Electrodialysis membrane with high separation efficiency

Abstract

The application provides a high-separation-efficiency electrodialysis membrane, raw materials of which comprise polyether sulfone microporous membranes and impregnation mixed solution I and impregnation mixed solution II; wherein the impregnation mixed solution I is composed of 2-acrylamide-2-methylpropane sulfonic acid 300-320 parts, N-methyl pyrrolidone 220-260 parts, triethylamine 60-70 parts, divinylbenzene 30-40 parts, methyl methacrylate 10-20 parts and azobisisobutyronitrile 2-3 parts according to weight fraction; the impregnation mixed solution II is composed of sodium dodecyl benzene sulfonate 10-12 parts, acid modified montmorillonite 6-8 parts and ethanol 500-600 parts according to weight fraction. The high-separation-efficiency electrodialysis membrane adopts unique materials, can efficiently separate ions in a solution under the action of an electric field, realizes higher separation efficiency by optimizing the pore size distribution and surface properties of the membrane material, and simultaneously has good durability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of membrane separation technology, in particular to a high separation efficiency electrodialysis membrane. BACKGROUND

[0002] In the field of modern industrial production and environmental protection water treatment, membrane separation technology is widely concerned for its high efficiency, energy saving and environmental protection. Among them, electrodialysis technology as an important membrane separation technology, with its unique separation mechanism and wide application prospect, plays an important role in water treatment, seawater desalination, chemical separation and other fields.

[0003] Electrodialysis is a technology that uses the selective permeability of semi-permeable membrane and the ion migration principle under the action of electric field to separate the solution. Under the action of electric field, the anions and cations in the solution migrate to the positive and negative electrodes respectively, and enter the adjacent small chamber through the corresponding ion exchange membrane, so as to realize the separation and concentration of ions in the solution. Based on this, the present application provides a high separation efficiency electrodialysis membrane. SUMMARY

[0004] The purpose of the present application is to provide a high separation efficiency electrodialysis membrane, which aims to improve the cation selective permeability and durability in the electrodialysis process.

[0005] The present application provides a high separation efficiency electrodialysis membrane, which is obtained by the following treatment method, the treatment method comprising the following steps: putting the polyether sulfone microporous membrane into the impregnation mixed solution one and the impregnation mixed solution two in turn for impregnation.

[0006] Among them, the impregnation mixed solution one is composed of 2-acrylamide-2-methylpropane sulfonic acid 300-320 parts, N-methyl pyrrolidone 220-260 parts, triethylamine 60-70 parts, divinylbenzene 30-40 parts, methyl methacrylate 10-20 parts and azobisisobutyronitrile 2-3 parts by weight fraction.

[0007] The impregnation mixed solution two is composed of sodium dodecyl benzene sulfonate 10-12 parts, acid modified montmorillonite 6-8 parts, and ethanol 500-600 parts by weight fraction.

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

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

[0010] Further, the preparation method of the electrodialysis membrane comprises: soaking the polyethersulfone microporous membrane into impregnation mixed solution one for the first soaking, and then placing it in impregnation mixed solution two at room temperature for the second soaking; after the soaking is completed, placing the substrate between two pieces of polyethylene terephthalate film, removing the air bubbles between the polyethersulfone microporous membrane and the polyethylene terephthalate film, forming a composite membrane with the substrate and the two pieces of film, and peeling off the two pieces of film after drying the composite membrane to obtain the electrodialysis membrane.

[0011] Further, the preparation method of the impregnation mixed solution one comprises: mixing 2-acrylamide-2-methylpropanesulfonic acid, N-methylpyrrolidone, triethylamine, divinylbenzene, methyl methacrylate and azobisisobutyronitrile to prepare the impregnation mixed solution one under stirring at a speed of 200-300 rpm for 60-80 min.

[0012] Further, the preparation method of the impregnation mixed solution two comprises: mixing sodium dodecylbenzenesulfonate, acid-modified montmorillonite and ethanol to prepare the impregnation mixed solution two under stirring at a speed of 200-300 rpm for 40-60 min.

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

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

[0015] Further, the drying method is placing in an oven at 60-80 DEG C for 8-10 h.

[0016] The present application has the following beneficial effects:

[0017] The electrodialysis membrane with high separation efficiency disclosed by the present application adopts a unique material, can efficiently separate ions in a solution under the action of an electric field, forms a dense cation exchange layer and a stable membrane structure on the surface of the polyethersulfone microporous membrane through the selection of the polyethersulfone microporous membrane material and the cross-linking reaction in the first soaking step. This structure can resist mechanical stress and chemical corrosion during long-term use, prolonging the service life of the membrane.

[0018] And the high molecular film enters the inner wall of the support membrane pore through the first soaking step, the coating forms a dense surface layer, the surface properties of the material are adjusted, the ion transmission efficiency in the membrane is improved, so that higher separation efficiency is achieved; at the same time, the electrodialysis membrane also has good durability, can maintain stable separation performance during long-term use, prolongs the service life of the membrane, and reduces the use cost.

