Covalent cross-linked anion exchange membrane as well as preparation method and application thereof
The preparation of anion exchange membranes by covalent cross-linking method solves the problems of easy dissolution and insufficient selectivity of ionic liquids, achieves high selectivity and structural stability, reduces preparation costs, and is suitable for large-scale production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-25
- Publication Date
- 2026-04-10
AI Technical Summary
Existing anion exchange membranes suffer from problems such as easy dissolution of ionic liquids, insufficient selective adsorption capacity, and poor cycle stability. Furthermore, their preparation processes are complex and costly, making it difficult to meet the needs of large-scale industrial production.
Anion exchange membranes were prepared using a covalent cross-linking method. A stable polyionic liquid-polymer covalent network was formed through the covalent network structure of 1-vinyl-3-propylimidazolium chloride, acrylic monomers, and amide monomers. Combined with UV-initiated polymerization and protonation treatment, a high-density uniform distribution of functional sites and structural stability were achieved.
It improves ion exchange capacity and selectivity, extends membrane lifespan, reduces preparation costs, adapts to the dynamic requirements of electroadsorption desalination, and is suitable for large-scale production.
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Figure CN121824835A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of supercapacitor electrode materials, and particularly relates to a covalently cross-linked anion exchange membrane and a preparation method and application thereof. BACKGROUND
[0002] As a core functional material in the fields of electrosorption desalination, fuel cells, water treatment, etc., the performance of an anion exchange membrane directly determines the ion transmission efficiency, selectivity and long-term stability of the system. At present, traditional anion exchange membranes mainly realize anion adsorption and conduction by introducing quaternary ammonium salt, imidazolium and other cationic sites into the polymer skeleton. However, there are still many problems to be solved in the prior art.
[0003] On the one hand, the combination mode of introducing quaternary ammonium salt, imidazolium and other cationic functional sites into the polymer skeleton is unreasonable, resulting in a high risk of ion liquid dissolution. Most existing membrane materials introduce ion liquid into the polymer matrix by physical blending. Due to the lack of chemical bonding, the ion liquid is easy to be lost in the aqueous solution environment, causing the attenuation of ion exchange capacity and the decline of selectivity, and seriously affecting the service life of the membrane in circulation. Some membrane materials using chemical grafting modification also have problems of low grafting rate and uneven distribution of sites, making it difficult to realize uniform arrangement of high-density functional sites.
[0004] On the other hand, the adaptability of the polymer skeleton to the electrosorption system is insufficient. The skeleton design of traditional membrane materials often focuses on a single performance (such as mechanical strength or hydrophilicity), ignoring the dynamic requirements of "fast adsorption-thorough desorption" in the electrosorption process: if the skeleton hydrophilicity is too strong, it is easy to cause the membrane to swell excessively in the aqueous solution, damaging the structural stability; if the skeleton rigidity is too strong, it will limit the dynamic adjustment of the ion transmission channel, prolong the desorption time, and reduce the charge utilization efficiency. In addition, the assembly process of traditional membranes and electrodes is easy to produce contact resistance, affecting the charge transmission efficiency, and further restricting the improvement of electrosorption desalination performance.
[0005] At the same time, the preparation process of existing high-performance anion exchange membranes depends on complex synthesis routes, expensive special reagents or special equipment, resulting in high preparation cost and complicated process, which is difficult to meet the needs of large-scale industrial production. Therefore, developing an anion exchange membrane with stable functional sites, strong skeleton adaptability and simple preparation process has become a key to promoting the industrial application of electrosorption desalination and other technologies. SUMMARY
[0006] The application provides a covalently cross-linked anion exchange membrane and a preparation method and application thereof, aiming to solve the problems of existing covalently cross-linked anion exchange membranes, such as dependence on inorganic material dispersion, easy dissolution of ion liquid, insufficient selective adsorption capacity and poor cycle stability.
[0007] The first aspect of the present application provides a covalently cross-linked anion exchange membrane, comprising the following raw materials by mass fraction: 1-vinyl-3-propylimidazole chloride 35-55 parts, acrylic monomer 20-35 parts, amide monomer 10-25 parts and cross-linking agent 2-6 parts.
[0008] According to some embodiments of the covalently cross-linked anion exchange membrane according to the present application, the acrylic monomer comprises one or more of hydroxyethyl methacrylate, hydroxypropyl acrylate (GMA), glycidyl methacrylate (HPA) and polyethylene glycol methacrylate (PEGMA).
[0009] According to some embodiments of the covalently cross-linked anion exchange membrane according to the present application, the amide monomer comprises one or more of N,N-dimethyl acrylamide, N-isopropyl acrylamide (NIPAM) and N-hydroxymethyl acrylamide (NMA).
[0010] According to some embodiments of the covalently cross-linked anion exchange membrane according to the present application, the cross-linking agent comprises one or more of ethylene glycol dimethacrylate, diethylene glycol dimethacrylate (DEGDMA) and trimethylolpropane trimethacrylate (TMPTMA).
[0011] The second aspect of the present application provides a preparation method of the covalently cross-linked anion exchange membrane according to the first aspect of the present application, comprising the following steps: (1) mixing 1-vinyl-3-propylimidazole chloride, acrylic monomer, amide monomer, cross-linking agent, photoinitiator and organic solvent to obtain a mixed solution; (2) performing defoaming treatment on the mixed solution of step (1), then coating on the surface of a substrate, and then sequentially performing ultraviolet irradiation and drying treatment to obtain a composite film; (3) contacting the composite film of step (2) with an acid for protonation treatment to obtain the covalently cross-linked anion exchange membrane.
[0012] According to some embodiments of the preparation method of the covalently cross-linked anion exchange membrane according to the present application, the preparation method of the covalently cross-linked anion exchange membrane further comprises the step of preparing 1-vinyl-3-propylimidazole chloride; The specific operation steps include: a. mixing 1-vinylimidazole, 1-bromopropane and anhydrous ethanol, and performing reflux reaction to obtain a reaction solution; b. adjusting the pH of the reaction solution to alkaline, filtering and concentrating the filtrate to obtain a viscous liquid; c. redissolving the viscous liquid with anhydrous ethanol, and then cooling and crystallizing to obtain the 1-vinyl-3-propylimidazole chloride.
[0013] According to some embodiments of the method for preparing the covalently cross-linked anion exchange membrane described in this application, in step a, the molar ratio of 1-vinylimidazolium and 1-bromopropane is 1:(1-1.2).
[0014] According to some embodiments of the preparation method of the covalently cross-linked anion exchange membrane described in this application, in step a, the temperature of the reflux reaction is 60-70°C, and the time of the reflux reaction is 12-16 h.
[0015] According to some embodiments of the preparation method of the covalently cross-linked anion exchange membrane described in this application, in step b, the pH of the reaction solution is adjusted using a sodium hydroxide aqueous solution with a mass concentration of 10%-15%.
[0016] According to some embodiments of the preparation method of the covalently cross-linked anion exchange membrane described in this application, in step b, the pH of the reaction solution is 8.0-9.0.
[0017] According to some embodiments of the preparation method of the covalently cross-linked anion exchange membrane described in this application, in step c, the cooling crystallization temperature is 0-5℃, and the cooling crystallization time is 8-12h.
[0018] According to some embodiments of the method for preparing covalently cross-linked anion exchange membranes described in this application, in step (1), the photoinitiator includes benzoin ether and / or 2-hydroxy-2-methyl-1-phenyl-1-propanone.
[0019] According to some embodiments of the preparation method of the covalently cross-linked anion exchange membrane described in this application, the added mass of the photoinitiator is 1%-3% of the total amount of 1-vinyl-3-propylimidazolium chloride, acrylic monomers and amide monomers.
[0020] According to some embodiments of the preparation method of the covalently cross-linked anion exchange membrane described in this application, in step (1), the organic solvent includes one or more of N,N-dimethylacetamide, N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP) and N,N-diethylformamide (DEF).
