Anionic electrodialysis membrane and preparation method thereof

Abstract

The invention belongs to the technical field of dialysis membranes, and particularly relates to an anionic electrodialysis membrane and a preparation method thereof. The preparation method comprises the following steps: (1) preparing a polytetrafluoroethylene film with modified carbon nanotubes deposited on the surface; (2) preparing an anionic monomer; (3) uniformly mixing an anionic monomer, an anionic monofunctional monomer, ethylene glycol dimethacrylate, a monofunctional nonionic monomer, ammonium persulfate and water to obtain a mixed solution; and (4) completely soaking the polytetrafluoroethylene membrane with the modified carbon nanotubes deposited on the surface into the mixed solution at 20-30 DEG C for 2-3 hours, taking out the polytetrafluoroethylene membrane, and carrying out heating polymerization in a drying oven to obtain the anionic electrodialysis membrane. The anionic electrodialysis membrane prepared by the invention is excellent in comprehensive performance and long in service life.

Description

Technical Field

[0001] The present invention belongs to the technical field of dialysis membranes, and particularly relates to an anionic electrodialysis membrane and a preparation method thereof. Background Art

[0002] An anion exchange membrane (AEM) is a semi-permeable membrane specifically designed to allow anions to pass through while blocking cations and non-ionic substances. This type of membrane is widely used in water treatment, resource recovery, chemical separation and other fields, especially playing an important role in the electrodialysis process.

[0003] There are indeed some technical challenges and problems with anion exchange membranes (AEMs) in the electrodialysis process, mainly including: 1. Low performance: Compared with proton exchange membrane electrolyzers, the performance of AEM electrolyzers is still relatively low. This is mainly reflected in the relatively high irreversible voltage loss, which is usually related to the electrode reaction kinetics and the transport of electrons, ions and gas-phase products during the electrolysis process. 2. Membrane stability issues: AEMs need to have good chemical and thermal stability to withstand the conditions during the electrodialysis process. However, in practical applications, the membrane may be affected by degradation, especially under higher temperature or extreme pH conditions. 3. Balance between selectivity and conductivity: An ideal AEM should have high ion selectivity and high conductivity. However, in practice, it is often difficult to achieve both. Increasing the selectivity of the membrane may reduce its conductivity, and vice versa. 3. Durability: Under long-term operation, the membrane may suffer physical damage or performance degradation due to pollutant accumulation, affecting the service life of the equipment.

[0004] To overcome these problems, the existing technology mainly adopts strategies in multiple aspects such as exploring new materials, improving the membrane structure design, and optimizing operating conditions. For example, developing new polymer materials, introducing nanotechnology to enhance the membrane performance, and reducing membrane fouling through pretreatment and cleaning techniques, aiming to improve the overall performance of AEMs and make them more suitable for large-scale industrial applications. However, the durability of the current electrodialysis membranes on the market still cannot meet the market demand.

[0005] Chinese Patent 202410287433.3 provides an anionic electrodialysis membrane, a preparation method thereof and an application, but the durability of the anionic electrodialysis membrane prepared by this method is not ideal.

[0006] Therefore, there is an urgent need for an anionic electrodialysis membrane and a preparation method thereof. Summary of the Invention

[0007] The object of the present invention is to provide an anionic electrodialysis membrane and a preparation method thereof.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A preparation method of an anionic electrodialysis membrane, comprising the following steps:

[0010] (1) Mix modified carbon nanotubes, polytetrafluoroethylene emulsion and silane coupling agent to obtain a dispersion; attach the dispersion to a polytetrafluoroethylene membrane by suction filtration; heat and cure to obtain a polytetrafluoroethylene membrane with carbon nanotubes deposited on the surface;

[0011] (2) Mix disodium polyethylene glycol, 7-chloroheptanoic acid and N,N-dimethylformamide, and react for 3-4 h; add 3-chloro-1-propene and react for 5-6 h; then add sodium bicarbonate and react for 1-1.5 h, and remove N,N-dimethylformamide by rotary evaporation under reduced pressure to obtain an anionic monomer;

