Electrodialysis membrane with high separation benefit

Abstract

The invention provides an electrodialysis membrane with high separation benefit. The electrodialysis membrane is prepared from the following raw materials: a polyethersulfone microporous membrane, a dipping mixed solution I and a dipping mixed solution II, wherein the dipping mixed solution I is prepared from the following components in parts by weight: 300 to 320 parts of 2-acrylamide-2-methylpropanesulfonic acid, 220 to 260 parts of N-methyl pyrrolidone, 60 to 70 parts of triethylamine, 30 to 40 parts of divinyl benzene, 10 to 20 parts of methyl methacrylate and 2 to 3 parts of azodiisobutyronitrile; the dipping mixed solution II is prepared from the following components in parts by weight: 10 to 12 parts of sodium dodecyl benzene sulfonate, 6 to 8 parts of acid modified montmorillonite and 500 to 600 parts of ethanol. According to the electrodialysis membrane with the high separation benefit, the unique material is adopted, ions in a solution can be efficiently separated under the action of an electric field, and the higher separation benefit is achieved by optimizing the pore size distribution and the surface property of the membrane material; meanwhile, the electrodialysis membrane also has good durability.

Description

Technical Field

[0001] The present invention relates to the technical field of membrane separation, and particularly relates to an electrodialysis membrane with high separation efficiency. Background Art

[0002] In the fields of modern industrial production and environmental protection water treatment, membrane separation technology has received wide attention due to its characteristics of high efficiency, energy conservation, and environmental protection. Among them, as an important membrane separation technology, electrodialysis technology plays an important role in the fields of water treatment, seawater desalination, chemical separation, etc. by virtue of its unique separation mechanism and broad application prospects.

[0003] Electrodialysis is a technology for separating solutions by utilizing the selective permeability of semi-permeable membranes and the principle of ion migration under the action of an electric field. Under the action of an electric field, anions and cations in the solution migrate to the positive and negative electrodes respectively, and enter the adjacent small chambers through their corresponding ion exchange membranes, thereby realizing the separation and concentration of ions in the solution. Based on this, the present invention provides an electrodialysis membrane with high separation efficiency. Summary of the Invention

[0004] The purpose of the present invention is to provide an electrodialysis membrane with high separation efficiency, aiming to improve the cation selective permeability and durability in the electrodialysis process.

[0005] The present invention provides an electrodialysis membrane with high separation efficiency, and the electrodialysis membrane is obtained through the following treatment method. The treatment method includes the following steps: immersing the polyethersulfone microporous membrane in immersion mixture one and immersion mixture two in sequence;

[0006] Among them, the immersion mixture one is composed of 300-320 parts of 2-acrylamido-2-methylpropanesulfonic acid, 220-260 parts of N-methylpyrrolidone, 60-70 parts of triethylamine, 30-40 parts of divinylbenzene, 10-20 parts of methyl methacrylate, and 2-3 parts of azobisisobutyronitrile by weight;

[0007] The immersion mixture two is composed of 10-12 parts of sodium dodecylbenzenesulfonate, 6-8 parts of acid-modified montmorillonite, and 500-600 parts of ethanol by weight.

[0008] Further, the pore size of the polyethersulfone microporous membrane is 0.5-0.6 μm, the porosity is 55-65%, and the thickness is 0.14-0.18 mm.

[0009] Further, the preparation method of the acid-modified montmorillonite includes: soaking montmorillonite in a sulfuric acid aqueous solution with a temperature of 50-60 °C and a mass fraction of 15-25% for 20-24 h, then rinsing with deionized water until neutral, and drying at a temperature of 55-65 °C for 23-25 h to obtain it.

[0010] Further, the preparation method of the electrodialysis membrane includes: soaking the polyethersulfone microporous membrane in the first impregnation mixture for the first soaking, and then placing it in the second impregnation mixture at room temperature for the second soaking; after the soaking is completed, it is placed between two polyethylene terephthalate films, and the bubbles between the polyethersulfone microporous membrane and the polyethylene terephthalate films are removed, so that the substrate and the two films form a composite membrane. After the composite membrane is dried, the two films are peeled off to obtain the electrodialysis membrane.

[0011] Further, the preparation method of the first impregnation mixture includes: mixing 2-acrylamido-2-methylpropanesulfonic acid, N-methylpyrrolidone, triethylamine, divinylbenzene, methyl methacrylate and azobisisobutyronitrile, and stirring at a rotation speed of 200-300 rpm for 60-80 min to prepare the first impregnation mixture.

[0012] Further, the preparation method of the second impregnation mixture includes: mixing sodium dodecylbenzenesulfonate, acid-modified montmorillonite and ethanol, and stirring at a rotation speed of 200-300 rpm for 40-60 min to prepare the second impregnation mixture.

[0013] Further, the first soaking time is 10-20 min, and the soaking temperature is 60-80 °C.

[0014] Further, the second soaking time is 40-60 min.

[0015] Further, the drying method is to place it in an oven at 60-80 °C for 8-10 h.

[0016] The beneficial effects of the present invention are as follows:

[0017] An electrodialysis membrane with high separation efficiency proposed by the present invention. This electrodialysis membrane uses unique materials and can efficiently separate ions in a solution under the action of an electric field. Through the selection of the polyethersulfone microporous membrane material and the introduction of the cross-linking reaction occurring in the first impregnation step, a dense cation exchange layer and a stable membrane structure are formed on the surface of the polyethersulfone microporous membrane. This structure can resist mechanical stress and chemical corrosion during long-term use, and extend the service life of the membrane.