[0021] According to some embodiments of the preparation method of the covalently cross-linked anion exchange membrane described in this application, in step (1), the mass concentration of 1-vinyl-3-propylimidazolium chloride in the mixed solution is 8%-15%.
[0022] According to some embodiments of the preparation method of the covalently cross-linked anion exchange membrane described in this application, in step (2), the degassing treatment includes placing the mixed solution in a vacuum degassing machine and degassing it for 1-3 hours under conditions of vacuum degree of -0.08 to -0.1 MPa and temperature of 20-30°C.
[0023] According to some embodiments of the preparation method of the covalently cross-linked anion exchange membrane described in this application, in step (2), the wavelength of the ultraviolet irradiation is 320-360 nm, and the irradiation power is 25-35 mW / cm². 2 The irradiation time is 30-50 minutes.
[0024] According to some embodiments of the preparation method of the covalently cross-linked anion exchange membrane described in this application, the drying temperature is 50-70°C and the drying time is 5-7 hours.
[0025] According to some embodiments of the preparation method of the covalently cross-linked anion exchange membrane described in this application, the acid includes one or more of sulfuric acid, hydrochloric acid, nitric acid and phosphoric acid; preferably, the concentration of the acid is 0.3-0.7 mol / L.
[0026] According to some embodiments of the preparation method of the covalently cross-linked anion exchange membrane described in this application, the protonation treatment is carried out at a temperature of 20-30°C for 10-14 hours.
[0027] The third aspect of this application provides an application of the covalently cross-linked anion exchange membrane described in the first aspect of this application or the covalently cross-linked anion exchange membrane prepared by the method described in the second aspect of this application in separation.
[0028] According to some embodiments of the application described in this application, the separation process includes water electrolysis or seawater desalination.
[0029] A fourth aspect of this application provides an integrated electrode, the integrated electrode comprising an electroadsorption electrode and an anion functional layer coated on the surface of the electroadsorption electrode; The anion functional layer is either the covalently cross-linked anion exchange membrane described in the first aspect of this application or the covalently cross-linked anion exchange membrane obtained by the preparation method described in the second aspect of this application.
[0030] The fifth aspect of this application provides an electroadsorption desalination device, including the integrated electrode described in the fourth aspect of this application.
[0031] The beneficial effects of this application include: in the covalently cross-linked anion exchange membrane described in this application, the vinyl groups of 1-vinyl-3-propylimidazolium chloride undergo copolymerization reactions with the double bonds of acrylic and amide monomers to form a stable "polyionic liquid-polymer" covalent network, thus solving the problem of ionic liquid dissolution from a mechanistic perspective; simultaneously, the high-density and uniform distribution of imidazolium cations in the polyionic liquid enhances the resistance to Cl... - The specific electrostatic adsorption of acrylic monomers and the cross-linking structure of cross-linking agent EGDMA synergistically regulate the film swelling rate (15%-20%), achieving a synergistic effect of high selectivity and structural stability. Attached Figure Description
[0032] Figure 1 The desalination effect of the MCDI device assembled from the covalently cross-linked anion exchange membrane described in Example 1 of this application under different hydraulic retention times; Figure 2 The effect of different influent ion concentrations on the adsorption performance of the MCDI device assembled from the covalently cross-linked anion exchange membrane described in Example 1 of this application; Figure 3 The effect of different voltages on the adsorption performance of the MCDI device assembled from the covalently cross-linked anion exchange membrane described in Example 1 of this application. Detailed Implementation
[0033] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.
[0034] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.
[0035] This application provides a covalently cross-linked anion exchange membrane, comprising the following raw materials in parts by weight: 35-55 parts of 1-vinyl-3-propylimidazolium chloride, 20-35 parts of acrylic monomers, 10-25 parts of amide monomers, and 2-6 parts of cross-linking agent.
[0036] The covalently cross-linked anion exchange membrane described in this application contains acrylic monomers such as hydroxyethyl methacrylate, which contain polar groups such as hydroxyl groups (-OH), endowing the membrane with excellent hydrophilicity and providing channels for ion transport. Simultaneously, its acrylate structure (-COO-) has a weak interaction with the imidazolium cation of the polyionic liquid (VPImCl), stabilizing the distribution of functional sites. Amide monomers such as N,N-dimethylacrylamide, with their flexible segments and amide bonds (-CON-), enhance the membrane's mechanical toughness and fatigue resistance, avoiding membrane embrittlement caused by an excessively high proportion of acrylic monomers. The "rigid-flexible" alternating network formed by the copolymerization of these two monomers ensures both ion transport efficiency and adapts to the mechanical requirements of electroadsorption cycle operation. Both types of monomers contain unsaturated double bonds (-CH=CH2), which have matching copolymerization activity with the vinyl group of VPImCl. They can achieve molecular-level homogeneous polymerization under UV light initiation, avoiding functional site shielding caused by phase separation. Furthermore, the polarity of the amide bond is close to that of the ester group, which can reduce the interfacial tension between monomers, ensure the stability of the polymerization system, and provide a structural basis for the synergistic effect of high ion exchange capacity and low resistance.
[0037] The covalently cross-linked anion exchange membrane described in this application achieves covalent integration of functional sites and polymer backbone, breaking through the performance bottleneck of traditional physical blending or inorganic filler-based membranes. Traditional anion exchange membranes often introduce ionic liquids through physical blending, which easily leads to ionic liquid dissolution and loss of effective sites due to the lack of chemical bonding; or they rely on nanomaterials, resulting in uneven dispersion and complex preparation processes. In contrast, the covalently cross-linked anion exchange membrane described in this application copolymerizes the vinyl groups of 1-vinyl-3-propylimidazolium chloride with the double bonds of acrylic and amide monomers, forming a stable "polyionic liquid-polymer" covalent network, thus solving the ionic liquid dissolution problem mechanistically; simultaneously, the high-density and uniform distribution of imidazolium cations in the polyionic liquid enhances the resistance to Cl-. - The specific electrostatic adsorption of acrylic monomers and the cross-linking structure of cross-linking agent EGDMA synergistically regulate the film swelling rate (15%-20%), achieving a synergistic effect of high selectivity and structural stability.
[0038] In some embodiments of this application, the acrylic monomers include one or more of hydroxyethyl methacrylate, hydroxypropyl acrylate (GMA), glycidyl methacrylate (HPA), and polyethylene glycol methacrylate (PEGMA).
[0039] In some embodiments of this application, the amide monomer includes one or more of N,N-dimethylacrylamide, N-isopropylacrylamide (NIPAM), and N-hydroxymethylacrylamide (NMA).
[0040] In some embodiments of this application, the crosslinking agent includes one or more of ethylene glycol dimethacrylate, diethylene glycol dimethacrylate (DEGDMA), and trimethylolpropane trimethacrylate (TMPTMA). Ethylene glycol dimethacrylate (EGDMA), as a crosslinking agent, has diacrylate functional groups whose reactivity matches that of the monomers in the system, enabling rapid formation of a three-dimensional crosslinked network. This effectively inhibits excessive swelling of the membrane (swelling rate 15%-20%), improving structural stability and mechanical strength. The moderately flexible ethylene glycol segments neither block ion transport channels nor hinder channel wettability through the hydrophilicity of ether bonds, balancing structural stability and ion conduction efficiency. Furthermore, it exhibits good compatibility with organic solvents, and its crosslinking rate is synchronized with the copolymerization process, making it suitable for large-scale preparation processes and ensuring uniform membrane performance.
[0041] This application also provides a method for preparing the covalently cross-linked anion exchange membrane described in the first aspect of this application, comprising the following steps: (1) Mix 1-vinyl-3-propylimidazolium chloride, acrylic monomers, amide monomers, crosslinking agents, photoinitiators and organic solvents to obtain a mixed solution; (2) The mixed solution described in step (1) is degassed and then coated onto the surface of the substrate. Then, it is subjected to ultraviolet irradiation and drying treatment in sequence to obtain a composite film. (3) The composite membrane described in step (2) is contacted with acid and protonated to obtain the covalently cross-linked anion exchange membrane.