[0019] The polyether sulfone microporous membrane in the application has a pore size of 0.5-0.6 microns, a porosity of 55-65%, and a thickness of 0.14-0.18 mm. The initial macropore facilitates the penetration of the impregnation liquid, and the subsequent coating reduces the effective pore size to achieve ion sieving. This helps to optimize the ion transport channel, reduce the diffusion resistance of ions in the membrane, and thus improve the migration rate and separation efficiency of ions. The appropriate pore size and porosity also ensure that the membrane has sufficient mechanical strength and stability to withstand the pressure and electric field during the electrodialysis process.

[0020] In the application, the 2-acrylamide-2-methylpropane sulfonic acid, N-methyl pyrrolidone, and triethylamine in the impregnation mixed solution I have excellent ion exchange and conduction performance. The sulfonic acid group in the 2-acrylamide-2-methylpropane sulfonic acid is a strong acidic ion exchange group that can dissociate H+ in water to form negatively charged sulfonate (-SO 3- ). These negative groups adsorb cations through electrostatic attraction to achieve selective transport. The sulfonic acid groups are distributed along the inner wall of the channel to form a negatively charged surface that selectively adsorbs cations through the Donnan exclusion effect, forming an effective ion transport channel in the membrane. Divinylbenzene and methyl methacrylate act as cross-linking agents and monomers, enhancing the structural stability and chemical stability of the membrane to prevent deformation or degradation during long-term use. Azobisisobutyronitrile as an initiator can initiate the polymerization of monomers to form a dense ion exchange layer, further improving the selective separation capacity of ions.

[0021] During the acid modification of the montmorillonite in the application, the dissolution of part of the metal cations not only expands the interlayer spacing but also increases the specific surface area of the montmorillonite. A larger specific surface area means more ion exchange sites, which helps to improve the ion separation efficiency and capacity. Moreover, using sulfuric acid to modify the montmorillonite has higher ion separation efficiency and durability compared to hydrochloric acid and sodium hydroxide. This is due to the expansion of the interlayer spacing, the increase of the specific surface area, and the improvement of the chemical and structural stability of the montmorillonite after modification. These changes enable the montmorillonite to more effectively adsorb and separate cations during electrodialysis while maintaining its performance stability and durability.

[0022] Further, the hydrogen ions in the sulfuric acid exchange with the metal cations (such as K + , Na + , Ca 2+ , Mg 2+ ) between the layers of the montmorillonite. Since H +The radius of the ion is smaller than the replaced ion, so it will cause the interlayer lattice of the montmorillonite to crack, and the interlayer distance to expand. This structural change allows more ions to enter and pass through the interlayer of the montmorillonite, thereby improving the ion separation efficiency. In contrast, although hydrochloric acid can also perform ion exchange, the expansion of the interlayer distance may not be as effective as sulfuric acid due to the presence of chloride ions and their potential impact on the interlayer structure. As an alkali, sodium hydroxide can react with the cations in the interlayer of the montmorillonite to form precipitates, which is not conducive to the expansion of the interlayer distance and the transmission of ions. - The reaction of ions with the cations in the interlayer of the montmorillonite will generate precipitates, which is not conducive to the expansion of the interlayer distance and the transmission of ions. From the perspective of chemical stability, the interlayer structure and surface properties of the montmorillonite modified by sulfuric acid have changed significantly, which helps to improve its chemical stability; in the process of electrodialysis, the montmorillonite can resist the erosion of chemicals such as acid, base and salt, thereby maintaining the stability of its ion separation performance. In contrast, the modification of hydrochloric acid may cause chloride ions to remain in the montmorillonite, affecting its chemical stability. The modification of sodium hydroxide may damage the interlayer structure of the montmorillonite, reducing its durability.

[0023] The sodium dodecyl benzene sulfonate in the second impregnation mixture can improve the hydrophilicity and wettability of the membrane surface, which helps to improve the uniform distribution and transmission of ions; it makes the membrane more easily combined 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, thereby improving the ion separation efficiency. At the same time, acid modification can also improve the compatibility between the montmorillonite and the membrane substrate, enhancing the durability of the membrane.

[0024] The sodium dodecyl benzene sulfonate used in the present application is a commonly used anionic surfactant with excellent ion exchange and transmission performance. Its hydrophobic group is dodecyl benzene group, and its hydrophilic group is sulfonic acid group. This structure allows it to form an effective ion transmission channel in the membrane. The long branched chain structure causes the sulfonic acid group to be wrapped inside the molecule, reducing its exposure and reducing the effective ion exchange sites. The branched chain hinders the diffusion path of ions in the membrane, prolongs the migration distance, and reduces the ion flux, so the ion exchange and transmission performance of sodium dodecyl benzene sulfonate is affected by its molecular chain length and branched structure. Sodium dibutyl naphthalene sulfonate 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 effect to improve the performance of the membrane. In addition, sodium dodecyl benzene sulfonate may have a good synergistic effect with montmorillonite, and can improve the dispersibility and compatibility of montmorillonite in the membrane, thereby enhancing the overall performance of the membrane. At the same time, the layered structure of the montmorillonite also provides more ion exchange sites for sodium dodecyl benzene sulfonate, which helps to improve the ion separation efficiency. DETAILED DESCRIPTION

[0025] The technical solutions of the present application are described below clearly and completely. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application. It should be noted that the montmorillonite type is K-10, the CAS number is 1318-93-0; the kaolin type is SAP-200, the CAS number is 1318-74-7; the attapulgite CAS number is 1337-76-4, which is purchased from Nanjing Bemoda Biotechnology Co., Ltd.; and other raw materials not mentioned can also be commercially available.