[0012] (3) Mix the anionic monomer, anionic monofunctional monomer, ethylene glycol dimethacrylate, monofunctional nonionic monomer, ammonium persulfate and water uniformly to obtain a mixed solution;

[0013] (4) Immerse the polytetrafluoroethylene membrane with carbon nanotubes deposited on the surface completely in the mixed solution for 2-3 h, and then heat and polymerize to obtain an anionic electrodialysis membrane;

[0014] The preparation method of the modified carbon nanotubes comprises the following steps:

[0015] S1. Add carbon nanotubes to an alkaline solution and a hydrogen peroxide solution in sequence for treatment to obtain pretreated carbon nanotubes;

[0016] S2. Mix carbon nanotubes and 3-aminopropyltriethoxysilane in a solvent, stir and react, and then dry to obtain amino-functionalized carbon nanotubes;

[0017] S3. Mix amino-functionalized carbon nanotubes, ethylene oxide and dichloromethane, react and dry to obtain hydroxylated carbon nanotubes;

[0018] S4. Mix the hydroxylated carbon nanotubes, polyethylene glycol monomethyl ether, N,N'-dicyclohexylcarbodiimide and dichloromethane, react and dry to obtain modified carbon nanotubes.

[0019] Further, the preparation method of the modified carbon nanotubes comprises the following steps:

[0020] S1. Add 1 g of carbon nanotubes to 10 mL of a NaOH solution with a concentration of 4-6 mol / L, and ultrasonically disperse; slowly add 6-8 mL of a H2O2 solution with a mass fraction of 25-30%, ultrasonically disperse and stir; perform centrifugation treatment, wash until neutral; dry to obtain pretreated carbon nanotubes;

[0021] S2. Mix the pretreated carbon nanotubes, absolute ethanol, and 3-aminopropyltriethoxysilane with a weight ratio of 1:(8 - 10):(0.1 - 0.15), stir at 35 - 50 °C for 5 - 7 h, filter, and dry to obtain amino-functionalized carbon nanotubes;

[0022] S3. Mix 1 g of amino-functionalized carbon nanotubes, 10 - 20 mmol of ethylene oxide, and 10 - 15 mL of dichloromethane, react at 60 - 80 °C for 8 - 10 h, filter, and dry to obtain hydroxyl-functionalized carbon nanotubes;

[0023] S4. Mix 1 g of hydroxyl-functionalized carbon nanotubes, 10 - 20 mmol of methoxypolyethylene glycol, 1.2 mol of N,N'-dicyclohexylcarbodiimide, and 10 - 15 mL of dichloromethane, react at 25 - 40 °C for 12 - 15 h, filter, and dry to obtain modified carbon nanotubes.

[0024] Further, in step (1): Mix the modified carbon nanotubes, polytetrafluoroethylene emulsion, and silane coupling agent, first stir mechanically and then disperse ultrasonically to obtain a dispersion; Place the dispersion in a suction filtration device with a polytetrafluoroethylene membrane, perform vacuum suction filtration for 1 - 2 h, then turn the polytetrafluoroethylene membrane over and continue vacuum suction filtration in the suction filtration device with the polytetrafluoroethylene membrane for 1 - 2 h. After suction filtration on both sides of the polytetrafluoroethylene membrane is completed, heat and cure. After curing is completed, obtain a polytetrafluoroethylene membrane with surface-deposited modified carbon nanotubes.

[0025] In step (2): Mix 4 parts by weight of disodium polyethylene glycol, 0.8 - 1 part by weight of 7-chloroheptanoic acid, and 10 - 12 parts by weight of N,N-dimethylformamide, react at 20 - 30 °C for 3 - 4 h, then continue to add 0.7 - 0.9 part by weight of 3-chloro-1-propene, react at 20 - 30 °C for 5 - 6 h, and finally add 1.1 - 1.3 parts by weight of sodium bicarbonate, stir and react at 20 - 30 °C for 1 - 1.5 h, and rotary evaporate to remove N,N-dimethylformamide to obtain an anionic monomer.

[0026] In step (3): Mix the anionic monomer, anionic monofunctional monomer, ethylene glycol dimethacrylate, monofunctional nonionic monomer, ammonium persulfate, and water evenly to obtain a mixed solution.

