Composite cation exchange membrane as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of ion exchange membranes, and particularly relates to a composite cation exchange membrane and a preparation method and application thereof. The composite cation exchange membrane is prepared from the following raw materials in parts by weight: 45-55 parts of sulfonated polyether ether ketone, 30-40 parts of polyetherimide, 2-8 parts of surface amino functional modified zirconium phosphate and 2-5 parts of a cross-linking agent. The composite cation exchange membrane disclosed by the invention has the beneficial effects that through chemical copolymerization of sulfonated polyether-ether-ketone (SPEEK) and polyetherimide (PEI), a dense interpenetrating network is constructed by utilizing a cross-linking reaction of a sulfonic acid group (-SO3H) and an amino group (-NH2), and inorganic layered support of surface amino functional modified zirconium phosphate (KH-a-ZrP) is matched; rich ion exchange sites of SPEEK are reserved, and swelling of the membrane is inhibited through a rigid chain segment of PEI and physical barrier of KH-a-ZrP, so that the composite cation exchange membrane has relatively high conduction efficiency and structural stability.

Description

Technical Field

[0001] This application belongs to the field of ion exchange membrane technology, specifically relating to a composite cation exchange membrane, its preparation method, and its application. Background Technology

[0002] As a core functional material in desalination technologies such as electrodialysis and capacitive membrane deionization (MCDI), ion exchange membranes directly determine desalination efficiency, energy consumption, and system stability, playing an irreplaceable role in seawater desalination, industrial wastewater treatment, and pure water production. An ideal ion exchange membrane must simultaneously possess high ion exchange capacity, low surface resistivity, low swelling ratio, and excellent mechanical and thermal stability. However, current technologies still face numerous bottlenecks, making it difficult to achieve synergistic optimization of these multiple properties.

[0003] Traditional ion exchange membranes are mainly divided into two categories: single organic membranes and simple inorganic-organic blend membranes. Single organic membranes (such as sulfonated polysulfone and sulfonated polyether ether ketone) rely on sulfonic acid groups on the polymer chain to provide ion exchange sites, but their structural stability is poor. In aqueous solutions, the ion transport channels are easily distorted due to the hydrophilic swelling of the chain segments, resulting in increased sheet resistance. Furthermore, they are prone to swelling and cracking after long-term use. At the same time, the ion adsorption selectivity of single organic groups is limited, and co-ion permeation is easily accompanied during desalination, reducing desalination efficiency and charge efficiency. To improve structural stability, existing technologies often employ chemical crosslinking modification (such as adding crosslinking agents such as formaldehyde and epichlorohydrin). However, such crosslinking reactions require high temperature (80-120℃) and long time (6-12h), which not only consumes a lot of energy but may also lead to the decomposition of sulfonic acid groups, thereby reducing the ion exchange capacity. In addition, some crosslinking agents pose a risk of toxic residues, limiting the environmentally friendly application of the membranes.

[0004] Simple inorganic-organic blend membranes attempt to suppress membrane swelling by physically mixing inorganic fillers (such as silica and montmorillonite) with organic polymers, utilizing the physical support of the inorganic phase. However, due to poor interfacial compatibility between inorganic fillers and organic polymers, aggregation easily occurs, leading to defects within the membrane and increased ion transport resistance. Furthermore, physical blending cannot form stable chemical bonds, and after long-term immersion or repeated use, the inorganic filler easily detaches from the membrane matrix, causing rapid degradation of membrane performance. For example, the ion exchange capacity of existing SPEEK / inorganic particle blend membranes is typically below 1.6 mmol / g, and the sheet resistance exceeds 5 Ω. cm 2 With a swelling rate exceeding 18%, it is difficult to meet the high-efficiency and long-lasting requirements of electrodialysis desalination.

[0005] Furthermore, existing ion exchange membrane preparation processes suffer from insufficient economic and environmental benefits: some processes rely on expensive functional monomers or toxic solvents (such as fluorinated solvents), and solvent recovery rates are low; byproducts generated during chemical cross-linking can easily cause environmental pollution. Therefore, developing a mild, structurally stable, and highly efficient ion exchange membrane preparation technology is crucial to overcoming the bottlenecks of existing desalination technologies and is of great significance for promoting the industrialization of seawater desalination and wastewater resource utilization. Summary of the Invention

[0006] This application provides a composite cation exchange membrane, its preparation method, and its application, aiming to solve the problems in the preparation of existing cation exchange membranes, such as "reliance on chemical crosslinking leading to harsh reaction conditions, insufficient ion selectivity, and limited desalination performance."

[0007] The first aspect of this application provides a composite cation exchange membrane comprising the following raw materials: 45-55 parts of sulfonated polyether ether ketone, 30-40 parts of polyetherimide, 2-8 parts of surface amino-functionalized zirconium phosphate, and 2-5 parts of crosslinking agent.

[0008] According to some embodiments of the composite cation exchange membrane described in this application, the following raw materials are included: 45-55 parts of sulfonated polyether ether ketone, 30-40 parts of polyether imide, 4-6 parts of surface amino-functionalized zirconium phosphate, and 3 parts of crosslinking agent.

[0009] According to some embodiments of the composite cation exchange membrane described in this application, the degree of sulfonation of the sulfonated polyether ether ketone is 40%-80%.

[0010] According to some embodiments of the composite cation exchange membrane described in this application, the crosslinking agent includes one or more of sulfonyl chloride, phosphorus oxychloride (POCl3), p-toluenesulfonyl chloride (TsCl), and sulfoxide (SOCl2).

[0011] A second aspect of this application provides a method for preparing the composite cation exchange membrane described in the first aspect of this application, comprising the following steps: (1) Sulfonated polyether ether ketone, polyether imide, surface amino-functionalized zirconium phosphate, crosslinking agent and organic solvent are mixed and reacted to obtain a reaction solution; (2) Mix the reaction solution and defoamer, and perform defoaming treatment to obtain the composite membrane solution; (3) The composite membrane liquid is formed into a membrane and then activated by contacting it with acid to obtain the composite cation exchange membrane.

[0012] According to some embodiments of the preparation method of the composite cation exchange membrane described in this application, in step (1), the organic solvent includes one or more of N-methylpyrrolidone, N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMAc).

[0013] According to some embodiments of the preparation method of the composite cation exchange membrane described in this application, the mass ratio of the sulfonated polyether ether ketone to the organic solvent is 1:(2-3).

[0014] According to some embodiments of the preparation method of the composite cation exchange membrane described in this application, in step (1), the temperature of the mixing reaction is 50-60°C and the time of the mixing reaction is 8-12h.

[0015] According to some embodiments of the preparation method of the composite cation exchange membrane described in this application, in step (2), the defoamer includes one or more of polyether modified silicone oil, organosilicon defoamer (such as methyl silicone oil), polyether defoamer (such as polyethylene glycol) and mineral oil defoamer.

[0016] According to some embodiments of the preparation method of the composite cation exchange membrane described in this application, the amount of defoamer added is 0.3%-0.7% of the mass of the reaction solution.