[0042] The method for preparing the covalently cross-linked anion exchange membrane described in this application uses 1-vinyl-3-propylimidazolium chloride (VPImCl) as the polyionic liquid functional monomer, and hydroxyethyl methacrylate (HEMA) and N,N-dimethylacrylamide (DMAA) as the polymer backbone monomers. Under the action of a cross-linking agent, an integrated network structure covalently cross-linked anion exchange membrane is prepared through a process of "precise monomer copolymerization-UV-initiated polymerization-protonation activation of ion sites". This allows the polyionic liquid cation sites to interact with Cl... - Its specific electrostatic effect, combined with the structural stability of the polymer skeleton, is adapted to the "rapid adsorption-complete desorption" cycle requirement of electroadsorption.
[0043] The covalently cross-linked anion exchange membrane described in this application has a process mechanism that better meets the core requirements of electro-adsorption desalination. Traditional membrane preparation processes are prone to problems such as functional site shielding and high membrane-electrode contact resistance, affecting adsorption-desorption efficiency. The preparation method described in this application adopts a "direct coating of titanium mesh electrode-UV-initiated polymerization" process, resulting in a tight bond between the membrane and electrode interface and reducing charge transport resistance. The flexible segments of the polyionic liquid can be rapidly relaxed under reverse voltage, promoting Cl... -Desorption, combined with protonation activation process to enhance the activity of cation sites, forms a dynamic mechanism of "high-density adsorption-rapid desorption"; and the dual monomer framework has both hydrophilicity and mechanical toughness, making it suitable for aqueous environment and cyclic operation, thus extending the service life of the membrane.
[0044] In some embodiments of this application, the method for preparing the covalently crosslinked anion exchange membrane further includes the step of preparing 1-vinyl-3-propylimidazolium chloride; The specific operating steps include: a. Mix 1-vinylimidazole, 1-bromopropane and anhydrous ethanol and reflux to obtain a reaction solution; b. Adjust the pH of the reaction solution to alkaline, filter, and concentrate the filtrate to obtain a viscous liquid; c. The viscous liquid is redissolved with anhydrous ethanol and then cooled to crystallize, yielding the 1-vinyl-3-propylimidazolium chloride.
[0045] In some embodiments of this application, in step a, the molar ratio of 1-vinylimidazole and 1-bromopropane is 1:(1-1.2).
[0046] In some embodiments of this application, in step a, the temperature of the reflux reaction is 60-70°C, for example 60°C, 63°C, 65°C, 67°C, or 70°C, and the time of the reflux reaction is 12-16 hours, for example 12 hours, 13 hours, 15 hours, or 16 hours.
[0047] In some embodiments of this application, in step b, an aqueous sodium hydroxide solution with a mass concentration of 10%-15% is used to adjust the pH of the reaction solution.
[0048] In some embodiments of this application, in step b, the pH of the reaction solution is 8.0-9.0, such as 8.0, 8.2, 8.5, 8.6, 8.8, 9.0, etc.
[0049] In some embodiments of this application, in step c, the temperature of the cooling crystallization is 0-5°C, for example 0°C, and the cooling crystallization time is 8-12h, for example 8h, 9h, 10h, 12h, etc.
[0050] In some embodiments of this application, 1-vinylimidazole and 1-bromopropane were accurately weighed in a molar ratio of 1:1.1 and placed in a 500 mL round-bottom flask. 200-250 mL of anhydrous ethanol was added as a solvent. A reflux condenser was installed, and the mixture was refluxed for 12-16 hours at a magnetic stirrer speed of 250-300 r / min and a temperature of 60-70°C. After the reaction was complete, the reaction solution was cooled to room temperature, and a 10%-15% (w / w) sodium hydroxide aqueous solution was slowly added to adjust the pH to 8.0-9.0. After stirring for 30 minutes, the mixture was filtered to remove solid impurities. The filtrate was transferred to a rotary evaporator and distilled at 50-60°C and a vacuum of 0.08-0.09 MPa to remove the solvent and unreacted monomers, yielding a pale yellow viscous liquid. 100-15% (w / w) sodium hydroxide solution was added to the viscous liquid. Dissolve the 1-vinyl-3-propylimidazolium chloride (VPImCl) monomer by heating to 40-50℃ with anhydrous ethanol, then cooling to 0-5℃ and allowing it to stand for crystallization for 8-12 hours. Collect the crystals by filtration, wash them 2-3 times with cold anhydrous ethanol, and finally dry them in a vacuum drying oven at 45-55℃ for 10-12 hours to obtain the monomer. Store the monomer in a sealed container away from light for later use.
[0051] In some embodiments of this application, in step (1), the photoinitiator includes 2-hydroxy-2-methyl-1-phenyl-1-propanone and / or benzoin ether; In some embodiments of this application, the added mass of the photoinitiator is 1%-3% of the total amount of 1-vinyl-3-propylimidazolium chloride, acrylic monomers, and amide monomers; for example, 1%, 1.5%, 2%, 2.8%, 3%, etc.
[0052] In some embodiments of this application, the organic solvent in step (1) includes one or more of N,N-dimethylacetamide, N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), and N,N-diethylformamide (DEF).
[0053] In some embodiments of this application, in step (1), the mass concentration of 1-vinyl-3-propylimidazolium chloride in the mixed solution is 8%-15%; for example, 8%, 10%, 12%, 15%, etc.
[0054] In some embodiments of this application, step (2) includes degassing the mixed solution in a vacuum degassing machine at a vacuum degree of -0.08 to -0.1 MPa, such as -0.08 MPa, -0.09 MPa, -0.1 MPa, etc., and a temperature of 20-30°C for 1-3 hours, such as 1 hour, 2 hours, 3 hours, etc. During the degassing process, gas is released every 30 minutes to remove air bubbles from the solution.
[0055] In some embodiments of this application, in step (2), the wavelength of the ultraviolet irradiation is 320-360 nm, and the irradiation power is 25-35 mW / cm². 2 For example, 25mW / cm 2 28mW / cm 2 30mW / cm 2 32mW / cm 2 35mW / cm 2 Irradiation time is 30-50 minutes; for example, 30 minutes, 32 minutes, 35 minutes, 46 minutes, 50 minutes, etc.
[0056] In some embodiments of this application, the drying temperature is 50-70°C, such as 50°C, 55°C, 60°C, 65°C, 70°C, etc., and the drying time is 5-7 hours, such as 5 hours, 6 hours, 7 hours, etc.
[0057] In some embodiments of this application, the titanium mesh is cut into 4-6cm×4-6cm specifications, and ultrasonically cleaned sequentially with acetone, ethanol, and deionized water for 10-20 minutes each (ultrasonic power 200-500W). It is then dried in a vacuum drying oven at 50-70℃ for 1-3 hours to complete the pretreatment. The pretreated titanium mesh is then laid flat on a horizontal substrate and fixed. A 150-250μm thickness coater is used to uniformly coat the mixed solution described in step (1) along the same direction. The coated substrate is then placed in an ultraviolet irradiation device at a wavelength of 320-360nm and a power of 25-35mW / cm. 2 Irradiate for 30-50 minutes under the specified conditions to initiate cross-linking polymerization; after irradiation, transfer the titanium mesh-film composite to a vacuum drying oven and dry for 5-7 hours at 50-70℃ and a vacuum of 0.07-0.09MPa to remove residual solvent, thereby obtaining a preliminary polyionic liquid composite film with a thickness of 70-100μm.
[0058] In some embodiments of this application, the acid includes one or more of sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid; preferably, the concentration of the acid is 0.3-0.7 mol / L; for example, 0.3 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, etc.
[0059] In some embodiments of this application, the protonation treatment is performed at a temperature of 20-30°C, such as 20°C, 25°C, 28°C, 30°C, etc., and for a time of 10-14 hours, such as 10 hours, 12 hours, 14 hours, etc.
