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

Abstract

The invention belongs to the technical field of anion exchange membrane materials, and particularly relates to a composite anion exchange membrane as well as a preparation method and application thereof. The preparation method comprises the following steps: by taking a rigid monomer containing a strong polar group as a skeleton support phase, a functional monomer containing a tertiary amine group as an ion site reserve phase and a quaternization functional inorganic phase as a synergistic reinforcement phase, adding a free radical initiator; the composite anion exchange membrane is prepared through three steps of preparation of a quaternization functional inorganic phase, membrane formation through free radical polymerization of rigid-functional monomers and quaternization activation. By regulating and controlling parameters such as quaternization inorganic phase dosage, monomer ratio and the like, a synergistic structure of'free radical copolymerization network-dual quaternary ammonium ion site-regular transmission channel 'in the membrane is optimized. The composite anion exchange membrane prepared by the invention realizes the balance of high ion exchange capacity, low surface resistance, low swelling ratio, excellent mechanical strength and chemical stability.

Description

Technical Field

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

[0002] Anion exchange membranes are core functional materials in fields such as capacitive deionization, electrodialysis, and fuel cells. Their performance directly determines the ion transport efficiency, desalination effect, and long-term stability of the system, playing an irreplaceable role in scenarios such as seawater desalination, industrial wastewater treatment, and pure water production. An ideal anion exchange membrane needs to simultaneously meet multiple performance requirements, including high ion exchange capacity (IEC), low surface resistivity, low swelling ratio, and excellent mechanical strength and chemical stability. However, current technologies still face bottlenecks in the synergistic optimization of multi-dimensional performance.

[0003] Traditional anion exchange membrane preparation mainly relies on the "halogenation and quaternization of single-functional polymers" or "simple inorganic-organic physical blending" pathways, which have significant drawbacks: First, the process lacks environmental friendliness and safety. Most membranes use toxic halogenated hydrocarbons such as chloromethyl ethers for halogenation and quaternization, which not only involve highly toxic and corrosive reagents but also pose environmental pollution and health risks to personnel during production. Second, balancing performance is difficult. Increasing the content of hydrophilic quaternary ammonium groups in single-functional polymer membranes to improve IEC (interfacial exchange efficiency) can easily lead to excessive swelling of the membrane in aqueous solution, damaging ion transport channels and increasing sheet resistivity. Conversely, strengthening rigidity to suppress swelling limits ion site density and reduces ion conduction efficiency. Third, composite membranes have poor stability. The inorganic phase and polymer interface of physically blended composite membranes have weak compatibility, making them prone to aggregation and shedding, leading to defects within the membrane and rapid performance degradation after long-term cyclic use. Fourth, the process lacks economic efficiency. Some high-performance membranes rely on scarce functional monomers, expensive inorganic fillers, or high-temperature and high-pressure equipment, resulting in high raw material costs and energy consumption, making them unsuitable for large-scale production.

[0004] In recent years, although some studies have attempted to improve the structural stability of membranes through copolymerization processes, most of these solutions have not yet broken through the limitations of "single polymer system" or rely on complex functionalization modification steps, failing to balance performance, environmental friendliness and economy.

[0005] Therefore, developing an anion exchange membrane preparation technology that is "mild and environmentally friendly, can achieve high ion capacity, low swelling, long stability synergy, and is suitable for large-scale production" has become the key to breaking through the existing technological bottlenecks. It is of great practical significance for promoting the industrial upgrading of desalination and separation technology and practicing the concept of green chemical industry. Summary of the Invention

[0006] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention propose a method for preparing a composite anion exchange membrane.

[0007] The method for preparing the composite anion exchange membrane according to an embodiment of the present invention includes the following steps: (1) Add a rigid monomer containing a strong polar group, a functional monomer containing a tertiary amine group, a quaternized functional inorganic phase and a free radical initiator to a polar organic solvent, carry out free radical polymerization under inert gas protection, add an antifoaming agent after the reaction is completed, cool down and stir to obtain a homogeneous and stable "rigid-functional copolymer / quaternized functional inorganic phase" composite film liquid; (2) After degassing the composite film liquid obtained in step (1), it is coated onto the surface of the substrate. After coating, it is allowed to stand and level naturally. (3) After drying the leveled liquid film, a composite membrane is obtained. The composite membrane is then subjected to quaternization activation treatment to obtain a rigid-functional free radical copolymer composite anion exchange membrane containing a quaternized inorganic phase.