[0018] And through the first soaking step, the polymer membrane enters the inner wall of the support membrane pores, and the coating forms a dense surface layer, which adjusts the surface properties of the material and improves the ion transport efficiency in the membrane, thus achieving higher separation efficiency; at the same time, this electrodialysis membrane also has good durability, can maintain stable separation performance during long-term use, extends the service life of the membrane, and reduces the use cost.

[0019] In the present invention, the polyethersulfone microporous membrane has a pore size of 0.5 - 0.6 μm, a porosity of 55 - 65%, and a thickness of 0.14 - 0.18 mm. The initial macropores facilitate the penetration of the impregnating solution, and subsequently, the effective pore size is reduced through coating to achieve ion sieving, which helps optimize the ion transport channels, reduce the diffusion resistance of ions in the membrane, and thus improve the ion migration rate and separation efficiency. Appropriate pore size and porosity can also ensure that the membrane has sufficient mechanical strength and stability to withstand the pressure and electric field effects during the electrodialysis process.

[0020] In the impregnating mixture I of the present invention, the components of 2 - acrylamido - 2 - methylpropanesulfonic acid, N - methylpyrrolidone, and triethylamine have excellent ion exchange and conduction properties. The sulfonic acid group in 2 - acrylamido - 2 - methylpropanesulfonic acid is a strong acidic ion exchange group, which can dissociate H+ in water to form a negatively charged sulfonate group (-SO 3- ). These negatively charged groups selectively adsorb cations through electrostatic interaction to achieve selective transport. The sulfonic acid groups are distributed along the inner wall of the channel to form a negatively charged surface, and selectively adsorb cations through the Donnan exclusion effect, which can form an effective ion transport channel in the membrane; divinylbenzene and methyl methacrylate, as cross - linking agent and monomer, can enhance the structural stability and chemical stability of the membrane, preventing the membrane from deforming or degrading during long - term use; azobisisobutyronitrile, as an initiator, can initiate the polymerization reaction of monomers to form a dense ion - exchange layer, further improving the selective separation ability of ions.

[0021] During the acid modification of montmorillonite in the present invention, the dissolution of some metal cations not only expands the layer spacing but also increases the specific surface area of montmorillonite; a larger specific surface area means more ion - exchange sites, which helps improve the ion separation efficiency and capacity. And in the present invention, using sulfuric acid to acid - modify montmorillonite has higher ion separation efficiency and durability compared to hydrochloric acid and sodium hydroxide. This benefits from the expansion of the montmorillonite layer spacing, the increase in specific surface area, and the improvement of chemical and structural stability after sulfuric acid modification. These changes enable montmorillonite to more effectively adsorb and separate cations during the electrodialysis process while maintaining the stability and durability of its performance.

[0022] Furthermore, the hydrogen ions in sulfuric acid exchange ions with the metal cations (such as K + , Na + , Ca 2+ , Mg 2+ ) between the montmorillonite layers. Since H +has a smaller radius than the replaced ions, which can cause the interlayer lattice of montmorillonite to crack and the interlayer spacing to expand. This structural change allows more ions to enter and pass through the interlayer of montmorillonite, thus improving the ion separation efficiency. In contrast, although hydrochloric acid can also perform ion exchange, the presence of chloride ions and their potential impact on the interlayer structure may result in a less effective expansion of the interlayer spacing compared to sulfuric acid. As a base, sodium hydroxide reacts with the cations in the interlayer of montmorillonite to form precipitates, which is not conducive to the expansion of the interlayer spacing and the transport of ions. From the perspective of chemical stability, the interlayer structure and surface properties of montmorillonite modified by sulfuric acid have changed significantly, which helps to improve its chemical stability; during the electrodialysis process, montmorillonite can resist the erosion of chemicals such as acids, bases, and salts, thus maintaining the stability of its ion separation performance. In contrast, hydrochloric acid modification may cause chloride ions to remain in montmorillonite, affecting its chemical stability. And sodium hydroxide modification may damage the interlayer structure of montmorillonite, reducing its durability. - The reaction of OH ions with the cations in the interlayer of montmorillonite will form precipitates, which is not conducive to the expansion of the interlayer spacing and the transport of ions. From the perspective of chemical stability, the interlayer structure and surface properties of montmorillonite modified by sulfuric acid have changed significantly, which helps to improve its chemical stability; during the electrodialysis process, montmorillonite can resist the erosion of chemicals such as acids, bases, and salts, thus maintaining the stability of its ion separation performance. In contrast, hydrochloric acid modification may cause chloride ions to remain in montmorillonite, affecting its chemical stability. And sodium hydroxide modification may damage the interlayer structure of montmorillonite, reducing its durability.

[0023] Sodium dodecylbenzenesulfonate in the impregnation mixture II of the present invention, as a surfactant, can improve the hydrophilicity and wettability of the membrane surface, which helps the uniform distribution and transport of ions; it makes the membrane more likely to combine with water molecules to form a stable hydration layer, which helps to reduce the cracking phenomenon of the membrane during use and improve the durability of the membrane. Acid-modified montmorillonite has a layered structure and a large specific surface area, which can adsorb and fix more ions, thus improving the ion separation efficiency. At the same time, acid modification can also improve the compatibility between montmorillonite and the membrane substrate, enhancing the durability of the membrane.

