Preparation method of conductive carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane and electrochemical coupling membrane separation assembly

Abstract

The application discloses a preparation method of a conductive carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane and an electrochemical coupling membrane separation assembly, and belongs to the technical field of separation membrane preparation. In the application, carbon nanotubes are used as conductive fillers, dispersants are used to enhance the dispersibility of the carbon nanotubes in polyvinylidene fluoride, and a composite hollow fiber membrane is prepared through a wet spinning process. The hollow fiber membrane is conductively packaged and connected to construct an electrochemical coupling membrane separation assembly capable of realizing the combination of electrochemical action and membrane separation function, thereby strengthening the anti-pollution ability of the separation membrane and relieving the contradiction between the permeability and the selectivity of the separation membrane. The preparation process of the hollow fiber membrane is simple, the hollow fiber membrane has excellent conductive performance, electrochemical stability and mechanical strength, and the membrane performance is controllable. The electrochemical coupling membrane separation assembly has a reasonable and compact structure, is convenient to use, can enhance the membrane performance under the electrochemical auxiliary action, and is suitable for different specifications and different operation modes.

Description

Technical Field

[0001] This invention belongs to the field of separation membrane preparation technology, specifically relating to a method for preparing a conductive carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane and an electrochemical coupling membrane separation component. Background Technology

[0002] Membrane separation technology, due to its simplicity and high efficiency, is widely used in water treatment, gas separation, food processing, and pharmaceutical purification, and is an important technology for solving problems such as resource scarcity and environmental pollution. However, traditional membrane separation technologies still suffer from severe membrane fouling and the mutual restriction between membrane permeability and selectivity, preventing them from effectively utilizing their performance. Electrochemical water treatment technology removes pollutants from water by applying an external electric field to induce electrochemical reactions or electrochemical interactions at the solid-liquid interface between the electrode and water. Coupled with membrane separation, utilizing electrostatic repulsion, electrochemical oxidation-reduction, and electro-assisted adsorption, this technology holds promise for solving the problems of severe membrane fouling and the mutual restriction between membrane permeability and selectivity, making it a novel membrane separation technology with great practical application potential.

[0003] Although electrochemical processes can mitigate membrane fouling and alleviate the trade-off between membrane permeability and selectivity, research on electrochemically coupled membrane separation technology has primarily focused on theoretical exploration. The lack of suitable separation membranes is the main reason limiting the practical application of electro-assisted membrane separation technology. Electro-assisted membrane separation technology utilizes both conductive and non-conductive membranes. Non-conductive membrane-based electro-assisted separation technology requires an external high-voltage electric field to induce membrane polarization, and its high energy consumption restricts its application. In contrast, conductive membrane-based electro-assisted separation technology can directly apply a lower voltage to the membrane, achieving the electro-assisted effect more energy-efficiently and effectively. Therefore, conductive membrane-based electro-assisted separation technology has greater application prospects. Currently, the conductive separation membranes under research mainly include carbon membranes, metal membranes, conductive polymer membranes, and conductive ceramic membranes. These conductive separation membranes have poor stability and mechanical strength, and their preparation processes are complex, which is not conducive to practical applications.

[0004] Constructing composite conductive polymers using carbon nanotubes and traditional polymers offers a potential solution to this predicament. Conductive polymers can be categorized into composite conductive polymers and structural conductive polymers. The conductivity mechanism of composite conductive polymers differs from that of structural conductive polymers (such as polyaniline, polypyrrole, and polythiophene). Composite conductive polymers achieve electron conduction by adding conductive fillers to traditional polymers. Once the concentration of the conductive filler reaches a critical value, a conductive network forms within the polymer. Therefore, incorporating carbon nanotubes as conductive fillers into polymers to prepare composite conductive polymers not only imparts conductivity to traditional polymer membranes but also retains their stability and mechanical strength. Furthermore, the preparation method is simple, promising the development of conductive separation membranes with practical applications.