[0017] According to some embodiments of the preparation method of the composite cation exchange membrane described in this application, in step (2), the mixing temperature is 25-35℃ and the mixing time is 20-40min.

[0018] According to some embodiments of the preparation method of the composite cation exchange membrane described in this application, in step (2), the vacuum degree of the degassing treatment is -0.08 to -0.1 MPa, the temperature is 25-35℃, and the time is 1-2h.

[0019] According to some embodiments of the preparation method of the composite cation exchange membrane described in this application, in step (3), the acid solution includes one or more of sulfuric acid solution, hydrochloric acid solution, phosphoric acid solution and nitric acid solution, and the concentration of the acid solution is 0.3-0.7 mol / L.

[0020] According to some embodiments of the preparation method of the composite cation exchange membrane described in this application, the activation treatment is performed at a temperature of 20-30°C for 8-12 hours.

[0021] According to some embodiments of the method for preparing the composite cation exchange membrane described in this application, the method further includes the step of preparing surface amino-functionalized zirconium phosphate; The preparation method of the surface amino-functionalized modified zirconium phosphate includes the following steps: a. Zirconium oxychloride and phosphoric acid solution are mixed and reacted to obtain layered zirconium phosphate; b. Mix the layered zirconium phosphate, γ-aminopropyltriethoxysilane and solvent to obtain surface amino-functionalized zirconium phosphate.

[0022] According to some embodiments of the preparation method of the composite cation exchange membrane described in this application, in step a, the concentration of the phosphoric acid solution is 7-9 mol / L.

[0023] According to some embodiments of the preparation method of the composite cation exchange membrane described in this application, the mass ratio of zirconium oxychloride to phosphoric acid is (40-90):1.

[0024] According to some embodiments of the preparation method of the composite cation exchange membrane described in this application, in step a, the temperature of the mixing reaction is 110-130℃ and the time is 20-28h.

[0025] According to some embodiments of the preparation method of the composite cation exchange membrane described in this application, in step b, the mass ratio of the layered zirconium phosphate and γ-aminopropyltriethoxysilane is (3-8):1.

[0026] According to some embodiments of the method for preparing the composite cation exchange membrane described in this application, in step b, the solvent includes N-methylpyrrolidone.

[0027] According to some embodiments of the preparation method of the composite cation exchange membrane described in this application, in step b, the mixing temperature is 65-75°C and the time is 4-8 hours.

[0028] Application of the composite cation exchange membrane described in the first aspect of this application or the composite cation exchange membrane obtained by the preparation method described in the second aspect of this application in separation.

[0029] According to some embodiments of the application described in this application, the separation includes water electrolysis or seawater desalination.

[0030] The beneficial effects of this application include: the composite cation exchange membrane described in this application is constructed by chemical copolymerization of sulfonated polyether ether ketone (SPEEK) and polyether imide (PEI), utilizing the crosslinking reaction of sulfonic acid groups (-SO3H) and amine groups (-NH2) to build a dense interpenetrating network, combined with the inorganic layered support of surface amino-functionalized zirconium phosphate (KH-a-ZrP), which not only retains the abundant ion exchange sites of SPEEK, but also inhibits membrane swelling through the rigid segments of PEI and the physical barrier of KH-a-ZrP, so that the composite cation exchange membrane has high conductivity and structural stability.

[0031] The composite cation exchange membrane described in this application uses conventional chemical raw materials. The solvent used has a recovery rate of over 80% after vacuum distillation, and the amount of crosslinking agent used is only 2%-5% of the total mass of the system. The reaction conditions are mild and no special high-pressure equipment is required. At the same time, the ionization modification is carried out by acid treatment, with no heavy metal or organic residues. The waste acid can be neutralized and recycled, which reduces energy consumption and pollution from the mechanism, lowers production costs, and is more suitable for large-scale industrial production. Attached Figure Description

[0032] Figure 1 This is a TGA curve of the composite cation exchange membrane described in Example 4 of this application; Figure 2 This is a voltage-time relationship diagram during the electrodialysis process of the composite cation exchange membrane described in Example 4 and Comparative Example 1 of this application; Figure 3 This is a conductivity-time graph of the composite cation exchange membrane described in Example 4 and Comparative Example 3 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 composite cation exchange membrane comprising the following raw materials: 45-55 parts of sulfonated polyether ether ketone (SPEEK), 30-40 parts of polyetherimide, 2-8 parts of surface-amino-functionalized zirconium phosphate, and 2-5 parts of a crosslinking agent. The composite cation exchange membrane described in this application is constructed by chemical copolymerization of sulfonated polyether ether ketone (SPEEK) and polyetherimide (PEI), utilizing the crosslinking reaction between sulfonic acid groups (-SO3H) and amino groups (-NH2) to build a dense interpenetrating network. Combined with the inorganic layered support of surface-amino-functionalized zirconium phosphate (KH-a-ZrP), it retains the abundant ion exchange sites of SPEEK while inhibiting membrane swelling through the rigid segments of PEI and the physical barrier of KH-a-ZrP, resulting in high conductivity and structural stability of the composite cation exchange membrane.

[0036] In the composite cation exchange membrane described in this application, the phosphate groups (-PO3H2) on the surface of the amino-functionalized zirconium phosphate (KH-a-ZrP) form "dual ion exchange centers" with the sulfonic acid groups of SPEEK, which increases the ion exchange capacity (IEC) by 23% compared to pure organic membranes. Combined with the regular ion channels constructed by the copolymer network, the sheet resistance is significantly reduced. At the same time, the layered structure of KH-a-ZrP improves cation selectivity, which meets the high-efficiency requirements of electrodialysis desalination.

[0037] In some embodiments of this application, the following raw materials are included: 45-55 parts of sulfonated polyether ether ketone, 30-40 parts of polyetherimide, 4-6 parts of surface-amino-functionalized zirconium phosphate, and 3 parts of crosslinking agent. Sulfonated polyether ether ketone (45-55 parts): As the core ion-conducting phase, this amount ensures a high-density distribution of sulfonic acid groups (-SO3H) within the membrane, providing sufficient sites for cation exchange and stabilizing the ion exchange capacity (IEC) at 1.8-1.95 mmol / g; it also avoids excessive hydrophilicity due to an excessively high proportion, effectively suppressing the swelling rate. If the amount is less than 45 parts, the concentration of sulfonic acid groups is insufficient, the IEC drops below 1.7 mmol / g, and the ion transport resistance increases; if the amount is more than 55 parts, the membrane segments over-stretch in aqueous solution, the swelling rate exceeds 19%, and the regularity of the ion transport channels is disrupted.

[0038] Polyetherimide (30-40 parts): As a rigid reinforcing phase, this amount forms a dense interpenetrating network structure with SPEEK. The amine groups (-NH2) of PEI are fully crosslinked with the -SO3H groups of SPEEK, which not only strengthens the mechanical strength of the film (tensile strength ≥18MPa) but also restricts the hydrophilic swelling of SPEEK segments through the rigid framework. If the amount is less than 30 parts, the crosslinking points are insufficient, the network structure is loose, the swelling rate exceeds 18%, and it is prone to deformation after long-term use; if the amount is more than 40 parts, it will crowd out the ion conduction space, causing the sheet resistivity to rise to 4.5Ω. cm 2 The above reduces ion transport efficiency.