[0027] In step (4): Completely immerse the polytetrafluoroethylene membrane with surface-deposited modified carbon nanotubes in the mixed solution, soak at 20 - 30 °C for 2 - 3 h, take it out and place it in an oven for heat polymerization to obtain an anionic electrodialysis membrane.

[0028] Further, the anionic monofunctional monomer includes a mixture of sodium styrenesulfonate, sodium vinylsulfonate, and 2-methylacrylamide-2-methylpropanesulfonate with a weight ratio of 1:(1.2 - 1.4):(0.5 - 0.8).

[0029] Further, the monofunctional nonionic monomer comprises a mixture of hydroxypropyl acrylate, hydroxypropyl methacrylate, and N-vinylpyrrolidone in a weight ratio of 1:(0.5 - 0.8):(1.4 - 1.7).

[0030] Further, the inner diameter of the carbon nanotubes is 10 - 20 nm; the tube length is 5 - 15 μm, and the specific surface area is 120 - 180 m 2 / g.

[0031] Further, disodium polyethylene glycol can be prepared according to conventional methods in the art. Including but not limited to: dissolving polyethylene glycol in a solvent, adding metallic sodium, reacting in an inert gas atmosphere, and removing the solvent to obtain disodium polyethylene glycol.

[0032] Further, the weight ratio of the modified carbon nanotubes, polytetrafluoroethylene emulsion, and silane coupling agent is 1:(10 - 13):(0.01 - 0.03).

[0033] Further, the silane coupling agent is tridecafluorooctyltrimethoxysilane.

[0034] Further, the mixed solution is obtained by uniformly mixing 5 parts by weight of anionic monomer, 3 - 5 parts by weight of anionic monofunctional monomer, 0.1 - 0.3 parts by weight of ethylene glycol dimethacrylate, 6 - 8 parts by weight of monofunctional nonionic monomer, 0.04 - 0.06 parts by weight of ammonium persulfate, and 80 - 90 parts by weight of water.

[0035] Further, the heating polymerization is carried out at 60 - 70 °C for 70 - 80 min.

[0036] The present invention provides an anionic electrodialysis membrane prepared by the described preparation method.

[0037] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0038] 1. By depositing modified carbon nanotubes on the surface of the polytetrafluoroethylene membrane, the present invention can improve the conductivity and tensile strength of the electrodialysis membrane. The modified carbon nanotubes have a better interfacial combination with other components in the system, and the uniform dispersion of the modified carbon nanotubes is achieved through mechanical stirring and ultrasonic dispersion. The subsequent suction filtration process enables the modified carbon nanotubes and polytetrafluoroethylene particles to be uniformly deposited on the surface of the PTFE membrane, and finally, these components are tightly combined through heat curing, thereby improving the overall tensile strength of the composite material.

[0039] 2. Through the polymerization reaction of specific monomers, a stable polymer network is formed on the surface of the polytetrafluoroethylene membrane modified by deposited carbon nanotubes. This network not only enhances the mechanical properties of the membrane and extends its service life. By precisely controlling the ratio of monomers and polymerization conditions, it can ensure that the ion exchange layer of the membrane has high uniformity and stability. This not only improves the selective permeation performance of the membrane but also reduces the risk of membrane failure caused by local defects. Detailed implementation mode

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0041] The raw materials used in the following embodiments of the present invention are all commercially available products:

[0042] Polytetrafluoroethylene emulsion, Dongguan Nabaichuan Plastic Co., Ltd., brand DF301.

[0043] Silane coupling agent: tridecafluorooctyltrimethoxysilane.

[0044] The polytetrafluoroethylene membrane is Pall imported from the United States, with the product number PTF020LHOP-MAST.

[0045] The preparation method of disodium polyethylene glycol is as follows: Dissolve 1 mole of polyethylene glycol-400 in 15 moles of toluene, add 2 mol of metallic sodium, react at 20 °C and 80 rpm for 1 h under the protection of inert gas nitrogen to generate sodium polyethylene glycol salt, and remove toluene by rotary evaporation under reduced pressure to obtain disodium polyethylene glycol.

