solution reached 98%; after one filtration, the catalytic degradation removal rate of the composite membrane for bisphenol A with a concentration of 10 ppm in the solution reached 95%. The composite membrane was applied to the treatment of wastewater from a coal chemical industry with a sodium chloride concentration of up to 15,000 ppm. Through total organic carbon (TOC) analysis and testing, after one filtration, the mineralization rate of organic pollutants in the high-salt coal chemical wastewater by the composite catalytic membrane was only 27% (the inlet TOC was 280 and the outlet TOC was 204).

[0085] Through the active oxygen quenching test, the molar proportion of singlet oxygen in the active oxygen generated by the composite catalytic membrane activating PMS is 19%. It can be seen that the conventional metal-organic framework nanocatalyst has a good performance in activating PMS to generate free radical active oxygen, and can show good catalytic degradation performance for organic pollutants; but when there is a high concentration of sodium chloride and other salts in the wastewater, the free radical active oxygen is easily captured and quenched by anions, causing the catalytic degradation performance of the system to drop sharply.

[0086] Comparative Example 2

[0087] Keeping the other steps of Example 2 unchanged, step 5) is adjusted as follows: placing the cobalt-iron-copper trimetallic MOFs / polytetrafluoroethylene hollow fiber composite membrane obtained in step 4) in a tubular furnace, heating to 80°C at a rate of 3.0°C / min in an argon environment, keeping the temperature for 10 hours, and then naturally cooling to room temperature to obtain a polytetrafluoroethylene hollow fiber composite membrane.

[0088] like Fig.10 The figure is a partial enlarged photograph of the cross section of the polytetrafluoroethylene hollow fiber composite membrane obtained in this comparative example. Fig. 9 By comparison, after drying at 80°C, the nanoparticles loaded on the interface of the internal polytetrafluoroethylene fibers have similar morphology. However, for the composite membrane that is only dried at low temperature and has not undergone a certain carbonization calcination, the nanoparticles at the fiber interface have obvious shedding phenomenon.

[0089] The obtained polytetrafluoroethylene hollow fiber composite membrane was used for catalytic degradation and removal of organic small molecules, which are emerging pollutants in water. The results showed that the pure water flux of the composite catalytic membrane was about 630 L / m2·hour·bar. Through comparative analysis of ultraviolet absorption spectra, after one filtration, the catalytic degradation removal rate of the composite catalytic membrane for rhodamine B with a concentration of 15 ppm in the solution reached 97%; after one filtration, the catalytic degradation removal rate of the composite catalytic membrane for sulfonylmethoxazole with a concentration of 8 ppm in the solution reached 96%; after one filtration, the catalytic degradation removal rate of the composite catalytic membrane for tetracycline with a concentration of 10 ppm in the solution reached 96%; after one filtration, the catalytic degradation removal rate of the composite catalytic membrane for methylene blue with a concentration of 20 ppm in the solution reached 99%; after one filtration, the catalytic degradation removal rate of the composite catalytic membrane for bisphenol A with a concentration of 12 ppm in the solution reached 97%. The composite catalytic membrane was applied to the treatment of wastewater from a coal chemical industry with a sodium chloride concentration of up to 16,000 ppm. Through total organic carbon (TOC) analysis and testing, after one filtration, the mineralization rate of organic pollutants in the high-salt coal chemical wastewater by the composite catalytic membrane was only 25% (the inlet TOC was 300 and the outlet TOC was 225).

[0090] Through the active oxygen quenching test, the molar proportion of singlet oxygen in the active oxygen generated by the composite catalytic membrane to activate PMS is 17%. It can be seen that the conventional metal-organic framework nanocatalyst has a good performance in activating PMS to generate free radical active oxygen, and can show good catalytic degradation performance for organic pollutants; but when there is a high concentration of sodium chloride and other salts in the wastewater, the free radical active oxygen is easily captured and quenched by anions, causing the catalytic degradation performance of the system to drop sharply.