[0026] Embodiment 1

[0027] The present embodiment provides a high separation efficiency electrodialysis membrane, which is obtained by the following treatment method, and the treatment method comprises the following steps: sequentially immersing a polyether sulfone microporous membrane in immersion mixed solution one and immersion mixed solution two; the pore size of the polyether sulfone microporous membrane is 0.55 μm, the porosity is 60%, and the thickness is 0.16 mm;

[0028] The immersion mixed solution one is composed of 2-acrylamide-2-methylpropane sulfonic acid 310 parts, N-methyl pyrrolidone 240 parts, triethylamine 65 parts, divinylbenzene 35 parts, methyl methacrylate 15 parts, and azobisisobutyronitrile 2.5 parts according to weight fraction;

[0029] The immersion mixed solution two is composed of sodium dodecylbenzenesulfonate 11 parts, acid modified montmorillonite 7 parts, and ethanol 550 parts according to weight fraction.

[0030] The preparation method of the acid modified montmorillonite comprises: immersing the montmorillonite in a 20% sulfuric acid aqueous solution with a temperature of 55℃ for 22h, then washing with deionized water until neutral, and drying at a temperature of 60℃ for 24h to obtain the acid modified montmorillonite;

[0031] The preparation method of the electrodialysis membrane in the present embodiment comprises:

[0032] The preparation method of the impregnation mixture one comprises the following steps: mixing 2-acrylamide-2-methylpropanesulfonic acid, N-methylpyrrolidone, triethylamine, divinylbenzene, methyl methacrylate and azobisisobutyronitrile, stirring at a temperature of 70℃ and a speed of 250 rpm for 70 min to prepare the impregnation mixture one; the preparation method of the impregnation mixture two comprises the following steps: mixing sodium dodecylbenzenesulfonate, acid modified montmorillonite and ethanol, stirring at a speed of 250 rpm for 50 min to prepare the impregnation mixture two; soaking the polyethersulfone microporous membrane in the impregnation mixture one for the first time, the first soaking time being 15 min, and then placing the polyethersulfone microporous membrane in the impregnation mixture two at room temperature for the second time, the second soaking time being 50 min; after the soaking is completed, placing the polyethersulfone microporous membrane between two pieces of polyethylene terephthalate film, removing the bubbles between the polyethersulfone microporous membrane and the polyethylene terephthalate film, and making the substrate and the two pieces of film form a composite film, and then peeling off the two pieces of film after the composite film is dried to obtain the membrane.

[0033] Example 2

[0034] The embodiment provides a high-separation-efficiency electrodialysis membrane, and the electrodialysis membrane is obtained through the following treatment method, and the treatment method comprises the following steps: sequentially placing a polyethersulfone microporous membrane in an impregnation mixture one and an impregnation mixture two for impregnation; the polyethersulfone microporous membrane has a pore size of 0.55 μm, a porosity of 60% and a thickness of 0.16 mm;

[0035] The impregnation mixture one is composed of 2-acrylamide-2-methylpropanesulfonic acid 300 parts, N-methylpyrrolidone 230 parts, triethylamine 65 parts, divinylbenzene 35 parts, methyl methacrylate 16 parts and azobisisobutyronitrile 2.5 parts according to weight fraction.

[0036] The impregnation mixture two is composed of sodium dodecylbenzenesulfonate 11 parts, acid modified montmorillonite 7 parts and ethanol 500 parts according to weight fraction.

[0037] The preparation method of the acid modified montmorillonite comprises the following steps: soaking montmorillonite in a 20% sulfuric acid aqueous solution at a temperature of 50℃ for 20 h, then washing with deionized water until neutral, and drying at a temperature of 55℃ for 23 h to obtain the acid modified montmorillonite.

[0038] The preparation method of the electrodialysis membrane in the embodiment comprises the following steps:

[0039] The preparation method of the impregnation mixture one comprises the following steps: mixing 2-acrylamide-2-methylpropanesulfonic acid, N-methylpyrrolidone, triethylamine, divinylbenzene, methyl methacrylate and azobisisobutyronitrile, stirring at a temperature of 70℃ and a speed of 250 rpm for 60 min to prepare the impregnation mixture one; the preparation method of the impregnation mixture two comprises the following steps: mixing sodium dodecylbenzenesulfonate, acid modified montmorillonite and ethanol, stirring at a speed of 200 rpm for 40 min to prepare the impregnation mixture two; soaking the polyethersulfone microporous membrane in the impregnation mixture one for the first time, the first soaking time being 10 min, and then placing the polyethersulfone microporous membrane in the impregnation mixture two at room temperature for the second time, the second soaking time being 40 min; after the soaking is completed, placing the polyethersulfone microporous membrane between two pieces of polyethylene terephthalate film, removing the bubbles between the polyethersulfone microporous membrane and the polyethylene terephthalate film, and making the substrate and the two pieces of film form a composite film; and peeling off the two pieces of film after the composite film is dried to obtain the product.