[0024] Sodium dodecylbenzenesulfonate used in the present invention is a commonly used anionic surfactant with excellent ion exchange and transport properties. Its hydrophobic group is dodecylphenyl and its hydrophilic group is sulfonic acid group. This structure enables it to form effective ion transport channels within the membrane. The long branched-chain structure will cause the sulfonic acid groups to be wrapped inside the molecule, reducing their exposure degree, decreasing the effective ion exchange sites, and the branched chains hinder the diffusion path of ions within the membrane, prolonging the migration distance and reducing the ion flux. Therefore, the ion exchange and transport properties of sodium dibutylnaphthalenesulfonate are affected by its molecular chain length and branched-chain structure. Sodium diisooctyl sulfosuccinate is mainly used as a wetting agent, emulsifier, and surface tension improver, and its ion exchange performance may be relatively weak, relying more on its wetting and emulsifying effects to improve the membrane performance. In addition, there may be a good synergistic effect between sodium dodecylbenzenesulfonate and montmorillonite, and it can improve the dispersibility and compatibility of montmorillonite in the membrane, thus enhancing the overall performance of the membrane. At the same time, the layered structure of montmorillonite also provides more ion exchange sites for sodium dodecylbenzenesulfonate, which helps to improve the ion separation efficiency. Detailed implementation methods

[0025] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the protection scope of the present invention. It should be noted that the montmorillonite model is K-10, and the CAS number is 1318-93-0; the kaolin model is SAP-200, and the CAS number is 1318-74-7; the attapulgite CAS number is 1337-76-4, purchased from Nanjing Bermuda Biotechnology Co., Ltd.; other raw materials not specified can also be obtained commercially.

[0026] Example 1

[0027] This example provides an electrodialysis membrane with high separation efficiency. The electrodialysis membrane is obtained through the following treatment method, and the treatment method includes the following steps: soaking the polyethersulfone microporous membrane in the first impregnation mixture and the second impregnation mixture in sequence; the pore diameter of the polyethersulfone microporous membrane is 0.55 μm, the porosity is 60%, and the thickness is 0.16 mm.

[0028] Among them, the first impregnation mixture is composed of 310 parts of 2-acrylamido-2-methylpropanesulfonic acid, 240 parts of N-methylpyrrolidone, 65 parts of triethylamine, 35 parts of divinylbenzene, 15 parts of methyl methacrylate, and 2.5 parts of azobisisobutyronitrile by weight.

[0029] The second impregnation mixture is composed of 11 parts of sodium dodecylbenzenesulfonate, 7 parts of acid-modified montmorillonite, and 550 parts of ethanol by weight.

[0030] Among them, the preparation method of the acid-modified montmorillonite includes: soaking the montmorillonite in a sulfuric acid aqueous solution with a temperature of 55 °C and a mass fraction of 20% for 22 h, then rinsing with deionized water until neutral, and drying at a temperature of 60 °C for 24 h to obtain it.

[0031] The preparation method of the electrodialysis membrane in this example includes:

[0032] The preparation method of impregnation mixture I includes: mixing 2-acrylamido-2-methylpropanesulfonic acid, N-methylpyrrolidone, triethylamine, divinylbenzene, methyl methacrylate and azobisisobutyronitrile, and stirring at a temperature of 70 °C and a rotation speed of 250 rpm for 70 min to obtain impregnation mixture I; the preparation method of impregnation mixture II includes: mixing sodium dodecylbenzenesulfonate, acid-modified montmorillonite and ethanol and stirring at a rotation speed of 250 rpm for 50 min to obtain impregnation mixture II; soaking the polyethersulfone microporous membrane in impregnation mixture I for the first soaking, with the first soaking time being 15 min, and then placing it in impregnation mixture II at room temperature for the second soaking, with the second soaking time being 50 min; after the soaking is completed, place it between two polyethylene terephthalate films, and remove the bubbles between the polyethersulfone microporous membrane and the polyethylene terephthalate films, so that the substrate and the two films form a composite membrane. After drying the composite membrane, peel off the two films to obtain the product.

[0033] Example 2

[0034] This example provides an electrodialysis membrane with high separation efficiency. The electrodialysis membrane is obtained through the following treatment method, and the treatment method includes the following steps: soaking the polyethersulfone microporous membrane in impregnation mixture I and impregnation mixture II in sequence; the pore diameter of the polyethersulfone microporous membrane is 0.55 μm, the porosity is 60%, and the thickness is 0.16 mm;

[0035] Among them, the impregnation mixture I is composed of 300 parts of 2-acrylamido-2-methylpropanesulfonic acid, 230 parts of N-methylpyrrolidone, 65 parts of triethylamine, 35 parts of divinylbenzene, 16 parts of methyl methacrylate and 2.5 parts of azobisisobutyronitrile by weight;

[0036] The impregnation mixture II is composed of 11 parts of sodium dodecylbenzenesulfonate, 7 parts of acid-modified montmorillonite and 500 parts of ethanol by weight.

[0037] Among them, the preparation method of the acid-modified montmorillonite includes: soaking montmorillonite in a sulfuric acid aqueous solution with a temperature of 50 °C and a mass fraction of 20% for 20 h, then rinsing with deionized water until neutral, and drying at a temperature of 55 °C for 23 h to obtain it;

[0038] The preparation method of the electrodialysis membrane in this example includes:

[0039] The preparation method of impregnation mixture one includes: mixing 2-acrylamide-2-methylpropanesulfonic acid, N-methylpyrrolidone, triethylamine, divinylbenzene, methyl methacrylate and azobisisobutyronitrile, and stirring at a temperature of 70 °C and a rotation speed of 250 rpm for 60 min to obtain impregnation mixture one; the preparation method of impregnation mixture two includes: mixing sodium dodecylbenzenesulfonate, acid-modified montmorillonite and ethanol and stirring at a rotation speed of 200 rpm for 40 min to obtain impregnation mixture two; soaking the polyethersulfone microporous membrane in impregnation mixture one for the first soaking, with the first soaking time being 10 min, and then placing it in impregnation mixture two at room temperature for the second soaking, with the second soaking time being 40 min; after the soaking is completed, place it between two polyethylene terephthalate films, and remove the bubbles between the polyethersulfone microporous membrane and the polyethylene terephthalate films, so that the substrate and the two films form a composite membrane, and after drying the composite membrane, peel off the two films to obtain it.

