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

Abstract

A preparation method for a conductive carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane, which preparation method comprises the following steps: (1) formulation of a spinning solution, which involves: adding carboxylated carbon nanotubes and a dispersing agent to a solvent, stirring the mixture at 40-80ºC to uniformly disperse the carbon nanotubes, then adding polyvinylidene fluoride, and then continuously stirring same to completely dissolve polyvinylidene fluoride, so as to obtain a spinning solution; and (2) preparing a carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane by means of wet spinning, wherein the hollow fiber membrane is subjected to conductive encapsulation and connection to construct an electrochemical coupling membrane separation assembly that can achieve the combination of an electrochemical effect and a membrane separation function, thereby improving the anti-pollution capacity of a separation membrane.

Description

Preparation method of conductive carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane and electrochemically coupled membrane separation component Technical Field

[0001] The present invention belongs to the technical field of separation membrane preparation, and in particular relates to a method for preparing a conductive carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane and an electrochemically coupled membrane separation component. Background Art

[0002] Membrane separation technology, due to its simplicity and high efficiency, is widely used in water treatment, gas separation, food processing, and drug purification. It is an important technology for solving problems such as resource shortages and environmental pollution. However, traditional membrane separation technology still has problems such as serious membrane fouling and the mutual restriction of membrane permeability and selectivity, which cannot effectively exert its performance. Electrochemical water treatment technology is a technology that removes pollutants from water by applying an external electric field to cause the pollutants to react with the electric field or electrochemical reaction at the solid-liquid interface between the electrode and water. Coupling electrochemical technology with membrane separation and utilizing electrostatic repulsion, electrochemical redox, and electrically assisted adsorption is expected to solve the problems of serious membrane fouling and the mutual restriction of membrane permeability and selectivity in membrane separation technology. It is a new membrane separation technology with great practical application potential.

[0003] Although electrochemical reactions can reduce membrane fouling and alleviate the conflicting relationship 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 a major limitation on the practical application of electrochemically coupled membrane separation technology. Electrochemically coupled membrane separation technology utilizes two types of membranes: conductive and non-conductive. Electrochemically coupled membrane separation technology based on non-conductive membranes requires an external high-voltage electric field to induce polarization of the membrane, which limits its application due to high energy consumption. Electrochemically coupled membrane separation technology based on conductive membranes, on the other hand, can directly apply a lower voltage to the membrane, achieving the electro-assisted effect in a more energy-efficient and efficient manner. Therefore, electrochemically coupled membrane separation technology based on conductive membranes has greater application prospects. Currently, the conductive separation membranes under research primarily include carbon membranes, metal membranes, conductive polymer membranes, and conductive ceramic membranes. These conductive separation membranes suffer from poor stability and mechanical strength, and their complex preparation processes hinder their practical application.

[0004] The use of carbon nanotubes and traditional polymer materials to construct composite conductive polymer materials can bring a turning point to this dilemma. Conductive polymer materials can be divided into composite conductive polymer materials and structural conductive polymer materials. The conductive mechanism of composite conductive polymer materials is different from that of structural conductive polymer materials (polyaniline, polypyrrole, polythiophene, etc.). It is achieved by adding conductive fillers to traditional polymer materials. After the concentration of the conductive material reaches a critical value, a conductive network is formed in the polymer, which can realize the conduction of electrons. Therefore, adding carbon nanotubes as conductive fillers to polymer materials to prepare composite conductive polymer materials can not only give traditional polymer membrane materials conductivity, but also retain the advantages of good stability and mechanical strength of traditional polymer membrane materials. The preparation method is simple, and it is expected to prepare conductive separation membranes with practical application prospects.

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

[0006] Summary of the Invention

[0007] In response to the above-mentioned problems existing in the prior art, the purpose of the present invention is to provide a method for preparing a conductive carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane and an electrochemically coupled membrane separation component. The conductive carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane uses carbon nanotubes as conductive fillers, utilizes a dispersant to enhance the dispersibility of carbon nanotubes in polyvinylidene fluoride, is prepared by a wet spinning process, and the hollow fiber membrane is conductively encapsulated and connected to construct an electrochemically coupled membrane separation component that can combine electrochemical action with membrane separation function, enhance the anti-pollution ability of the separation membrane, and alleviate the contradiction between its permeability and selectivity.