[0046] Example 1

[0047] This example provides a preparation method of an anionic electrodialysis membrane, including the following steps:

[0048] (1) Mix modified carbon nanotubes, polytetrafluoroethylene emulsion and silane coupling agent at a weight ratio of 1:12:0.02, first stir mechanically at 400 rpm for 1.5 h, and then disperse ultrasonically for 25 min to obtain a dispersion; Place the dispersion in a suction filtration device containing a polytetrafluoroethylene membrane, perform vacuum suction filtration for 1.5 h, then turn the polytetrafluoroethylene membrane over, and continue vacuum suction filtration in the suction filtration device containing the polytetrafluoroethylene membrane for 1.5 h. After the suction filtration on both sides of the polytetrafluoroethylene membrane is completed, place it in a blast drying oven and heat and cure at 105 °C for 1.4 h. After the curing is completed, obtain a polytetrafluoroethylene membrane with modified carbon nanotubes deposited on the surface;

[0049] (2) Mix 4 parts by weight of disodium polyethylene glycol with 0.9 parts by weight of 7-chloroheptanoic acid and 11 parts by weight of N,N-dimethylformamide, react at 25 °C for 3.4 h, then add 0.8 parts by weight of 3-chloro-1-propene, react at 25 °C for 5.5 h, and finally add 1.2 parts by weight of sodium bicarbonate, stir and react at 25 °C for 1.2 h. Remove the solvent by rotary evaporation to obtain an anionic monomer;

[0050] The structural formula of the anionic monomer is: Among them, R is (CH2)6, and the value of n is determined by the polyethylene glycol used as the raw material for synthesizing disodium polyethylene glycol.

[0051] (3) Mix 5 parts by weight of anionic monomer, 4 parts by weight of anionic monofunctional monomer, 0.2 parts by weight of ethylene glycol dimethacrylate, 7 parts by weight of monofunctional nonionic monomer, 0.05 parts by weight of ammonium persulfate and 85 parts by weight of water evenly to obtain a mixed solution;

[0052] (4) Completely immerse the polytetrafluoroethylene membrane with surface-deposited modified carbon nanotubes in the mixed solution, soak at 25 °C for 2.5 h, take it out and place it in an oven at 65 °C for heat polymerization for 75 min to obtain an anionic electrodialysis membrane.

[0053] The preparation method of the modified carbon nanotubes includes the following steps:

[0054] S1. Add 1 g of carbon nanotubes to 10 mL of NaOH solution with a concentration of 5 mol / L, and disperse them by ultrasonic wave; slowly add 7 mL of H2O2 solution with a mass fraction of 27%, disperse them by ultrasonic wave and stir; perform centrifugation treatment, wash until neutral; dry to obtain pretreated carbon nanotubes;

[0055] S2. Mix pretreated carbon nanotubes, absolute ethanol and 3-aminopropyltriethoxysilane with a weight ratio of 1:9:0.12, stir at 40 °C for 6 h, filter and dry to obtain amino-functionalized carbon nanotubes;

[0056] S3. Mix 1 g of amino-functionalized carbon nanotubes, 15 mmol of ethylene oxide and 12 mL of dichloromethane, react at 70 °C for 9 h, filter and dry to obtain hydroxylated carbon nanotubes;

[0057] (4) Mix 1 g of hydroxylated carbon nanotubes, 15 mmol of methoxypolyethylene glycol, 1.2 mmol of N,N'-dicyclohexylcarbodiimide and 12 mL of dichloromethane, react at 30 °C for 14 h, filter and dry to obtain modified carbon nanotubes.

[0058] The inner diameter of the carbon nanotubes is 10-20 nm; the tube length is 5-15 μm, and the specific surface area is 120-180 m 2 / g.

[0059] The anionic monofunctional monomer comprises a mixture of sodium styrenesulfonate, sodium vinylsulfonate and sodium 2-methyl-2-propenamide-2-methylpropanesulfonate in a weight ratio of 1:1.2:0.7.

[0060] The nonionic monofunctional monomer comprises a mixture of hydroxypropyl acrylate, hydroxypropyl methacrylate and N-vinylpyrrolidone in a weight ratio of 1:0.6:1.5.