[0040] Example 3

[0041] This example provides an electrodialysis membrane with high separation efficiency. The electrodialysis membrane is obtained through the following treatment method. The treatment method includes the following steps: soaking the polyethersulfone microporous membrane in impregnation mixture one and impregnation mixture two in sequence; the pore diameter of the polyethersulfone microporous membrane is 0.5 μm, the porosity is 55%, and the thickness is 0.14 mm.

[0042] Among them, the impregnation mixture one is composed of 300 parts of 2-acrylamide-2-methylpropanesulfonic acid, 220 parts of N-methylpyrrolidone, 60 parts of triethylamine, 30 parts of divinylbenzene, 10 parts of methyl methacrylate and 2 parts of azobisisobutyronitrile by weight.

[0043] The impregnation mixture two is composed of 10 parts of sodium dodecylbenzenesulfonate, 6 parts of acid-modified montmorillonite and 500 parts of ethanol by weight.

[0044] Among them, the preparation method of the acid-modified montmorillonite includes: soaking montmorillonite in a sulfuric acid aqueous solution with a temperature of 50 °C and a mass fraction of 15% for 20 h, then rinsing with deionized water until neutral, and drying at a temperature of 55 °C for 23 h to obtain it.

[0045] The preparation method of the electrodialysis membrane in this example includes:

[0046] The preparation method of impregnation mixture one includes: mixing 2-acrylamido-2-methylpropanesulfonic acid, N-methylpyrrolidone, triethylamine, divinylbenzene, methyl methacrylate and azobisisobutyronitrile, and stirring at a temperature of 70°C and a rotation speed of 200 rpm for 60 min to obtain impregnation mixture one; the preparation method of impregnation mixture two includes: mixing sodium dodecylbenzenesulfonate, acid-modified montmorillonite and ethanol and stirring at a rotation speed of 200 rpm for 40 min to obtain impregnation mixture two; soaking the polyethersulfone microporous membrane in impregnation mixture one for the first soaking, with the first soaking time being 10 min, and then placing it in impregnation mixture two at room temperature for the second soaking, with the second soaking time being 40 min; after the soaking is completed, place it between two polyethylene terephthalate films, and remove the bubbles between the polyethersulfone microporous membrane and the polyethylene terephthalate films to form a composite membrane between the substrate and the two films. After drying the composite membrane, peel off the two films to obtain it.

[0047] Example 4

[0048] This example provides an electrodialysis membrane with high separation efficiency. The raw materials include a polyethersulfone microporous membrane, impregnation mixture one, and impregnation mixture two; the pore size of the polyethersulfone microporous membrane is 0.6 μm, the porosity is 65%, and the thickness is 0.18 mm.

[0049] Among them, the impregnation mixture one is composed of 320 parts of 2-acrylamido-2-methylpropanesulfonic acid, 260 parts of N-methylpyrrolidone, 70 parts of triethylamine, 40 parts of divinylbenzene, 20 parts of methyl methacrylate, and 3 parts of azobisisobutyronitrile by weight.

[0050] The impregnation mixture two is composed of 12 parts of sodium dodecylbenzenesulfonate, 8 parts of acid-modified montmorillonite, and 600 parts of ethanol by weight.

[0051] Among them, the preparation method of the acid-modified montmorillonite includes: soaking montmorillonite in a sulfuric acid aqueous solution with a temperature of 60°C and a mass fraction of 25% for 24 h, then rinsing with deionized water until neutral, and drying at a temperature of 65°C for 25 h to obtain it.

[0052] The preparation method of the electrodialysis membrane in this example includes:

[0053] The preparation method of impregnation mixture I includes: mixing 2-acrylamido-2-methylpropanesulfonic acid, N-methylpyrrolidone, triethylamine, divinylbenzene, methyl methacrylate and azobisisobutyronitrile, and stirring at a temperature of 70°C and a rotation speed of 300 rpm for 80 min to obtain impregnation mixture I; the preparation method of impregnation mixture II includes: mixing sodium dodecylbenzenesulfonate, acid-modified montmorillonite and ethanol and stirring at a rotation speed of 300 rpm for 60 min to obtain impregnation mixture II; soaking the polyethersulfone microporous membrane in impregnation mixture I for the first soaking, with the first soaking time being 20 min, and then placing it in impregnation mixture II at room temperature for the second soaking, with the second soaking time being 60 min; after the soaking is completed, place it between two polyethylene terephthalate films, and remove the bubbles between the polyethersulfone microporous membrane and the polyethylene terephthalate films to form a composite membrane between the substrate and the two films. After drying the composite membrane, peel off the two films to obtain the product.

[0054] Comparative Example 1

[0055] This comparative example provides an electrodialysis membrane with high separation efficiency. The electrodialysis membrane is obtained through the following treatment method. The treatment method includes the following steps: soaking the polyethersulfone microporous membrane in impregnation mixture I and impregnation mixture II in sequence; the pore size of the polyethersulfone microporous membrane is 0.55 μm, the porosity is 60%, and the thickness is 0.16 mm.

[0056] Among them, the impregnation mixture I is composed of 310 parts of 2-acrylamido-2-methylpropanesulfonic acid, 240 parts of N-methylpyrrolidone, 65 parts of triethylamine, 35 parts of divinylbenzene, 15 parts of methyl methacrylate and 2.5 parts of azobisisobutyronitrile by weight.