[0005] In addition, the membrane modules on the market are all designed for traditional membrane separation processes and cannot achieve electrochemically coupled membrane separation. The research and development of new electrochemically coupled membrane separation modules is of great significance to promoting the application and development of electrochemically coupled membrane separation technology. Summary of the Invention

[0006] To address the aforementioned problems in the existing technology, the purpose of this invention is to provide a method for preparing a conductive carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane and an electrochemical coupling membrane separation component. The conductive carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane uses carbon nanotubes as a conductive filler, utilizes a dispersant to enhance the dispersibility of carbon nanotubes in polyvinylidene fluoride, and is prepared through a wet spinning process. The hollow fiber membrane is then conductively encapsulated and connected to construct an electrochemical coupling membrane separation component that combines electrochemical action with membrane separation function, thereby enhancing the membrane's antifouling ability and alleviating the contradiction between its permeability and selectivity.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for preparing a conductive carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane includes the following steps:

[0009] (1) Preparation of spinning solution

[0010] Carboxylated carbon nanotubes and a dispersant are added to a solvent and stirred at 40–80°C for 6–12 h to disperse the carbon nanotubes evenly. Then, polyvinylidene fluoride is added and stirred for another 4–8 h to completely dissolve the polyvinylidene fluoride to obtain a spinning solution.

[0011] (2) Preparation of carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane by wet spinning

[0012] The wet spinning method for preparing carbon nanotube-polyvinylidene fluoride composite hollow fiber membranes includes self-supporting composite hollow fiber membranes and composite hollow fiber membranes with inner linings.

[0013] The preparation process of the self-supporting composite hollow fiber membrane is as follows: the spinning solution is degassed under vacuum and used as the shell solution, and water is used as the core solution. At the same time, the flow rate of the shell solution and the flow rate of the core solution are controlled by the spinneret of the spinning machine and spun into the water coagulation bath at a certain speed ratio to obtain the self-supporting composite hollow fiber membrane.

[0014] The preparation process of the composite hollow fiber membrane with liner is as follows: the spinning solution is degassed under vacuum and used as the shell solution. The speed of the spinning solution injection pump and the speed of the winding roller pulling the liner are controlled. The spinning solution and the liner are mixed and spun into the water coagulation bath through the spinneret to obtain the composite hollow fiber membrane with liner.

[0015] The pre-cured carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane is wound onto a spinning roller. After spinning, it is soaked in water for 24-72 hours to remove excess organic solvents and dispersants, then air-dried and collected.

[0016] Based on the above technical solution, further, the carboxylated carbon nanotubes in step (1) are single-walled carbon nanotubes, double-walled carbon nanotubes or multi-walled carbon nanotubes; the carboxyl content is 0.5wt% to 5wt%, preferably 2wt% to 3wt%. Too low a carboxyl content will result in poor dispersion of carbon nanotubes, and too high a carboxyl content will result in poor conductivity of the composite hollow fiber membrane.

[0017] Based on the above technical solution, further, the dispersant in step (1) is one or a mixture of two or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, hexadecyltrimethylammonium bromide, commercial TNACPS dispersant, commercial TNDPS dispersant, commercial Disponer 983 dispersant, and commercial XFZ33 NMP dispersant; the mass ratio of carboxylated carbon nanotubes to dispersant is 0.5 to 5:1, preferably 0.5 to 2:1.

[0018] Based on the above technical solution, further, the solvent in step (1) is one or a mixture of two or more of N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone, and the mass fraction of the solute in the solution is controlled to be 15% to 30%, preferably 20% to 25%.

[0019] Based on the above technical solution, in step (1), the mass ratio of carboxylated carbon nanotubes to polyvinylidene fluoride is 15-100:100, preferably 1:2. Too low a proportion of carboxylated carbon nanotubes will result in poor conductivity of the composite hollow fiber membrane, and too high a proportion of carboxylated carbon nanotubes will result in poor mechanical strength of the composite hollow fiber membrane.

[0020] Based on the above technical solution, further, in step (2), the ratio of the shell liquid flow rate to the core liquid flow rate of the self-supporting composite hollow fiber membrane is 0.5 to 5:1, preferably 1:1.

[0021] Based on the above technical solution, further, in step (2), the speed of the injection pump for the spinning solution of the composite hollow fiber membrane with inner lining is 10-50 rpm / min, the speed of the winding roller traction of the inner lining is 10-30 m / min, preferably the injection pump speed is 20-30 rpm / min, and the speed of the winding roller traction of the inner lining is 13-18 m / min.