[0060] The preparation method of the covalently cross-linked anion exchange membrane described in this application significantly improves its economy and practicality. Some existing high-performance covalently cross-linked anion exchange membranes rely on expensive reagents or complex equipment, resulting in high preparation costs and hindering large-scale application. The monomers, cross-linking agents, and initiators used in the preparation method described in this application are all conventional chemical reagents. 1-Vinyl-3-propylimidazolium chloride can be prepared in-house with a simple process (anhydrous ethanol as solvent, reflux reaction is sufficient), and N,N-dimethylacetamide (DMAc) can be recycled and reused. The preparation process does not require high-temperature and high-pressure equipment; the UV-initiated polymerization conditions are mild (wavelength 320-360 nm, power 25-35 mW / cm²); and post-treatment only requires acid washing and water washing. This simplifies the process, reduces energy consumption and costs, and is more suitable for industrial production needs.
[0061] This application also provides an application of the covalently cross-linked anion exchange membrane described in the first aspect of this application or the covalently cross-linked anion exchange membrane prepared by the method described in the second aspect of this application in separation.
[0062] In some embodiments of this application, the separation process includes water electrolysis or seawater desalination.
[0063] This application embodiment also provides an integrated electrode, the integrated electrode including an electroadsorption electrode and an anion functional layer coated on the surface of the electroadsorption electrode; The anion functional layer is either the covalently cross-linked anion exchange membrane described in the first aspect of this application or the covalently cross-linked anion exchange membrane obtained by the preparation method described in the second aspect of this application.
[0064] This application also provides an electroadsorption desalination device, including the integrated electrode described in the fourth aspect of this application.
[0065] The technical solution of this application will be further described below with reference to specific embodiments.
[0066] Example 1 A method for preparing a covalently cross-linked anion exchange membrane includes the following steps: (1) Preparation of 1-vinyl-3-propylimidazolium chloride (VPImCl) Accurately weigh 1-vinylimidazole and 1-bromopropane in a molar ratio of 1:1.1 and place them in a 500 mL round-bottom flask. Add 250 mL of anhydrous ethanol as a solvent, install a reflux condenser, and set the magnetic stirrer to 300 rpm. The reaction was carried out at a speed of r / min and a temperature of 70℃ for 12 hours under reflux. After the reaction was completed, the reaction solution was cooled to room temperature, and a 10% sodium hydroxide aqueous solution was slowly added to adjust the pH of the reaction solution to 8.0. After stirring for 30 minutes, the solution was filtered to remove solid impurities. The filtrate was transferred to a rotary evaporator and distilled at 50℃ and a vacuum of 0.08MPa to remove the solvent and unreacted monomers, resulting in a pale yellow viscous liquid. 150 mL of anhydrous ethanol was added to the viscous liquid and heated to 50℃ with stirring to dissolve. The solution was then cooled to 2℃ and allowed to stand for crystallization for 10 hours. The crystals were collected by filtration, washed three times with anhydrous ethanol at 5℃, and then dried in a vacuum drying oven at 50℃ for 10 hours to obtain 1-vinyl-3-propylimidazolium chloride (VPImCl) monomer, which was sealed and stored in the dark for later use.
[0067] (2) Weigh 35g of 1-vinyl-3-propylimidazolium chloride (VPImCl), 20g of hydroxyethyl methacrylate (HEMA), 10g of N,N-dimethylacrylamide (DMAA), and 3g of ethylene glycol dimethacrylate (EGDMA), place them in a three-necked flask, add 260g of N,N-dimethylacetamide (DMAc), and magnetically stir for 30 minutes at 300r / min and 25℃ to form a homogeneous and transparent monomer mixture; add the above monomer mixture to The photoinitiator benzoin ether (the added mass of the photoinitiator is 2% of the total mass of 1-vinyl-3-propylimidazolium chloride, hydroxyethyl methacrylate, and N,N-dimethylacrylamide) was added and stirred at 250 r / min for 30 minutes in a dark environment until the photoinitiator was completely dissolved. Then the mixture was transferred to a vacuum degassing machine and degassed at a vacuum of -0.08 MPa and a temperature of 25°C for 2 hours, during which gas was released every 30 minutes to remove air bubbles from the solution, resulting in a mixed solution. The titanium mesh was cut into 6cm×6cm pieces and ultrasonically cleaned sequentially with acetone, ethanol, and deionized water for 10 minutes each (ultrasonic power 300W). It was then dried in a vacuum oven at 60℃ for 2 hours to complete the pretreatment. The pretreated titanium mesh was laid flat on a horizontal substrate and fixed. Using a 200μm thickness coater, the above-mentioned mixed solution was uniformly coated in the same direction at the same speed. The coated substrate was then placed in an ultraviolet irradiation device at a wavelength of 360nm and a power of 30mW / cm². 2 Irradiate for 30 minutes under the specified conditions to initiate cross-linking polymerization; after irradiation, transfer the titanium mesh-film composite to a vacuum drying oven and dry for 6 hours at 60°C and 0.08 MPa to remove residual solvent, resulting in a composite film with a thickness of 100 μm.
[0068] (3) Prepare a 0.5 mol / L hydrochloric acid solution. After peeling the composite membrane obtained in step (2) from the titanium mesh, immerse it completely in the hydrochloric acid solution and statically soak it in a constant temperature water bath at 20°C for 12 hours to fully protonate the imidazolium cation. After soaking, take out the composite membrane and wash it repeatedly with deionized water until the pH value of the washing solution is 7.0. Place the washed membrane sample in a vacuum drying oven and dry it at 50°C and a vacuum degree of 0.08 MPa for 8 hours until the membrane quality is constant, and obtain the covalently cross-linked anion exchange membrane.
[0069] Example 2 The only difference between the preparation method of the covalently cross-linked anion exchange membrane in Example 2 and that in Example 1 is that the acrylic monomer used in the preparation process of the covalently cross-linked anion exchange membrane in Example 2 is hydroxypropyl acrylate (HPA).
[0070] Example 3 The only difference between the preparation method of the covalently cross-linked anion exchange membrane in Example 3 and that in Example 1 is that the acrylic monomer used in the preparation process of the covalently cross-linked anion exchange membrane in Example 3 is glycidyl methacrylate (GMA).
[0071] Example 4 The only difference between the preparation method of the covalently cross-linked anion exchange membrane in Example 4 and that in Example 1 is that the amide monomer used in the preparation process of the covalently cross-linked anion exchange membrane in Example 4 is N-isopropylacrylamide (NIPAM).
[0072] Example 5 The only difference between the preparation method of the covalently cross-linked anion exchange membrane in Example 5 and that in Example 1 is that the amide monomer used in the preparation process of the covalently cross-linked anion exchange membrane in Example 5 is N-hydroxymethylacrylamide (NMA).
[0073] Example 6 The only difference between the preparation method of the covalently cross-linked anion exchange membrane in Example 6 and that in Example 1 is that the cross-linking agent used in the preparation process of the covalently cross-linked anion exchange membrane in Example 6 is diethylene glycol dimethacrylate (DEGDMA).
[0074] Example 7 The only difference between the preparation method of the covalently cross-linked anion exchange membrane in Example 7 and that in Example 1 is that the cross-linking agent used in the preparation process of the covalently cross-linked anion exchange membrane in Example 7 is trimethylolpropane trimethacrylate (TMPTMA).
[0075] Example 8 The only difference between the preparation method of the covalently cross-linked anion exchange membrane described in Example 8 and that in Example 1 is that the ratio of 1-vinyl-3-propylimidazolium chloride, acrylic monomers, and amide monomers used in the preparation process of the covalently cross-linked anion exchange membrane in Example 8 is different from that in Example 1.
