An anion electrodialysis membrane and a method of making

Abstract

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

Description

Technical Field

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

[0002] Anion Exchange Membrane (AEM) is a semipermeable membrane specifically designed to allow the passage of anions while blocking the passage of cations and non-ionic substances. This type of membrane is widely used in water treatment, resource recovery, chemical separation, and other fields, especially playing a key role in the electrodialysis process.

[0003] Anion exchange membranes (AEMs) do present some technical challenges and issues in electrodialysis, primarily including: 1. Low performance: Compared to proton exchange membrane electrolyzers, AEM electrolyzers have relatively low performance. This is primarily reflected in higher irreversible voltage losses, which are typically related to the electrode reaction kinetics and the transport of electrons, ions, and gaseous products during the electrolysis process. 2. Membrane stability: AEMs require excellent chemical and thermal stability to withstand the conditions of the electrodialysis process. However, in practical applications, membranes may be susceptible to degradation, especially at higher temperatures or extreme pH values. 3. Balance between selectivity and conductivity: An ideal AEM should possess both high ion selectivity and high conductivity. However, in practice, achieving both is often difficult. Improving membrane selectivity may reduce its conductivity, and vice versa. 3. Durability: Over long-term operation, the membrane may suffer physical damage or performance degradation due to contaminant accumulation, impacting the lifespan of the device.

[0004] To overcome these issues, existing technologies primarily employ strategies such as exploring new materials, improving membrane structural design, and optimizing operating conditions. For example, efforts are underway to develop novel polymer materials, introduce nanotechnology to enhance membrane performance, and reduce membrane fouling through pretreatment and cleaning techniques. These measures aim to improve the overall performance of AEMs and make them more suitable for large-scale industrial applications. However, the durability of currently available electrodialysis membranes still fails to meet market demand.

[0005] Chinese Patent 202410287433.3 provides an anionic electrodialysis membrane, a preparation method, and an application thereof. 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. Summary of the Invention

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

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

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

[0010] (1) mixing modified carbon nanotubes, polytetrafluoroethylene emulsion and silane coupling agent to obtain a dispersion liquid; dispersing the dispersion liquid and polytetrafluoroethylene membrane by means of suction filtration to realize the attachment of the dispersion liquid on the polytetrafluoroethylene membrane; and heating and curing to obtain a polytetrafluoroethylene membrane with carbon nanotubes deposited on the surface;

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

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

[0013] (4) completely immersing the polytetrafluoroethylene membrane with carbon nanotubes deposited on the surface in the mixed liquid, immersing for 2-3 h, and then heating and polymerizing to obtain an anion electrodialysis membrane;

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

[0015] S1, carbon nanotubes are sequentially treated in an alkaline solution and a hydrogen peroxide solution to obtain pretreated carbon nanotubes;

[0016] S2, carbon nanotubes and 3-aminopropyltriethoxysilane are mixed in a solvent, stirred and reacted, and then dried to obtain aminated carbon nanotubes;

[0017] S3, the aminated carbon nanotubes, ethylene oxide and dichloromethane are mixed, reacted, and dried to obtain hydroxylated carbon nanotubes;

[0018] S4, the hydroxylated carbon nanotubes, polyethylene glycol monomethyl ether, N,N'-dicyclohexyl carbodiimide and dichloromethane are mixed, reacted, and dried to obtain modified carbon nanotubes.

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

[0020] S1, 1 g of carbon nanotubes is added into 10 mL of NaOH solution with a concentration of 4-6 mol / L, and ultrasonic dispersion is performed; 6-8 mL of H2O2 solution with a mass fraction of 25-30% is slowly added, and ultrasonic dispersion and stirring are performed; centrifugal treatment is performed, and washing is performed until neutral; and drying is performed to obtain pretreated carbon nanotubes;

[0021] 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-treated carbon nanotubes;

[0022] S3, 1 g of amino-treated carbon nanotubes, 10-20 mmol of ethylene oxide, and 10-15 mL of dichloromethane were mixed, reacted at 60-80°C for 8-10 h, filtered, and dried to obtain hydroxylated carbon nanotubes;

[0023] S4. Mix 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, react at 25-40°C for 12-15 h, filter, and dry to obtain modified carbon nanotubes.