[0022] Based on the above technical solution, the inner lining of the composite hollow fiber membrane with inner lining is either a woven tubular inner lining or a hook-woven tubular inner lining, and the material of the inner lining is not limited.

[0023] In another aspect, the present invention provides a conductive carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane obtained by the above preparation method.

[0024] Based on the above technical solution, the electrical conductivity of the composite hollow fiber membrane is further defined as being in the range of 0.1 S / m to 100 S / m.

[0025] The present invention also provides an electrochemical coupling membrane separation component, wherein the electrochemical coupling membrane separation component comprises the above-mentioned composite hollow fiber membrane.

[0026] Based on the above technical solution, the electrochemical coupling membrane separation assembly further includes an immersion electrochemical coupling membrane separation assembly and an external pressure electrochemical coupling membrane separation assembly.

[0027] Based on the above technical solution, the immersion electrochemical coupling membrane separation component is further described as a curtain-type membrane component, mainly comprising a composite hollow fiber membrane, an insulating layer, a counter electrode, and a water collection pipe. The innermost layer of the component is a composite hollow fiber membrane arranged in parallel, which serves as the working electrode. Both ends of the composite hollow fiber membrane are sealed in the water collection pipe to keep the hollow pores of the fiber membrane unobstructed. The outermost layer of the component is a counter electrode that surrounds the entire composite hollow fiber membrane. An insulating layer is provided between the composite hollow fiber membrane and the counter electrode to prevent short-circuit connection between the conductive hollow fiber membrane and the counter electrode. To enhance the overall conductivity uniformity of the hollow fiber membrane, a conductive layer is fixed on the surface of the composite hollow fiber membrane. The conductive layer and the composite hollow fiber membrane are connected to an external power source by lead wires to provide electrochemical assistance for the electrochemical coupling membrane separation component.

[0028] Based on the above technical solution, the external pressure electrochemical coupling membrane separation component is a columnar membrane component, mainly comprising a pressure-resistant columnar shell, a counter electrode, an insulating layer, a composite hollow fiber membrane, and a water collection pipe. The counter electrode is fixed inside the component shell, and an insulating layer is provided between the counter electrode and the conductive composite hollow fiber membrane, fixed to the counter electrode. To enhance the electrochemical auxiliary effect of the component, an auxiliary counter electrode can be optionally built into the center of the component. A perforated plastic tube surrounds the auxiliary counter electrode to isolate the conductive hollow fiber membrane and the auxiliary counter electrode, and the components are bundled together. The composite hollow fiber membrane of the bundle is fixed at both ends to the inlet and outlet of the module with sealing material. The inlet is composed of two layers of sealing material and one layer of conductive adhesive to encapsulate the hollow fiber membrane port, with the conductive adhesive located between the two layers of sealing material. The outlet is encapsulated by one layer of sealing material and one layer of conductive adhesive. After encapsulation, half of the sealing material layer is cut off to ensure that the hollow pores of the fiber membrane can flow water smoothly. The wires connecting the conductive composite hollow fiber membrane and the wires connecting the auxiliary counter electrode and the counter electrode are all connected from the side outlet, providing electrochemical assistance to the electrochemical coupling membrane separation module through an external power source.

[0029] Based on the above technical solution, further, the insulating layer in the electrochemical coupling membrane separation component is preferably an insulating material such as non-woven fabric or perforated plastic mesh; the counter electrode is preferably a conductive material such as metal wire mesh or carbon fiber cloth, and the type of metal used for the metal wire mesh is not limited, but titanium metal and its alloys are preferred; the sealing material is preferably an adhesive material such as epoxy resin; the conductive layer is preferably a conductive material such as metal strip or metal foil; the auxiliary counter electrode is preferably a conductive material such as metal pillar or carbon rod, and the type of metal used for the metal pillar is not limited, but titanium metal and its alloys are preferred; the conductive adhesive is preferably conductive silver paste or conductive carbon paste; the wire is titanium wire, copper wire, or stainless steel wire; the external power supply is a DC regulated power supply, an AC regulated power supply, or a pulse power supply.