[0061] Example 2

[0062] This example provides a method for preparing an anionic electrodialysis membrane, comprising the following steps:

[0063] (1) Mix modified carbon nanotubes, polytetrafluoroethylene emulsion and silane coupling agent in a weight ratio of 1:13:0.01, first stir mechanically at 300 rpm for 1.5 h, then disperse ultrasonically for 30 min to obtain a dispersion; place the dispersion in a suction filtration device containing a polytetrafluoroethylene membrane, perform vacuum suction filtration for 2 h, then turn the polytetrafluoroethylene membrane over, continue vacuum suction filtration in the suction filtration device containing the polytetrafluoroethylene membrane for 2 h. After the suction filtration on both sides of the polytetrafluoroethylene membrane is completed, place it in a forced air drying oven and heat and cure at 100 °C for 2 h. After the curing is completed, a polytetrafluoroethylene membrane with surface-deposited modified carbon nanotubes is obtained;

[0064] (2) Mix 4 parts by weight of disodium polyethylene glycol, 1 part by weight of 7-chloroheptanoic acid and 10 parts by weight of N,N-dimethylformamide, react at 30 °C for 4 h, continue to add 0.9 part by weight of 3-chloro-1-propene, react at 30 °C for 5 h, and finally add 1.3 parts by weight of sodium bicarbonate, stir and react at 30 °C for 1 h, and remove the solvent by rotary evaporation to obtain an anionic monomer;

[0065] (3) Mix 5 parts by weight of anionic monomer, 5 parts by weight of anionic monofunctional monomer, 0.1 part by weight of ethylene glycol dimethacrylate, 8 parts by weight of nonionic monofunctional monomer, 0.04 part by weight of ammonium persulfate and 90 parts by weight of water evenly to obtain a mixed solution;

[0066] (4) Completely immerse the polytetrafluoroethylene membrane with surface-deposited modified carbon nanotubes in the mixed solution, soak at 30 °C for 2 h, take it out and place it in an oven at 70 °C for heat polymerization for 70 min to obtain an anionic electrodialysis membrane.

[0067] The preparation method of the modified carbon nanotubes comprises the following steps:

[0068] S1. Add 1 g of carbon nanotubes to 10 mL of NaOH solution with a concentration of 6 mol / L, disperse ultrasonically; slowly add 6 mL of H2O2 solution with a mass fraction of 30%, disperse ultrasonically and stir; perform centrifugation treatment, wash until neutral; dry to obtain pretreated carbon nanotubes;

[0069] S2. Mix the pretreated carbon nanotubes, absolute ethanol, and 3-aminopropyltriethoxysilane at a weight ratio of 1:8:0.15, stir at 50 °C for 5 h, filter, and dry to obtain amino-functionalized carbon nanotubes;

[0070] S3. Mix 1 g of amino-functionalized carbon nanotubes, 10 mmol of ethylene oxide, and 15 mL of dichloromethane, react at 60 °C for 10 h, filter, and dry to obtain hydroxyl-functionalized carbon nanotubes;

[0071] (4) Mix 1 g of hydroxyl-functionalized carbon nanotubes, 10 mmol of methoxypolyethylene glycol, 1.2 mol of N,N'-dicyclohexylcarbodiimide, and 15 mL of dichloromethane, react at 40 °C for 12 h, filter, and dry to obtain modified carbon nanotubes.

[0072] The inner diameter of the carbon nanotubes is 10 - 20 nm; the tube length is 5 - 15 μm, and the specific surface area is 120 - 180 m 2 / g.

[0073] The anionic monofunctional monomer includes a mixture of sodium styrenesulfonate, sodium vinylsulfonate, and 2-methylacrylamide-2-methylpropanesulfonate at a weight ratio of 1:1.2:0.8.

[0074] The monofunctional nonionic monomer includes a mixture of hydroxypropyl acrylate, hydroxypropyl methacrylate, and N-vinylpyrrolidone at a weight ratio of 1:0.5:1.7.

[0075] Comparative Example 1

[0076] The difference between this comparative example and Example 1 is that the polytetrafluoroethylene membrane is not surface-deposited with modified carbon nanotubes.

