Hollow fiber composite electro-catalytic membrane and preparation method thereof

Abstract

The invention belongs to the field of novel membrane materials, and relates to a hollow fiber composite electro-catalysis membrane and a preparation method thereof. The preparation method comprises the following steps: firstly, treating titanium powder, titanium dioxide powder and a polymer as raw materials to obtain a membrane casting solution, and carrying out wet spinning and drying to obtain a hollow fiber membrane blank; and then carrying out pre-oxidation and high-temperature sintering to obtain the hollow fiber composite electro-catalytic membrane. The basic conception of the invention is that the ratio of titanium powder to titanium dioxide powder is precisely regulated and controlled, the titanium powder is directly used as a reducing agent in the high-temperature sintering process to reduce titanium dioxide into reduced titanium dioxide, and meanwhile, a polymer with high carbon residue directly derives a carbon material component, so that the reduced titanium dioxide / carbon composite hollow fiber electro-catalytic membrane is prepared. The reduction-state titanium dioxide / carbon composite electro-catalytic membrane is prepared in one step through a phase inversion / sintering process, the preparation method is flexible and efficient, and the composite membrane has excellent electro-catalytic activity and good adsorption performance.

Description

Technical Field

[0001] The invention belongs to the field of novel membrane materials and relates to a hollow fiber composite electrocatalytic membrane and a preparation method thereof. Background Art

[0002] Electrocatalytic membrane filtration technology is a new membrane separation technology that couples membrane separation technology with electrochemical advanced oxidation process (EAOP). This technology can achieve good water treatment performance at low voltage. At the same time, using conductive membrane as electrode can effectively reduce energy consumption and lower costs.

[0003] The material used to prepare the electrocatalytic membrane is the key to determining the function and performance of the membrane. Metal oxide-based membrane materials are generally non-conductive at room temperature and have high charge transfer resistance, which limits their application. Reduced titanium dioxide has high conductivity and chemical stability at room temperature. Due to its unique electronic structure and surface properties, it has higher catalytic activity and reaction rate. However, reduced titanium dioxide is usually reduced by hydrogen as a reducing agent, and there are problems such as the reduction process is prone to explosion and easy oxidation. Carbon-based membrane materials such as graphene oxide, activated carbon, and carbon nanotubes have the advantages of high mechanical strength, ease of availability, good electrochemical stability, and high adjustability of structure and performance. They are widely used in the preparation of electrocatalytic membranes, but their insufficient activity and other problems limit their application. In addition, the core of membrane technology lies in separation membranes, among which hollow fiber membranes with high packing density have received widespread attention, but they have problems such as reduced mechanical strength and insufficient conductivity. Summary of the Invention

[0004] To address the problems of the prior art, the present invention develops a hollow fiber composite electrocatalytic membrane and its preparation method through a wet spinning-high-temperature sintering process. Titanium powder and titanium dioxide powder of specific particle sizes and ratios are directly blended with a polymer with a high carbon content. The polymer's ease of molding is leveraged to create an excellent precursor material. After pre-oxidation and high-temperature sintering, the titanium powder acts as a reducing agent to reduce the titanium dioxide to reduced titanium dioxide, which exhibits high electrical conductivity and electrocatalytic activity. The carbon material formed after polymer carbonization improves the membrane material's adsorption performance and electron transfer rate. The present invention's preparation process is simple and convenient, enabling the preparation of a reduced titanium dioxide / carbon hollow fiber composite electrocatalytic membrane in a single step.

[0005] The present invention provides a method for preparing a hollow fiber composite electrocatalytic membrane, comprising the following steps:

[0006] (1) preparing a casting solution: adding titanium powder, titanium dioxide powder, and polymer to an organic solvent in sequence, stirring evenly, and standing to degas to form a casting solution;

[0007] (2) Spinning: using coaxial wet spinning technology, selecting a coaxial spinning needle, using deionized water or a mixture of ethanol and deionized water as the inner layer feed liquid, using the casting liquid obtained in step (1) as the outer layer feed liquid, injecting the inner and outer layer feed liquids into a coagulation bath simultaneously through an injection pump, taking them out after sufficient immersion, and then drying to obtain a hollow fiber membrane embryo; wherein the coagulation bath is water;

[0008] (3) High-temperature sintering: The green body obtained in step (2) is placed in a tubular furnace for pre-oxidation and then sintered at high temperature to obtain the hollow fiber composite electrocatalytic membrane.