[0008] In order to achieve the above object, the present invention provides the following technical solutions:

[0009] A method for preparing a conductive carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane comprises the following steps:

[0010] (1) Preparation of spinning solution

[0011] Adding carboxylated carbon nanotubes and a dispersant to a solvent, stirring at 40 to 80° C. for 6 to 12 hours to uniformly disperse the carbon nanotubes, then adding polyvinylidene fluoride, and continuing to stir for 4 to 8 hours to completely dissolve the polyvinylidene fluoride to obtain a spinning solution;

[0012] (2) Preparation of carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane by wet spinning

[0013] Preparation of carbon nanotube-polyvinylidene fluoride composite hollow fiber membranes by wet spinning, including self-supporting composite hollow fiber membranes and lined composite hollow fiber membranes;

[0014] The preparation process of the self-supporting composite hollow fiber membrane is as follows: the spinning solution is vacuum degassed as the shell liquid, and water is used as the core liquid. The spinning solution is simultaneously passed through the spinneret of the spinning machine, and the flow rates of the shell liquid and the core liquid are controlled at a certain speed ratio and spun into a water coagulation bath to obtain the self-supporting composite hollow fiber membrane;

[0015] The preparation process of the composite hollow fiber membrane with lining is as follows: the spinning solution is vacuum degassed to serve as the shell solution, the speed of the spinning solution feeding pump and the speed of the winding roller pulling the lining are controlled, the spinning solution and the lining are mixed and spun into a water coagulation bath through a spinneret to obtain the composite hollow fiber membrane with lining;

[0016] The preliminarily solidified carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane is wound on a winding roller, and after the spinning is completed, it is soaked in water for 24 to 72 hours to remove excess organic solvent and dispersant, and then naturally air-dried and collected.

[0017] 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%. If the carboxyl content is too low, the dispersion of the carbon nanotubes will be too poor, and if the carboxyl content is too high, the conductivity of the composite hollow fiber membrane will be too poor.

[0018] 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 dodecylbenzenesulfonate, hexadecyltrimethylammonium bromide, commercial TNACPS dispersant, commercial TNDPS dispersant, commercial Disponer983 dispersant, and commercial XFZ33NMP dispersant; the mass ratio of carboxylated carbon nanotubes to dispersant is 0.5 to 5:1, and preferably the mass ratio of carboxylated carbon nanotubes to dispersant is 0.5 to 2:1.

[0019] 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 (carboxylated carbon nanotubes and dispersant) in the solution is controlled to be 15% to 30%, preferably 20% to 25%.

[0020] Based on the above technical solution, further, in step (1), the mass ratio of carboxylated carbon nanotubes to polyvinylidene fluoride is 15 to 100:100, preferably the mass ratio of carboxylated carbon nanotubes to polyvinylidene fluoride is 1:2. If the proportion of carboxylated carbon nanotubes is too low, the conductivity of the composite hollow fiber membrane will be too poor, and if the proportion of carboxylated carbon nanotubes is too high, the mechanical strength of the composite hollow fiber membrane will be too poor.

[0021] Based on the above technical solution, further, the shell liquid flow rate to core liquid flow rate ratio of the self-supporting composite hollow fiber membrane in step (2) is 0.5 to 5:1, preferably the shell liquid flow rate to core liquid flow rate ratio is 1:1.

[0022] Based on the above technical solution, further, in step (2), the speed of the spinning solution injection pump of the lined composite hollow fiber membrane is 10-50 rpm / min, and the speed of the winding roller pulling the lining is 10-30 m / min. Preferably, the speed of the injection pump is 20-30 rpm / min, and the speed of the winding roller pulling the lining is 13-18 m / min.

[0023] Based on the above technical solution, further, the lining of the lined composite hollow fiber membrane is a braided tube lining or a crocheted tube lining, and the material of the lining is not limited.

[0024] Another aspect of the present invention provides a conductive carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane obtained by the above preparation method.

[0025] Based on the above technical solution, further, the conductivity of the composite hollow fiber membrane ranges from 0.1 S / m to 100 S / m.

[0026] The present invention also provides an electrochemically coupled membrane separation component, which contains the composite hollow fiber membrane.

[0027] Based on the above technical solution, further, the electrochemically coupled membrane separation component includes an immersed electrochemically coupled membrane separation component and an external pressure electrochemically coupled membrane separation component.