[0057] The impregnation mixture II is composed of 11 parts of sodium dodecylbenzenesulfonate, 7 parts of acid-modified montmorillonite and 550 parts of ethanol by weight.

[0058] Among them, the preparation method of the acid-modified montmorillonite includes: soaking montmorillonite in a hydrochloric acid aqueous solution with a temperature of 55°C and a mass fraction of 20% for 22 h, then rinsing with deionized water until neutral, and drying at a temperature of 60°C for 24 h to obtain it.

[0059] The preparation method of the electrodialysis membrane in this comparative example includes:

[0060] The preparation method of impregnation mixture I includes: mixing 2-acrylamido-2-methylpropanesulfonic acid, N-methylpyrrolidone, triethylamine, divinylbenzene, methyl methacrylate and azobisisobutyronitrile, and stirring at a temperature of 70 °C and a rotation speed of 250 rpm for 70 min to obtain impregnation mixture I; the preparation method of impregnation mixture II includes: mixing sodium dodecylbenzenesulfonate, acid-modified montmorillonite and ethanol and stirring at a rotation speed of 250 rpm for 50 min to obtain impregnation mixture II; soaking the polyethersulfone microporous membrane in impregnation mixture I for the first soaking, with the first soaking time being 15 min, and then placing it in impregnation mixture II at room temperature for the second soaking, with the second soaking time being 50 min; after the soaking is completed, place it between two polyethylene terephthalate films, and remove the bubbles between the polyethersulfone microporous membrane and the polyethylene terephthalate films to form a composite membrane between the substrate and the two films. After drying the composite membrane, peel off the two films to obtain the product.

[0061] Comparative Example 2

[0062] This comparative example provides an electrodialysis membrane with high separation efficiency. The electrodialysis membrane is obtained through the following treatment method, and the treatment method includes the following steps: soaking the polyethersulfone microporous membrane in impregnation mixture I and impregnation mixture II in sequence; the pore diameter of the polyethersulfone microporous membrane is 0.55 μm, the porosity is 60%, and the thickness is 0.16 mm.

[0063] Among them, the impregnation mixture I is composed of 310 parts of 2-acrylamido-2-methylpropanesulfonic acid, 240 parts of N-methylpyrrolidone, 65 parts of triethylamine, 35 parts of divinylbenzene, 15 parts of methyl methacrylate and 2.5 parts of azobisisobutyronitrile by weight.

[0064] The impregnation mixture II is composed of 11 parts of sodium dodecylbenzenesulfonate, 7 parts of acid-modified montmorillonite and 550 parts of ethanol by weight.

[0065] Among them, the preparation method of the acid-modified montmorillonite includes: soaking montmorillonite in an aqueous sodium hydroxide solution with a temperature of 55 °C and a mass fraction of 20% for 22 h, then rinsing with deionized water until neutral, and drying at a temperature of 60 °C for 24 h to obtain it.

[0066] The preparation method of the electrodialysis membrane in this comparative example includes:

[0067] The preparation method of impregnation mixture I includes: mixing 2-acrylamido-2-methylpropanesulfonic acid, N-methylpyrrolidone, triethylamine, divinylbenzene, methyl methacrylate and azobisisobutyronitrile, and stirring at a temperature of 70 °C and a rotation speed of 250 rpm for 70 min to obtain impregnation mixture I; the preparation method of impregnation mixture II includes: mixing sodium dodecylbenzenesulfonate, acid-modified montmorillonite and ethanol and stirring at a rotation speed of 250 rpm for 50 min to obtain impregnation mixture II; soaking the polyethersulfone microporous membrane in impregnation mixture I for the first soaking, with the first soaking time being 15 min, and then placing it in impregnation mixture II at room temperature for the second soaking, with the second soaking time being 50 min; after the soaking is completed, place it between two polyethylene terephthalate films, and remove the bubbles between the polyethersulfone microporous membrane and the polyethylene terephthalate films, so that the substrate and the two films form a composite membrane. After drying the composite membrane, peel off the two films to obtain the product.

[0068] Comparative Example 3

[0069] This comparative example provides an electrodialysis membrane with high separation efficiency. The electrodialysis membrane is obtained through the following treatment method. The treatment method includes the following steps: soaking the polyethersulfone microporous membrane in impregnation mixture I and impregnation mixture II in sequence; the pore size of the polyethersulfone microporous membrane is 0.55 μm, the porosity is 60%, and the thickness is 0.16 mm;

[0070] Among them, the impregnation mixture I is composed of 310 parts of 2-acrylamido-2-methylpropanesulfonic acid, 240 parts of N-methylpyrrolidone, 65 parts of triethylamine, 35 parts of divinylbenzene, 15 parts of methyl methacrylate and 2.5 parts of azobisisobutyronitrile by weight;

[0071] The impregnation mixture II is composed of 11 parts of sodium dibutylnaphthalenesulfonate, 7 parts of acid-modified montmorillonite and 550 parts of ethanol by weight.