[0030] The present invention has the following advantages over the prior art:

[0031] The hollow fiber membrane of this invention has a simple preparation process, excellent electrical conductivity, electrochemical stability and mechanical strength, controllable membrane performance, and the membrane pore size can be adjusted in the range from microfiltration to ultrafiltration. The electrochemically coupled membrane separation component has a reasonable and compact structure, is easy to use, and can enhance membrane performance under electrochemical assistance. It is suitable for different specifications and different operating modes. Attached Figure Description

[0032] To more clearly illustrate the embodiments of the present invention, the accompanying drawings involved in the embodiments will be briefly described below.

[0033] Figure 1This is a schematic diagram of the composition of the immersion electrochemical coupling membrane separation component of the present invention. In this diagram, I is a schematic diagram of the hollow fiber membrane encapsulation of the immersion electrochemical coupling membrane separation component, II is a schematic diagram of the appearance of the immersion electrochemical coupling membrane separation component, and III is a schematic diagram of the cross-section of the immersion electrochemical coupling membrane separation component. The specific components are as follows: 1 is a water collection pipe, 2 is a conductive layer, 3 is a conductive carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane, 4 is a wire connecting the hollow fiber membrane, 5 is a wire connecting the counter electrode, 6 is the counter electrode, and 7 is an insulating layer.

[0034] Figure 2 This is a schematic diagram of the composition of the external pressure electrochemical coupling membrane separation component of the present invention. I is a schematic diagram of a single bundle of hollow fiber membrane encapsulation in the external pressure electrochemical coupling membrane separation component, and II is a schematic diagram of a longitudinal section of the external pressure electrochemical coupling membrane separation component. Specific components include: 1 is epoxy resin, 2 is conductive adhesive, 3 is a conductive carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane, 4 is the component inlet, 5 is a porous plastic tube, 6 is an auxiliary counter electrode, 7 is the component outer shell and inner counter electrode, 8 is the outlet, 9 is a cross-flow outlet, 10 is a water collection pipe, 11 is a wire connecting the conductive hollow fiber membrane and a wire outlet connecting the counter electrode and the auxiliary counter electrode, 12 is a wire connecting the counter electrode and the auxiliary counter electrode, 13 is a wire connecting the conductive hollow fiber membrane, and 14 is a hollow fiber membrane encapsulation pipe. Detailed Implementation

[0035] The following describes the specific implementation of the present invention through three examples, in conjunction with the technical solution, to illustrate the preparation method of the conductive carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane and the application method of the electrochemical coupling membrane separation component. However, the present invention is not limited to the following examples.

[0036] Example 1

[0037] The preparation of a carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane with an inner liner and microfiltration pore size includes the following steps:

[0038] (1) Add a certain amount of carboxylated carbon nanotubes (carboxyl content of 2.58%) and dispersant to N,N-dimethylformamide, control the mass ratio of carboxylated carbon nanotubes to dispersant to be 0.5, and use commercial TNACPS dispersant. Stir at high speed at 60℃ for 6h to disperse the carbon nanotubes evenly. Then add an appropriate amount of polyvinylidene fluoride, control the mass ratio of carboxylated carbon nanotubes to polyvinylidene fluoride to be 0.5, and the mass fraction of solute to be 20%. Continue stirring for 4h to completely dissolve the polyvinylidene fluoride to obtain the spinning solution.

[0039] (2) The spinning solution was degassed under vacuum and used as the shell solution. The speed of the spinning solution injection pump was controlled at 30 rpm / min, and the speed of the winding roller pulling the liner was 18 m / min. The spinning solution and the liner were mixed through a spinneret and spun into a water coagulation bath to obtain a composite hollow fiber membrane with a liner. The pre-cured carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane was wound onto the winding roller. After spinning, it was soaked in water for 72 h to remove excess organic solvent and dispersant, and then air-dried and collected. The prepared hollow fiber membrane had an average pore size of 100 nm, a permeation flux of 1000 LMH, and a conductivity of 50 S / m.