[0039] Surface-amino-functionalized zirconium phosphate (2-8 parts): As a bifunctional phase combining "ion replenishment + physical enhancement," this dosage achieves interfacial synergy with the copolymer film. It replenishes ion exchange sites through phosphate groups (-PO3H2), increasing IEC by 0.1-0.2 mmol / g; and its layered structure forms a physical barrier, further suppressing swelling (reducing it by 3%-5% compared to the unfilled system), while simultaneously reducing ion transport resistance (surface resistivity reduced to 3.8-4.2 Ω). cm 2 If the amount is less than 2 parts, the ion replenishment and enhancement effects are limited, with an IEC increase of less than 0.08 mmol / g and poor swelling control; if the amount is more than 6 parts, the filler is prone to agglomeration, disrupting the continuity of the membrane and causing the sheet resistivity to rise to 4.8Ω. cm 2 In the above cases, the mechanical strength actually decreases.

[0040] Crosslinking agent (2-5 parts): This amount ensures complete crosslinking of SPEEK's -SO3H and PEI's -NH2, forming a stable interpenetrating network. If less than 2 parts, the crosslinking reaction is incomplete, the network structure is loose, the swelling rate exceeds 19%, and ion channels are easily distorted. If more than 5 parts, excessive crosslinking leads to membrane densification, hindering cation migration and increasing the sheet resistivity to 4.6Ω. cm 2 This also reduces the membrane's flexibility.

[0041] In some embodiments of this application, the degree of sulfonation of the sulfonated polyether ether ketone is 65%-78%. If the degree of sulfonation of the sulfonated polyether ether ketone is less than 65%, the number of -SO3H on the SPEEK molecular chain is insufficient, the IEC is only 1.6-1.7 mmol / g, and the ion conduction efficiency is low. If the degree of sulfonation is higher than 78%, the molecular chain is too hydrophilic, the swelling rate of the membrane in aqueous solution exceeds 20%, and the chemical stability of SPEEK decreases, making it prone to chain segment degradation after long-term immersion. A sulfonation degree of 65%-78% can stabilize the IEC at 1.8-1.95 mmol / g, control the swelling rate at 14%-17%, and retain the rigid framework structure of SPEEK, forming a synergistic effect with PEI and modified zirconium phosphate, ensuring the mechanical strength and long-term stability of the membrane.

[0042] In some embodiments of this application, the crosslinking agent includes one or more of sulfonyl chloride, phosphorus oxychloride (POCl3), p-toluenesulfonyl chloride (TsCl), and sulfoxide (SOCl2). Sulfonyl chloride crosslinking agents exhibit strong reaction specificity, excellent system compatibility, easily and precisely controllable crosslinking density, and superior process adaptability: sulfonyl chloride can precisely crosslink with the sulfonic acid groups of SPEEK, the amino groups of PEI, and the amino groups of modified zirconium phosphate, rapidly constructing a stable interpenetrating network among the three (reaction conversion rate exceeding 90%). It also exhibits good solubility in solvents such as NMP and DMF, does not produce side reactions that interfere with ion transport, and the reaction products are easily removed by washing. Its moderate reactivity allows for precise balancing of the crosslinking density through a dosage of 2-5 parts, avoiding excessive swelling due to an overly sparse network or ion transport obstruction caused by an overly dense network. Furthermore, as a commonly used industrial reagent, it is inexpensive, operates under mild reaction conditions (50-60℃), requires no special equipment, and is highly compatible with the preparation process of this application, facilitating large-scale production.

[0043] This application also provides a method for preparing the composite cation exchange membrane described in the first aspect of this application, comprising the following steps: (1) Sulfonated polyether ether ketone, polyether imide, surface amino-functionalized zirconium phosphate, crosslinking agent and organic solvent are mixed and reacted to obtain a reaction solution; (2) Mix the reaction solution and defoamer, and perform defoaming treatment to obtain the composite membrane solution; (3) The composite membrane liquid is formed into a membrane and then activated by contacting it with acid to obtain the composite cation exchange membrane.

[0044] The composite cation exchange membrane described in this application uses conventional chemical raw materials. The solvent used has a recovery rate of over 80% after vacuum distillation, and the amount of crosslinking agent used is only 2%-5% of the total mass of the system. The reaction conditions are mild and no special high-pressure equipment is required. At the same time, the ionization modification is carried out by acid treatment, with no heavy metal or organic residues. The waste acid can be neutralized and recycled, which reduces energy consumption and pollution from the mechanism, lowers production costs, and is more suitable for large-scale industrial production.

[0045] In some embodiments of this application, in step (1), the organic solvent includes one or more of N-methylpyrrolidone, N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMAc).

[0046] In some embodiments of this application, the mass ratio of the sulfonated polyether ether ketone to the organic solvent is 1:(2-3); for example, 1:2, 1:2.5, 1:3, etc.

[0047] In some embodiments of this application, in step (1), the temperature of the mixing reaction is 50-60°C, for example 50°C, 55°C, 60°C, and the time of the mixing reaction is 8-12h, for example 8h, 10h, 12h, etc.

[0048] In some embodiments of this application, the preparation method of sulfonated polyether ether ketone is as follows: 10-15g of polyether ether ketone (PEEK) particles and 100-150mL of 95%-98% concentrated sulfuric acid are weighed and placed in a 250mL three-necked flask. Under nitrogen protection, the mixture is magnetically stirred at 40-50℃ and 250-350r / min for 6-10 hours to carry out the sulfonation reaction. After the reaction is completed, the reaction solution is slowly poured into 300-400mL of ice water, and a pale yellow precipitate is precipitated by stirring. The precipitate is collected by filtration. The precipitate is repeatedly washed with deionized water until the pH of the washing solution is ≥4.0. Then, the precipitate is placed in a vacuum drying oven and dried at 60-80℃ and 0.08MPa for 12-16 hours to obtain sulfonated polyether ether ketone (SPEEK), which is then ground into powder for later use.

[0049] In some embodiments of this application, in step (2), the defoamer includes one or more of polyether modified silicone oil, organosilicon defoamer (such as methyl silicone oil), polyether defoamer (such as polyethylene glycol), and mineral oil defoamer.

[0050] In some embodiments of this application, the amount of defoamer added is 0.3%-0.7% of the mass of the reaction solution, such as 0.3%, 0.4%, 0.5%, 0.7%, etc.

[0051] In some embodiments of this application, in step (2), the mixing temperature is 25-35°C, such as 25°C, 30°C, 35°C, etc., and the mixing time is 20-40 min; such as 20 min, 25 min, 30 min, 35 min, 40 min, etc.

[0052] In some embodiments of this application, in step (2), the vacuum degree of the degassing treatment is -0.08 to -0.1 MPa, the temperature is 25-35°C, and the time is 1-2 hours. During the degassing treatment, gas is released every 20-40 minutes to completely remove dissolved gas and residual bubbles from the membrane solution.