[0024] Furthermore, 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 filtering both sides of the polytetrafluoroethylene membrane, heating and curing are completed. After curing, a polytetrafluoroethylene membrane with modified carbon nanotubes deposited on the surface is obtained.

[0025] The step (2) comprises mixing 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, reacting at 20-30° C. for 3-4 hours, continuously adding 0.7-0.9 parts by weight of 3-chloro-1-propylene, reacting at 20-30° C. for 5-6 hours, and finally adding 1.1-1.3 parts by weight of sodium bicarbonate, stirring and reacting at 20-30° C. for 1-1.5 hours, and removing N,N-dimethylformamide by rotary evaporation to obtain an anionic monomer.

[0026] The step (3) comprises uniformly mixing anionic monomers, anionic monofunctional monomers, ethylene glycol dimethacrylate, monofunctional nonionic monomers, ammonium persulfate and water to obtain a mixed solution.

[0027] 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.

[0028] Furthermore, 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).

[0029] Furthermore, 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).

[0030] Furthermore, the carbon nanotubes have 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.

[0031] Furthermore, 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] Furthermore, the weight ratio of the modified carbon nanotubes, the polytetrafluoroethylene emulsion and the silane coupling agent is 1:(10-13):(0.01-0.03).

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

[0034] Furthermore, 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] Furthermore, the heating polymerization is: heating polymerization at 60-70° C. for 70-80 minutes.

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

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

[0038] 1. The present invention improves the conductivity and tensile strength of electrodialysis membranes by depositing modified carbon nanotubes on the surface of a polytetrafluoroethylene (PTFE) membrane. The modified carbon nanotubes achieve better interfacial bonding with other components in the system, and uniform dispersion of the modified carbon nanotubes is achieved through mechanical stirring and ultrasonic dispersion. Subsequent filtration allows the modified carbon nanotubes and polytetrafluoroethylene (PTFE) particles to be evenly deposited on the PTFE membrane surface. Finally, heat curing allows these components to bond tightly, thereby improving the overall tensile strength of the composite material.

[0039] 2. This invention forms a stable polymer network on the surface of a polytetrafluoroethylene membrane containing modified carbon nanotubes through the polymerization reaction of specific monomers. This network not only enhances the membrane's mechanical properties but also extends its service life. By precisely controlling the monomer ratio and polymerization conditions, the membrane's ion exchange layer is ensured to have high uniformity and stability. This not only improves the membrane's selective permeability but also reduces the risk of membrane failure due to local defects. DETAILED DESCRIPTION

[0040] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

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

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

[0043] Silane coupling agent: tridecafluorooctyltrimethoxysilane.

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

[0045] The preparation method of disodium polyethylene glycol is as follows: 1 mol of polyethylene glycol-400 is dissolved in 15 mol of toluene, 2 mol of sodium metal is added, and the mixture is reacted at 20°C and 80 rpm under inert nitrogen protection for 1 hour to generate polyethylene glycol sodium salt, and the toluene is removed by vacuum rotary evaporation to obtain disodium polyethylene glycol.

[0046] Example 1

[0047] This embodiment provides a method for preparing an anionic electrodialysis membrane, comprising the following steps:

[0048] (1) Modified carbon nanotubes, polytetrafluoroethylene emulsion and silane coupling agent in a weight ratio of 1:12:0.02 were mixed, mechanically stirred at 400 rpm for 1.5 hours, and then ultrasonically dispersed for 25 minutes to obtain a dispersion; the dispersion was placed in a filtration device containing a polytetrafluoroethylene membrane and vacuum filtered for 1.5 hours, and then the polytetrafluoroethylene membrane was turned over and continued to be vacuum filtered in the filtration device containing the polytetrafluoroethylene membrane for 1.5 hours. After both sides of the polytetrafluoroethylene membrane were filtered, it was placed in a blast drying oven at 105°C for heating and curing for 1.4 hours. After the curing was completed, a polytetrafluoroethylene membrane with modified carbon nanotubes deposited on the surface was obtained;