[0076] The specific operating steps include: (2) Weigh 45g of 1-vinyl-3-propylimidazolium chloride (VPImCl), 25g of hydroxyethyl methacrylate (HEMA), 15g of N,N-dimethylacrylamide (DMAA), and 3g of ethylene glycol dimethacrylate (EGDMA), place them in a three-necked flask, add 100g of N,N-dimethylacetamide (DMAc), and magnetically stir for 30 minutes at 300r / min and 25℃ to form a homogeneous and transparent monomer mixture; add photoinitiator acetamide to the above monomer mixture. The photoinitiator (2% of the total mass of 1-vinyl-3-propylimidazolium chloride, hydroxyethyl methacrylate, and N,N-dimethylacrylamide) was stirred at 250 rpm for 30 minutes in a dark environment until the photoinitiator was completely dissolved. The mixture was then transferred to a vacuum degassing machine and degassed at a vacuum of -0.08 MPa and a temperature of 25°C for 2 hours, with gas released every 30 minutes to remove air bubbles and obtain a mixed solution. The remaining steps were the same as in Example 1.
[0077] Example 9 The only difference between the preparation method of the covalently cross-linked anion exchange membrane described in Example 9 and that in Example 1 is that the ratio of 1-vinyl-3-propylimidazolium chloride, acrylic monomers, and amide monomers used in the preparation process of the covalently cross-linked anion exchange membrane in Example 9 is different from that in Example 1.
[0078] The specific operating steps include: (2) Weigh 55g of 1-vinyl-3-propylimidazolium chloride (VPImCl), 20g of hydroxyethyl methacrylate (HEMA), 10g of N,N-dimethylacrylamide (DMAA), and 3g of ethylene glycol dimethacrylate (EGDMA), place them in a three-necked flask, add 100g of N,N-dimethylacetamide (DMAc), and magnetically stir for 30 minutes at 300r / min and 25℃ to form a homogeneous and transparent monomer mixture; add photoinitiator acetamide to the above monomer mixture. The photoinitiator (2% of the total mass of 1-vinyl-3-propylimidazolium chloride, hydroxyethyl methacrylate, and N,N-dimethylacrylamide) was stirred at 250 rpm for 30 minutes in a dark environment until the photoinitiator was completely dissolved. The mixture was then transferred to a vacuum degassing machine and degassed at a vacuum of -0.08 MPa and a temperature of 25°C for 2 hours, with gas released every 30 minutes to remove air bubbles and obtain a mixed solution. The remaining steps were the same as in Example 1. Example 10 The only difference between the preparation method of the covalently cross-linked anion exchange membrane described in Example 10 and that in Example 1 is that the ratio of 1-vinyl-3-propylimidazolium chloride, acrylic monomers, and amide monomers used in the preparation process of the covalently cross-linked anion exchange membrane in Example 10 is different from that in Example 1.
[0079] The specific operating steps include: (2) Weigh 35g of 1-vinyl-3-propylimidazolium chloride (VPImCl), 35g of hydroxyethyl methacrylate (HEMA), 25g of N,N-dimethylacrylamide (DMAA), and 3g of ethylene glycol dimethacrylate (EGDMA), place them in a three-necked flask, add 100g of N,N-dimethylacetamide (DMAc), and magnetically stir for 30 minutes at 300r / min and 25℃ to form a homogeneous and transparent monomer mixture; add photoinitiator acetamide to the above monomer mixture. The photoinitiator (2% of the total mass of 1-vinyl-3-propylimidazolium chloride, hydroxyethyl methacrylate, and N,N-dimethylacrylamide) was stirred at 250 rpm for 30 minutes in a dark environment until the photoinitiator was completely dissolved. The mixture was then transferred to a vacuum degassing machine and degassed at a vacuum of -0.08 MPa and a temperature of 25°C for 2 hours, with gas released every 30 minutes to remove air bubbles and obtain a mixed solution. The remaining steps were the same as in Example 1. Example 11 The only difference between the preparation method of the covalently cross-linked anion exchange membrane in Example 11 and that in Example 1 is that the ultraviolet irradiation time during the preparation of the covalently cross-linked anion exchange membrane in Example 11 is 15 min.
[0080] Example 12 The only difference between the preparation method of the covalently cross-linked anion exchange membrane in Example 12 and that in Example 1 is that the ultraviolet irradiation time during the preparation of the covalently cross-linked anion exchange membrane in Example 12 is 45 min.
[0081] Example 13 The only difference between the preparation method of the covalently cross-linked anion exchange membrane in Example 13 and that in Example 1 is that the ultraviolet irradiation time during the preparation of the covalently cross-linked anion exchange membrane in Example 13 is 40 min.
[0082] Example 14 The only difference between the preparation method of the covalently cross-linked anion exchange membrane described in Example 14 and that in Example 1 is that the amount of cross-linking agent used in the preparation process of the covalently cross-linked anion exchange membrane described in Example 14 is different from that in Example 1.
[0083] The specific operating steps include: (2) Weigh 35g of 1-vinyl-3-propylimidazolium chloride (VPImCl), 20g of hydroxyethyl methacrylate (HEMA), 10g of N,N-dimethylacrylamide (DMAA), and 2g of ethylene glycol dimethacrylate (EGDMA), place them in a three-necked flask, add 100g of N,N-dimethylacetamide (DMAc), and magnetically stir for 30 minutes at 300r / min and 25℃ to form a homogeneous and transparent monomer mixture; add photoinitiator to the above monomer mixture. Benzoin ether (the photoinitiator is added at 2% of the total mass of 1-vinyl-3-propylimidazolium chloride, hydroxyethyl methacrylate, and N,N-dimethylacrylamide) was stirred at 250 rpm for 30 minutes in a dark environment until the photoinitiator was completely dissolved. The mixture was then transferred to a vacuum degassing machine and degassed at a vacuum of -0.08 MPa and a temperature of 25°C for 2 hours, with gas released every 30 minutes to remove air bubbles from the solution, resulting in a mixed solution. The remaining operations were the same as in Example 1.
[0084] Example 15 The only difference between the preparation method of the covalently cross-linked anion exchange membrane described in Example 15 and that in Example 1 is that the amount of cross-linking agent used in the preparation process of the covalently cross-linked anion exchange membrane described in Example 15 is different from that in Example 1.
[0085] The specific operating steps include: (2) Weigh 35g of 1-vinyl-3-propylimidazolium chloride (VPImCl), 20g of hydroxyethyl methacrylate (HEMA), 10g of N,N-dimethylacrylamide (DMAA), and 6g of ethylene glycol dimethacrylate (EGDMA), place them in a three-necked flask, add 100g of N,N-dimethylacetamide (DMAc), and magnetically stir for 30 minutes at 300r / min and 25℃ to form a homogeneous and transparent monomer mixture; add photoinitiator to the above monomer mixture. Benzoin ether (the photoinitiator is added at 2% of the total mass of 1-vinyl-3-propylimidazolium chloride, hydroxyethyl methacrylate, and N,N-dimethylacrylamide) was stirred at 250 rpm for 30 minutes in a dark environment until the photoinitiator was completely dissolved. The mixture was then transferred to a vacuum degassing machine and degassed at a vacuum of -0.08 MPa and a temperature of 25°C for 2 hours, with gas released every 30 minutes to remove air bubbles from the solution, resulting in a mixed solution. The remaining operations were the same as in Example 1.
[0086] Example 16 The only difference between the preparation method of the covalently cross-linked anion exchange membrane described in Example 16 and that in Example 1 is that the amount of cross-linking agent used in the preparation process of the covalently cross-linked anion exchange membrane described in Example 16 is different from that in Example 1.
[0087] The specific operating steps include: (2) Weigh 35g of 1-vinyl-3-propylimidazolium chloride (VPImCl), 20g of hydroxyethyl methacrylate (HEMA), 10g of N,N-dimethylacrylamide (DMAA), and 4g of ethylene glycol dimethacrylate (EGDMA), place them in a three-necked flask, add 100g of N,N-dimethylacetamide (DMAc), and magnetically stir for 30 minutes at 300r / min and 25℃ to form a homogeneous and transparent monomer mixture; add photoinitiator to the above monomer mixture. Benzoin ether (the photoinitiator is added at 2% of the total mass of 1-vinyl-3-propylimidazolium chloride, hydroxyethyl methacrylate, and N,N-dimethylacrylamide) was stirred at 250 rpm for 30 minutes in a dark environment until the photoinitiator was completely dissolved. The mixture was then transferred to a vacuum degassing machine and degassed at a vacuum of -0.08 MPa and a temperature of 25°C for 2 hours, with gas released every 30 minutes to remove air bubbles from the solution, resulting in a mixed solution. The remaining operations were the same as in Example 1.