[0008] The advantages and technical effects of the preparation method of the composite anion exchange membrane in this invention are as follows: 1. The method of this invention uses a rigid monomer with strongly polar groups to construct a dense free radical copolymer network, which inhibits excessive swelling of the membrane. The tertiary amine groups in the functional monomer are quaternized to provide ion sites. The quaternized inorganic phase not only supplements ion sites but also strengthens the network structure through physical enhancement. The three work synergistically to achieve a balance of "high ion capacity (IEC≥1.8mmol / g) + low swelling rate (≤14%)", which increases the ion capacity by 26% and reduces the swelling rate by 35% compared with a single polymer membrane. 2. The method of this invention uses free radical polymerization, which has mild reaction conditions and does not require toxic halogenated reagents. It initiates the breaking of carbon-carbon double bonds between the rigid monomer and the functional monomer, forming a chain-like free radical polymerization reaction. The strongly polar groups of the rigid monomer and the ester and tertiary amine groups of the functional monomer form hydrogen bonds and electrostatic interactions. The quaternized inorganic phase is uniformly dispersed in the polymer matrix, and a slightly cross-linked structure is formed through chain transfer reaction between monomers, which improves the structural stability of the membrane; 3. The method of this embodiment of the invention performs quaternization activation treatment, which causes the tertiary amine groups (-N(R1)2) on the functional monomer molecular chain to undergo quaternization reaction, transforming them into stable quaternary ammonium groups, forming dual stable sites with the quaternary ammonium groups of the quaternized inorganic phase. The alkali resistance stability is significantly better than that of traditional membranes, solving the pain points of "high process toxicity and rapid performance degradation"; 4. The rigid monomers and functional monomers used in the method of this embodiment of the invention are all conventional chemical raw materials, and the quaternized inorganic phase can be prepared by modifying common inorganic substrates; the solvent recovery rate is over 80%, which can be recycled and reused; the process does not require special equipment, and the reaction parameters are controllable, which reduces raw material costs and energy consumption from the mechanism, and is more in line with the environmental protection and economic requirements of large-scale industrial production.

[0009] In some embodiments, in step (1), the rigid monomer includes at least one of acrylonitrile, styrene, or methacrylonitrile; And / or, in step (1), the functional monomer containing a tertiary amine group includes at least one of dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, or N,N-dimethylacrylamide; And / or, in step (1), the quaternized functional inorganic phase includes at least one of quaternized graphene oxide, quaternized silicon dioxide, quaternized titanium dioxide, or quaternized montmorillonite; the particle size of the quaternized functional inorganic phase is 50~200nm; And / or, in step (1), the free radical initiator includes at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide or di-tert-butyl peroxide; And / or, in step (1), the polar organic solvent includes at least one of N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, or N,N-dimethylacetamide.

[0010] In some embodiments, in step (1), the mass ratio of the polar organic solvent, rigid monomer, functional monomer containing tertiary amine group, quaternized functional inorganic phase and free radical initiator is: (150~180):(45~55):(35~45):(3~8):(0.8~1.5). And / or, in step (1), the temperature of the free radical polymerization is 65~75℃, the time of the free radical polymerization is 8~12 hours, the free radical polymerization is carried out under stirring, and the stirring speed is 350~450r / min.

[0011] And / or, in step (1), the defoamer includes at least one of polyether-modified silicone oil, organosilicon defoamer, or polyoxyethylene polyoxypropylene ether, and the amount of the defoamer added is 0.3% to 0.6% of the total mass of the system; And / or, in step (1), the temperature is lowered to 30~35℃ and the stirring time is 25~35min.

[0012] In some embodiments, the preparation method of the quaternized functional inorganic phase in step (1) includes the following steps: (a) Disperse an inorganic substrate containing oxygen-containing active groups in a polar dispersion medium, ultrasonically disperse it for 40-50 minutes at a power of 200-300W, add a tertiary amine reagent and magnetically stir for 30-50 minutes, then heat it to 60-70℃ and keep it at that temperature for 8-10 hours. (b) After the heat preservation reaction is completed, cool down to 30~35℃, add quaternization reagent to the system and continue stirring for 6~8 hours. After the reaction is completed, centrifuge at 4000~4500r / min for 20~25 minutes, collect the precipitate, wash repeatedly with polar dispersion medium until the washing solution is free of halogen ions or sulfate ions, and then wash with anhydrous ethanol at least twice. (c) Place the precipitate in a vacuum drying oven and dry it at 60~80℃ and 0.06~0.1MPa for 12~16 hours. Grind it into a fine powder and store it in a sealed container for later use.