[0077] A preparation method of an anionic electrodialysis membrane includes the following steps:

[0078] (1) Mix 4 parts by weight of disodium polyethylene glycol, 0.9 parts by weight of 7-chloroheptanoic acid, and 11 parts by weight of N,N-dimethylformamide, react at 25 °C for 3.4 h, then add 0.8 parts by weight of 3-chloro-1-propene, react at 25 °C for 5.5 h, and finally add 1.2 parts by weight of sodium bicarbonate, stir and react at 25 °C for 1.2 h, rotary evaporate to remove the solvent to obtain an anionic monomer;

[0079] (2) Mix 5 parts by weight of the anionic monomer, 4 parts by weight of the anionic monofunctional monomer, 0.2 parts by weight of ethylene glycol dimethacrylate, 7 parts by weight of the monofunctional nonionic monomer, 0.05 parts by weight of ammonium persulfate, and 85 parts by weight of water evenly to obtain a mixed solution;

[0080] (3) Immerse the polytetrafluoroethylene membrane completely in the mixed solution, soak it at 25 °C for 2.5 h, take it out and place it in an oven at 65 °C for heating polymerization for 75 min to obtain an anionic electrodialysis membrane.

[0081] The anionic monofunctional monomer includes a mixture of sodium styrenesulfonate, sodium vinylsulfonate, and 2-methylacrylamide-2-methylpropanesulfonate in a weight ratio of 1:1.2:0.7.

[0082] The monofunctional nonionic monomer includes a mixture of hydroxypropyl acrylate, hydroxypropyl methacrylate, and N-vinylpyrrolidone in a weight ratio of 1:0.6:1.5.

[0083] Comparative Example 2

[0084] The difference between this comparative example and Example 1 is that the carbon nanotubes have an inner diameter of 30-50 nm, a tube length of 20-30 μm, and a specific surface area of 50-80 m 2 / g.

[0085] Comparative Example 3

[0086] The difference between this comparative example and Example 1 is that the anionic monofunctional monomer includes a mixture of sodium styrenesulfonate, sodium vinylsulfonate, and 2-methylacrylamide-2-methylpropanesulfonate in a weight ratio of 1:1:1.

[0087] Comparative Example 4

[0088] The difference between this comparative example and Example 1 is that the monofunctional nonionic monomer includes a mixture of hydroxypropyl acrylate, hydroxypropyl methacrylate, and N-vinylpyrrolidone in a weight ratio of 1:1:1.

[0089] Performance Test

[0090] Perform performance tests on the anionic electrodialysis membranes prepared in Examples 1-2 and Comparative Examples 1-4.

[0091] 1. Tensile strength test: Use a CTM2050 automatic mechanical strength tester for testing. Cut the anionic electrodialysis membrane into small pieces of 2×10 cm 2 at a tensile speed of 2 mm / min. Terminate the test after the membrane breaks, record the tensile strength of the membrane, repeat the measurement 3 times, and take the average value.

[0092] 2. Surface resistance test: Before the test, immerse the anionic electrodialysis membrane in a 0.5 mol / L NaCl solution for 24 h; then cut it into 1×1 cm 2Small pieces were cut, the Ag / AgCl electrode was inserted into the electrolyte and placed close to both sides of the membrane, and connected to the working electrode and reference electrode of the electrochemical workstation respectively; the alternating current impedance method was selected for testing. The termination frequency was set to 1 Hz and the alternating current amplitude was set to 10 mV; then a 0.5 mol / L NaCl solution was circulated through the electrolytic cells on both sides.

[0093] 3. Test of ion selective permeability: The anionic electrodialysis membrane was cut into small pieces of 1×1 cm 2 and immersed in a 0.15 mol / L KCl solution for 12 h, then the small pieces were placed in the electrolytic cell and fixed; the tip of the Ag / AgCl electrode was placed close to the membrane, but avoiding touching the surface of the membrane; then a peristaltic pump was used to circulate a 0.1 mol / L and a 0.2 mol / L KCl solution through the electrolytic cell respectively. The specific method refers to Chinese Patent CN202410287433.3. At the same time, it was continuously operated, and the number of days with an ion selective permeability ≥ 95% was counted.