[0009] Based on the above technical solution, further, in step (1), the average particle size of the titanium powder is 1-10 μm, and the average particle size of the titanium dioxide powder is 0.1-5 μm.

[0010] Based on the above technical solution, further, in step (1), the carbon content of the polymer is 40-80%, preferably a mixture of one or more of polyacrylonitrile (PAN), polyethersulfone (PES), polyimide (PI), polybenzimidazole (PBI), polyetheretherketone (PEEK), polybenzoxazole (PBO), benzoxazine resin (PBZ), and polybenzothiazole (PBT).

[0011] Based on the above technical solution, further, in step (1), the organic solvent is a mixture of one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), N-methyl-2-pyrrolidone (NMP), and dimethyl sulfoxide (DMSO).

[0012] Based on the above technical solution, further, in step (1), the titanium powder, titanium dioxide powder and polymer are placed in an oven for sufficient drying before use.

[0013] Based on the above technical solution, further, in step (1), the mass ratio of the sum of the titanium dioxide powder and the titanium powder to the polymer is 1:0.1-0.2, wherein the mass ratio of the titanium dioxide powder to the titanium powder is: titanium dioxide: titanium = 1:0.08-0.15.

[0014] Based on the above technical solution, further, in step (1), the standing time is 12-24 hours.

[0015] Based on the above technical solution, further, in step (2), the inner diameter of the coaxial spinning needle is 0.3-4 mm, and the outer diameter is 0.5-5 mm; the feeding speed of the inner and outer layers is 1:1-4.

[0016] Based on the above technical solution, further, in step (2), the inner and outer layer feed liquids are simultaneously injected into the coagulation bath through an injection pump to obtain a precursor membrane of a hollow fiber structure; the obtained precursor base membrane is fully soaked in water and then taken out, and then dried to obtain a hollow fiber membrane embryo; the precursor membrane is soaked in water for 12-48 hours.

[0017] Based on the above technical solution, further, in step (3), pre-oxidation is carried out at 1-5°C·min -1 The heating rate is raised to 150-300℃, the constant temperature time is 1-6h, and the pre-oxidation process is carried out in air; the high temperature sintering is carried out at 1-10℃·min -1 The heating rate is increased to 1000-1300℃, the constant temperature time is 1-12h, and the sintering process is carried out under argon protection.

[0018] A hollow fiber composite electrocatalytic membrane is prepared by the above method.

[0019] A hollow fiber composite electrocatalytic membrane is used in water treatment to remove common organic pollutants from water, including emerging organic pollutants (such as antibiotics like tetracycline and amoxicillin), synthetic dyes (such as rhodamine B), and phenolic organic pollutants (such as phenol and bisphenol A). During the water treatment process, the hollow fiber composite electrocatalytic membrane acts as the anode and the metal plate as the cathode, degrading the target pollutants under the action of an electric field.

[0020] Based on the above technical solution, further, the metal plate material is one of titanium, platinum, copper, and nickel; the voltage is 0-3V; and the pollutant concentration is 5-20ppm.

[0021] The present invention first uses titanium powder, titanium dioxide powder and polymer as raw materials for processing to obtain a casting solution, and obtains a hollow fiber membrane embryo through wet spinning and drying; then pre-oxidation and high-temperature sintering are performed to obtain a hollow fiber composite electrocatalytic membrane. The basic concept of the present invention is to accurately control the ratio of titanium powder and titanium dioxide powder. During the high-temperature sintering process, the titanium powder directly acts as a reducing agent to reduce titanium dioxide to reduced titanium dioxide. At the same time, the polymer with a high amount of residual carbon directly derives a carbon material component, thereby preparing a reduced titanium dioxide / carbon composite hollow fiber electrocatalytic membrane. The present invention prepares a reduced titanium dioxide / carbon composite electrocatalytic membrane in one step through a phase conversion / sintering process. The preparation method is flexible and efficient, and the composite membrane has both excellent electrocatalytic activity and good adsorption properties.

