CN-116571101-B - Preparation method of conductive carbon nano tube-polyvinylidene fluoride composite hollow fiber membrane and electrochemical coupling membrane separation assembly

Abstract

The invention discloses a preparation method of a conductive carbon nano tube-polyvinylidene fluoride composite hollow fiber membrane and an electrochemical coupling membrane separation assembly, and belongs to the technical field of separation membrane preparation. According to the invention, the carbon nano tube is used as a conductive filler, the dispersibility of the carbon nano tube in polyvinylidene fluoride is enhanced by using a dispersing agent, a composite hollow fiber membrane is prepared by a wet spinning process, and the hollow fiber membrane is subjected to conductive encapsulation and connection, so that an electrochemical coupling membrane separation assembly capable of realizing the combination of electrochemical action and membrane separation function is constructed, the pollution resistance of the separation membrane is enhanced, and the contradiction between the permeability and the selectivity of the separation membrane is relieved. The hollow fiber membrane has the advantages of simple preparation process, excellent conductivity, electrochemical stability and mechanical strength, controllable membrane performance, reasonable and compact structure of the electrochemical coupling membrane separation assembly, convenient use, capability of enhancing the membrane performance under the electrochemical auxiliary effect, and suitability for different specifications and different operation modes.

Inventors

• QUAN XIE
• DU LEI
• WEI GAOLIANG
• CHEN SHUO

Assignees

• 大连理工大学

Dates

Publication Date

20260512

Application Date

20230614

Claims (2)

1. 1. The electrochemical coupling membrane separation assembly is characterized by comprising a conductive carbon nano tube-polyvinylidene fluoride composite hollow fiber membrane, and comprises an immersed electrochemical coupling membrane separation assembly and an external pressure type electrochemical coupling membrane separation assembly; The preparation method of the conductive carbon nano tube-polyvinylidene fluoride composite hollow fiber membrane comprises the following steps: (1) Preparation of spinning solution Adding carboxylated carbon nanotubes and a dispersing agent into a solvent, stirring at 40-80 ℃ to uniformly disperse the carbon nanotubes, then adding polyvinylidene fluoride, and continuing stirring to completely dissolve the polyvinylidene fluoride to obtain a spinning solution; (2) Wet spinning preparation of carbon nanotube-polyvinylidene fluoride composite hollow fiber membrane The carbon nano tube-polyvinylidene fluoride composite hollow fiber membrane prepared by wet spinning comprises a self-supporting composite hollow fiber membrane and a composite hollow fiber membrane with a lining; The preparation process of the self-supporting composite hollow fiber membrane comprises the steps of taking spinning solution as shell solution and water as core solution after vacuum defoamation, and simultaneously controlling the shell solution flow rate and the core solution flow rate to spin into a coagulating bath according to a certain speed ratio by a spinneret plate of a spinning machine to obtain the self-supporting composite hollow fiber membrane; Taking the spinning solution after vacuum defoamation as a shell solution, controlling the speed of a spinning solution injection pump and the speed of a wire winding roller traction lining, and mixing the spinning solution and the lining through a spinneret plate to spin into a coagulating bath to obtain the composite hollow fiber membrane with the lining; Winding the preliminarily solidified carbon nano tube-polyvinylidene fluoride composite hollow fiber membrane on a filament winding roller, soaking in water after spinning, removing an organic solvent and a dispersing agent, and naturally air-drying and collecting; The carboxylated carbon nanotubes are single-wall carbon nanotubes, double-wall carbon nanotubes or multi-wall carbon nanotubes, the carboxyl content is 0.5-5wt%, the dispersing agent is one or a mixture of more than two of sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, cetyltrimethylammonium bromide, commercial TNACPS dispersing agent, commercial TNDPS dispersing agent, commercial Disponer983 dispersing agent and commercial XFZ33 NMP dispersing agent, and the mass ratio of the carboxylated carbon nanotubes to the dispersing agent is 0.5-5:1; The solvent in the step (1) is one or a mixture of more than two of N, N-dimethylformamide, N-dimethylacetamide and N-methylpyrrolidone, the solute is controlled to account for 15-30% of the mass fraction of the solution, and the mass ratio of carboxylated carbon nanotubes to polyvinylidene fluoride is 15-100:100; the ratio of the flow rate of the shell liquid to the core liquid of the self-supporting composite hollow fiber membrane in the step (2) is 0.5-5:1; In the step (2), the speed of a spinning solution sample injection pump of the composite hollow fiber membrane with the lining is 10-50 rpm/min, and the speed of a wire winding roller traction lining is 10-30 m/min; The immersed electrochemical coupling membrane separation assembly is a curtain-type membrane assembly and mainly comprises a composite hollow fiber membrane, an insulating layer, a counter electrode and a water collecting pipe fitting, wherein the innermost layer of the assembly is a composite hollow fiber membrane which is arranged in parallel, the composite hollow fiber membrane is used as a working electrode, two ends of the composite hollow fiber membrane are sealed in the water collecting pipe fitting, the hollow holes of the fiber membrane are kept smooth, the outermost side of the assembly is provided with a layer of counter electrode which surrounds the whole composite hollow fiber membrane, and 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; the external pressure type electrochemical coupling membrane separation assembly is a column type membrane assembly and mainly comprises a pressure-resistant column type 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 shell, the insulating layer is arranged between the counter electrode and the conductive composite hollow fiber membrane and is fixed on the counter electrode, an auxiliary counter electrode is arranged in the center of the assembly, the outer side of the auxiliary counter electrode surrounds a porous plastic pipe to isolate the conductive hollow fiber membrane and the auxiliary counter electrode, two ends of the bundled composite hollow fiber membrane are fixed on a water inlet and a water outlet of the assembly through sealing materials, the water inlet is formed by sealing two layers of sealing materials and a layer of conductive adhesive, the port is formed by sealing the hollow fiber membrane port of the two layers of sealing materials, the water outlet is sealed by the sealing material layer and the conductive adhesive layer, the hollow hole of the fiber membrane can be smoothly discharged after the sealing material layer is cut, a wire for connecting the conductive composite hollow fiber membrane and a wire for connecting the auxiliary counter electrode are connected from a side outlet, and electrochemical coupling membrane separation assembly is provided with electrochemical assistance through an external power supply.
2. 2. The electrochemical coupling membrane separation assembly according to claim 1, wherein an insulating layer in the electrochemical coupling membrane separation assembly is made of non-woven fabrics and hollow plastic net insulating materials, a counter electrode is made of metal wire mesh and carbon fiber cloth conducting materials, the metal wire mesh is made of titanium metal and alloys thereof, a sealing material is made of epoxy resin bonding materials, the conducting layer is made of metal strips and metal foil conducting materials, the auxiliary counter electrode is made of metal columns and carbon rod conducting materials, the adopted metal columns are made of titanium metal and alloys thereof, the conducting adhesive is conductive silver paste or conductive carbon paste, the conducting wires are made of titanium wires, copper wires and stainless steel wires, and the external power supply is a direct-current regulated power supply, an alternating-current regulated power supply or a pulse power supply.