[0040] Example 3

[0041] The embodiment provides a high-separation-efficiency electrodialysis membrane, and the electrodialysis membrane is obtained through the following treatment method, and the treatment method comprises the following steps: sequentially placing a polyethersulfone microporous membrane in an impregnation mixture one and an impregnation mixture two for impregnation; the polyethersulfone microporous membrane has a pore size of 0.5 μm, a porosity of 55% and a thickness of 0.14 mm;

[0042] The impregnation mixture one is composed of 2-acrylamide-2-methylpropanesulfonic acid 300 parts, N-methylpyrrolidone 220 parts, triethylamine 60 parts, divinylbenzene 30 parts, methyl methacrylate 10 parts and azobisisobutyronitrile 2 parts according to weight fractions.

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

[0044] The preparation method of the acid modified montmorillonite comprises the following steps: soaking montmorillonite in a 15% sulfuric acid aqueous solution at a temperature of 50℃ for 20 h, then washing with deionized water until neutral, and drying at a temperature of 55℃ for 23 h to obtain the acid modified montmorillonite.

[0045] The preparation method of the electrodialysis membrane in the embodiment comprises the following steps:

[0046] The preparation method of the impregnation mixture one comprises the following steps: mixing 2-acrylamide-2-methylpropanesulfonic acid, N-methylpyrrolidone, triethylamine, divinylbenzene, methyl methacrylate and azobisisobutyronitrile, stirring at a temperature of 70 DEG C and a speed of 200 rpm for 60 min to prepare the impregnation mixture one; the preparation method of the impregnation mixture two comprises the following steps: mixing sodium dodecylbenzenesulfonate, acid modified montmorillonite and ethanol, stirring at a speed of 200 rpm for 40 min to prepare the impregnation mixture two; soaking the polyethersulfone microporous membrane in the impregnation mixture one for the first time, and then placing the polyethersulfone microporous membrane in the impregnation mixture two at room temperature for the second time; placing the polyethersulfone microporous membrane between two polyethylene terephthalate films after soaking, removing the bubbles between the polyethersulfone microporous membrane and the polyethylene terephthalate films, and forming a composite film by the substrate and the two films; and peeling off the two films after drying the composite film to obtain the product.

[0047] Example 4

[0048] The embodiment provides a high-separation-efficiency electrodialysis membrane, raw materials of which comprise a polyethersulfone microporous membrane and impregnation mixtures one and two; the polyethersulfone microporous membrane has a pore size of 0.6 μm, a porosity of 65% and a thickness of 0.18 mm;

[0049] The impregnation mixture one comprises, by weight fraction, 2-acrylamide-2-methylpropanesulfonic acid 320 parts, N-methylpyrrolidone 260 parts, triethylamine 70 parts, divinylbenzene 40 parts, methyl methacrylate 20 parts and azobisisobutyronitrile 3 parts.

[0050] The impregnation mixture two comprises, by weight fraction, sodium dodecylbenzenesulfonate 12 parts, acid modified montmorillonite 8 parts and ethanol 600 parts.

[0051] The acid modified montmorillonite is prepared by the following steps: soaking montmorillonite in a 25% sulfuric acid aqueous solution at a temperature of 60 DEG C for 24 h, then washing with deionized water until neutral, and drying at a temperature of 65 DEG C for 25 h.

[0052] The preparation method of the electrodialysis membrane in the embodiment comprises the following steps:

[0053] The preparation method of the impregnation mixture one comprises the following steps: mixing 2-acrylamide-2-methylpropanesulfonic acid, N-methylpyrrolidone, triethylamine, divinylbenzene, methyl methacrylate and azobisisobutyronitrile, stirring at a temperature of 70 DEG C and a speed of 300 rpm for 80 min to prepare the impregnation mixture one; the preparation method of the impregnation mixture two comprises the following steps: mixing sodium dodecylbenzenesulfonate, acid modified montmorillonite and ethanol, stirring at a speed of 300 rpm for 60 min to prepare the impregnation mixture two; soaking the polyethersulfone microporous membrane in the impregnation mixture one for the first time, the first soaking time being 20 min, then placing the polyethersulfone microporous membrane in the impregnation mixture two at room temperature for the second time, the second soaking time being 60 min; after the soaking is completed, placing the polyethersulfone microporous membrane between two pieces of polyethylene terephthalate film, removing the air bubbles between the polyethersulfone microporous membrane and the polyethylene terephthalate film, making the substrate and the two pieces of film form a composite film, and peeling off the two pieces of film after the composite film is dried to obtain the polyethersulfone microporous membrane.

[0054] Comparative Example 1

[0055] The present comparative example provides a high separation efficiency electrodialysis membrane, which is obtained by the following treatment method, the treatment method comprising the following steps: sequentially placing a polyethersulfone microporous membrane in an impregnation mixture one and an impregnation mixture two for impregnation; the pore size of the polyethersulfone microporous membrane is 0.55 μm, the porosity is 60%, and the thickness is 0.16 mm;

[0056] The impregnation mixture one is composed of 2-acrylamide-2-methylpropanesulfonic acid 310 parts, N-methylpyrrolidone 240 parts, triethylamine 65 parts, divinylbenzene 35 parts, methyl methacrylate 15 parts and azobisisobutyronitrile 2.5 parts according to weight fraction;

[0057] The impregnation mixture two is composed of sodium dodecylbenzenesulfonate 11 parts, acid modified montmorillonite 7 parts and ethanol 550 parts according to weight fraction.