[0022] The present invention has the following characteristics:

[0023] By combining wet spinning and high-temperature sintering, a hollow fiber composite electrocatalytic membrane with diverse functions and controllable performance was successfully prepared. Using the electrocatalytic membrane as an electrode can reduce energy consumption, lower costs, and enhance the mass transfer process, and has broad application prospects.

[0024] Beneficial effects

[0025] 1. Titanium dioxide is selected as the raw material and a small amount of titanium is added as a reducing agent to prepare reduced titanium dioxide. The preparation process is simple, the conditions are mild, and the use of a reducing atmosphere is avoided.

[0026] 2. The carbon material component directly derived from the polymer required for the spinning phase transformation has good adsorption properties and direct electron transfer ability, and the reduced titanium dioxide has excellent electrocatalytic properties, and the two complement each other.

[0027] 3. The preparation process is one-time molding and simple to operate. Compared with traditional flat membranes and tubular membranes, hollow fiber membranes have the advantages of high filling density and specific surface area, reduced volume of membrane components, and reduced floor space, and have broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following detailed description, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0029] Figure 1 This is a physical photograph of the hollow fiber composite electrocatalytic membrane prepared in Example 1 of the present invention (the white one is the hollow fiber membrane green body before calcination, and the black one is the hollow fiber composite electrocatalytic membrane after calcination).

[0030] Figure 2 These are electron microscope photographs of the (a1-a2) surface and (b1-b2) cross-section of the hollow fiber composite electrocatalytic membrane prepared in Example 2 of the present invention.

[0031] Figure 3 This is the XRD of the hollow fiber composite electrocatalytic membrane prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0032] In order to better understand the technical solution of the present invention, the present invention is further described in detail below through three embodiments. However, the following embodiments are only simplified examples of the present invention and are not limited to the following embodiments.

[0033] Example 1

[0034] The first step: titanium powder with an average particle size of 5μm, titanium dioxide powder of 1μm and polyacrylonitrile (PAN) with a molecular weight of 100,000 were placed in a 60°C oven and dried for 24 hours. After drying and cooling to room temperature, 1g titanium powder, 11g titanium dioxide and 2.4g polyacrylonitrile (PAN) were added to 5.6g N-methyl-2-pyrrolidone solvent in a specific ratio. The mixture was sealed and stirred for 24 hours. After standing for 12 hours to degas, a casting solution was obtained. A coaxial spinning needle with an inner diameter of 1.36mm and an outer diameter of 3.8mm was used to prepare a hollow fiber membrane by wet spinning technology. The inner and outer layer feed liquids were injected into a deionized water coagulation bath. The inner layer feed liquid was deionized water at a liquid supply rate of 10mL / h; the outer layer feed liquid was the casting solution at a liquid supply rate of 20mL / h. After being fully soaked in deionized water for 12 hours, it was taken out and straightened to dry.

[0035] The second step: the hollow fiber membrane obtained in the first step was placed in a tubular furnace, pre-oxidized, heated to 230 ° C at a rate of 2 ° C / min in an air atmosphere and maintained for 2 h, and then sintered at high temperature. The sintering atmosphere was argon. It was first heated at a constant temperature of 600 ° C for 2 h, then heated to 1100 ° C at a rate of 5 ° C / min, sintered for 4 h, and finally naturally cooled to room temperature and taken out to obtain a hollow fiber composite electrocatalytic membrane (denoted as TiO X ), the main component is Ti3O5 (XRD Figure 3 Scanning electron microscopy results show that the surface of the prepared hollow fiber composite electrocatalytic membrane has no obvious defects. The prepared hollow fiber composite electrocatalytic membrane has a resistivity of 3.5mΩ·cm, a mechanical strength of 42.6MPa, and a water flux of 2545.1L·m -2 ·h -1 bar -1 .