[0072] Among them, the preparation method of the acid-modified montmorillonite includes: soaking montmorillonite in a sulfuric acid aqueous solution with a temperature of 55 °C and a mass fraction of 20% for 22 h, then rinsing with deionized water until neutral, and drying at a temperature of 60 °C for 24 h to obtain it;

[0073] The preparation method of the electrodialysis membrane in this comparative example includes:

[0074] The preparation method of impregnation mixture I includes: mixing 2-acrylamide-2-methylpropanesulfonic acid, N-methylpyrrolidone, triethylamine, divinylbenzene, methyl methacrylate and azobisisobutyronitrile, and stirring at a temperature of 70°C and a rotation speed of 250 rpm for 70 min to obtain impregnation mixture I; the preparation method of impregnation mixture II includes: mixing sodium dibutylnaphthalenesulfonate, acid-modified montmorillonite and ethanol and stirring at a rotation speed of 250 rpm for 50 min to obtain impregnation mixture II; soaking the polyethersulfone microporous membrane in impregnation mixture I for the first soaking, with the first soaking time being 15 min, and then placing it in impregnation mixture II at room temperature for the second soaking, with the second soaking time being 50 min; after soaking, place it between two polyethylene terephthalate films, and remove the bubbles between the polyethersulfone microporous membrane and the polyethylene terephthalate films, so that the substrate and the two films form a composite membrane. After drying the composite membrane, peel off the two films to obtain the product.

[0075] Comparative Example 4

[0076] This comparative example provides an electrodialysis membrane with high separation efficiency. The electrodialysis membrane is obtained through the following treatment method. The treatment method includes the following steps: soaking the polyethersulfone microporous membrane in impregnation mixture I and impregnation mixture II in sequence; the pore diameter of the polyethersulfone microporous membrane is 0.55 μm, the porosity is 60%, and the thickness is 0.16 mm.

[0077] Among them, the impregnation mixture I is composed of 310 parts of 2-acrylamide-2-methylpropanesulfonic acid, 240 parts of N-methylpyrrolidone, 65 parts of triethylamine, 35 parts of divinylbenzene, 15 parts of methyl methacrylate and 2.5 parts of azobisisobutyronitrile by weight.

[0078] The impregnation mixture II is composed of 11 parts of sodium diisooctyl sulfosuccinate, 7 parts of acid-modified montmorillonite and 550 parts of ethanol by weight.

[0079] Among them, the preparation method of the acid-modified montmorillonite includes: soaking montmorillonite in a sulfuric acid aqueous solution with a temperature of 55°C and a mass fraction of 20% for 22 h, then rinsing with deionized water until neutral, and drying at a temperature of 60°C for 24 h to obtain it.

[0080] The preparation method of the electrodialysis membrane in this comparative example includes:

[0081] The preparation method of impregnation mixture I includes: mixing 2-acrylamido-2-methylpropanesulfonic acid, N-methylpyrrolidone, triethylamine, divinylbenzene, methyl methacrylate and azobisisobutyronitrile, and stirring at a temperature of 70°C and a rotation speed of 250 rpm for 70 min to obtain impregnation mixture I; the preparation method of impregnation mixture II includes: mixing sodium diisooctyl sulfosuccinate, acid-modified montmorillonite and ethanol and stirring at a rotation speed of 250 rpm for 50 min to obtain impregnation mixture II; soaking the polyethersulfone microporous membrane in impregnation mixture I for the first soaking, with the first soaking time being 15 min, and then placing it in impregnation mixture II at room temperature for the second soaking, with the second soaking time being 50 min; after the soaking is completed, place it between two polyethylene terephthalate films, and remove the bubbles between the polyethersulfone microporous membrane and the polyethylene terephthalate films to form a composite membrane between the substrate and the two films. After drying the composite membrane, peel off the two films to obtain the product.

[0082] Comparative Example 5

[0083] This comparative example provides an electrodialysis membrane with high separation efficiency. The electrodialysis membrane is obtained through the following treatment method. The treatment method includes the following steps: soaking the polyethersulfone microporous membrane in impregnation mixture I and impregnation mixture II in sequence; the pore diameter of the polyethersulfone microporous membrane is 0.55 μm, the porosity is 60%, and the thickness is 0.16 mm;

[0084] Among them, the impregnation mixture I is composed of 310 parts of 2-acrylamido-2-methylpropanesulfonic acid, 240 parts of N-methylpyrrolidone, 65 parts of triethylamine, 35 parts of divinylbenzene, 15 parts of methyl methacrylate and 2.5 parts of azobisisobutyronitrile by weight;

[0085] The impregnation mixture II is composed of 11 parts of sodium dodecylbenzenesulfonate, 7 parts of acid-modified kaolin, and 550 parts of ethanol by weight.

[0086] Among them, the preparation method of the acid-modified kaolin includes: soaking kaolin in a sulfuric acid aqueous solution with a temperature of 55°C and a mass fraction of 20% for 22 h, then rinsing with deionized water until neutral, and drying at a temperature of 60°C for 24 h to obtain it;

[0087] The preparation method of the electrodialysis membrane in this comparative example includes:

[0088] The preparation method of impregnation mixture I includes: mixing 2-acrylamide-2-methylpropanesulfonic acid, N-methylpyrrolidone, triethylamine, divinylbenzene, methyl methacrylate and azobisisobutyronitrile, and stirring at a temperature of 70 °C and a rotation speed of 250 rpm for 70 min to obtain impregnation mixture I; the preparation method of impregnation mixture II includes: mixing sodium dodecylbenzenesulfonate, acid-modified kaolin and ethanol and stirring at a rotation speed of 250 rpm for 50 min to obtain impregnation mixture II; soaking the polyethersulfone microporous membrane in impregnation mixture I for the first soaking, with the first soaking time being 15 min, and then placing it in impregnation mixture II at room temperature for the second soaking, with the second soaking time being 50 min; after soaking, place it between two polyethylene terephthalate films, and remove the bubbles between the polyethersulfone microporous membrane and the polyethylene terephthalate films, so that the substrate and the two films form a composite membrane, and after drying the composite membrane, peel off the two films to obtain it.