[0088] Comparative Example 1 The only difference between the preparation method of the covalently cross-linked anion exchange membrane described in Comparative Example 1 and Example 1 is that the covalently cross-linked anion exchange membrane described in Comparative Example 1 did not use 1-vinyl-3-propylimidazolium chloride as a raw material during the preparation process.
[0089] The specific operating steps include: (2) Weigh 20g of hydroxyethyl methacrylate (HEMA), 10g of N,N-dimethylacrylamide (DMAA), and 3g of ethylene glycol dimethacrylate (EGDMA), place them in a three-necked flask, add 100g of N,N-dimethylacetamide (DMAc), and magnetically stir for 30 minutes at 300r / min and 25°C to form a homogeneous and transparent monomer mixture; add benzoin ether (the mass of the photoinitiator added is 2% of the total mass of 1-vinyl-3-propylimidazolium chloride, hydroxyethyl methacrylate, and N,N-dimethylacrylamide) to the above monomer mixture, and stir at 250r / min for 30 minutes in a dark environment until the photoinitiator is completely dissolved; then transfer the mixture to a vacuum degassing machine, and degas for 2 hours at a vacuum of -0.08MPa and 25°C, releasing the gas every 30 minutes to remove bubbles from the solution to obtain a mixed solution; the remaining operations are the same as in Example 1.
[0090] Comparative Example 2 The only difference between the preparation method of the covalently cross-linked anion exchange membrane in Comparative Example 2 and that in Example 1 is that no cross-linking agent was used in the preparation process of the covalently cross-linked anion exchange membrane in Comparative Example 2.
[0091] The specific operating steps include: The specific operating steps include: (2) Weigh 35g of 1-vinyl-3-propylimidazolium chloride (VPImCl), 20g of hydroxyethyl methacrylate (HEMA), and 10g of N,N-dimethylacrylamide (DMAA), place them in a three-necked flask, add 100g of N,N-dimethylacetamide (DMAc), and magnetically stir for 30 minutes at 300r / min and 25℃ to form a homogeneous and transparent monomer mixture; add benzoin ether (photoinitiator) to the above monomer mixture. The addition of 1-vinyl-3-propylimidazolium chloride, hydroxyethyl methacrylate, and N,N-dimethylacrylamide was 2% of the total mass. The mixture was stirred at 250 rpm for 30 minutes in a dark environment until the photoinitiator was completely dissolved. The mixture was then transferred to a vacuum degassing machine and degassed at a vacuum of -0.08 MPa and a temperature of 25°C for 2 hours, during which gas was released every 30 minutes to remove air bubbles from the solution, resulting in a mixed solution. The remaining operations were the same as in Example 1. Comparative Example 3 The only difference between the preparation method of the covalently cross-linked anion exchange membrane described in Comparative Example 3 and Example 1 is that a photoinitiator was added during the preparation of the covalently cross-linked anion exchange membrane described in Comparative Example 3, and no ultraviolet irradiation was performed.
[0092] The specific operating steps include: (1) Preparation of 1-vinyl-3-propylimidazolium chloride (VPImCl) was carried out using the same method as in Example 1; (2) Weigh 35g of 1-vinyl-3-propylimidazolium chloride (VPImCl), 20g of hydroxyethyl methacrylate (HEMA), 10g of N,N-dimethylacrylamide (DMAA), and 3g of ethylene glycol dimethacrylate (EGDMA), place them in a three-necked flask, add 100g of N,N-dimethylacetamide (DMAc), and magnetically stir for 30 minutes at a speed of 300r / min and a temperature of 25℃ to form a homogeneous and transparent monomer mixture; then transfer the mixture to a vacuum degassing machine and degas for 2 hours at a vacuum of -0.08MPa and a temperature of 25℃, releasing the gas once every 30 minutes during the process to remove the bubbles in the solution and obtain a mixed solution; the remaining operations are the same as in Example 1.
[0093] 1. Performance study of the covalently cross-linked anion exchange membranes described in Examples 1-16 and Comparative Examples 1-3 of this application. Ion transport number: determined by membrane potential method.
[0094] The specific procedure is as follows: The ion exchange membrane to be tested is fixed in a two-chamber electrolytic cell, serving as a barrier separating the two chambers. Equal volumes of 0.1 mol / L NaCl solution are added to both the left and right chambers, ensuring the solution levels on both sides of the membrane are flush and there is no pressure difference. A saturated calomel electrode is used as a reference electrode, inserted into the solutions in both chambers, and connected to an electrochemical workstation to record the membrane potential values across the membrane. Based on the measured membrane potential, combined with the Nernst equation and the ratio of anion to cation migration rates, the cation transport number t is calculated. + This value directly reflects the membrane's selective transport capability for cations.
[0095] Ion exchange capacity: Accurately weigh the covalently cross-linked anion exchange membrane samples dried to constant weight (the covalently cross-linked anion exchange membranes described in Examples 1-16 and Comparative Examples 1-3 of this application, with mass denoted as m, accurate to 0.001 g), and completely immerse them in 50 mL of 0.5 mol / L hydrochloric acid solution, statically soaking at 25°C for 12 h to allow sufficient anion exchange equilibrium within the membrane; remove the membrane samples and repeatedly wash them with deionized water until the washing solution is free of Cl. -(Test with 0.1 mol / L silver nitrate solution to ensure no white precipitate is found). Collect all washing and soaking solutions and bring the volume to 100 mL. Take 20 mL of the diluted solution and titrate with 0.1 mol / L sodium hydroxide standard solution using phenolphthalein as an indicator until the solution turns pink and does not fade for 30 seconds. Record the volume (V) of sodium hydroxide standard solution consumed. Calculate the ion exchange capacity using the formula IEC=(c×V×5) / m (where c is the concentration of sodium hydroxide standard solution, mol / L; 5 is the volume adjustment factor; and m is the dry weight of the membrane sample, g). Perform parallel tests on each sample three times and take the average value as the final result.
[0096] Desalination adsorption capacity: determined by an electro-adsorption desalination device.
[0097] The specific operating method is as follows: A three-electrode system is constructed, using the membrane sample (the covalently cross-linked anion exchange membrane described in Examples 1-16 and Comparative Examples 1-3 of this application) modified electrode as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode. The covalently cross-linked anion exchange membranes are tightly attached to the surface of the working electrode, and both are placed in 100 mL of NaCl solution with an initial concentration of 1000 mg / L. An electroadsorption experiment is conducted at a constant voltage of 1.2 V for 2 hours, with samples taken every 10 minutes. The conductivity of the solution is measured using a conductivity meter and converted to salt concentration. After the experiment, the initial concentration C is used to determine the salt concentration. o Final concentration C e The desalination adsorption capacity is calculated using the formula: (C = solution volume V and dry weight m of the covalently cross-linked anion exchange membrane) / (V = solution volume V and dry weight m of the covalently cross-linked anion exchange membrane). o -C e The desalination performance of the membrane is directly reflected by the formula (V / m) × V / m, with the unit being mg / g.
[0098] Charge efficiency: calculated based on experimental data of electroadsorption desalination.
[0099] The specific operating method is as follows: First, calculate the theoretical amount of electricity required to remove a certain amount of salt based on the desalination adsorption capacity (using Faraday's law, combined with the conversion between ion valence state and molar charge); simultaneously, record the current-time curve during the electroadsorption process using an electrochemical workstation, and integrate the curve to obtain the total amount of electricity consumed during the experiment. The charge efficiency is calculated using the formula: Charge efficiency = (Theoretical charge / Total charge) × 100%. This value reflects the effectiveness of charge utilization by the membrane during electroadsorption, avoiding ineffective side reactions that consume electricity.