[0036] Step 3: The hollow fiber membrane prepared above was used as the anode, the titanium sheet as the counter electrode, and 0.1M sodium sulfate (Na2SO4) as the electrolyte. A voltage of 3V was applied to the hollow fiber membrane, and the flow rate of wastewater permeating the membrane from the outside was 150L·h -1 ·m -2 The removal rate of rhodamine b in 10ppm rhodamine b solution is 96.53%, and the removal rate of phenol in 10ppm phenol solution is 97.01%.

[0037] Example 2

[0038] The first step: titanium powder with an average particle size of 5μm, titanium dioxide powder with a molecular weight of 1μm, and polyethersulfone (PES) with a molecular weight of 58000 were placed in a 60℃ oven and dried for 24h. After drying and cooling to room temperature, 0.6g titanium powder, 11.4g titanium dioxide, and 2.4g polyethersulfone (PES) were added to 5.6g N-methyl-2-pyrrolidone solvent in a specific ratio. The mixture was sealed and stirred for 24h. After standing for 12h to degas, a casting solution was obtained. A coaxial spinning needle with an inner diameter of 1.36mm and an outer diameter of 3.8mm was used to prepare a hollow fiber membrane by wet spinning technology. The inner and outer layer feed liquids were injected into a deionized water coagulation bath. The inner layer feed liquid was deionized water at a liquid supply rate of 12mL / h; the outer layer feed liquid was the casting solution at a liquid supply rate of 24mL / h. After being fully soaked in deionized water for 12h, it was taken out and straightened to dry.

[0039] Step 2: Place the hollow fiber membrane obtained in the first step in a tubular furnace, pre-oxidize it, heat it to 230°C at a rate of 2°C / min in an air atmosphere and maintain it for 2 hours, then perform high-temperature sintering. The sintering atmosphere is argon. First, heat it at a constant temperature of 600°C for 2 hours, then heat it to 1100°C at a rate of 5°C / min, sinter it for 4 hours, and finally cool it naturally to room temperature and take it out to obtain a hollow fiber composite electrocatalytic membrane, the main component of which is Ti4O7. Scanning electron microscopy results show that the surface of the prepared hollow fiber conductive membrane has no obvious defects. The resistivity of the prepared hollow fiber composite electrocatalytic membrane is 2.3mΩ·cm, the mechanical strength is 38.5MPa, and the water flux of the membrane is 2214.5L·m -2 ·h -1 bar -1 .

[0040] Step 3: The hollow fiber membrane prepared above was used as the anode, the titanium sheet as the counter electrode, and 0.1M sodium sulfate (Na2SO4) as the electrolyte. A voltage of 3V was applied to the hollow fiber membrane, and the flow rate of wastewater permeating the membrane from the outside was 120L·h -1 ·m -2 The removal rate of tetracycline in 10ppm tetracycline solution was 98.96%, and the removal rate of amoxicillin in 10ppm amoxicillin solution was 98.43%.

[0041] Example 3

[0042] The first step: titanium powder with an average particle size of 5μm, titanium dioxide powder of 2μm and polyimide (PI) with a molecular weight of 50,000 are placed in a 60°C oven and dried for 24 hours. After drying and cooling to room temperature, 0.8g titanium powder, 11.2g titanium dioxide and 2.4g polyethersulfone (PES) are added to 5.6g N, N-dimethylformamide solvent in a specific proportion. The mixture is sealed and stirred for 24 hours. After standing for 12 hours to degas, a casting solution is obtained. A coaxial spinning needle with an inner diameter of 1.36mm and an outer diameter of 3.8mm is used to prepare a hollow fiber membrane by wet spinning technology. The inner and outer layer feed liquids are injected into the hydrogel bath. The inner layer feed liquid is deionized water at a liquid supply rate of 10mL / h; the outer layer feed liquid is the casting solution at a liquid supply rate of 20mL / h. After being fully soaked in deionized water for 12 hours, it is taken out and straightened to dry.