[0058] The preparation method of the acid modified montmorillonite comprises the following steps: soaking montmorillonite in a 20% hydrochloric acid aqueous solution at a temperature of 55 DEG C for 22 h, then washing with deionized water until neutral, and drying at a temperature of 60 DEG C for 24 h to obtain the acid modified montmorillonite;

[0059] The preparation method of the electrodialysis membrane in the present comparative example comprises the following steps:

[0060] The preparation method of the impregnation mixture one comprises the following steps: mixing 2-acrylamide-2-methylpropanesulfonic acid, N-methylpyrrolidone, triethylamine, divinylbenzene, methyl methacrylate and azobisisobutyronitrile, stirring at a temperature of 70℃ and a speed of 250 rpm for 70 min to prepare the impregnation mixture one; the preparation method of the impregnation mixture two comprises the following steps: mixing sodium dodecylbenzenesulfonate, acid modified montmorillonite and ethanol, stirring at a speed of 250 rpm for 50 min to prepare the impregnation mixture two; soaking the polyethersulfone microporous membrane in the impregnation mixture one for the first time, the first soaking time being 15 min, and then placing the polyethersulfone microporous membrane in the impregnation mixture two at room temperature for the second time, the second soaking time being 50 min; after the soaking is completed, placing the polyethersulfone microporous membrane between two pieces of polyethylene terephthalate film, removing the bubbles between the polyethersulfone microporous membrane and the polyethylene terephthalate film, and forming a composite film by the substrate and the two pieces of film, and then peeling off the two pieces of film after the composite film is dried to obtain the polyethersulfone microporous membrane.

[0061] Comparative Example 2

[0062] The present comparative example provides a high separation efficiency electrodialysis membrane, which is obtained by the following treatment method, the treatment method comprising the following steps: sequentially placing a polyethersulfone microporous membrane into an impregnation mixture one and an impregnation mixture two for impregnation; the pore size of the polyethersulfone microporous membrane is 0.55 μm, the porosity is 60%, and the thickness is 0.16 mm;

[0063] The impregnation mixture one is composed of 2-acrylamide-2-methylpropanesulfonic acid 310 parts, N-methylpyrrolidone 240 parts, triethylamine 65 parts, divinylbenzene 35 parts, methyl methacrylate 15 parts and azobisisobutyronitrile 2.5 parts by weight fraction.

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

[0065] The preparation method of the acid modified montmorillonite comprises the following steps: soaking montmorillonite in a 20% sodium hydroxide aqueous solution at a temperature of 55℃ for 22 h, then washing with deionized water until neutral, and drying at a temperature of 60℃ for 24 h to obtain the acid modified montmorillonite.

[0066] The preparation method of the electrodialysis membrane in the present comparative example comprises the following steps:

[0067] The preparation method of the impregnation mixture one comprises the following steps: mixing 2-acrylamide-2-methylpropanesulfonic acid, N-methylpyrrolidone, triethylamine, divinylbenzene, methyl methacrylate and azobisisobutyronitrile, stirring at a temperature of 70℃ and a speed of 250 rpm for 70 min to prepare the impregnation mixture one; the preparation method of the impregnation mixture two comprises the following steps: mixing sodium dodecylbenzenesulfonate, acid modified montmorillonite and ethanol, stirring at a speed of 250 rpm for 50 min to prepare the impregnation mixture two; the polyethersulfone microporous membrane is soaked in the impregnation mixture one for the first time, the first soaking time is 15 min, and then the polyethersulfone microporous membrane is placed in the impregnation mixture two at room temperature for the second time, the second soaking time is 50 min; after the soaking is completed, the polyethersulfone microporous membrane is placed between two pieces of polyethylene terephthalate films, the bubbles between the polyethersulfone microporous membrane and the polyethylene terephthalate films are removed, the substrate and the two pieces of films form a composite film, and the two pieces of films are peeled off after the composite film is dried.

[0068] Comparative Example 3

[0069] The present comparative example provides an electrodialysis membrane with high separation efficiency, which is obtained by the following treatment method, the treatment method comprising the following steps: sequentially placing a polyethersulfone microporous membrane in an impregnation mixture one and an impregnation mixture two for impregnation; the pore size of the polyethersulfone microporous membrane is 0.55 μm, the porosity is 60%, and the thickness is 0.16 mm;

[0070] The impregnation mixture one is composed of 2-acrylamide-2-methylpropanesulfonic acid 310 parts, N-methylpyrrolidone 240 parts, triethylamine 65 parts, divinylbenzene 35 parts, methyl methacrylate 15 parts and azobisisobutyronitrile 2.5 parts according to weight fraction;

[0071] The impregnation mixture two is composed of sodium dodecylbenzenesulfonate 11 parts, acid modified montmorillonite 7 parts and ethanol 550 parts according to weight fraction.