[0053] In some embodiments of this application, the steps for forming a composite film include: taking a clean and dry glass plate of 8-12cm × 8-12cm, wiping the surface with anhydrous ethanol and blowing it dry, and fixing it on a horizontal coating stage; transferring 8-12mL of degassed composite film liquid, evenly inverting it onto one end of the glass plate, and using a 150-250μm thickness coater to uniformly coat it in the same direction to form a continuous and uniform liquid film, and letting it stand for 3-8 minutes to level naturally; placing the leveled liquid film along with the glass plate into a forced-air drying oven, and using a gradient temperature drying process: the first stage is to keep it at 45-55℃ for 2-3 hours to slowly evaporate the solvent; the second stage is to keep it at 70-80℃ for 2-3 hours to strengthen the interfacial bonding between the copolymer network and KH-a-ZrP; the third stage is to keep it at 90-100℃ for 1.5-2.5 hours, and drying it under a vacuum of 0.06-0.1MPa to completely remove residual NMP; after drying, cooling to room temperature, and peeling off the initially formed composite film.

[0054] In some embodiments of this application, in step (3), the acid solution includes one or more of sulfuric acid solution, hydrochloric acid solution, phosphoric acid solution and nitric acid solution. Preferably, the concentration of the acid solution 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.

[0055] In some embodiments of this application, the activation process 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 8-12 hours, such as 8 hours, 10 hours, 12 hours, etc.

[0056] In some embodiments of this application, the pre-formed composite membrane is immersed in a 0.3-0.7 mol / L sulfuric acid solution and statically soaked in a constant temperature water bath at 20-30°C for 8-12 hours to activate the sulfonic acid groups of SPEEK and the phosphate groups of KH-a-ZrP, thereby giving it high-efficiency cation exchange activity. After soaking, the membrane is repeatedly washed with deionized water until the pH of the washing solution is 6.5-7.5 to remove residual sulfuric acid. Then, it is placed in a vacuum drying oven and dried at 45-55°C and 0.06-0.1 MPa for 6-10 hours until the membrane quality is constant, thus obtaining a sulfonated polyether ether ketone / polyether imide copolymer modified zirconium phosphate composite cation exchange membrane.

[0057] In some embodiments of this application, the step of preparing surface amino-functionalized zirconium phosphate is also included; The preparation method of the surface amino-functionalized modified zirconium phosphate includes the following steps: a. Zirconium oxychloride and phosphoric acid solution are mixed and reacted to obtain layered zirconium phosphate; b. Mix the layered zirconium phosphate, γ-aminopropyltriethoxysilane and solvent to obtain surface amino-functionalized zirconium phosphate.

[0058] In some embodiments of this application, in step a, the concentration of the phosphoric acid solution is 7-9 mol / L; for example, 7 mol / L, 8 mol / L, 9 mol / L, etc.

[0059] In some embodiments of this application, the mass ratio of zirconium oxychloride to phosphoric acid is (40-90):1; for example, 40:1, 50:1, 60:1, 80:1, 90:1, etc.

[0060] In some embodiments of this application, in step a, the temperature of the mixing reaction is 110-130°C, such as 110°C, 115°C, 120°C, 125°C, 130°C, etc., and the time is 20-28h, such as 20h, 25h, 28h, etc.

[0061] In some embodiments of this application, in step b, the mass ratio of the layered zirconium phosphate and γ-aminopropyltriethoxysilane is (3-8):1; for example, 3:1, 5:1, 6:1, 8:1, etc.

[0062] In some embodiments of this application, in step b, the solvent includes N-methylpyrrolidone.

[0063] In some embodiments of this application, in step b, the mixing temperature is 65-75°C, such as 65°C, 70°C, 72°C, 75°C, etc., and the time is 4-8h, such as 4h, 5h, 6h, 8h, etc.

[0064] In some embodiments of this application, the surface-amino-functionalized zirconium phosphate includes the following steps: Weigh out 1.5-2.5g of zirconium oxychloride (ZrOCl2). Zirconium oxychloride (ZrO) powder and 25-35 mL of 7-9 mol / L phosphoric acid solution are placed in a 50-100 mL beaker and magnetically stirred at 250-350 rpm for 10-20 minutes to form a homogeneous suspension. The suspension is then transferred to a polytetrafluoroethylene-lined reactor, sealed, and placed in a forced-air drying oven for hydrothermal reaction at 110-130℃ for 20-28 hours to allow zirconium oxychloride and phosphoric acid to fully react and form layered zirconium phosphate (a-ZrP). After the reaction is complete, the mixture is cooled to room temperature, and the reaction solution is transferred to centrifuge tubes and centrifuged at 3000-4000 rpm. Centrifuge at 10-20 rpm for 10-20 minutes and collect the white precipitate at the bottom. Wash the precipitate repeatedly with deionized water, centrifuging at 3000-4000 rpm for 10-20 minutes after each wash until the pH of the supernatant is ≥5.0-5.5 to remove excess phosphate and impurity ions. Place the washed precipitate in a vacuum freeze dryer and dry at -60 to -40°C and 0.06-0.1 MPa for 20-28 hours to obtain pure white layered α-ZrP powder. Weigh 0.8-1.2g of the above-mentioned a-ZrP powder, 40-60mL of N-methylpyrrolidone (NMP), and 0.15-0.25g of γ-aminopropyltriethoxysilane (KH-550), and place them in a 100-250mL three-necked flask. Stir magnetically at 200-300r / min for 4-8 hours in a water bath at 65-75℃ to achieve amino functionalization modification of the a-ZrP surface. After the modification reaction is completed, collect the precipitate by centrifugation at 3000-4000r / min for 10-20 minutes. Wash with NMP 2-3 times and deionized water 1-2 times to remove unreacted KH-550. Freeze-dry under vacuum for 10-14 hours to obtain surface amino functionalized modified zirconium phosphate (KH-a-ZrP), and store it in a sealed, dry place for later use.

[0065] This application also provides an application of the composite cation exchange membrane described in the first aspect of this application or the composite cation exchange membrane prepared by the method described in the second aspect of this application in separation.

[0066] In some embodiments of this application, the separation includes water electrolysis or seawater desalination.

[0067] The technical solution of this application will be further described below with reference to specific embodiments.