[0043] Step 2: The hollow fiber membrane obtained in the first step is placed in a tubular furnace, pre-oxidized, heated to 230°C at a rate of 2°C / min in an air atmosphere and maintained for 2 hours, and then sintered at high temperature. The sintering atmosphere is argon. It is first heated at a constant temperature of 600°C for 2 hours, then heated to 1100°C at a rate of 5°C / min, sintered for 4 hours, and finally naturally cooled to room temperature and taken out to obtain a hollow fiber composite electrocatalytic membrane, the main components of which are Ti3O5 and Ti4O7. Scanning electron microscopy results show that the surface of the prepared hollow fiber conductive membrane has no obvious defects. The resistivity of the prepared hollow fiber composite electrocatalytic membrane is 3.2mΩ·cm, the mechanical strength is 41.3MPa, and the water flux of the membrane is 2378.9L·m -2 ·h -1 bar -1 .

[0044] Step 3: The hollow fiber membrane prepared above was used as the anode, the titanium sheet as the counter electrode, and 0.1M sodium sulfate (Na2SO4) as the electrolyte. A voltage of 3V was applied to the hollow fiber membrane, and the flow rate of wastewater permeating the membrane from the outside was 140L·h -1 ·m -2 The removal rate of bisphenol A in 10ppm bisphenol A solution reached 97.75%.

Claims

1. A method for preparing a hollow fiber composite electrocatalytic membrane, characterized in that: The steps include: (1) preparing a casting solution: adding titanium powder, titanium dioxide powder, and polymer to an organic solvent in sequence, stirring evenly, and standing to degas to form a casting solution; (2) Spinning: using coaxial wet spinning technology, using deionized water or a mixture of ethanol and deionized water as the inner layer feed liquid, using the casting liquid obtained in step (1) as the outer layer feed liquid, injecting the inner and outer layer feed liquids into a coagulation bath, taking them out after sufficient immersion, and then drying them to obtain a hollow fiber membrane embryo; wherein the coagulation bath is water; (3) High-temperature sintering: The green body obtained in step (2) is placed in a tubular furnace for pre-oxidation, and then sintered at high temperature to obtain the hollow fiber composite electrocatalytic membrane.

2. The method according to claim 1, characterized in that In step (1), the average particle size of the titanium powder is 1-10 μm, the average particle size of the titanium dioxide powder is 0.1-5 μm; and the carbon content of the polymer is 40-80%.

3. The method according to claim 1, characterized in that In step (1), the polymer is a mixture of one or more of polyacrylonitrile, polyethersulfone, polyimide, polybenzimidazole, polyetheretherketone, polybenzoxazole, benzoxazine resin, and polybenzothiazole.

4. The method according to claim 1, wherein In step (1), the organic solvent is a mixture of one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and dimethyl sulfoxide.

5. The method according to claim 1, wherein Step (1): placing titanium powder, titanium dioxide powder and polymer in an oven for drying before use.

6. The method according to claim 1, characterized in that In step (1), the mass ratio of the sum of the titanium dioxide powder and the titanium powder to the polymer is 1:0.1-0.2, wherein the mass ratio of the titanium dioxide powder to the titanium powder is 1:0.08-0.

15.

7. The method according to claim 1, characterized in that In step (2), the needle used in the coaxial wet spinning technology has an inner diameter of 0.3-4 mm and an outer diameter of 0.5-5 mm; the feeding speed of the inner and outer layers is 1:1-4; and the base membrane is immersed in the aqueous solution for 12-48 hours.

8. The method according to claim 1, characterized in that In step (3), pre-oxidation is carried out at 1-5°C·min -1 The heating rate is raised to 150-300℃, the constant temperature time is 1-6h, and the pre-oxidation process is carried out in air atmosphere; the high temperature sintering is carried out at 1-10℃·min -1 The heating rate is increased to 1000-1300℃, the constant temperature time is 1-12h, and the sintering process is carried out under argon protection.

9. A hollow fiber composite electrocatalytic membrane, characterized in that: The method is prepared by any one of claims 1 to 8.

10. Use of the hollow fiber composite electrocatalytic membrane according to claim 9 in water treatment.

Images