[0072] The preparation method of the acid modified montmorillonite comprises the following steps: soaking montmorillonite in a 20% sulfuric acid aqueous solution at a temperature of 55℃ for 22 h, then washing with deionized water until neutral, and drying at a temperature of 60℃ for 24 h to obtain the acid modified montmorillonite;

[0073] The preparation method of the electrodialysis membrane in the present comparative example comprises the following steps:

[0074] The preparation method of the impregnation mixture one comprises the following steps: mixing 2-acrylamide-2-methylpropanesulfonic acid, N-methylpyrrolidone, triethylamine, divinylbenzene, methyl methacrylate and azobisisobutyronitrile, stirring at a temperature of 70℃ and a speed of 250 rpm for 70 min to prepare the impregnation mixture one; the preparation method of the impregnation mixture two comprises the following steps: mixing sodium dibutyl naphthalene sulfonate, acid modified montmorillonite and ethanol, stirring at a speed of 250 rpm for 50 min to prepare the impregnation mixture two; soaking the polyethersulfone microporous membrane in the impregnation mixture one for the first time, the first soaking time being 15 min, and then placing the polyethersulfone microporous membrane in the impregnation mixture two at room temperature for the second time, the second soaking time being 50 min; after the soaking is completed, placing the polyethersulfone microporous membrane between two pieces of polyethylene terephthalate film, removing the bubbles between the polyethersulfone microporous membrane and the polyethylene terephthalate film, and making the substrate and the two pieces of film form a composite film; after the composite film is dried, the two pieces of film are peeled off to obtain the polyethersulfone microporous membrane.

[0075] Comparative Example 4

[0076] The present comparative example provides a high separation efficiency electrodialysis membrane, which is obtained by the following treatment method, the treatment method comprising the following steps: sequentially placing a polyethersulfone microporous membrane in an impregnation mixture one and an impregnation mixture two for impregnation; the pore size of the polyethersulfone microporous membrane is 0.55 μm, the porosity is 60%, and the thickness is 0.16 mm;

[0077] The impregnation mixture one is composed of 2-acrylamide-2-methylpropanesulfonic acid 310 parts, N-methylpyrrolidone 240 parts, triethylamine 65 parts, divinylbenzene 35 parts, methyl methacrylate 15 parts and azobisisobutyronitrile 2.5 parts by weight;

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

[0079] The preparation method of the acid modified montmorillonite comprises the following steps: soaking montmorillonite in a 20% sulfuric acid aqueous solution at a temperature of 55℃ for 22 h, then washing with deionized water until neutral, and drying at a temperature of 60℃ for 24 h to obtain the acid modified montmorillonite;

[0080] The preparation method of the electrodialysis membrane in the present comparative example comprises the following steps:

[0081] The preparation method of the impregnation mixture one comprises the following steps: mixing 2-acrylamide-2-methylpropanesulfonic acid, N-methylpyrrolidone, triethylamine, divinylbenzene, methyl methacrylate and azobisisobutyronitrile, stirring at a temperature of 70℃ and a speed of 250 rpm for 70 min to prepare the impregnation mixture one; the preparation method of the impregnation mixture two comprises the following steps: mixing sodium diisooctyl sulfosuccinate, acid-modified montmorillonite and ethanol, stirring at a speed of 250 rpm for 50 min to prepare the impregnation mixture two; soaking the polyethersulfone microporous membrane in the impregnation mixture one for the first time, the first soaking time being 15 min, and then placing the polyethersulfone microporous membrane in the impregnation mixture two at room temperature for the second time, the second soaking time being 50 min; after the soaking is completed, placing the polyethersulfone microporous membrane between two pieces of polyethylene terephthalate film, removing the bubbles between the polyethersulfone microporous membrane and the polyethylene terephthalate film, and forming a composite film by the substrate and the two pieces of film, and then peeling off the two pieces of film after the composite film is dried to obtain the polyethersulfone microporous membrane.

[0082] Comparative Example 5

[0083] The present comparative example provides a high separation efficiency electrodialysis membrane, which is obtained by the following treatment method, the treatment method comprising the following steps: sequentially placing a polyethersulfone microporous membrane in an impregnation mixture one and an impregnation mixture two for impregnation; the pore size of the polyethersulfone microporous membrane is 0.55 μm, the porosity is 60%, and the thickness is 0.16 mm;

[0084] The impregnation mixture one comprises 2-acrylamide-2-methylpropanesulfonic acid 310 parts, N-methylpyrrolidone 240 parts, triethylamine 65 parts, divinylbenzene 35 parts, methyl methacrylate 15 parts and azobisisobutyronitrile 2.5 parts by weight.

[0085] The impregnation mixture two comprises sodium dodecylbenzenesulfonate 11 parts, acid-modified kaolin 7 parts and ethanol 550 parts by weight.

[0086] The preparation method of the acid-modified kaolin comprises the following steps: soaking kaolin in a 20% sulfuric acid aqueous solution at a temperature of 55℃ for 22 h, then washing with deionized water until neutral, and drying at a temperature of 60℃ for 24 h to obtain the acid-modified kaolin.