[0028] Based on the above technical solution, further, the submerged electrochemical coupled membrane separation component is a curtain membrane component, which mainly includes a composite hollow fiber membrane, an insulating layer, a counter electrode and a water collection pipe. The innermost layer of the component is a parallel arranged composite hollow fiber membrane. The composite hollow fiber membrane serves as a working electrode, and both ends are sealed in the water collection pipe to keep the hollow holes of the fiber membrane unobstructed. The outermost layer of the component is a counter electrode, which surrounds the entire composite hollow fiber membrane. An insulating layer is arranged 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. In order to enhance the overall conductive uniformity of the hollow fiber membrane, a circle of conductive layer is fixed on the surface of the composite hollow fiber membrane, and the conductive layer and the composite hollow fiber membrane lead out wires to connect to an external power supply to provide electrochemical assistance for the electrochemical coupled membrane separation component.

[0029] Based on the above technical solution, further, the external pressure electrochemical coupled membrane separation component is a columnar membrane component, which mainly includes a pressure-resistant columnar shell, a counter electrode, an insulating layer, a composite hollow fiber membrane and a water collection pipe, wherein the counter electrode is fixed on the inner side of the component shell, and an insulating layer is arranged between the counter electrode and the conductive composite hollow fiber membrane, and the insulating layer is fixed on the counter electrode. In order to enhance the electrochemical auxiliary effect of the component, an auxiliary counter electrode can be optionally built into the center of the component, and a porous plastic tube is wrapped around the outside of the auxiliary counter electrode to isolate the conductive hollow fiber membrane and the auxiliary counter electrode, and they are bundled into The two ends of the bundled composite hollow fiber membrane are fixed to the water inlet and outlet of the component with sealing materials, wherein the water inlet is composed of two layers of sealing materials and a layer of conductive glue to encapsulate the hollow fiber membrane port, and the conductive glue is located between the two layers of sealing materials. The water outlet is encapsulated by a layer of sealing material and a layer of conductive glue. After encapsulation, half of the sealing material layer is cut off to ensure that the hollow holes of the fiber membrane can flow out 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, and electrochemical assistance is provided to the electrochemical coupled membrane separation component through an external power supply.

[0030] 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, hollow plastic mesh, etc.; the counter electrode is preferably a conductive material such as metal wire mesh, carbon fiber cloth, and the metal wire mesh used is not limited to the type of metal, and is preferably titanium metal and its alloys; the sealing material is preferably an adhesive material such as epoxy resin; the conductive layer is preferably a conductive material such as metal strip, metal foil, etc.; the auxiliary counter electrode is preferably a conductive material such as metal column, carbon rod, etc., and the metal column used is not limited to the type of metal, and is preferably titanium metal and its alloys; the conductive glue is preferably conductive silver paste or conductive carbon paste; the wire is titanium wire, copper wire, stainless steel wire; the external power supply is a DC regulated power supply, an AC regulated power supply or a pulsed power supply.

[0031] The present invention has the following beneficial effects compared to the prior art:

[0032] The hollow fiber membrane of the present invention has a simple preparation process, excellent electrical conductivity, electrochemical stability and mechanical strength, controllable membrane performance, and the membrane pore size can be regulated in the range of microfiltration to ultrafiltration; the electrochemically coupled membrane separation component has a reasonable and compact structure, is easy to use, can enhance membrane performance under electrochemical assistance, and is suitable for different specifications and different operating modes. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention, the drawings related to the embodiments are briefly introduced below.

[0034] Figure 1 is a schematic diagram of the composition of the submerged electrochemical coupled membrane separation assembly of the present invention, wherein I is a schematic diagram of the hollow fiber membrane packaging of the submerged electrochemical coupled membrane separation assembly, II is a schematic diagram of the appearance of the submerged electrochemical coupled membrane separation assembly, and III is a schematic diagram of the cross-section of the submerged electrochemical coupled membrane separation assembly. The specific components are: 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.

[0035] Figure 2 is a schematic diagram of the composition of the external pressure electrochemical coupled membrane separation component of the present invention, wherein I is a schematic diagram of the packaging of a single bundle of hollow fiber membranes in the external pressure electrochemical coupled membrane separation component, II is a schematic diagram of the longitudinal cross-section of the external pressure electrochemical coupled membrane separation component, and the specific components are: 1 is epoxy resin, 2 is conductive glue, 3 is a conductive carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane, 4 is the water inlet of the component, 5 is a porous plastic tube, 6 is an auxiliary counter electrode, 7 is the component shell and the inner counter electrode, 8 is the water outlet, 9 is the 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 packaging pipe. DETAILED DESCRIPTION

[0036] The following is a technical solution and three examples are provided to further introduce the specific implementation of the present invention, illustrating the preparation method of the conductive carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane and the application method of the electrochemically coupled membrane separation component, but the present invention is not limited to the following examples.