[0068] Example 1 A method for preparing a composite cation exchange membrane includes the following steps: (1) Preparation of surface amino-functionalized zirconium phosphate Weigh 2.0g of zirconium oxychloride (ZrOCl2) Zirconium oxychloride (ZrO) powder and 30 mL of 8 mol / L phosphoric acid solution were placed in a 100 mL beaker and magnetically stirred at 300 r / min for 15 min to form a homogeneous suspension. The suspension was transferred to a polytetrafluoroethylene-lined reactor, sealed, and placed in a forced-air drying oven for hydrothermal reaction at 120 °C for 24 hours to allow zirconium oxychloride and phosphoric acid to fully react and generate layered zirconium phosphate (a-ZrP). After the reaction was completed and cooled to room temperature, the reaction solution was transferred to a centrifuge tube and centrifuged at 3000 r / min for 15 min to collect the white precipitate at the bottom. The precipitate was washed with deionized water, centrifuged at 3000 r / min for 15 min after each wash, until the pH of the supernatant was ≥5.0 (pH 5.5 in this example) to remove excess phosphoric acid and impurity ions. The washed precipitate was placed in a vacuum freeze dryer and dried at -50 °C and 0.1 MPa for 24 h to obtain pure white layered a-ZrP powder. Weigh 1.0 g of the above-mentioned α-ZrP powder, 50 mL of N-methylpyrrolidone (NMP) and 0.2 g of γ-aminopropyltriethoxysilane (KH-550), place them in a 250 mL three-necked flask, and stir magnetically at 250 r / min for 6 h in a 70 °C water bath to achieve amino functionalization modification of the α-ZrP surface. After the modification reaction is completed, collect the precipitate by centrifugation at 3000 r / min for 15 min, wash it 3 times with NMP and 2 times with deionized water to remove unreacted KH-550, and freeze-dry it at -50 °C for 10 h to obtain surface amino functionalized zirconium phosphate (KH-α-ZrP), which is then sealed, dried and stored for later use.

[0069] (2) Weigh 50g of pre-prepared sulfonated polyether ether ketone powder (SPEEK, sulfonation degree 72%), 35g of polyetherimide (PEI) powder, and 4g of surface amino-functionalized zirconium phosphate (KH-a-ZrP) into a 500mL three-necked flask by mass; add 150ml of [unclear text - possibly a typo, should be "to the flask"] to the flask. Using NMP as a solvent, the temperature was set at 45℃ and the stirring speed at 400 r / min, and magnetic stirring was carried out for 12 hours to initially disperse and dissolve the three materials. 3g of sulfonyl chloride (SO2Cl2) was added to the system as a crosslinking agent, the temperature was raised to 55℃, and stirring was continued for 8 hours to initiate a crosslinking copolymerization reaction between the sulfonic acid groups (-SO3H) of SPEEK and the amino groups (-NH2) of PEI, forming a "SPEEK-PEI" interpenetrating network structure. 0.5% of the total mass of defoamer (polyether modified silicone oil) was added to the copolymerization system, the temperature was lowered to 30℃, and stirring was continued for 30 minutes to remove the bubbles generated during the reaction, resulting in a homogeneous and stable SPEEK / PEI / KH-a-ZrP composite membrane solution.

[0070] (3) Transfer the composite membrane liquid prepared in step (2) to a vacuum degassing machine, set the vacuum degree to -0.1MPa and the temperature to 30℃, degas for 1h, and release the gas once every 30min during the period to completely remove the dissolved gas and residual bubbles in the membrane liquid; take a clean and dry glass plate of 10cm×10cm, wipe the surface with anhydrous ethanol and blow dry, and fix it on a horizontal coating stage; transfer 10mL of the degassed composite membrane liquid, evenly pour it onto one end of the glass plate, use a 200μm thickness coater, and scrape it at a uniform speed in the same direction to form a continuous and uniform liquid film, let it stand for 5min to level naturally; put the leveled liquid film together with the glass plate into a forced-air drying oven, and use a gradient temperature drying process: the first stage is to keep it at 50℃ for 2h to slowly evaporate the solvent; the second stage is to keep it at 75℃. The membrane was heated to 2.5 h to strengthen the interfacial bonding between the copolymer network and KH-a-ZrP; in the third stage, it was kept at 95℃ for 2 h and dried under a vacuum of 0.1 MPa to completely remove residual NMP; after drying, it was cooled to room temperature, the preliminarily formed composite membrane was peeled off, and immersed in 0.5 mol / L sulfuric acid solution for static soaking in a constant temperature water bath at 25℃ for 10 h to activate the sulfonic acid groups of SPEEK and the phosphate groups of KH-a-ZrP, giving it high efficiency cation exchange activity. The membrane was repeatedly washed with deionized water until the pH of the washing solution was 7.0 to remove residual sulfuric acid, and then placed in a vacuum drying oven and dried at 50℃ and 0.1 MPa for 8 h until the membrane quality was constant, thus obtaining the sulfonated polyether ether ketone / polyether imide copolymer modified zirconium phosphate composite cation exchange membrane.

[0071] Example 2 The only difference between the preparation method of the composite cation exchange membrane in Example 2 and that in Example 1 is that the amount of surface amino-functionalized zirconium phosphate used in the preparation process of the composite cation exchange membrane in Example 2 is 2g.

[0072] Example 3 The only difference between the preparation method of the composite cation exchange membrane in Example 3 and that in Example 1 is that the amount of surface amino-functionalized zirconium phosphate used in the preparation process of the composite cation exchange membrane in Example 3 is 6g.

[0073] Example 4 The only difference between the preparation method of the composite cation exchange membrane in Example 4 and that in Example 1 is that the amount of surface amino-functionalized zirconium phosphate used in the preparation process of the composite cation exchange membrane in Example 4 is 8g.

[0074] Example 5 The only difference between the preparation method of the composite cation exchange membrane in Example 5 and that in Example 1 is that the ratio of sulfonated polyether ether ketone and polyether imide used in the preparation process of the composite cation exchange membrane in Example 5 is different from that in Example 1.

[0075] The specific operating steps include: Weigh out 48g of pre-prepared sulfonated polyether ether ketone powder (SPEEK, sulfonation degree 72%), 37g of polyether imide (PEI) powder, and 4g of surface amino-functionalized zirconium phosphate (KH-a-ZrP) into a 500mL three-necked flask by weight; add 150ml of [unclear text - possibly a specific ingredient or solution] to the flask. Using NMP as a solvent, the temperature was set at 45℃ and the stirring speed at 400 r / min, and magnetic stirring was carried out for 12 hours to initially disperse and dissolve the three materials. 3g of sulfonyl chloride (SO2Cl2) was added to the system as a crosslinking agent, the temperature was raised to 55℃, and stirring was continued for 8 hours to initiate a crosslinking copolymerization reaction between the sulfonic acid groups (-SO3H) of SPEEK and the amino groups (-NH2) of PEI, forming a "SPEEK-PEI" interpenetrating network structure. 0.5% of the total mass of defoamer (polyether modified silicone oil) was added to the copolymerization system, the temperature was lowered to 30℃, and stirring was continued for 30 minutes to remove the bubbles generated during the reaction, resulting in a homogeneous and stable SPEEK / PEI / KH-a-ZrP composite membrane solution. The remaining operation steps were the same as in Example 1.

[0076] Example 6 The only difference between the preparation method of the composite cation exchange membrane described in Example 6 and that in Example 1 is that the ratio of sulfonated polyether ether ketone and polyether imide used in the preparation process of the composite cation exchange membrane in Example 6 is different from that in Example 1.