[0100] Membrane thickness: Measured using a micrometer screw gauge.
[0101] The dried covalently cross-linked anion exchange membrane sample was laid flat on a horizontal table, ensuring the membrane surface was smooth and wrinkle-free. Using a micrometer with an accuracy of 0.001 mm, measurements were taken at different areas of the membrane (including at least five evenly distributed measurement points around the center and perimeter). The micrometer zero point was calibrated before each measurement, and excessive pressure was avoided during measurement to prevent membrane deformation. The average of the five measurements was taken as the final membrane thickness in mm. This parameter affects the membrane's mechanical properties and ion transport path length.
[0102] The results are shown in Table 1.
[0103] Table 1
[0104] As can be seen from Table 1, the test data clearly show that the selection of raw materials, optimization of the ratio, and control of process parameters have a significant regulatory effect on the core performance of covalently cross-linked anion exchange membranes. Example 1 uses a combination system of hydroxyethyl methacrylate (HEMA), N,N-dimethylacrylamide (DMAA), and ethylene glycol dimethacrylate (EGDMA), which has an ion exchange capacity of 1.58 mmol / g, a desalination adsorption capacity of 65 mg / g, and a charge efficiency of 92%, and its overall performance is better than other monomer replacement groups (Examples 2-7). This is because the hydroxyl density and spatial configuration of HEMA can form a stable synergistic effect with the imidazolium cation of 1-vinyl-3-propylimidazolium chloride (VPImCl), constructing an efficient ion transport channel. DMAA ensures the uniformity of the copolymer network due to its excellent compatibility. The bifunctional structure of EGDMA can precisely control the crosslinking density, avoiding site dispersion caused by the excessive flexibility of hydroxypropyl acrylate (HPA) segments, channel blockage caused by excessive crosslinking of glycidyl methacrylate (GMA), and problems of hydrophobicity enhancement or network densification caused by diethylene glycol dimethacrylate (DEGDMA) and trimethylolpropane trimethacrylate (TMPTMA).
[0105] Comparing Examples 1 and 9-10, it can be seen that Example 9 uses the upper limit ratio of 55 parts VPImCl. Due to the maximization of functional site density, the ion exchange capacity reaches 1.80 mmol / g and the desalination adsorption capacity is 78 mg / g. This fully verifies the scientific validity of the ratio of 35-55 parts VPImCl, 20-35 parts acrylic monomers, and 10-25 parts amide monomers. This ratio can achieve synergistic optimization of ion adsorption and structural stability by adjusting the balance between hydrophilicity and mechanical strength.
[0106] Comparing Examples 1 and 11-13, it can be seen that the covalently cross-linked anion exchange membrane obtained when the UV irradiation time is 30-40 min exhibits better performance. Comparing Examples 1 and 14-16, it can be seen that the covalently cross-linked anion exchange membrane obtained when the amount of cross-linking agent added is 3-4 g exhibits better performance. Under these conditions, the monomer polymerization conversion rate is ≥95%, and the degree of cross-linking is controlled within the ideal range of 75%-80%, ensuring the unobstructed ion transport channels while avoiding the problems of incomplete polymerization due to insufficient irradiation or decreased porosity caused by excessive cross-linking agent.
[0107] The performance degradation of the comparative examples further confirms the necessity of core raw materials and key processes: Comparative Example 1, lacking the addition of VPImCl, lacked specific anion adsorption sites, resulting in an ion exchange capacity of only 0.18 mmol / g, a desalination adsorption capacity reduced to 12 mg / g, and an ion transference number as high as 0.35, making effective desalination and separation impossible; Comparative Example 2, lacking a three-dimensional network structure support due to the absence of a crosslinking agent, experienced a membrane swelling rate exceeding 80% in aqueous solution, leading to easy loss of ion sites, a charge efficiency of only 60%, and mechanical strength approaching 0, failing to meet practical application requirements; Comparative Example 3, without ultraviolet irradiation, had its photoinitiator not activated, and the monomers did not undergo copolymerization, forming only a physical mixture, resulting in a membrane structure prone to delamination and collapse, a desalination adsorption capacity of only 10 mg / g, and no practical functional value. This is because the imidazolium cations provided by VPImCl are the core basis for achieving selective adsorption and transport of anions. The crosslinking agent inhibits excessive swelling by constructing a stable three-dimensional network, while ultraviolet irradiation ensures the uniform copolymerization of monomers and the complete formation of the functional network. The synergistic effect of the three ultimately achieves the synergistic performance of high selectivity, high adsorption capacity and long cycle stability of the covalently crosslinked anion exchange membrane.
[0108] 2. Desalination effect of the MCDI device assembled from the covalently cross-linked anion exchange membrane described in Example 1 of this application under different hydraulic retention times. The experimental method was as follows: The covalently cross-linked anion exchange membrane prepared in Example 1 was assembled with the corresponding cation exchange membrane and a carbon-based electrode into a single-chamber MCDI reactor with an effective reaction volume of 50 mL. Simulated wastewater with an initial concentration of 40 mg / L NaCl was prepared, and the pH of the solution was adjusted to neutral (7.0 ± 0.2). The operating voltage was set to 1.2 V (to avoid water electrolysis side reactions). Sodium chloride solution was introduced into the single-chamber MCDI reactor using a peristaltic pump. The influent flow rate was adjusted, and the hydraulic retention time was controlled at 85 seconds and 120 seconds respectively, while maintaining a constant reaction temperature of 25℃. The change in effluent concentration was monitored in real time using a conductivity meter, with data recorded every 5 minutes. The test was repeated three times under each hydraulic retention time condition, and the average value was used to calculate the concentration ratio (effluent concentration / initial concentration). An adsorption performance curve over time was plotted, and the results are shown below. Figure 1 As shown.
[0109] from Figure 1 As can be seen, under different hydraulic residence times (85 seconds and 120 seconds), the adsorption performance of MCDI (membrane capacitive deionization) shows a trend of gradually decreasing concentration ratio over time (minutes), and the hydraulic residence time has a significant impact on the adsorption performance. The hydraulic residence time reflects the duration of contact between the solution and the electrode material. When the hydraulic residence time is 120 seconds, the contact between the solution and the electrode is more sufficient, and ions have more time to migrate to the electrode surface and be adsorbed under the influence of the electric field. Therefore, the concentration ratio decreases relatively slowly, indicating a more stable adsorption process and more uniform utilization of adsorption capacity. However, when the hydraulic residence time is 85 seconds, the contact time between the solution and the electrode is shorter, limiting the time for ion migration and adsorption. The adsorption rate may be faster in the early stages, but as time progresses, the number of available adsorption sites on the electrode surface gradually decreases, and the resistance to ion transport may increase, leading to a faster rate of decrease in the concentration ratio, and even a significant decay in the later stages. This phenomenon reflects the synergistic mechanism of ion migration, electric field adsorption, and hydraulic residence time in MCDI. A reasonable hydraulic residence time can optimize the ion adsorption kinetics, thereby improving the overall adsorption performance and stability of MCDI.
[0110] 3. The effect of different influent ion concentrations on the adsorption performance of the MCDI device assembled from the covalently cross-linked anion exchange membrane described in Example 1 of this application. The test method was as follows: using the same MCDI reactor configuration as described above, with a fixed operating voltage of 1.2V, a hydraulic residence time of 100 seconds, and a reaction temperature of 25℃; simulated wastewater with initial NaCl concentrations of 30mg / L, 40mg / L, and 50mg / L was prepared, and the pH was adjusted to 7.0±0.2; the simulated wastewater was continuously fed into the reactor through a peristaltic pump, and the effluent concentration was monitored in real time using a conductivity meter. Data was recorded every 5 minutes, and each concentration gradient was tested three times. The average value was used to plot the desalination effect over time.
[0111] The results are as follows Figure 2 As stated above.