[0040] The prepared carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane is encapsulated into an immersion electrochemical coupling membrane separation module. The immersion electrochemical coupling membrane separation module is a curtain-type membrane module. The module includes a hollow fiber membrane body, an insulating layer, a metal mesh, and a water collection pipe. The innermost layer of the module is a hollow fiber membrane arranged in parallel. The two ends of the hollow fiber membrane are sealed in the water collection pipe 1 using epoxy resin. The outermost layer of the module is a layer of metal mesh 6, which serves as the counter electrode for electrochemical function. It surrounds the entire conductive carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane 3. A layer of non-woven fabric 7 is arranged between the hollow fiber membrane 3 and the metal mesh 6, which serves to insulate the conductive hollow fiber membrane and the metal mesh. The hollow fiber membrane 3 is connected by a ring of conductive copper foil 2, and an external wire 4 is led out as the working electrode. The metal mesh 6 is directly connected to the wire 5 as the counter electrode. The voltage of the entire electrochemical coupling membrane separation module is provided by an external power source.

[0041] A submerged electrochemically coupled membrane separation unit was placed in the membrane tank of a membrane bioreactor, employing an internal filtration method. During operation, the unit was connected to a DC regulated power supply. A carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane was used as the cathode, with a voltage of 1.2V applied to the membrane. The influent COD was 503 mg / L, and the effluent COD was 218 mg / L. Alternatively, a carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane could be used as the anode, with a voltage of 1V applied to the membrane. The influent COD was 503 mg / L, ammonia nitrogen was 25 mg / L, and the effluent COD was 61 mg / L, with the effluent ammonia nitrogen concentration below 2 mg / L.

[0042] Using a carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane as the anode, a voltage of 1V is applied to the membrane. During a 60-day operating cycle, the membrane module only needs one backwash to restore the membrane flux, and the backwash can achieve a flux recovery rate of 97.2%.

[0043] Example 2

[0044] The preparation of a carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane with an inner lining for ultrafiltration pores includes the following steps:

[0045] (1) Add a certain amount of carboxylated carbon nanotubes (carboxyl content of 2.58%) and dispersant to N,N-dimethylformamide, control the mass ratio of carboxylated carbon nanotubes to dispersant to be 2, and use commercial TNACPS dispersant. Stir at high speed at 60℃ for 12h to disperse the carbon nanotubes evenly. Then add an appropriate amount of polyvinylidene fluoride, control the mass ratio of carboxylated carbon nanotubes to polyvinylidene fluoride to be 0.5, and the mass fraction of solute to be 23%. Continue stirring for 8h to completely dissolve the polyvinylidene fluoride to obtain the spinning solution.

[0046] (2) The spinning solution was degassed under vacuum and used as the shell solution. The speed of the spinning solution injection pump was controlled at 25 rpm / min, and the speed of the winding roller pulling the liner was 14.5 m / min. The spinning solution and the liner were mixed through a spinneret and spun into a water coagulation bath to obtain a composite hollow fiber membrane with a liner. The pre-cured carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane was wound onto the winding roller. After spinning, it was soaked in water for 72 h to remove excess organic solvent and dispersant, and then air-dried and collected. The prepared membrane had an average pore size of 10 nm, a permeation flux of 140 LMH, and a conductivity of 46 S / m.

[0047] The prepared carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane was encapsulated into an external pressure electrochemical coupling membrane separation module. This external pressure electrochemical coupling membrane separation module is a columnar membrane module. A 5mm thick metal column 6 is embedded in the center of the module as an auxiliary counter electrode. A porous plastic tube 5 surrounds the outside of the metal column 6 to isolate the conductive carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane 3 from the metal column 6. A layer of metal mesh 7 is fixed inside the module shell as a counter electrode. A layer of non-woven fabric is arranged between the metal mesh 7 and the conductive hollow fiber membrane 3 to provide insulation. The hollow fiber membrane 2, bundled together and fixed to the metal wire mesh, is fixed at both ends to the inlet 4 and outlet 8 of the component with epoxy resin 1. The inlet 4 is composed of a layer of epoxy resin 1, a layer of conductive silver paste 2, and a layer of epoxy resin 1 sealing the hollow pores of the entire hollow fiber membrane. The outlet 8 is fixed with a layer of epoxy resin 1 and a layer of conductive silver paste 2 to keep the hollow pores unobstructed so that water can flow out. The titanium wire 13 connecting the conductive hollow fiber membrane and the wire 12 connecting the metal column and the metal wire mesh are all connected from the side outlet, and the voltage is provided to the entire electrochemical coupling membrane separation component by an external power source.