[0013] In some embodiments, the inorganic substrate containing oxygen-containing active groups includes at least one of graphene oxide, silicon dioxide, titanium dioxide, and montmorillonite, with a particle size of 1-5 μm, and the oxygen-containing active groups include at least one of hydroxyl, epoxy, or carboxyl groups, with a content of 20-30 wt%; The polar dispersion medium includes at least one of deionized water, anhydrous ethanol, or ethylene glycol; The tertiary amine reagent includes at least one of N,N-dimethylethylenediamine, N,N-dimethylpropylenediamine, or triethylenetetramine; The quaternizing agent includes at least one of methyl iodide, methyl bromide, or dimethyl sulfate; The mass ratio of the inorganic substrate, polar dispersion medium, tertiary amine reagent and quaternizing reagent is (2~3):(60~80):(8~12):(5~8).

[0014] In some embodiments, in step (2), the degassing process includes: transferring the composite membrane liquid to a vacuum degassing machine, setting the vacuum degree to -0.08 to -0.1 MPa and the temperature to 30 to 35°C, and degassing for 2 to 3 hours, during which the gas is released once every 20 to 40 minutes; And / or, in step (2), the coating specifically includes: after pretreating the substrate, the degassed composite film liquid is evenly poured onto one end of the substrate, and a 200~280μm thickness coater is used to uniformly coat the film in the same direction at a speed of 5~8cm / s to form a continuous and uniform liquid film.

[0015] In some embodiments, in step (3), the drying process is gradient drying, which specifically includes: a first stage of holding at 55~65℃ for 3~4 hours; a second stage of holding at 80~90℃ for 2.5~3.5 hours; and a third stage of holding at 100~110℃ for 2~3 hours, and drying under a vacuum of 0.06~0.1MPa.

[0016] In some embodiments, in step (3), the quaternization activation treatment includes: immersing the composite membrane in a quaternization activation reagent, washing the membrane repeatedly with deionized water after soaking, detecting the pH value of the washing solution after each wash until pH=7.0~8.0, and placing the washed membrane in a vacuum drying oven for drying. The concentration of the quaternization activating reagent is 0.8~1.2 mol / L, and the quaternization activating reagent includes an aqueous solution and / or an ethanolic solution of at least one of trimethylamine, triethylamine, benzyl chloride or dimethyl sulfate; the drying treatment is to dry at 55~65℃ and 0.06~0.1MPa for 8~12 hours.

[0017] This invention also provides a composite anion exchange membrane, which is prepared using the above-described preparation method.

[0018] The embodiments of the present invention provide the composite anion exchange membrane prepared by the above preparation method or the application of the above composite anion exchange membrane in the fields of capacitive deionization, electrodialysis or fuel cells. Attached Figure Description

[0019] Figure 1 This is a graph showing the desorption current variation in C-MCDI for Example 3; Figure 2 This is a graph showing the change in solution conductivity of the membrane in the C-MCDI system during five consecutive operating cycles in Example 3; Figure 3 These are stress-strain curves of Example 1, Example 2, Comparative Example 4, and Comparative Example 1. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0021] The method for preparing the composite anion exchange membrane according to an embodiment of the present invention includes the following steps: (1) Add a rigid monomer containing a strong polar group, a functional monomer containing a tertiary amine group, a quaternized functional inorganic phase and a free radical initiator to a polar organic solvent, carry out free radical polymerization under inert gas protection, add an antifoaming agent after the reaction is completed, cool down and stir to obtain a homogeneous and stable "rigid-functional copolymer / quaternized functional inorganic phase" composite film liquid; (2) After degassing the composite film liquid obtained in step (1), it is coated onto the surface of the substrate. After coating, it is allowed to stand and level naturally. (3) After drying the leveled liquid film, a composite membrane is obtained. The composite membrane is then subjected to quaternization activation treatment to obtain a rigid-functional free radical copolymer composite anion exchange membrane containing a quaternized inorganic phase.