[0091] Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A method for preparing a polytetrafluoroethylene hollow fiber composite catalytic membrane, It is characterized in that The following steps are involved: S1, preparing a hydrophilic polytetrafluoroethylene hollow fiber-based membrane, and performing amination modification on the surface and / or internal polytetrafluoroethylene fibers and / or node interfaces; S2. Preparing a precursor A solution and a precursor B solution respectively, wherein the precursor A solution is an aqueous solution composed of one or more metal salts of cobalt, iron, zinc, manganese, and copper and water; the precursor B solution is an aqueous solution composed of one or more metal salts of ferrocyanate, ferrocyanate, and cobalt cyanate and water; S3, placing the aminated polytetrafluoroethylene hollow fiber-based membrane in the precursor A solution, so that the surface and / or the internal pore interface are in-situ impregnated with the complex precursor A; S4, placing the polytetrafluoroethylene hollow fiber-based membrane treated in step S3 in a precursor B solution, so that the bimetallic or multimetallic-organic framework material is synthesized in situ on the fiber and / or node interface on its surface and / or inside; S5. Wash the polytetrafluoroethylene hollow fiber composite membrane treated in step S4 with deionized water, dry it, and then place it in a tubular furnace. Heat it to 250-350°C at a rate of 2-5°C / min in an inert gas environment. The heating rate is 2-5°C / min, and the temperature is kept at this temperature for 3-10 hours. Then, it is naturally cooled to room temperature to obtain a polytetrafluoroethylene hollow fiber composite catalytic membrane.

2. The method for preparing the polytetrafluoroethylene hollow fiber composite catalytic membrane according to claim 1, It is characterized in that In the step S1, the fibers and / or node interfaces of the polytetrafluoroethylene hollow fiber-based membrane are subjected to amination modification, specifically by a hydrothermal self-crosslinking network reaction of a silane coupling agent, including intertwining an amino-containing silane coupling agent network with the fibers and / or node interfaces of the polytetrafluoroethylene hollow fiber-based membrane, and / or intertwining a polyethyleneimine and an epoxy-containing silane coupling agent network with the fibers and / or node interfaces of the polytetrafluoroethylene hollow fiber-based membrane.

3. The method for preparing the polytetrafluoroethylene hollow fiber composite catalytic membrane according to claim 1, It is characterized in that The step S3 specifically includes flowing the precursor A solution from one side of the polytetrafluoroethylene hollow fiber-based membrane to the other side for 5-30 minutes, so that the polytetrafluoroethylene fibers and / or node interfaces on the surface and / or inside thereof are in situ impregnated with the complex precursor A, and then removing the precursor A solution; The step S4 specifically includes flowing the precursor B solution from one side of the polytetrafluoroethylene hollow fiber-based membrane treated in step S3 to the other side for 5-30 minutes, so as to in-situ synthesize the bimetallic or multimetallic-organic framework material on the surface and / or internal polytetrafluoroethylene fibers and / or at the node interface.

4. A polytetrafluoroethylene hollow fiber composite catalytic membrane, It is characterized in that The polytetrafluoroethylene hollow fiber composite catalytic membrane is prepared by the preparation method as described in any one of claims 1 to 3, comprising a polytetrafluoroethylene hollow fiber base membrane, and a carbon-based nanocatalyst distributed on the surface and / or inside of the polytetrafluoroethylene hollow fiber base membrane and / or at the polytetrafluoroethylene fibers and / or nodes, wherein the carbon-based nanocatalyst contains two or more metal element components.

5. The polytetrafluoroethylene hollow fiber composite catalytic membrane according to claim 4, It is characterized in that The polytetrafluoroethylene hollow fiber-based membrane is a homogeneous symmetrical polytetrafluoroethylene hollow fiber membrane or a homogeneous asymmetrical polytetrafluoroethylene hollow fiber membrane. The polytetrafluoroethylene hollow fiber-based membrane is hydrophilic, and the surface water droplet complete infiltration time is less than or equal to 30 seconds.

6. The polytetrafluoroethylene hollow fiber composite catalytic membrane according to claim 5, It is characterized in that The polytetrafluoroethylene hollow fiber composite catalytic membrane is hydrophilic, and the time required for water droplets on its surface to completely soak it is less than or equal to 60 seconds.

7. The polytetrafluoroethylene hollow fiber composite catalyst membrane according to claim 4, It is characterized in that The mass fraction of the nano catalyst in the polytetrafluoroethylene hollow fiber composite catalyst membrane is 1% to 10%, and the particle size of the nano catalyst is less than or equal to 1 μm.

8. The polytetrafluoroethylene hollow fiber composite catalytic membrane according to any one of claims 4 to 7, It is characterized in that The polytetrafluoroethylene hollow fiber composite catalytic membrane is suitable for activating persulfate to produce singlet oxygen, and the molar proportion of the produced singlet oxygen in the total active oxygen is 60% to 90%.

9. Application of a polytetrafluoroethylene hollow fiber composite catalytic membrane, It is characterized in that The polytetrafluoroethylene hollow fiber composite catalytic membrane as claimed in claim 4 is used for wastewater treatment.

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