[0077] The specific operating steps include: Weigh out 52g of pre-prepared sulfonated polyether ether ketone powder (SPEEK, sulfonation degree 72%), 33g of polyether imide (PEI) powder, and 4g of surface amino-functionalized zirconium phosphate (KH-a-ZrP) into a 500mL three-necked flask by weight; add 150ml of [unclear text - possibly a specific ingredient or solution] to the flask. Using NMP as a solvent, the temperature was set at 45℃ and the stirring speed at 400 r / min, and magnetic stirring was carried out for 12 hours to initially disperse and dissolve the three materials. 3g of sulfonyl chloride (SO2Cl2) was added to the system as a crosslinking agent, the temperature was raised to 55℃, and stirring was continued for 8 hours to initiate a crosslinking copolymerization reaction between the sulfonic acid groups (-SO3H) of SPEEK and the amino groups (-NH2) of PEI, forming a "SPEEK-PEI" interpenetrating network structure. 0.5% of the total mass of defoamer (polyether modified silicone oil) was added to the copolymerization system, the temperature was lowered to 30℃, and stirring was continued for 30 minutes to remove the bubbles generated during the reaction, resulting in a homogeneous and stable SPEEK / PEI / KH-a-ZrP composite membrane solution. The remaining operation steps were the same as in Example 1.

[0078] Example 7 The only difference between the preparation method of the composite cation exchange membrane in Example 7 and that in Example 1 is that the ratio of sulfonated polyether ether ketone and polyether imide used in the preparation process of the composite cation exchange membrane in Example 7 is different from that in Example 1.

[0079] The specific operating steps include: Weigh out 49g of pre-prepared sulfonated polyether ether ketone powder (SPEEK, sulfonation degree 72%), 36g of polyether imide (PEI) powder, and 4g of surface amino-functionalized zirconium phosphate (KH-a-ZrP) into a 500mL three-necked flask by weight; add 150ml of [unclear text - possibly a specific ingredient or solution] to the flask. Using NMP as a solvent, the temperature was set at 45℃ and the stirring speed at 400 r / min, and magnetic stirring was carried out for 12 hours to initially disperse and dissolve the three materials. 3g of sulfonyl chloride (SO2Cl2) was added to the system as a crosslinking agent, the temperature was raised to 55℃, and stirring was continued for 8 hours to initiate a crosslinking copolymerization reaction between the sulfonic acid groups (-SO3H) of SPEEK and the amino groups (-NH2) of PEI, forming a "SPEEK-PEI" interpenetrating network structure. 0.5% of the total mass of defoamer (polyether modified silicone oil) was added to the copolymerization system, the temperature was lowered to 30℃, and stirring was continued for 30 minutes to remove the bubbles generated during the reaction, resulting in a homogeneous and stable SPEEK / PEI / KH-a-ZrP composite membrane solution. The remaining operation steps were the same as in Example 1.

[0080] Example 8 The only difference between the preparation method of the composite cation exchange membrane in Example 8 and that in Example 1 is that the amount of crosslinking agent used in the preparation process of the composite cation exchange membrane in Example 8 is 2g.

[0081] Example 9 The only difference between the preparation method of the composite cation exchange membrane in Example 9 and that in Example 1 is that the amount of crosslinking agent used in the preparation process of the composite cation exchange membrane in Example 9 is 5g.

[0082] Example 10 The only difference between the preparation method of the composite cation exchange membrane in Example 10 and that in Example 1 is that phosphorus oxychloride (POCl3) is used instead of sulfonyl chloride as the crosslinking agent in the preparation process of the composite cation exchange membrane in Example 10.

[0083] Example 11 The only difference between the preparation method of the composite cation exchange membrane in Example 11 and that in Example 1 is that p-toluenesulfonyl chloride is used instead of sulfonyl chloride as the crosslinking agent in the preparation process of the composite cation exchange membrane in Example 11.

[0084] Comparative Example 1 The only difference between the preparation method of the composite cation exchange membrane described in Comparative Example 1 and that in Example 1 is that no amino-functionalized zirconium phosphate is added during the preparation of the composite cation exchange membrane described in Comparative Example 1; the rest of the operations are the same as in Example 1.

[0085] Comparative Example 2 The only difference between the preparation method of the composite cation exchange membrane in Comparative Example 2 and that in Example 1 is that no raw material crosslinking agent is added during the preparation of the composite cation exchange membrane in Comparative Example 2, and the rest of the operation is the same as in Example 1.

[0086] Comparative Example 3 The only difference between the preparation method of the composite cation exchange membrane described in Comparative Example 3 and Example 1 is that no raw material polyetherimide is added during the preparation of the composite cation exchange membrane described in Comparative Example 3, and the amount of sulfonated polyether ether ketone added is adjusted to 85g. The rest of the operation is the same as in Example 1.

[0087] Comparative Example 4 The only difference between the preparation method of the composite cation exchange membrane described in Comparative Example 4 and that in Example 1 is that zirconium phosphate is used instead of surface amino-functionalized zirconium phosphate in the preparation process of the composite cation exchange membrane described in Comparative Example 4, and the rest of the operation is the same as in Example 1.

[0088] 1. Performance Study of the Composite Cation Exchange Membranes Described in Examples 1-11 and Comparative Examples 1-4 of this Application Film thickness: Measured using a micrometer screw gauge.

[0089] The dried composite cation exchange membrane sample was laid flat on a level table, ensuring the membrane surface was smooth and wrinkle-free. Using a micrometer with an accuracy of 0.001 mm, measurements were taken at at least five evenly distributed measurement points in different areas of the membrane (including the center and surrounding areas). 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.

[0090] Moisture content: Take a composite cation exchange membrane sample dried to constant mass and weigh it using an analytical balance with an accuracy of 0.01% (recorded as m0). Immerse the sample completely in deionized water at 25℃ and statically soak for 24 hours to ensure the membrane is fully saturated with water. Remove the saturated sample and gently wipe the membrane surface with clean filter paper to quickly absorb the surface moisture (do not squeeze the membrane to prevent internal moisture loss). Immediately weigh the sample after water absorption using the same analytical balance (recorded as m1). Calculate the moisture content using the formula "Moisture content (%) = (m1-m0) / m0×100%". Perform parallel testing on each group of samples three times and take the average value. This index reflects the hydrophilicity of the membrane and directly affects the wetting degree and conduction efficiency of the ion transport channel.

[0091] Swelling rate: Take a composite cation exchange membrane sample dried to constant mass, measure the initial length (L0) and width (W0) with a vernier caliper with an accuracy of 0.01 mm, and weigh the initial mass (m0) with an analytical balance of 0.01 g. Immerse the sample in deionized water at 25℃ and statically soak for 24 h until swelling equilibrium is reached. After taking it out, blot the surface moisture with filter paper, and immediately measure the length (L1) and width (W1) after swelling and weigh (m1). Calculate the two swelling rates according to "area swelling rate (%) = [(L1×W1–L0×W0) / (L0×W0)]×100% and mass swelling rate (%) = (m1-m0) / m0×100%". Perform three parallel tests for each group and take the average value. This parameter comprehensively reflects the structural stability of the membrane in aqueous solution and avoids ion channel distortion or membrane rupture due to excessive swelling.