[0049] (2) 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 were mixed, reacted at 25° C. for 3.4 hours, 0.8 parts by weight of 3-chloro-1-propene was added, and the reaction was continued at 25° C. for 5.5 hours. Finally, 1.2 parts by weight of sodium bicarbonate was added, and the reaction was stirred at 25° C. for 1.2 hours. The solvent was removed by rotary evaporation to obtain an anionic monomer;

[0050] The structural formula of the anionic monomer is: Wherein, R is (CH2)6, and the value of n is determined by the raw material polyethylene glycol used to synthesize disodium polyethylene glycol.

[0051] (3) 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 were mixed to obtain a mixed solution;

[0052] (4) The polytetrafluoroethylene membrane with modified carbon nanotubes deposited on its surface was completely immersed in the mixed solution at 25°C for 2.5 hours, and then taken out and placed in an oven at 65°C for heating and polymerization for 75 minutes to obtain an anionic electrodialysis membrane.

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

[0054] S1. Add 1 g of carbon nanotubes to 10 mL of 5 mol / L NaOH solution and disperse by ultrasonication; slowly add 7 mL of 27% H2O2 solution and disperse by ultrasonication while stirring; centrifuge and wash until neutral; and dry to obtain pretreated carbon nanotubes;

[0055] S2, mixing the pretreated carbon nanotubes, anhydrous ethanol, and 3-aminopropyltriethoxysilane in a weight ratio of 1:9:0.12, stirring at 40° C. for 6 h, filtering, and drying to obtain amino-treated carbon nanotubes;

[0056] S3, 1 g of amino-treated carbon nanotubes, 15 mmol of ethylene oxide, and 12 mL of dichloromethane were mixed, reacted at 70°C for 9 h, filtered, and dried to obtain hydroxylated carbon nanotubes;

[0057] (4) 1 g of hydroxylated carbon nanotubes, 15 mmol of polyethylene glycol monomethyl ether, 1.2 mol of N,N'-dicyclohexylcarbodiimide and 12 mL of dichloromethane were mixed, reacted at 30°C for 14 h, filtered and dried to obtain modified carbon nanotubes.

[0058] The carbon nanotubes have 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.

[0059] The anionic monofunctional monomer comprises sodium styrene sulfonate, sodium ethylene sulfonate and sodium 2-methyl-acrylamide-2-methylpropane sulfonate in a weight ratio of 1:1.2:0.7.

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

[0061] Example 2

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

[0063] (1) Modified carbon nanotubes, polytetrafluoroethylene emulsion and silane coupling agent in a weight ratio of 1:13:0.01 were mixed, mechanically stirred at 300 rpm for 1.5 hours, and then ultrasonically dispersed for 30 minutes to obtain a dispersion; the dispersion was placed in a filtration device containing a polytetrafluoroethylene membrane and vacuum filtered for 2 hours, and then the polytetrafluoroethylene membrane was turned over and continued to be vacuum filtered for 2 hours in the filtration device containing the polytetrafluoroethylene membrane. After both sides of the polytetrafluoroethylene membrane were filtered, the dispersion was placed in a blast drying oven at 100°C for heating and curing for 2 hours. After the curing was completed, a polytetrafluoroethylene membrane with modified carbon nanotubes deposited on the surface was obtained;

[0064] (2) 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 were mixed, reacted at 30° C. for 4 h, 0.9 parts by weight of 3-chloro-1-propene was added, reacted at 30° C. for 5 h, and finally 1.3 parts by weight of sodium bicarbonate was added, stirred and reacted at 30° C. for 1 h, and the solvent was removed by rotary evaporation to obtain an anionic monomer;

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

[0066] (4) The polytetrafluoroethylene membrane with modified carbon nanotubes deposited on its surface was completely immersed in the mixed solution at 30°C for 2 hours, and then taken out and placed in an oven at 70°C for heating and polymerization for 70 minutes to obtain an anionic electrodialysis membrane.