[0037] Example 1

[0038] Preparation of a carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane with an inner lining microfiltration pore size includes the following steps:

[0039] (1) Adding a certain amount of carboxylated carbon nanotubes (carboxyl content of 2.58%) and a dispersant to N,N-dimethylformamide, controlling the mass ratio of carboxylated carbon nanotubes to dispersant to be 0.5, using a commercial TNACPS dispersant, stirring at high speed for 6 h at 60 ° C to uniformly disperse the carbon nanotubes, then adding an appropriate amount of polyvinylidene fluoride, controlling the mass ratio of carboxylated carbon nanotubes to polyvinylidene fluoride to be 0.5, and the solute mass fraction to be 20%, and continuing stirring for 4 h to completely dissolve the polyvinylidene fluoride to obtain a spinning solution;

[0040] (2) The spinning solution was vacuum degassed and used as the shell solution. The spinning solution sampling pump speed was controlled at 30 rpm / min, and the winding roller pulling the liner speed was 18 m / min. The spinning solution and the liner were mixed and spun through the spinneret into a water coagulation bath to obtain a composite hollow fiber membrane with a liner. The preliminarily solidified carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane was wound on the winding roller. After the spinning was completed, it was soaked in water for 72 hours to remove excess organic solvent and dispersant, and then naturally 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.

[0041] The prepared carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane is encapsulated into an immersed electrochemically coupled membrane separation assembly (as shown in Figure 1). The immersed electrochemically coupled membrane separation assembly is a curtain membrane assembly, which includes a hollow fiber membrane body, an insulating layer, a metal mesh, and a water collection pipe. The innermost layer of the assembly is a parallel arrangement of hollow fiber membranes, the ends of which are sealed in the water collection pipe 1 using epoxy resin. The outermost layer of the assembly is a layer of metal mesh 6, which serves as an electrochemical counter electrode and surrounds the entire conductive carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane 3. A layer of non-woven fabric is arranged between the hollow fiber membrane 3 and the metal mesh 6 as an insulating layer 7, which insulates the conductive hollow fiber membrane and the metal mesh. The hollow fiber membrane 3 is connected by a loop of conductive copper foil (as the conductive layer 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 electrochemically coupled membrane separation assembly is provided by an external power supply.

[0042] The submerged electrochemical coupled membrane separation module was placed in the membrane tank of the membrane bioreactor, using an internal suction filtration method. During operation, the module was connected to a DC regulated power supply, with the carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane as the cathode and a voltage of 1.2V applied to the membrane. The inlet COD was 503mg / L, and the effluent COD was 218mg / L. When the carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane was used as the anode and a voltage of 1V was applied to the membrane, the inlet COD was 503mg / L, the ammonia nitrogen content was 25mg / L, and the effluent COD was 61mg / L, with the effluent ammonia nitrogen concentration below 2mg / L.

[0043] The carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane was used as the anode, and a voltage of 1V was applied to the membrane. During a 60-day operation cycle, the membrane assembly only needed one backwash to restore the membrane flux, and the backwashing could achieve a flux recovery rate of 97.2%.

[0044] Example 2

[0045] Preparation of a carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane with an inner lining ultrafiltration pore size includes the following steps:

[0046] (1) Adding a certain amount of carboxylated carbon nanotubes (carboxyl content of 2.58%) and a dispersant to N,N-dimethylformamide, controlling the mass ratio of carboxylated carbon nanotubes to dispersant to be 2, using a commercial TNACPS dispersant, stirring at high speed for 12 h at 60 ° C to uniformly disperse the carbon nanotubes, then adding an appropriate amount of polyvinylidene fluoride, controlling the mass ratio of carboxylated carbon nanotubes to polyvinylidene fluoride to be 0.5, and the solute mass fraction to be 23%, and continuing stirring for 8 h to completely dissolve the polyvinylidene fluoride to obtain a spinning solution;

[0047] (2) The spinning solution was vacuum degassed and used as the shell solution. The spinning solution sampling pump speed was controlled at 25 rpm / min, and the winding roller pulling the liner speed was 14.5 m / min. The spinning solution and liner were mixed and spun through the spinneret into a water coagulation bath to obtain a composite hollow fiber membrane with a liner. The preliminarily solidified carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane was wound on the winding roller. After spinning, it was soaked in water for 72 hours to remove excess organic solvent and dispersant, and then naturally 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.