[0092] Ion exchange capacity: Take a composite cation exchange membrane sample dried to constant mass (mass denoted as m0), cut it into small pieces, place it in a 250 mL Erlenmeyer flask, add 100 mL of 0.1 mol / L NaCl solution, seal, and magnetically stir at 25 °C for 24 h to allow H2 exchange capacity in the membrane. + With Na in solution + Complete the replacement process; measure 25 mL of the exchanged solution into an Erlenmeyer flask, add 2-3 drops of phenolphthalein indicator, and titrate with 0.01 mol / L NaOH standard solution until the solution turns light red and does not fade for 30 seconds, and record the volume of NaOH consumed (V); calculate according to the formula "IEC (mmol / g) = (C × V × 4) / m0" (C is the NaOH concentration, 4 is the solution dilution factor), and take the average value of each group of parallel tests. This index is the core parameter for measuring the cation exchange capacity of the membrane and directly determines the ion separation efficiency of the membrane.

[0093] Sheet resistance: A three-electrode system was used (platinum sheet as working / counter electrode, saturated calomel electrode as reference electrode), with a 0.5 mol / L H₂SO₄ solution as the electrolyte; the composite cation exchange membrane was cut into 16 mm diameter discs; during testing, the membrane was fixed between two platinum electrodes (ensuring tight contact between the membrane and electrodes without air bubbles), and the electrolyte was used to immerse both the electrodes and the membrane; using an electrochemical workstation, impedance testing was performed in the frequency range of 1 Hz-100 kHz and with an AC signal amplitude of 10 mV, and the Nyquist spectrum was recorded; the membrane impedance value (R) was read from the spectrum, combined with the effective contact area of ​​the electrodes (A ≈ 2.01 cm²). 2 According to "surface resistance (Ω)" cm 2 The formula is calculated as R×A”. Each group is tested in parallel for 3 times and the average value is taken. This parameter reflects the ion transport resistance of the membrane and is directly related to the energy loss and separation efficiency of the membrane in practical applications.

[0094] The results are shown in Table 1.

[0095] Table 1

[0096] As can be seen from Table 1, the synergistic effect of each component and the regulation of dosage are the main factors in optimizing performance, which revolves around the balance of "ion conduction site density - structural stability - ion transport resistance".

[0097] Examples 1-4 verified the key role of the bifunctional phase by adjusting the amount of KH-a-ZrP: Example 3, with sufficient phosphate groups to supplement ion sites, achieved an IEC of 1.92 mmol / g, while the layered structure formed a physical barrier, reducing the swelling ratio to 14.1%, resulting in more regular ion transport channels and a sheet resistivity as low as 3.8 Ω. cm 2 In Example 2, due to insufficient functional phase, the IEC was only 1.72 mmol / g, the swelling ratio increased to 17.8%, and the surface resistivity increased to 4.7 Ω. cm 2 In Example 4, the swelling rate rebounded due to filler agglomeration, and the surface resistivity rose back to 4.3Ω. cm 2 That is, when the amount of surface amino-functionalized zirconium phosphate used in the preparation of the composite cation exchange membrane is 4-6 parts, the resulting composite cation exchange membrane has better performance.

[0098] The SPEEK / PEI ratio control in Examples 5-7 shows that the ratio in Example 6 not only ensures the density of sulfonic acid groups provided by SPEEK (IEC 1.88 mmol / g), but also inhibits excessive swelling (15.7%) through the rigid framework of PEI, thus achieving a synergistic effect between conductivity efficiency and structural stability.

[0099] The crosslinking agent dosages in Examples 8-9 validated the importance of "moderate crosslinking." Example 8 showed a swelling rate of 18.9% due to a loose network, while Example 9 exhibited a sheet resistivity of 4.4 Ω due to excessive crosslinking hindering ion migration. cm 2 Example 1 showed the best crosslinking density and balanced overall performance.

[0100] A comparison of Examples 1 and 10-11 illustrates that the choice of crosslinking agent is a key factor affecting the performance of composite cation exchange membranes. When the crosslinking agent is sulfonyl chloride, the resulting composite cation exchange membrane exhibits superior performance.

[0101] 2. Stability study of the composite cation exchange membrane described in Example 4 of this application Research Methods: Thermogravimetric analysis (TGA) was used for testing. 5-10 mg of composite cation exchange membrane samples dried to constant mass were placed in an alumina crucible. The test conditions were set as follows: nitrogen atmosphere (flow rate 50 mL / min), heating rate 10 °C / min, and temperature range from room temperature (25 °C) to 800 °C. The mass change of the sample with temperature was recorded in real time to obtain the TGA spectrum. Each group of samples was tested in parallel twice, and the curve with good repeatability was taken as the final result. This method was used to characterize the thermal stability and thermal decomposition behavior of the membrane.

[0102] The results are as follows Figure 1 As shown.

[0103] from Figure 1 As can be seen, the TGA curve of the composite cation exchange membrane described in this application exhibits the characteristic of "low-temperature micro-weight loss - high-temperature steep drop". Only about 5% mass loss occurs before 400℃ (corresponding to residual solvent and adsorbed water), and the mass decreases rapidly after 400℃, indicating excellent initial thermal stability of the membrane (no significant thermal decomposition of the structure before 400℃). This is because Example 4 uses an 8-part KH-a-ZrP-reinforced SPEEK-PEI copolymer system: on the one hand, the sulfonic acid groups of SPEEK and the amino groups of PEI are cross-linked with sulfonyl chloride to form a dense interpenetrating network, which restricts the thermal movement of polymer chain segments and improves the thermal stability of the molecular chain; on the other hand, the high proportion of KH-a-ZrP's layered inorganic structure can act as a "thermal barrier," delaying the transfer of heat to the polymer interior, while the hydrogen bonding between its phosphate groups and the polymer chain further enhances the thermal stability of the system.

[0104] 3. Electrodialysis performance study of the composite cation exchange membrane described in Example 4 and Comparative Example 1 of this application. The research method was as follows: An electrodialysis apparatus was used for testing. A two-chamber electrodialysis system was constructed, consisting of an anode chamber, a cation exchange membrane, a concentration chamber, an anion exchange membrane, and a cathode chamber. Both the anode and cathode were titanium-coated ruthenium electrodes. 0.5 mol / L NaCl solution was added to the anode and cathode chambers as electrode solutions, 100 mL of 0.1 mol / L NaCl solution was added to the desalination chamber, and 100 mL of deionized water was added to the concentration chamber. A constant current density (5 mA / cm²) was set. 2 The method records the change of voltage between electrodes over time in real time, with a test duration of 160 minutes. Each sample is tested twice in parallel, and the average value of the voltage-time curve is taken for analysis. This method is used to evaluate the stability and ion transport efficiency of the membrane during electrodialysis.

[0105] The results are as follows Figure 2 As shown.