Description

Preparation method of conductive carbon nano tube-polyvinylidene fluoride composite hollow fiber membrane and electrochemical coupling membrane separation assembly Technical Field The invention belongs to the technical field of separation membrane preparation, and particularly relates to a preparation method of a conductive carbon nano tube-polyvinylidene fluoride composite hollow fiber membrane and an electrochemical coupling membrane separation assembly. Background The membrane separation technology is widely applied to the fields of water treatment, gas separation, food processing, medicine purification and the like because of the characteristics of simplicity and high efficiency, and is an important technology for solving the problems of resource shortage, environmental pollution and the like. However, the traditional membrane separation technology still has the problems of serious membrane pollution, mutual restriction of membrane permeability and selectivity and the like, and can not effectively exert the performance. The electrochemical water treatment technology is a technology for removing pollutants in water by applying an electric field to make the pollutants act on the solid-liquid interface of the electrode and the water or by electrochemical reaction. The electrochemical technology and the membrane separation are coupled, and the effects of electrostatic repulsion, electrochemical oxidation reduction, electric auxiliary adsorption and the like are utilized, so that the problems of serious membrane pollution and mutual restriction of membrane permeability and selectivity in the membrane separation technology are hopefully solved, and the membrane separation technology is a novel membrane separation technology with great practical application potential. Although electrochemical action can alleviate membrane pollution and alleviate the contradictory relationship between membrane permeability and selectivity, the related research of electrochemical coupling membrane separation technology is mainly focused on the theoretical exploration stage. The lack of a suitable separation membrane is a major reason limiting the practical application of electrically assisted membrane separation techniques. The separation membrane adopted by the electric auxiliary membrane separation technology comprises a conductive membrane and a non-conductive membrane, the electric auxiliary membrane separation technology based on the non-conductive membrane needs an external high-voltage electric field to conduct polarization induction on the membrane, the application of the membrane is restricted by high energy consumption, and the electric auxiliary membrane separation technology based on the conductive membrane can directly apply lower voltage on the membrane, so that the electric auxiliary effect is realized more energy-saving and efficient, and the electric auxiliary membrane separation technology based on the conductive membrane has a wider application prospect. At present, the conductive separation membranes in research mainly comprise a carbon membrane, a metal membrane, a conductive polymer membrane and a conductive ceramic membrane. The conductive separation membranes have poor stability and mechanical strength, and the preparation process is complex, which is unfavorable for practical application. The carbon nanotube and the traditional polymer material are utilized to construct the composite conductive polymer material, which can bring a turn to the dilemma. The conductive polymer materials can be divided into composite conductive polymer materials and structural conductive polymer materials, and the conductive mechanism of the composite conductive polymer materials is different from that of the structural conductive polymer materials (polyaniline, polypyrrole, polythiophene and the like), and the conductive network is formed in the polymer after the concentration of the conductive material reaches a critical value by adding conductive filler into the traditional polymer materials, so that the conduction of electrons can be realized. Therefore, the carbon nano tube is used as the conductive filler and added into the polymer material to prepare the composite conductive polymer material, so that the conductivity of the traditional polymer film material can be endowed, meanwhile, the advantages of good stability and mechanical strength of the traditional polymer film material are maintained, and the preparation method is simple and is expected to prepare the conductive separation film with practical application prospect. In addition, the membrane assemblies in the market are designed aiming at the traditional membrane separation process, the electrochemical coupling membrane separation function cannot be realized, and the research and development of the novel electrochemical coupling membrane separation assembly has important significance for promoting the application and development of the electrochemical coupling