[0087] The preparation method of the electrodialysis membrane in the present comparative example comprises the following steps:

[0088] The preparation method of the impregnation mixed solution one comprises the following steps: 2-acrylamide-2-methylpropanesulfonic acid, N-methylpyrrolidone, triethylamine, divinylbenzene, methyl methacrylate and azobisisobutyronitrile are mixed, and the impregnation mixed solution one is prepared by stirring at a temperature of 70℃ and a speed of 250 rpm for 70 min; the preparation method of the impregnation mixed solution two comprises the following steps: sodium dodecylbenzenesulfonate, acid modified kaolin and ethanol are mixed, and the impregnation mixed solution two is prepared by stirring at a speed of 250 rpm for 50 min; the polyethersulfone microporous membrane is soaked in the impregnation mixed solution one for the first time, the first soaking time is 15 min, and then the polyethersulfone microporous membrane is placed in the impregnation mixed solution two at room temperature for the second time, the second soaking time is 50 min; after the soaking is completed, the polyethersulfone microporous membrane is placed between two pieces of polyethylene terephthalate films, the bubbles between the polyethersulfone microporous membrane and the polyethylene terephthalate films are removed, the substrate and the two pieces of films form a composite film, and the two pieces of films are peeled off after the composite film is dried.

[0089] Comparative Example 6

[0090] The present comparative example provides a high separation efficiency electrodialysis membrane, which is obtained by the following treatment method, the treatment method comprising the following steps: the polyethersulfone microporous membrane is sequentially placed in the impregnation mixed solution one and the impregnation mixed solution two for impregnation; the pore size of the polyethersulfone microporous membrane is 0.55 μm, the porosity is 60%, and the thickness is 0.16 mm;

[0091] The impregnation mixed solution one is composed of 2-acrylamide-2-methylpropanesulfonic acid 310 parts, N-methylpyrrolidone 240 parts, triethylamine 65 parts, divinylbenzene 35 parts, methyl methacrylate 15 parts and azobisisobutyronitrile 2.5 parts according to weight fraction;

[0092] The impregnation mixed solution two is composed of sodium dodecylbenzenesulfonate 11 parts, acid modified attapulgite 7 parts and ethanol 550 parts according to weight fraction.

[0093] The preparation method of the acid modified attapulgite comprises the following steps: the attapulgite is soaked in a 20% sulfuric acid aqueous solution at a temperature of 55℃ for 22 h, then washed with deionized water until neutral, and dried at a temperature of 60℃ for 24 h to obtain the acid modified attapulgite;

[0094] The preparation method of the electrodialysis membrane in the present comparative example comprises the following steps:

[0095] The preparation method of the impregnation mixture one includes: mixing 2-acrylamide-2-methylpropanesulfonic acid, N-methylpyrrolidone, triethylamine, divinylbenzene, methyl methacrylate and azobisisobutyronitrile, stirring at 70℃ and 250rpm for 70min to obtain the impregnation mixture one; the preparation method of the impregnation mixture two includes: mixing sodium dodecylbenzenesulfonate, acid modified attapulgite and ethanol, stirring at 250rpm for 50min to obtain the impregnation mixture two; the polyethersulfone microporous membrane is soaked in the impregnation mixture one for the first time, the first soaking time is 15min, then placed in the impregnation mixture two at room temperature for the second time, the second soaking time is 50min; after soaking, placed in the middle of two pieces of polyethylene terephthalate film, remove the bubbles between the polyethersulfone microporous membrane and the polyethylene terephthalate film, make the substrate and the two pieces of film form a composite film, dry the composite film, then peel off the two pieces of film.

[0096] Comparative example 7

[0097] The embodiment provides a high separation efficiency electrodialysis membrane, the electrodialysis membrane is obtained through the following treatment method, the treatment method includes the following steps: sequentially placing a polyethersulfone microporous membrane into an impregnation mixture one for impregnation; the pore size of the polyethersulfone microporous membrane is 0.55μm, the porosity is 60%, and the thickness is 0.16mm;

[0098] The impregnation mixture one is composed of 2-acrylamide-2-methylpropanesulfonic acid 310 parts, N-methylpyrrolidone 240 parts, triethylamine 65 parts, divinylbenzene 35 parts, methyl methacrylate 15 parts and azobisisobutyronitrile 2.5 parts according to weight fraction.

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

[0100] The preparation method of the impregnation mixture one includes: mixing 2-acrylamide-2-methylpropanesulfonic acid, N-methylpyrrolidone, triethylamine, divinylbenzene, methyl methacrylate and azobisisobutyronitrile, stirring at 70℃ and 250rpm for 70min to obtain the impregnation mixture one; the polyethersulfone microporous membrane is soaked in the impregnation mixture one for the first time, the first soaking time is 15min; after soaking, placed in the middle of two pieces of polyethylene terephthalate film, remove the bubbles between the polyethersulfone microporous membrane and the polyethylene terephthalate film, make the substrate and the two pieces of film form a composite film, dry the composite film, then peel off the two pieces of film.

[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 using an electrochemical analyzer by an alternating current impedance method. The membrane was placed in a conductivity cell, and both sides of the membrane were filled with 0.5 mol / L sodium chloride aqueous solution, and the membrane surface resistance was measured.