[0048] A cross-flow filtration method was applied to advanced wastewater treatment. During operation, the component was connected to a DC regulated power supply, with the carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane serving as the cathode, and a 2V voltage applied to the membrane. The COD of the secondary effluent from coal chemical wastewater was 84.3 mg / L. After treatment by the electrochemically coupled membrane separation component, the COD of the effluent reached 51.2 mg / L, achieving a removal rate of 39.3%.

[0049] Example 3

[0050] The preparation of a self-supporting ultrafiltration pore size carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane includes the following steps:

[0051] (1) Add a certain amount of carboxylated carbon nanotubes (carboxyl content of 2.58%) and dispersant to N,N-dimethylformamide, control the mass ratio of carboxylated carbon nanotubes to dispersant to be 2, and use commercial TNDPS dispersant. Stir at high speed at 60℃ for 12h to disperse the carbon nanotubes evenly. Then add an appropriate amount of polyvinylidene fluoride, control the mass ratio of carboxylated carbon nanotubes to polyvinylidene fluoride to be 0.5, and the mass fraction of solute to be 23%. Continue stirring for 8h to completely dissolve the polyvinylidene fluoride to obtain the spinning solution.

[0052] (2) The spinning solution was degassed under vacuum and used as the shell solution, while water was used as the core solution. Simultaneously, the shell solution flow rate and the core solution flow rate were controlled at a 1:1 ratio and spun into a water coagulation bath through the spinneret of the spinning machine to obtain a self-supporting composite hollow fiber membrane. The pre-cured carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane was wound onto a winding roller. After spinning, it was immersed in water for 72 hours to remove excess organic solvents and dispersants, then air-dried and collected. The prepared membrane had an average pore size of less than 5 nm, a permeation flux of 5–10 LMH, and a conductivity of 46 S / m.

[0053] The embodiments described above are merely typical embodiments of the present invention and do not constitute an improper limitation of the present invention. Therefore, all obvious modifications described in the claims of the present invention, as well as other modifications that do not depart from the essence of the present invention, should be included within the protection scope of the present invention.

Claims

1. An electrochemically coupled membrane separation assembly, characterized in that, The electrochemical coupling membrane separation component contains a conductive carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane, and the electrochemical coupling membrane separation component includes an immersion electrochemical coupling membrane separation component and an external pressure electrochemical coupling membrane separation component. The preparation method of the conductive carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane includes the following steps: (1) Preparation of spinning solution Carboxylated carbon nanotubes and a dispersant are added to a solvent and stirred at 40-80 °C to disperse the carbon nanotubes evenly. Then, polyvinylidene fluoride is added and stirred until the polyvinylidene fluoride is completely dissolved to obtain a spinning solution. (2) Preparation of carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane by wet spinning The carbon nanotube-polyvinylidene fluoride composite hollow fiber membranes prepared by wet spinning include self-supporting composite hollow fiber membranes and composite hollow fiber membranes with inner linings. The preparation process of the self-supporting composite hollow fiber membrane is as follows: the spinning solution is vacuum degassed and used as the shell liquid, and water is used as the core liquid. At the same time, the flow rate of the shell liquid and the flow rate of the core liquid are controlled by the spinneret of the spinning machine and spun into the water coagulation bath at a certain speed ratio to obtain the self-supporting composite hollow fiber membrane. The preparation process of the composite hollow fiber membrane with liner is as follows: the spinning solution is degassed under vacuum and used as the shell solution. The speed of the spinning solution injection pump and the speed of the winding roller pulling the liner are controlled. The spinning solution and the liner are mixed and spun into the water coagulation bath through the spinneret to obtain the composite hollow fiber membrane with liner. The pre-cured carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane was wound onto a spinning roller, and after spinning, it was soaked in water to remove organic solvents and dispersants. Then it was air-dried and collected. The carboxylated carbon nanotubes mentioned in step (1) are single-walled carbon nanotubes, double-walled carbon nanotubes, or multi-walled carbon nanotubes; the carboxyl content is 0.5wt%~5wt%; the dispersant is one or a mixture of two or more of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, hexadecyltrimethylammonium bromide, commercial TNACPS dispersant, commercial TNDPS dispersant, commercial Disponer 983 dispersant, and commercial XFZ33 NMP dispersant; the mass ratio of carboxylated carbon nanotubes to dispersant is 0.5~5:1; The solvent mentioned in step (1) is one or a mixture of two or more of N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone, and the mass fraction of the solute in the solution is controlled to be 15% to 30%; the mass ratio of carboxylated carbon nanotubes to polyvinylidene fluoride is 15 to 100:

100. The ratio of the shell liquid flow rate to the core liquid flow rate of the self-supporting composite hollow fiber membrane in step (2) is 0.5~5:1; In step (2), the speed of the spinning solution injection pump for the composite hollow fiber membrane with inner lining is 10~50 rpm / min, and the speed of the winding roller pulling the inner lining is 10~30 m / min; The aforementioned immersion electrochemical coupling membrane separation module is a curtain-type membrane module, mainly comprising a composite hollow fiber membrane, an insulating layer, a counter electrode, and a water collection pipe. The innermost layer of the module consists of parallel-arranged composite hollow fiber membranes, which serve as the working electrode. Both ends of the composite hollow fiber membrane are sealed within the water collection pipe to maintain the unobstructed pores of the fiber membrane. The outermost layer of the module consists of a counter electrode that surrounds the entire composite hollow fiber membrane. An insulating layer is provided between the composite hollow fiber membrane and the counter electrode to prevent short-circuit connections between the conductive hollow fiber membrane and the counter electrode. A conductive layer is fixed on the surface of the composite hollow fiber membrane. Conductors leading from the conductive layer and the composite hollow fiber membrane are connected to an external power source to provide electrochemical assistance for the electrochemical coupling membrane separation module. The external pressure electrochemical coupling membrane separation module is a columnar membrane module, mainly comprising a pressure-resistant columnar shell, a counter electrode, an insulating layer, a composite hollow fiber membrane, and a water collection pipe. The counter electrode is fixed inside the module shell, and an insulating layer is placed between the counter electrode and the conductive composite hollow fiber membrane, with the insulating layer fixed to the counter electrode. An auxiliary counter electrode is built into the center of the module, and a perforated plastic tube surrounds the auxiliary counter electrode to isolate the conductive hollow fiber membrane from the auxiliary counter electrode. The bundled composite hollow fiber membrane is fixed at both ends to the module's inlet and outlet with sealing material. The inlet consists of two layers of sealing material and one layer of conductive adhesive sealing the hollow fiber membrane port, with the conductive adhesive located between the two layers of sealing material. The outlet consists of one layer of sealing material and one layer of conductive adhesive sealing, with half of the sealing material layer removed after sealing to ensure unobstructed water flow through the hollow pores of the fiber membrane. The wires connecting the conductive composite hollow fiber membrane and the wires connecting the auxiliary counter electrode and the counter electrode both exit from the side outlet, providing electrochemical assistance to the electrochemical coupling membrane separation module via an external power source.

2. The electrochemical coupling membrane separation assembly according to claim 1, characterized in that, The insulating layer of the electrochemical coupling membrane separation component is made of non-woven fabric or perforated plastic mesh; the counter electrode is made of metal wire mesh or carbon fiber cloth conductive material, with the metal wire mesh being made of titanium or its alloys; the sealing material is epoxy resin adhesive; the conductive layer is made of metal strip or metal foil conductive material; the auxiliary counter electrode is made of metal pillar or carbon rod conductive material, with the metal pillar being made of titanium or its alloys; the conductive adhesive is conductive silver paste or conductive carbon paste; the wires are made of titanium wire, copper wire, or stainless steel wire; and the external power supply is a DC regulated power supply, an AC regulated power supply, or a pulsed power supply.

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