[0022] The method for preparing the composite anion exchange membrane in this invention utilizes the highly polar groups in the rigid monomers to construct a dense free radical copolymer network, inhibiting excessive membrane swelling. The tertiary amine groups in the functional monomers, after quaternization, provide ion sites. The quaternized inorganic phase not only supplements ion sites but also physically strengthens the network structure. These three elements synergistically achieve a balance between "high ion capacity (IEC≥1.8mmol / g) + low swelling rate (≤14%)", resulting in a 26% increase in ion capacity and a 35% reduction in swelling rate compared to single polymer membranes. The method in this invention employs free radical polymerization, with mild reaction conditions and no need for toxic halogenated reagents. This initiates the breaking of carbon-carbon double bonds between the rigid and functional monomers, forming a chain-like free radical polymerization reaction. The highly polar groups of the rigid monomers form hydrogen bonds and electrostatic interactions with the ester and tertiary amine groups of the functional monomers. The quaternized functional inorganic phase is uniformly dispersed. Within the polymer matrix, a mildly cross-linked structure is formed simultaneously through chain transfer reactions between monomers, enhancing the structural stability of the membrane. In the method of this embodiment, the quaternization activation uses low-toxicity reagents such as trimethylamine. Quaternization activation causes the tertiary amine groups (-N(R1)2) on the functional monomer molecular chains to undergo a quaternization reaction, transforming them into stable quaternary ammonium groups. These groups form dual stable sites with the quaternary ammonium groups of the quaternized inorganic phase, resulting in significantly better alkali resistance than traditional membranes, thus solving the pain points of "high process toxicity and rapid performance degradation." In the method of this embodiment, the rigid monomers and functional monomers used are all conventional chemical raw materials, and the quaternized inorganic phase can be prepared by modifying common inorganic substrates. The solvent recovery rate reaches over 80%, allowing for recycling. The process requires no special equipment, and the reaction parameters are controllable, reducing raw material costs and energy consumption from a mechanistic perspective, thus better meeting the environmental and economic requirements of large-scale industrial production.

[0023] In some embodiments, preferably, in step (1), the rigid monomer includes at least one of acrylonitrile (AN), styrene (St), or methacrylonitrile (MAN); And / or, in step (1), the functional monomer containing a tertiary amine group includes at least one of dimethylaminoethyl methacrylate (DMAEMA), diethylaminoethyl methacrylate (DEAEMA), or N,N-dimethylacrylamide (DMAA). The selected rigid monomer contains strongly polar groups such as cyano groups and benzene rings to ensure the swelling resistance and mechanical strength of the anion exchange membrane.

[0024] In some embodiments, preferably, in step (1), the quaternized functional inorganic phase includes at least one of quaternized graphene oxide, quaternized silicon dioxide, quaternized titanium dioxide, or quaternized montmorillonite; the particle size of the quaternized functional inorganic phase is 50~200nm.

[0025] In this embodiment of the invention, the quaternized functional inorganic phase used is particulate, which results in a higher degree of quaternization and a higher surface quaternization efficiency, enabling the formation of a continuous ion transport layer. The particles can synergistically polymerize with rigid-functional monomers, avoiding the defects of nanotubes that hinder free radical polymerization. They are superior to nanotube morphologies in terms of ionic conductivity, mechanical strength, and chemical stability.

[0026] In some embodiments, preferably, in step (1), the free radical initiator includes at least one of azobisisobutyronitrile (AIBN), azobisisoheptanenitrile (ABVN), benzoyl peroxide (BPO), or di-tert-butyl peroxide (DTBP); And / or, in step (1), the polar organic solvent includes at least one of N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO) or N,N-dimethylacetamide (DMAc).

[0027] In some embodiments, preferably, in step (1), the mass ratio of the polar organic solvent, rigid monomer, functional monomer containing tertiary amine group, quaternized functional inorganic phase and free radical initiator is: (150~180):(45~55):(35~45):(3~8):(0.8~1.5). And / or, in step (1), the temperature of the free radical polymerization is 65~75℃, the time of the free radical polymerization is 8~12 hours, the free radical polymerization is carried out under stirring, and the stirring speed is 350~450r / min.

[0028] In some embodiments, preferably, in step (1), the defoamer includes at least one of polyether-modified silicone oil, organosilicon defoamer, or polyoxyethylene polyoxypropylene ether, and the amount of the defoamer added is 0.3% to 0.6% of the total mass of the system; And / or, in step (1), the temperature is lowered to 30~35℃, and the stirring time is 25~35min. This removes the bubbles and dissolved gases generated during the reaction, resulting in a homogeneous and stable composite membrane solution.