[0089] Comparative Example 6

[0090] This comparative example provides an electrodialysis membrane with high separation efficiency. The electrodialysis membrane is obtained through the following treatment method. The treatment method includes the following steps: soaking the polyethersulfone microporous membrane in impregnation mixture I and impregnation mixture II in sequence; the pore diameter of the polyethersulfone microporous membrane is 0.55 μm, the porosity is 60%, and the thickness is 0.16 mm.

[0091] Among them, the impregnation mixture I is composed of 310 parts of 2-acrylamide-2-methylpropanesulfonic acid, 240 parts of N-methylpyrrolidone, 65 parts of triethylamine, 35 parts of divinylbenzene, 15 parts of methyl methacrylate and 2.5 parts of azobisisobutyronitrile by weight.

[0092] The impregnation mixture II is composed of 11 parts of sodium dodecylbenzenesulfonate, 7 parts of acid-modified attapulgite and 550 parts of ethanol by weight.

[0093] Among them, the preparation method of the acid-modified attapulgite includes: soaking attapulgite in a sulfuric acid aqueous solution with a temperature of 55 °C and a mass fraction of 20% for 22 h, then rinsing with deionized water until neutral, and drying at a temperature of 60 °C for 24 h to obtain it.

[0094] The preparation method of the electrodialysis membrane in this comparative example includes:

[0095] The preparation method of impregnation mixture I includes: mixing 2-acrylamide-2-methylpropanesulfonic acid, N-methylpyrrolidone, triethylamine, divinylbenzene, methyl methacrylate and azobisisobutyronitrile, and stirring at a temperature of 70 °C and a rotation speed of 250 rpm for 70 min to obtain impregnation mixture I; the preparation method of impregnation mixture II includes: mixing sodium dodecylbenzenesulfonate, acid-modified attapulgite and ethanol and stirring at a rotation speed of 250 rpm for 50 min to obtain impregnation mixture II; soaking the polyethersulfone microporous membrane in impregnation mixture I for the first soaking, with the first soaking time being 15 min, and then placing it in impregnation mixture II at room temperature for the second soaking, with the second soaking time being 50 min; after soaking, place it between two polyethylene terephthalate films, and remove the bubbles between the polyethersulfone microporous membrane and the polyethylene terephthalate films to form a composite membrane with the substrate and the two films. After drying the composite membrane, peel off the two films to obtain the product.

[0096] Comparative Example 7

[0097] This example provides an electrodialysis membrane with high separation efficiency. The electrodialysis membrane is obtained through the following treatment method. The treatment method includes the following steps: soaking the polyethersulfone microporous membrane in impregnation mixture I in sequence; the pore diameter of the polyethersulfone microporous membrane is 0.55 μm, the porosity is 60%, and the thickness is 0.16 mm.

[0098] Among them, the impregnation mixture I is composed of 310 parts of 2-acrylamide-2-methylpropanesulfonic acid, 240 parts of N-methylpyrrolidone, 65 parts of triethylamine, 35 parts of divinylbenzene, 15 parts of methyl methacrylate and 2.5 parts of azobisisobutyronitrile by weight.

[0099] The preparation method of the electrodialysis membrane in this example includes:

[0100] The preparation method of impregnation mixture I includes: mixing 2-acrylamide-2-methylpropanesulfonic acid, N-methylpyrrolidone, triethylamine, divinylbenzene, methyl methacrylate and azobisisobutyronitrile, and stirring at a temperature of 70 °C and a rotation speed of 250 rpm for 70 min to obtain impregnation mixture I; soaking the polyethersulfone microporous membrane in impregnation mixture I for the first soaking, with the first soaking time being 15 min; after soaking, place it between two polyethylene terephthalate films, and remove the bubbles between the polyethersulfone microporous membrane and the polyethylene terephthalate films to form a composite membrane with the substrate and the two films. After drying the composite membrane, peel off the two films to obtain the product.

[0101] Test Example: The membrane surface resistance of the electrodialysis membranes prepared in the foregoing Examples 1-4 and Comparative Examples 1-7 was measured by an electrochemical analyzer using the AC impedance method. The membrane was placed in a conductivity cell, and 0.5 mol / L sodium chloride aqueous solution was filled on both sides of the membrane to test the membrane surface resistance.

[0102] By simulating the actual operating conditions with an electrodialysis device, the selective retention ability of the membrane for specific ions was measured under a constant current. The calculation formula for the retention rate is:

[0103] Retention rate (%) = [1 - (C permeate / C anode )] × 100%, where C anode is the initial concentration in the anode chamber (feed side), and C permeate is the concentration in the cathode chamber (permeate side) after operation.

[0104] The test steps are as follows: A two-chamber electrodialysis cell was used, with the effective membrane area of 10 cm 2 , and the volumes of the anode chamber and the cathode chamber were each 100 mL; Electrodes: Ru-coated titanium anode / stainless steel cathode, a constant current power supply (current density 5 mA / cm 2 ); The temperature was controlled at 25 ± 1 °C. A 0.5 mol / L NaCl or Na2SO4 solution (analytical pure) was injected into the anode chamber, and the cathode chamber was initially deionized water. The constant current power supply was turned on and operated for 1 hour. The cathode chamber solution was taken at 0 hour and 1 hour respectively, and the Cl - or SO4 2- concentration was measured using an ion chromatograph (ICS-2000, Dionex) to calculate the retention rate (initial value); The operation continued for 72 hours while keeping the current density constant. The anode chamber solution was replenished to the initial volume every 24 hours to avoid excessive concentration changes. After 72 hours, samples were taken and the concentration was measured in the same way to calculate the retention rate.

[0105] The results are shown in Table 1 below.