[0102] The selective retention ability of the membrane for specific ions was measured at a constant current by simulating actual operating conditions using an electrodialysis device. The retention rate calculation formula was:

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

[0104] The test procedure was as follows: a two-chamber electrodialysis cell was used, the effective area of the membrane was 10 cm 2 , the volume of the anode chamber and the cathode chamber was each 100 mL; the electrode was a titanium-coated ruthenium anode / stainless steel cathode, a constant current power supply (current density 5 mA / cm 2 ); the temperature was controlled at 25±1°C, and 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 the operation was continued for 1 hour, and the cathode chamber solution was taken at 0 hour and 1 hour, respectively, the Cl - or SO4 2- concentration was measured using an ion chromatograph (ICS-2000, Dionex), and the retention rate (initial value) was calculated; the operation was continued for 72 hours, the current density was kept constant, the anode chamber solution was replenished to the initial volume every 24 hours to avoid excessive changes in concentration, and the sample was taken after 72 hours, 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] The sulfuric acid modification in the present application expands the interlayer spacing of the montmorillonite, enhances the ion exchange capacity, while the hydrochloric acid and NaOH modification may cause structural damage or interference of residual ions. The use of sulfuric acid modified montmorillonite (Example 1) exhibits better ion separation efficiency and stability compared to hydrochloric acid (Comparative Example 1) and NaOH (Comparative Example 2) modification. The sulfonic acid group and hydrophobic chain of sodium dodecyl benzene sulfonate are more conducive to the formation of stable ion channels, which synergistically enhance the adsorption capacity of montmorillonite. Therefore, sodium dodecyl benzene sulfonate (Example 1) significantly improves the ion separation efficiency and stability compared to sodium dibutylnaphthalene sulfonate (Comparative Example 3) and sodium diisooctyl sulfosuccinate (Comparative Example 4). The layered structure of montmorillonite (Example 1) can also significantly improve the ion separation performance compared to 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 high retention rate, indicating that the optimized material combination reduces the ion transmission resistance. Comparative Examples 5-6 have significantly decreased separation efficiency due to the use of kaolin / attapulgite, which increases the resistance. Due to the enhanced chemical stability of the membrane structure by sulfuric acid modified montmorillonite and crosslinking agent (divinylbenzene), the retention rate of all examples decreases by ≤1% (e.g. from 99% to 98% for Example 1) after 72 hours of continuous operation, while the retention rate of the comparative examples generally decreases more significantly (e.g. from 77% to 72% for Comparative Example 6).

[0111] In Comparative Example 7, no impregnation mixture II is used, resulting in a polyether sulfone microporous membrane that is not surface-functionalized. The sodium dodecyl benzene sulfonate and acid-modified montmorillonite in impregnation mixture II play a key role in pore regulation and surface charge distribution of the membrane. The absence of this step will cause the membrane pore structure to be loose, the surface hydrophilicity to decrease, and the performance to decrease.

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

Claims

1. A high-separation-benefit electrodialysis membrane, characterized by, The electrodialysis membrane is obtained by a treatment method, which comprises the following steps: sequentially immersing a polyether sulfone microporous membrane in immersion mixed solution one and immersion mixed solution two; The immersion mixed solution one is composed of 2-acrylamide-2-methylpropanesulfonic acid 300-320 parts, N-methylpyrrolidone 220-260 parts, triethylamine 60-70 parts, divinylbenzene 30-40 parts, methyl methacrylate 10-20 parts and azobisisobutyronitrile 2-3 parts in terms of weight fraction; The immersion mixed solution two is composed of sodium dodecyl benzene sulfonate 10-12 parts, acid modified montmorillonite 6-8 parts and ethanol 500-600 parts in terms of weight fraction. The acid modified montmorillonite is prepared by the following method: soaking montmorillonite in a 15-25% sulfuric acid aqueous solution with a temperature of 50-60 ℃ for 20-24 h, then washing with deionized water until neutral, and drying at a temperature of 55-65 ℃ for 23-25 h.

2. The high-separation-benefit electrodialysis membrane according to claim 1, wherein, The polyether sulfone 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. The high-separation-benefit electrodialysis membrane according to claim 1, wherein, The preparation method of the electrodialysis membrane further comprises the following steps: after the soaking is completed, placing the polyether sulfone microporous membrane between two polyethylene terephthalate films, removing the air bubbles between the films to form a composite membrane, and then peeling off the two films after drying the composite membrane.

4. The high-separation-benefit electrodialysis membrane according to claim 1, wherein, The preparation method of the immersion mixed solution one comprises the following steps: mixing 2-acrylamide-2-methylpropanesulfonic acid, N-methylpyrrolidone, triethylamine, divinylbenzene, methyl methacrylate and azobisisobutyronitrile, and stirring at a speed of 200-300 rpm for 60-80 min to obtain the immersion mixed solution one.

5. The high-separation-benefit electrodialysis membrane according to claim 1, wherein, The preparation method of the immersion mixed solution two comprises the following steps: mixing sodium dodecyl benzene sulfonate, acid modified montmorillonite and ethanol, and stirring at a speed of 200-300 rpm for 40-60 min to obtain the immersion mixed solution two.

6. A high-separation-benefit electrodialysis membrane according to claim 5, characterized in that, The immersion time in the immersion mixed solution one is 10-20 min, and the immersion temperature is 60-80 ℃.

7. The high-separation-benefit electrodialysis membrane according to claim 1, wherein, The immersion time in the immersion mixed solution two is 40-60 min.

8. The high-separation-benefit electrodialysis membrane according to claim 3, wherein, The drying mode is placing in an oven at 60-80 ℃ for 8-10 h.

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