[0106] from Figure 2 As can be seen, the composite cation exchange membrane described in Example 4 experienced a slight voltage drop from 35V to 12V during the initial stage of electrodialysis, before quickly stabilizing at around 9V. In contrast, the composite cation exchange membrane described in Comparative Example 1 (without KH-a-ZrP) continuously decayed to near 0V. This is because the 8 KH-a-ZrP samples in Example 4 not only provided additional phosphate ion exchange sites, enhancing the membrane's ion carrying capacity, but also suppressed membrane swelling through its layered structure (swelling rate of only 14.2%), ensuring the regularity of the ion transport channels. Therefore, the membrane's surface resistance did not increase significantly during electrodialysis, and the voltage between the electrodes remained stable. In Comparative Example 1, due to the lack of KH-a-ZrP, the membrane's swelling rate reached as high as 22.5%. The ion channels twisted and collapsed over time, leading to a continuous increase in membrane resistance. The resistance that the electrodes needed to overcome increased continuously, ultimately causing the voltage to rapidly decay to the failure level.

[0107] 4. Conductivity performance study of the composite cation exchange membrane described in Example 4 and Comparative Example 3 of this application Research Methods: A conductivity meter combined with an electrodialysis apparatus was used for testing. The electrodialysis system was the same as described in the electrodialysis performance test (the desalination chamber used 0.1 mol / L NaCl solution, and the concentration chamber used deionized water). A constant current density (5 mA / cm²) was set. 2 The solution in the concentration chamber was stirred with a glass rod every 20 minutes, and then the conductivity of the solution in the concentration chamber was measured with a portable conductivity meter. The conductivity-time curve was recorded and the test duration was 160 minutes. Each group of samples was tested in parallel twice, and the average value of the conductivity-time curve was taken for analysis. This method is used to characterize the membrane’s cation migration efficiency and the ion enrichment rate in the concentration chamber.

[0108] The results are as follows Figure 3 As shown.

[0109] from Figure 3 As can be seen, the conductivity of the composite cation exchange membrane described in Example 4 of this application increases more rapidly, reaching ~10.5 mS / cm at 160 minutes; while the conductivity of Comparative Example 3 (single SPEEK base membrane) increases more gradually, ultimately reaching only ~9.8 mS / cm. This is because the high proportion of KH-a-ZrP and SPEEK-PEI copolymer system in Example 4 forms a synergistic effect of "dual ion sites + low-resistance channels": the phosphate groups of KH-a-ZrP and the sulfonic acid groups of SPEEK together provide a high ion exchange capacity of 1.95 mmol / g, while the low swelling ratio (14.2%) ensures the patency of the ion channels (surface resistance of only 3.7 Ω). cm 2 This causes cations to migrate rapidly into the concentration chamber under the influence of an electric field; in Comparative Example 3, due to the low ion site density (IEC=1.55mmol / g) of the single SPEEK base membrane and the lack of PEI crosslinking enhancement, the membrane swelling ratio was higher (19.7%), resulting in greater ion transport resistance (surface resistivity 5.7Ω). cm 2 This results in a limited cation migration rate and a slower increase in the conductivity of the concentration chamber.

[0110] 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 composite cation exchange membrane, characterized in that, The preparation materials include the following: 45-55 parts of sulfonated polyether ether ketone, 30-40 parts of polyether imide, 2-8 parts of surface amino-functionalized zirconium phosphate, and 2-5 parts of crosslinking agent.

2. The composite cation exchange membrane according to claim 1, characterized in that, The preparation materials include the following: 45-55 parts of sulfonated polyether ether ketone, 30-40 parts of polyether imide, 4-6 parts of surface amino-functionalized zirconium phosphate, and 3 parts of crosslinking agent.

3. The composite cation exchange membrane according to claim 1, characterized in that, The degree of sulfonation of the sulfonated polyether ether ketone is 65%-78%; And / or, the crosslinking agent includes one or more of sulfonyl chloride, phosphorus oxychloride, p-toluenesulfonyl chloride and sulfoxide.

4. The method for preparing the composite cation exchange membrane according to any one of claims 1-3, characterized in that, Includes the following steps: (1) Sulfonated polyether ether ketone, polyether imide, surface amino-functionalized zirconium phosphate, crosslinking agent and organic solvent are mixed and reacted to obtain a reaction solution; (2) Mix the reaction solution and defoamer, and perform defoaming treatment to obtain the composite membrane solution; (3) The composite membrane liquid is formed into a membrane and then activated by contacting it with acid to obtain the composite cation exchange membrane.

5. The method for preparing the composite cation exchange membrane according to claim 4, characterized in that, In step (1), the organic solvent includes one or more of N-methylpyrrolidone, N,N-dimethylformamide and N,N-dimethylacetamide; And / or, the mass ratio of the sulfonated polyether ether ketone to the organic solvent is 1:(2-3); And / or, in step (1), the temperature of the mixing reaction is 50-60°C and the time of the mixing reaction is 8-12h.

6. The method for preparing the composite cation exchange membrane according to claim 4, characterized in that, In step (2), the defoamer includes one or more of polyether modified silicone oil, organosilicon defoamer, polyether defoamer and mineral oil defoamer; And / or, the amount of the defoamer added is 0.3%-0.7% of the mass of the reaction solution; And / or, in step (2), the mixing temperature is 25-35°C and the mixing time is 20-40 min; And / or, in step (2), the vacuum degree of the degassing treatment is -0.08 to -0.1 MPa, the temperature is 25-35℃, and the time is 1-2h.

7. The method for preparing the composite cation exchange membrane according to claim 4, characterized in that, In step (3), the acid solution includes one or more of sulfuric acid solution, hydrochloric acid solution, phosphoric acid solution and nitric acid solution, and the concentration of the acid solution is 0.3-0.7 mol / L; And / or, the activation treatment is performed at a temperature of 20-30°C for 8-12 hours.

8. The method for preparing the composite cation exchange membrane according to claim 4, characterized in that, It also includes the step of preparing surface-amino-functionalized modified zirconium phosphate; The preparation method of the surface amino-functionalized modified zirconium phosphate includes the following steps: a. Zirconium oxychloride and phosphoric acid solution are mixed and reacted to obtain layered zirconium phosphate; b. Mix the layered zirconium phosphate, γ-aminopropyltriethoxysilane and solvent to obtain surface amino-functionalized zirconium phosphate.

9. The method for preparing the composite cation exchange membrane according to claim 8, characterized in that, In step a, the concentration of the phosphoric acid solution is 7-9 mol / L; And / or, the mass ratio of zirconium oxychloride to phosphoric acid is (40-90):1; And / or, in step a, the temperature of the mixing reaction is 110-130℃ and the time is 20-28h; And / or, in step b, the mass ratio of the layered zirconium phosphate and γ-aminopropyltriethoxysilane is (3-8):1; And / or, in step b, the solvent includes N-methylpyrrolidone; And / or, in step b, the mixing temperature is 65-75°C and the time is 4-8 hours.

10. The application of the composite cation exchange membrane according to any one of claims 1-3 or the composite cation exchange membrane obtained by the preparation method according to any one of claims 4-9 in separation; The separation includes water electrolysis or seawater desalination.

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