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

[0068] S1. Add 1 g of carbon nanotubes to 10 mL of 6 mol / L NaOH solution and disperse by ultrasonication; slowly add 6 mL of 30% H2O2 solution, disperse by ultrasonication and stir; centrifuge and wash until neutral; dry to obtain pretreated carbon nanotubes;

[0069] S2, mixing pretreated carbon nanotubes, anhydrous ethanol and 3-aminopropyl triethoxysilane in a weight ratio of 1:8:0.15, stirring at 50℃ for 5h, filtering, drying to obtain aminated carbon nanotubes;

[0070] S3, mixing 1g of aminated carbon nanotubes, 10mmol of oxirane and 15mL of dichloromethane, reacting at 60℃ for 10h, filtering, drying to obtain hydroxylated carbon nanotubes;

[0071] (4) mixing 1g of hydroxylated carbon nanotubes, 10mmol of polyethylene glycol monomethyl ether, 1.2mmol of N,N'-dicyclohexyl carbodiimide and 15mL of dichloromethane, reacting at 40℃ for 12h, filtering, drying to obtain modified carbon nanotubes.

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

[0073] The anionic monofunctional monomer includes mixing styrene sulfonic acid sodium, ethylene sulfonic acid sodium and 2-methyl-acrylamide-2-methyl propane sulfonic acid sodium in a weight ratio of 1:1.2:0.8.

[0074] The monofunctional nonionic monomer includes mixing hydroxypropyl acrylate, hydroxypropyl methacrylate and N-vinyl pyrrolidone in 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 film does not undergo surface deposition of modified carbon nanotubes.

[0077] A preparation method of an anion electrodialysis membrane, comprising the following steps:

[0078] (1) mixing 4 parts by weight of polyethylene glycol disodium with 0.9 parts by weight of 7-chloroheptanoic acid and 11 parts by weight of N,N-dimethylformamide, reacting at 25℃ for 3.4h, continuously adding 0.8 parts by weight of 3-chloro-1-propene, reacting at 25℃ for 5.5h, finally adding 1.2 parts by weight of sodium bicarbonate, stirring at 25℃ for 1.2h, and removing the solvent by rotary evaporation to obtain an anionic monomer;

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

[0080] (3) The polytetrafluoroethylene membrane was completely immersed in the mixed solution at 25°C for 2.5 hours, and then taken out and placed in an oven at 65°C for heating and polymerization for 75 minutes to obtain an anionic electrodialysis membrane.

[0081] The anionic monofunctional monomer comprises sodium styrene sulfonate, sodium ethylene sulfonate and sodium 2-methyl-acrylamide-2-methylpropane sulfonate in a weight ratio of 1:1.2:0.7.

[0082] The monofunctional nonionic monomer comprises hydroxypropyl acrylate, hydroxypropyl methacrylate and N-vinyl pyrrolidone 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 styrene sulfonate, sodium ethylene sulfonate and sodium 2-methyl-acrylamide-2-methylpropane sulfonate 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-vinyl pyrrolidone in a weight ratio of 1:1:1.

[0089] Performance Testing

[0090] The performance of the anion electrodialysis membranes prepared in Examples 1-2 and Comparative Examples 1-4 was tested.

[0091] 1. Tensile strength test: The CTM2050 automatic mechanical strength tester was used to test the anionic electrodialysis membrane. The anionic electrodialysis membrane was cut into 2×10cm 2 The tensile speed is 2 mm / min, and the test is terminated after the film breaks. The tensile strength of the film is recorded, and the measurement is repeated 3 times to take the average value.

[0092] 2. Surface resistance test: Before the test, the anionic electrodialysis membrane was immersed in 0.5 mol / L NaCl solution for 24 hours; then cut into 1×1 cm 2Insert the Ag / AgCl electrodes into the electrolyte close to the membrane on either side and connect them to the working and reference electrodes of the electrochemical workstation. Perform the AC impedance test. Set the end frequency to 1 Hz and the AC amplitude to 10 mV. Then, circulate a 0.5 mol / L NaCl solution through the electrolytic cells on both sides.