[0094] Table 1 Performance test results

[0095]

[0096] It can be seen from the above performance test results that the anionic electrodialysis membranes of Examples 1-2 have excellent comprehensive performance and good durability, especially the comprehensive performance of Example 1 is the most prominent.

[0097] In the comparative examples, because the necessary technical solutions were not adopted, their performance in the corresponding performance tests was significantly worse than that of the examples. In Comparative Example 1, modified carbon nanotubes were not deposited on the surface of the polytetrafluoroethylene membrane, and the surface resistance and tensile strength of the dialysis membrane decreased. In Comparative Example 2, the parameters of the carbon nanotubes were different, and the tensile strength decreased. In Comparative Example 3, the ratio of the anionic monofunctional monomer was different, and in Comparative Example 4, the ratio of the monofunctional nonionic monomer was different, resulting in a decrease in the durability of the anionic electrodialysis membrane. The above experimental results further prove the importance of the technical solutions defined in the present invention for its technical effects.

[0098] The above is the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing an anionic electrodialysis membrane, characterized in that: The following steps are involved: (1) mixing modified carbon nanotubes, polytetrafluoroethylene emulsion and silane coupling agent to obtain a dispersion; filtering the dispersion and the polytetrafluoroethylene membrane to allow the dispersion to adhere to the polytetrafluoroethylene membrane; heating and curing to obtain a polytetrafluoroethylene membrane with carbon nanotubes deposited on the surface; (2) mixing disodium polyethylene glycol, 7-chloroheptanoic acid and N,N-dimethylformamide, and reacting for 3-4 hours; adding 3-chloro-1-propylene, and reacting for 5-6 hours; then adding sodium bicarbonate, and reacting for 1-1.5 hours; and removing N,N-dimethylformamide by vacuum rotary evaporation to obtain an anionic monomer; (3) mixing anionic monomer, anionic monofunctional monomer, ethylene glycol dimethacrylate, monofunctional nonionic monomer, ammonium persulfate and water to obtain a mixed solution; (4) completely immersing the polytetrafluoroethylene membrane with carbon nanotubes deposited on the surface in the mixed solution for 2-3 hours, and then heating and polymerizing to obtain an anionic electrodialysis membrane; The method for preparing the modified carbon nanotubes comprises the following steps: S1, adding carbon nanotubes to an alkaline solution and a hydrogen peroxide solution for treatment in sequence to obtain pretreated carbon nanotubes; S2, mixing carbon nanotubes and 3-aminopropyltriethoxysilane in a solvent, stirring to react, and then drying to obtain amino carbon nanotubes; S3, mixing the amination carbon nanotubes, ethylene oxide and dichloromethane, reacting, and drying to obtain hydroxylation carbon nanotubes; S4, mixing the hydroxylated carbon nanotubes, polyethylene glycol monomethyl ether, N,N'-dicyclohexylcarbodiimide and dichloromethane, reacting, and drying to obtain modified carbon nanotubes.

2. A method for preparing an anionic electrodialysis membrane according to claim 1, characterized in that: The method for preparing the modified carbon nanotubes in step (1) comprises the following steps: S1. Add 1g of carbon nanotubes to 10mL of NaOH solution with a concentration of 4-6mol / L, and disperse by ultrasonic; slowly add 6-8mL of H2O2 solution with a mass fraction of 25-30%, disperse by ultrasonic and stir; centrifuge, wash to neutrality; dry to obtain pretreated carbon nanotubes; S2, mixing the pretreated carbon nanotubes, anhydrous ethanol and 3-aminopropyltriethoxysilane in a weight ratio of 1: (8-10): (0.1-0.15), stirring at 35-50° C. for 5-7 hours, filtering and drying to obtain amino carbon nanotubes; S3, 1 g of amino carbon nanotubes, 10-20 mmol of ethylene oxide and 10-15 mL of dichloromethane are mixed, reacted at 60-80° C. for 8-10 h, filtered and dried to obtain hydroxylated carbon nanotubes; S4, 1 g of hydroxylated carbon nanotubes, 10-20 mmol of polyethylene glycol monomethyl ether, 1.2 mol of N,N'-dicyclohexylcarbodiimide and 10-15 mL of dichloromethane were mixed, reacted at 25-40°C for 12-15 h, filtered and dried to obtain modified carbon nanotubes.