[0112] from Figure 2As can be seen, under different influent NaCl solution concentrations (30 mg / L, 40 mg / L, and 50 mg / L), the desalination effect of the electroadsorption device is characterized by a gradual decrease in solution concentration over time, with the higher the influent concentration, the more significant the final decrease in solution concentration. The core of electroadsorption is the adsorption of ions using the electric double layer on the electrode surface. When the influent concentration is high (e.g., 50 mg / L), the ion concentration gradient in the solution is larger, and under the influence of the electric field, the ions migrate more strongly to the electrode surface. The available adsorption sites on the electrode surface can more fully capture ions, resulting in a more significant rate and magnitude of concentration decrease. Conversely, when the influent concentration is low (e.g., 30 mg / L), the ion concentration gradient is small, the ion migration momentum is relatively weak, and the adsorption sites on the electrode surface cannot be fully utilized, resulting in a smaller and generally more gradual decrease in concentration. This phenomenon reflects the synergistic mechanism of "concentration gradient-ion migration-double layer adsorption" in electroadsorption. The influent concentration affects the driving force of ion migration and the utilization rate of adsorption sites, thereby regulating the desalination effect of electroadsorption. A reasonable influent concentration range can optimize the desalination efficiency of electroadsorption, providing a theoretical basis for adapting the influent water quality in practical applications.
[0113] 4. Effect of different voltages on the adsorption performance of the MCDI device assembled from the covalently cross-linked anion exchange membrane described in Example 1 of this application Experimental Methods: Maintaining the MCDI reactor configuration and effective reaction volume, simulated wastewater with an initial NaCl concentration of 40 mg / L (pH = 7.0 ± 0.2) was prepared. The hydraulic retention time was fixed at 100 seconds, and the reaction temperature at 25℃. Operating voltages were set to 1.0V, 1.2V, and 1.4V (all below the water electrolysis threshold of 1.23V to avoid Faraday side reactions). The effluent concentration was monitored in real-time using a conductivity meter, with data recorded every 5 minutes. Each voltage condition was tested three times, and the average value was used to calculate the concentration ratio. Adsorption performance over time was then plotted.
[0114] The results are as follows Figure 3 As shown.
[0115] from Figure 3 As can be seen, under different operating voltages (1.0V, 1.2V, 1.4V), the adsorption performance of the electroadsorption device shows that the concentration ratio gradually decreases with time, and the higher the operating voltage, the faster and greater the rate of decrease in the concentration ratio. The driving force of electroadsorption originates from the electric field strength between the electrodes, and the operating voltage directly determines the strength of the electric field. The higher the voltage (e.g., 1.4V), the stronger the electric field force between the electrodes, and the greater the concentration of NaCl ions (Na+) in the solution. + Cl -The faster the ions migrate to the electrode surface under the influence of an electric field, the more ions can be adsorbed by the electric double layer on the electrode surface, thus resulting in a more significant decrease in the concentration ratio. Conversely, at lower voltages (e.g., 1.0V), the electric field is weaker, the ion migration rate is slower, the utilization efficiency of the electrode adsorption sites is lower, and the decrease in the concentration ratio is relatively gradual. This phenomenon reflects the synergistic mechanism of "voltage-electric field strength-ion migration-electric double layer adsorption." The operating voltage, by regulating the magnitude of the electric field, affects the ion migration kinetics and the utilization rate of the electrode adsorption sites, thereby significantly altering the desalination efficiency of electroadsorption.
[0116] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.
Claims
1. A covalently cross-linked anion exchange membrane, characterized in that, The raw materials include the following parts by weight: 35-55 parts of 1-vinyl-3-propylimidazolium chloride, 20-35 parts of acrylic monomers, 10-25 parts of amide monomers, and 2-6 parts of crosslinking agent.
2. The covalently cross-linked anion exchange membrane according to claim 1, characterized in that, The acrylic monomers include one or more of hydroxyethyl methacrylate, hydroxypropyl acrylate, glycidyl methacrylate, and polyethylene glycol methacrylate; And / or, the amide monomers include one or more of N,N-dimethylacrylamide, N-isopropylacrylamide, and N-hydroxymethylacrylamide; And / or, the crosslinking agent includes one or more of ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and trimethylolpropane trimethacrylate.
3. The method for preparing the covalently cross-linked anion exchange membrane according to any one of claims 1-2, characterized in that, Includes the following steps: (1) Mix 1-vinyl-3-propylimidazolium chloride, acrylic monomers, amide monomers, crosslinking agents, photoinitiators and organic solvents to obtain a mixed solution; (2) The mixed solution described in step (1) is degassed and then coated onto the surface of the substrate. Then, it is subjected to ultraviolet irradiation and drying treatment in sequence to obtain a composite film. (3) The composite membrane described in step (2) is contacted with acid and protonated to obtain the covalently cross-linked anion exchange membrane.
4. The method for preparing the covalently cross-linked anion exchange membrane according to claim 3, characterized in that, The method for preparing the covalently cross-linked anion exchange membrane further includes the step of preparing 1-vinyl-3-propylimidazolium chloride; The specific operating steps include: a. Mix 1-vinylimidazole, 1-bromopropane and anhydrous ethanol and reflux to obtain a reaction solution; b. Adjust the pH of the reaction solution to alkaline, filter, and concentrate the filtrate to obtain a viscous liquid; c. The viscous liquid is redissolved with anhydrous ethanol and then cooled to crystallize, yielding the 1-vinyl-3-propylimidazolium chloride.
5. The method for preparing the covalently cross-linked anion exchange membrane according to claim 4, characterized in that, In step a, the molar ratio of 1-vinylimidazole to 1-bromopropane is 1:(1-1.2). And / or, in step a, the temperature of the reflux reaction is 60-70°C, and the time of the reflux reaction is 12-16 hours; And / or, in step b, the pH of the reaction solution is adjusted using a sodium hydroxide aqueous solution with a mass concentration of 10%-15%; And / or, in step b, the pH of the reaction solution is 8.0-9.0; And / or, in step c, the temperature for cooling crystallization is 0-5°C, and the cooling crystallization time is 8-12 hours.
6. The method for preparing the covalently cross-linked anion exchange membrane according to claim 3, characterized in that, In step (1), the photoinitiator includes benzoin ether and / or 2-hydroxy-2-methyl-1-phenyl-1-propanone; And / or, the photoinitiator added is 1%-3% of the total amount of 1-vinyl-3-propylimidazolium chloride, acrylic monomers, and amide monomers; And / or, in step (1), the organic solvent includes one or more of N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone and N,N-diethylformamide; And / or, in step (1), the mass concentration of 1-vinyl-3-propylimidazolium chloride in the mixed solution is 8%-15%; And / or, in step (2), the degassing treatment includes placing the mixed solution in a vacuum degassing machine and degassing it for 1-3 hours under conditions of vacuum degree of -0.08 to -0.1 MPa and temperature of 20-30°C.
7. The method for preparing the covalently cross-linked anion exchange membrane according to claim 3, characterized in that, In step (2), the wavelength of the ultraviolet irradiation is 320-360 nm, and the irradiation power is 25-35 mW / cm². 2 The irradiation time is 30-50 minutes; And / or, the drying temperature is 50-70°C, and the drying time is 5-7 hours; And / or, the acid includes one or more of sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid; preferably, the concentration of the acid is 0.3-0.7 mol / L; And / or, the protonation treatment is performed at a temperature of 20-30°C for a time of 10-14 hours.
8. The application of the covalently cross-linked anion exchange membrane according to any one of claims 1-2 or the covalently cross-linked anion exchange membrane obtained by the preparation method according to any one of claims 3-7 in separation; Preferably, the separation process includes water electrolysis or seawater desalination.
9. An integrated electrode, characterized in that, The integrated electrode includes an electroadsorption electrode and an anion functional layer coated on the surface of the electroadsorption electrode. Wherein, the anion functional layer is the covalently cross-linked anion exchange membrane according to any one of claims 1-2 or the covalently cross-linked anion exchange membrane obtained by the preparation method according to any one of claims 3-7.
10. An electro-adsorption desalination device, characterized in that, Includes the integrated electrode as described in claim 9.