[0093] 3. Test of ion selective permeability: Cut the anionic electrodialysis membrane into 1×1cm 2 A small piece of Ag / AgCl was soaked in a 0.15 mol / L KCl solution for 12 hours. The piece was then placed in an electrolytic cell and secured. The tip of the Ag / AgCl electrode was placed close to the membrane, but not touching the membrane surface. A peristaltic pump was then used to circulate 0.1 mol / L and 0.2 mol / L KCl solutions through the electrolytic cell, respectively. The specific method is described in Chinese patent CN202410287433.3. The system was operated continuously, and the number of days with an ion selectivity of ≥95% was counted.

[0094] Table 1 Performance test results

[0095]

[0096] From the above performance test results, it can be seen that the anion electrodialysis membranes of Examples 1-2 have excellent comprehensive performance and good durability, especially the comprehensive performance of Example 1 is the most outstanding.

[0097] However, the comparative examples, because they did not adopt the necessary technical solutions, were significantly inferior to the embodiments in the corresponding performance tests. 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 anionic monofunctional monomers was different, and in comparative example 4, the ratio of monofunctional nonionic monomers was different, and the durability of the anionic electrodialysis membrane decreased. The above experimental results further demonstrate the importance of the technical solutions defined in the present invention for its technical effects.

[0098] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection 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 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) 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; 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); (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 and treating them in sequence to obtain pretreated carbon nanotubes; The carbon nanotubes have 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; S2, mixing carbon nanotubes and 3-aminopropyltriethoxysilane in a solvent, stirring to react, and then drying to obtain amino-modified carbon nanotubes; S3, mixing the amino-treated carbon nanotubes, ethylene oxide and dichloromethane, reacting, and drying to obtain hydroxylated carbon nanotubes; S4. The hydroxylated carbon nanotubes, polyethylene glycol monomethyl ether, N,N'-dicyclohexylcarbodiimide and dichloromethane are mixed, reacted and dried to obtain modified carbon nanotubes.

2. The method for preparing an anionic electrodialysis membrane according to claim 1, wherein: The method for preparing the modified carbon nanotubes in step (1) comprises the following steps: S1. Add 1g of carbon nanotubes to 10mL of 4-6mol / L NaOH solution and disperse by ultrasonication; slowly add 6-8mL of 25-30% H2O2 solution, disperse by ultrasonication and stir; centrifuge and wash until neutral; 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-treated carbon nanotubes; S3, 1 g of amino-treated carbon nanotubes, 10-20 mmol of ethylene oxide, and 10-15 mL of dichloromethane were 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, wherein The step (1) comprises mixing 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 filtering both sides of the polytetrafluoroethylene membrane, heating and curing are completed. After curing, a polytetrafluoroethylene membrane with modified carbon nanotubes deposited on the surface is obtained; The step (2) comprises mixing 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, reacting at 20-30° C. for 3-4 hours, continuously adding 0.7-0.9 parts by weight of 3-chloro-1-propylene, reacting at 20-30° C. for 5-6 hours, and finally adding 1.1-1.3 parts by weight of sodium bicarbonate, stirring and reacting at 20-30° C. for 1-1.5 hours, and removing N,N-dimethylformamide by rotary evaporation to obtain an anionic monomer; The step (3) comprises uniformly 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 2, wherein The weight ratio of the modified carbon nanotube, polytetrafluoroethylene emulsion and silane coupling agent is 1: (10-13): (0.01-0.03).

5. The method for preparing anionic electrodialysis membrane according to claim 1, wherein The silane coupling agent is tridecafluorooctyltrimethoxysilane.

6. The method for preparing anionic electrodialysis membrane according to claim 1, wherein 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.

7. The method for preparing anionic electrodialysis membrane according to claim 1, wherein The heating polymerization is as follows: placing the mixture at 60-70° C. and performing heating polymerization for 70-80 minutes.

8. An anionic electrodialysis membrane prepared by the preparation method according to any one of claims 1 to 7.

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