3. The method for preparing anionic electrodialysis membrane according to claim 2, characterized in that: The step (1) comprises mixing the modified carbon nanotubes, polytetrafluoroethylene emulsion and silane coupling agent, first mechanically stirring, and then ultrasonically dispersing to obtain a dispersion; placing the dispersion in a filtration device containing a polytetrafluoroethylene membrane, vacuum filtering for 1-2 hours, then turning the polytetrafluoroethylene membrane over, and continuing to vacuum filter in the filtration device containing the polytetrafluoroethylene membrane for 1-2 hours. After the filtration of both sides of the polytetrafluoroethylene membrane is completed, heating and curing are performed. After the curing is completed, a polytetrafluoroethylene membrane with modified carbon nanotubes deposited on the surface is obtained; The step (2) is as follows: 4 parts by weight of disodium polyethylene glycol, 0.8-1 parts by weight of 7-chloroheptanoic acid and 10-12 parts by weight of N,N-dimethylformamide are mixed, reacted at 20-30° C. for 3-4 hours, 0.7-0.9 parts by weight of 3-chloro-1-propylene are added, reacted at 20-30° C. for 5-6 hours, and finally 1.1-1.3 parts by weight of sodium bicarbonate are added, stirred and reacted at 20-30° C. for 1-1.5 hours, and N,N-dimethylformamide is removed by rotary evaporation to obtain an anionic monomer; The step (3) comprises mixing anionic monomers, anionic monofunctional monomers, ethylene glycol dimethacrylate, monofunctional nonionic monomers, ammonium persulfate and water to obtain a mixed solution; The step (4) is to completely immerse the polytetrafluoroethylene membrane with modified carbon nanotubes deposited on the surface in the mixed solution at 20-30° C. for 2-3 hours, take it out and place it in an oven for heating and polymerization to obtain an anionic electrodialysis membrane.

4. The method for preparing anionic electrodialysis membrane according to claim 3, characterized in that: The anionic monofunctional monomer comprises a mixture of sodium styrene sulfonate, sodium ethylene sulfonate and sodium 2-methyl-acrylamide-2-methylpropane sulfonate in a weight ratio of 1: (1.2-1.4): (0.5-0.8); the monofunctional nonionic monomer comprises a mixture of hydroxypropyl acrylate, hydroxypropyl methacrylate and N-vinyl pyrrolidone in a weight ratio of 1: (0.5-0.8): (1.4-1.7).

5. The method for preparing anionic electrodialysis membrane according to claim 2, characterized in that: The carbon nanotube has an inner diameter of 10-20 nm, a tube length of 5-15 μm, and a specific surface area of ​​120-180 m 2 / g.

6. The method for preparing anionic electrodialysis membrane according to claim 2, characterized in that: The weight ratio of the modified carbon nanotube, polytetrafluoroethylene emulsion and silane coupling agent is 1:(10-13):(0.01-0.03).

7. The method for preparing anionic electrodialysis membrane according to claim 1, characterized in that: The silane coupling agent is tridecafluorooctyltrimethoxysilane.

8. The method for preparing anionic electrodialysis membrane according to claim 1, characterized in that: The mixed solution is obtained by uniformly mixing 5 parts by weight of anionic monomer, 3-5 parts by weight of anionic monofunctional monomer, 0.1-0.3 parts by weight of ethylene glycol dimethacrylate, 6-8 parts by weight of monofunctional nonionic monomer, 0.04-0.06 parts by weight of ammonium persulfate and 80-90 parts by weight of water.

9. The method for preparing anionic electrodialysis membrane according to claim 1, characterized in that: The heating polymerization is as follows: heating polymerization is carried out at 60-70° C. for 70-80 minutes.

10. An anionic electrodialysis membrane prepared by the preparation method according to any one of claims 1 to 9.

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