[0048] The prepared carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane is encapsulated into an external pressure electrochemical coupling membrane separation component (as shown in FIG2 ). The external pressure electrochemical coupling membrane separation component is a columnar membrane component. A 5mm thick metal column 6 is built into the center of the component 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 and the metal column 6. A layer of metal wire mesh 7 is fixed on the inside of the component shell as a counter electrode. A layer of non-woven fabric is arranged between the metal wire mesh 7 and the conductive hollow fiber membrane 3 to play an insulating role. The non-woven fabric is fixed on the metal wire mesh. The two ends of the bundled hollow fiber membrane 3 are sealed with epoxy resin. The grease 1 is fixed to the water inlet 4 and the water outlet 8 of the component and is enclosed in the water collecting pipe 10. The water 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 to seal the hollow hole of the entire hollow fiber membrane. The water outlet 8 is fixed with a layer of epoxy resin 1 and a layer of conductive silver paste 2 to keep the hollow hole unobstructed and able to discharge water. The titanium wire 13 connecting the conductive hollow fiber membrane and the wire 12 connecting the metal column and the metal wire mesh are both connected from the side outlet, and the voltage is provided to the entire electrochemical coupled membrane separation component through an external power supply.

[0049] Cross-flow filtration is used for advanced wastewater treatment. During operation, the module is connected to a DC regulated power supply, with the carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane acting as the cathode, and a 2V voltage applied to the membrane. The secondary effluent COD of coal chemical wastewater is 84.3 mg / L. After treatment with the electrochemically coupled membrane separation module, the effluent COD drops to 51.2 mg / L, achieving a removal rate of 39.3%.

[0050] Example 3

[0051] Preparation of a self-supporting ultrafiltration pore-size carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane comprises the following steps:

[0052] (1) Adding a certain amount of carboxylated carbon nanotubes (carboxyl content of 2.58%) and a dispersant to N,N-dimethylformamide, controlling the mass ratio of carboxylated carbon nanotubes to dispersant to be 2, using commercial TNDPS dispersant, stirring at high speed for 12 h at 60 ° C to uniformly disperse the carbon nanotubes, then adding an appropriate amount of polyvinylidene fluoride, controlling the mass ratio of carboxylated carbon nanotubes to polyvinylidene fluoride to be 0.5, and the solute mass fraction to be 23%, and continuing stirring for 8 h to completely dissolve the polyvinylidene fluoride to obtain a spinning solution;

[0053] (2) The spinning solution was vacuum degassed and used as the shell liquid, and water was used as the core liquid. The solution was simultaneously spun into a water coagulation bath through the spinneret of the spinning machine, with the shell liquid flow rate and the core liquid flow rate controlled at a ratio of 1:1, to obtain a self-supporting composite hollow fiber membrane. The preliminarily solidified carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane was wound on a winding roller. After spinning, the membrane was immersed in water for 72 hours to remove excess organic solvent and dispersant, and then naturally air-dried and collected. The average pore size of the prepared membrane was less than 5 nm, the permeation flux was 5-10 LMH, and the conductivity was 46 S / m.

[0054] The embodiments described above are only typical embodiments of the present invention and do not constitute an improper limitation of the present invention. Therefore, all obvious modifications described in the scope of the patent application of the present invention, as well as other modifications that do not deviate from the essence of the present invention, should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a conductive carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane, characterized in that: The steps include: (1) Preparation of spinning solution Adding carboxylated carbon nanotubes and a dispersant to a solvent, stirring at 40 to 80° C. to uniformly disperse the carbon nanotubes, then adding polyvinylidene fluoride, and continuing to stir to completely dissolve the polyvinylidene fluoride 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 membrane prepared by wet spinning includes a self-supporting composite hollow fiber membrane and a composite hollow fiber membrane with a liner; The preparation process of the self-supporting composite hollow fiber membrane is as follows: the spinning solution is vacuum degassed as the shell liquid and water is used as the core liquid, and the shell liquid flow rate and the core liquid flow rate are controlled to be spun into the water coagulation bath at a certain speed ratio through the spinneret of the spinning machine to obtain the self-supporting composite hollow fiber membrane; The preparation process of the composite hollow fiber membrane with inner lining is as follows: vacuum degassing the spinning solution as the shell solution, controlling the speed of the spinning solution injection pump and the speed of the winding roller pulling the inner lining, and mixing the spinning solution and the inner lining through the spinneret and spinning them into a water coagulation bath to obtain the composite hollow fiber membrane with inner lining; The initially solidified carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane is wound on a winding roller, and after spinning, it is immersed in water to remove the organic solvent and dispersant, and then naturally air-dried and collected.