[0106] Table 1: Test Results

[0107]

[0108]

[0109] In the present invention, sulfuric acid modification expands the interlayer spacing of montmorillonite and enhances the ion exchange capacity. However, hydrochloric acid and NaOH modification may cause structural damage or residual ion interference. Compared with hydrochloric acid (Comparative Example 1) and NaOH (Comparative Example 2) modification, montmorillonite modified with sulfuric acid (Example 1) exhibits better ion separation efficiency and stability. The sulfonic acid group and hydrophobic chain of sodium dodecylbenzenesulfonate are more conducive to forming stable ion channels, and cooperate with montmorillonite to enhance the adsorption capacity. Therefore, compared with sodium dibutylnaphthalenesulfonate (Comparative Example 3) and sodium diisooctyl sulfosuccinate (Comparative Example 4), sodium dodecylbenzenesulfonate (Example 1) significantly improves the ion separation efficiency and stability. Moreover, the layered structure of montmorillonite (Example 1) can also significantly improve the ion separation performance compared with kaolin (Comparative Example 5) and attapulgite (Comparative Example 6).

[0110] In addition, the low surface resistance (Example 1: 2.5 Ω / cm 2 ) corresponds to a high rejection rate, indicating that the optimized material combination reduces the ion transport resistance. In Comparative Examples 5-6, the use of kaolin / attapulgite leads to an increase in resistance and a significant decrease in separation efficiency. Due to the enhancement of the chemical stability of the membrane structure by sulfuric acid-modified montmorillonite and crosslinking agent (divinylbenzene), after 72 hours of continuous operation, the decrease in the rejection rate of all examples is ≤1% (for example, in Example 1, it changes from 99% to 98%), while the decrease in Comparative Examples is generally more obvious (for example, in Comparative Example 6, it changes from 77% to 72%).

[0111] In Comparative Example 7, Impregnation Mixture II was not used, resulting in the polyethersulfone microporous membrane not being surface-functionalized. Sodium dodecylbenzenesulfonate and acid-modified montmorillonite in Impregnation Mixture II play a key role in pore regulation and surface charge distribution of the membrane. The lack of this step will make the membrane pore structure loose and the surface hydrophilicity decrease, resulting in performance degradation.

[0112] Finally, it should be noted that the above examples are only used to illustrate the present invention and do not limit the technical solutions described in the present invention; those of ordinary skill in the art should understand that the present invention can still be modified or equivalently replaced; and all technical solutions and their improvements that do not depart from the spirit and scope of the present invention should be covered by the scope of the claims of the present invention.

Claims

1. An electrodialysis membrane with high separation efficiency, characterized in that: The electrodialysis membrane is obtained by the following treatment method, which comprises the following steps: immersing the polyethersulfone microporous membrane in the first impregnation mixed solution and the second impregnation mixed solution in sequence; The impregnation mixture is composed of 300-320 parts of 2-acrylamide-2-methylpropanesulfonic acid, 220-260 parts of N-methylpyrrolidone, 60-70 parts of triethylamine, 30-40 parts of divinylbenzene, 10-20 parts of methyl methacrylate and 2-3 parts of azobisisobutyronitrile in parts by weight. The second impregnation mixed solution comprises, by weight, 10-12 parts of sodium dodecylbenzene sulfonate, 6-8 parts of acid-modified montmorillonite, and 500-600 parts of ethanol.

2. An electrodialysis membrane with high separation efficiency according to claim 1, characterized in that: The polyethersulfone microporous membrane has a pore size of 0.5-0.6 μm, a porosity of 55-65%, and a thickness of 0.14-0.18 mm.

3. An electrodialysis membrane with high separation efficiency according to claim 1, characterized in that: The preparation method of the acid-modified montmorillonite comprises: soaking the montmorillonite in a sulfuric acid aqueous solution with a temperature of 50-60° C. and a mass fraction of 15-25% for 20-24 hours, then washing with deionized water until neutral, and drying at a temperature of 55-65° C. for 23-25 ​​hours to obtain the acid-modified montmorillonite.

4. The electrodialysis membrane with high separation efficiency according to claim 1, characterized in that: The preparation method of the electrodialysis membrane also includes: placing the electrodialysis membrane between two polyethylene terephthalate films after immersion, removing bubbles between the films to form a composite membrane, drying the composite membrane and then peeling off the two films.

5. The electrodialysis membrane with high separation efficiency according to claim 1, characterized in that: The preparation method of the impregnation mixed solution 1 includes: mixing 2-acrylamide-2-methylpropanesulfonic acid, N-methylpyrrolidone, triethylamine, divinylbenzene, methyl methacrylate and azobisisobutyronitrile, and stirring at a rotation speed of 200-300 rpm for 60-80 minutes to prepare the impregnation mixed solution 1.

6. The electrodialysis membrane with high separation efficiency according to claim 1, characterized in that: The preparation method of the second impregnation mixed solution comprises: mixing sodium dodecylbenzene sulfonate, acid-modified montmorillonite and ethanol, stirring at a rotation speed of 200-300 rpm for 40-60 minutes to prepare the second impregnation mixed solution.

7. An electrodialysis membrane with high separation efficiency according to claim 4, characterized in that: The immersion time in the immersion mixture is 10-20 minutes, and the immersion temperature is 60-80°C.

8. An electrodialysis membrane with high separation efficiency according to claim 1, characterized in that: The immersion time in the second immersion mixed solution is 40-60 minutes.

9. An electrodialysis membrane with high separation efficiency according to claim 4, characterized in that: The drying method is to place the product in an oven at 60-80° C. for 8-10 hours.

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