2. The preparation method according to claim 1, characterized in that: 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%; the dispersant 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 Disponer983 dispersant, and commercial XFZ33 NMP dispersant; and the mass ratio of carboxylated carbon nanotubes to dispersant is 0.5 to 5:

1.

3. The preparation method according to claim 1, characterized in that: 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%; the mass ratio of carboxylated carbon nanotubes to polyvinylidene fluoride is 15 to 100:

100.

4. The preparation method according to claim 1, characterized in that: 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 to 5:

1.

5. The preparation method according to claim 1, characterized in that: In step (2), the speed of the spinning solution injection pump of the composite hollow fiber membrane with lining is 10-50 rpm / min, and the speed of the winding roller pulling the lining is 10-30 m / min.

6. A conductive carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane obtained by the preparation method according to any one of claims 1 to 5.

7. An electrochemically coupled membrane separation component, characterized in that: The electrochemically coupled membrane separation component contains the composite hollow fiber membrane according to claim 6, and the electrochemically coupled membrane separation component includes an immersed electrochemically coupled membrane separation component and an external pressure electrochemically coupled membrane separation component.

8. The electrochemically coupled membrane separation assembly according to claim 7, characterized in that: The submerged electrochemical coupled membrane separation component is a curtain membrane component, which mainly includes a composite hollow fiber membrane, an insulating layer, a counter electrode and a water collecting pipe. The innermost layer of the component is a composite hollow fiber membrane arranged in parallel. The composite hollow fiber membrane serves as a working electrode, and both ends are sealed in the water collecting pipe to keep the hollow holes of the fiber membrane unobstructed. The outermost layer of the component is a counter electrode, which surrounds the entire composite hollow fiber membrane. An insulating layer is arranged 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; a circle of conductive layer is fixed on the surface of the composite hollow fiber membrane, and wires are led out from the conductive layer and the composite hollow fiber membrane to connect to an external power supply to provide electrochemical assistance for the electrochemical coupled membrane separation component.

9. The electrochemically coupled membrane separation assembly according to claim 7, characterized in that: The external pressure type electrochemical coupling membrane separation component is a columnar membrane component, which mainly includes a pressure-resistant columnar shell, a counter electrode, an insulating layer, a composite hollow fiber membrane and a water collecting pipe, wherein the counter electrode is fixed on the inner side of the component shell, and an insulating layer is arranged between the counter electrode and the conductive composite hollow fiber membrane, and the insulating layer is fixed on the counter electrode; an auxiliary counter electrode is built-in in the center of the component, and a porous plastic tube is surrounded on the outside of the auxiliary counter electrode to isolate the conductive hollow fiber membrane and the auxiliary counter electrode; both ends of the bundled composite hollow fiber membrane are fixed to the water inlet and outlet of the component with sealing materials, wherein the water inlet is composed of two layers of sealing materials and a layer of conductive glue to encapsulate the hollow fiber membrane port, and the conductive glue is located between the two layers of sealing materials, and the water outlet is encapsulated by a layer of sealing material and a layer of conductive glue. After encapsulation, half of the sealing material layer is cut off to keep the hollow holes of the fiber membrane unobstructed to discharge water; 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, and electrochemical assistance is provided to the electrochemical coupling membrane separation component through an external power supply.

10. The electrochemically coupled membrane separation assembly according to claim 8 or 9, characterized in that: The insulating layer in the electrochemical coupling membrane separation component is a non-woven fabric or a hollow plastic mesh insulating material; the counter electrode is a metal mesh or a carbon fiber cloth conductive material, and the metal mesh is made of titanium metal and its alloy; the sealing material is an epoxy resin bonding material; the conductive layer is a metal strip or a metal foil conductive material; the auxiliary counter electrode is a metal column or a carbon rod conductive material, and the metal column is made of titanium metal and its alloy; the conductive glue is a conductive silver paste or a conductive carbon paste; the conductive wire is a titanium wire, a copper wire, or a 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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