[0029] In some embodiments, preferably, the preparation method of the quaternized functional inorganic phase in step (1) includes the following steps: (a) Disperse an inorganic substrate containing oxygen-containing active groups in a polar dispersion medium, ultrasonically disperse it at a power of 200~300W for 40~50 minutes, add a tertiary amine reagent and magnetically stir for 30~50 minutes, then heat it to 60~70℃ and keep it at that temperature for 8~10 hours; the amine group of the tertiary amine reagent reacts with the carboxyl and hydroxyl groups on the surface of the inorganic substrate to undergo amidation or etherification reactions, thereby introducing tertiary amine groups; (b) After the heat treatment is completed, cool the temperature to 30-35°C, add the quaternizing agent to the system, and continue stirring for 6-8 hours to quaternize the tertiary amine group (-NH(CH3)2→-N). + (CH3)3X - X is I - ,Br - CH3SO4 - The crude product of quaternization functional inorganic phase was obtained. After the reaction was completed, the product was centrifuged at 4000-4500 r / min for 20-25 minutes, the precipitate was collected, and it was repeatedly washed with polar dispersion medium until the washing solution was free of halogen ions or sulfate ions. Then it was washed with anhydrous ethanol at least twice. (c) Place the precipitate in a vacuum drying oven and dry it at 60~80℃ and 0.06~0.1MPa for 12~16 hours. Grind it into a fine powder and store it in a sealed container for later use.

[0030] In some embodiments, preferably, the inorganic substrate containing oxygen-containing active groups includes at least one of graphene oxide (GO), silicon dioxide (SiO2), titanium dioxide (TiO2), and montmorillonite, with a particle size of 1-5 μm, and the oxygen-containing active groups include at least one of hydroxyl (-OH), epoxy (-O-), or carboxyl (-COOH), and the content of the oxygen-containing active groups is 20-30 wt%. The polar dispersion medium includes at least one of deionized water, anhydrous ethanol, or ethylene glycol; The tertiary amine reagent includes at least one of N,N-dimethylethylenediamine (DMEDA), N,N-dimethylpropylenediamine, or triethylenetetramine. The quaternizing agent includes at least one of methyl iodide (CH3I), methyl bromide, or dimethyl sulfate; The mass ratio of the inorganic substrate, polar dispersion medium, tertiary amine reagent and quaternizing reagent is (2~3):(60~80):(8~12):(5~8).

[0031] In some embodiments, preferably, in step (2), the degassing treatment includes: transferring the composite membrane liquid to a vacuum degassing machine, setting the vacuum degree to -0.08~-0.1MPa and the temperature to 30~35℃, and degassing for 2~3 hours, during which gas is released once every 20~40 minutes. This thoroughly removes dissolved gases and trace bubbles remaining from the polymerization reaction, preventing pinholes and cracks from appearing after film formation.

[0032] In some embodiments, preferably, step (2) of the coating specifically includes: after pretreating the substrate, uniformly inverting the degassed composite film liquid onto one end of the substrate, and using a 200~280μm thickness coater to uniformly coat it in the same direction at a speed of 5~8cm / s to form a continuous and uniform liquid film. The substrate is one of glass plate, polytetrafluoroethylene plate or stainless steel plate; the pretreatment includes wiping the surface of the substrate clean with anhydrous ethanol or acetone and drying it with nitrogen gas, fixing it on a horizontal coating table to ensure that the substrate surface is flat and without tilt.

[0033] In some embodiments, preferably, in step (3), the drying process is gradient drying, which specifically includes: a first stage of holding at 55~65℃ for 3~4 hours; a second stage of holding at 80~90℃ for 2.5~3.5 hours; and a third stage of holding at 100~110℃ for 2~3 hours, and drying under a vacuum of 0.06~0.1MPa.

[0034] In this embodiment of the invention, a gradient drying process is used for drying. In the first stage, the polar organic solvent is slowly evaporated to avoid rapid solvent evaporation that could cause the film to shrink and crack. In the second stage, residual solvent is further removed to strengthen the interfacial bonding between the polymer and the quaternized functional inorganic phase (the quaternary ammonium groups on the surface of the quaternized functional inorganic phase form hydrogen bonds and electrostatic interactions with the ester groups, cyano groups / benzene rings of the polymer). In the third stage, residual solvent is completely removed to improve the mechanical strength of the film. After drying, the film is naturally cooled to room temperature, and the initially formed composite film is gently peeled off.

[0035] In some embodiments, preferably, in step (3), the quaternization activation treatment includes: immersing the composite membrane in a quaternization activation reagent, repeatedly washing the membrane with deionized water after soaking, detecting the pH value of the washing solution after each wash until pH=7.0~8.0, and placing the washed membrane in a vacuum drying oven for drying. The concentration of the quaternization activating reagent is 0.8~1.2 mol / L, and the quaternization activating reagent includes an aqueous solution and / or an ethanolic solution of at least one of trimethylamine, triethylamine, benzyl chloride or dimethyl sulfate; the drying treatment is to dry at 55~65℃ and 0.06~0.1MPa for 8~12 hours.

[0036] In this embodiment of the invention, the selected quaternization activating reagent is low in toxicity and environmentally friendly, avoiding environmental pollution and health risks to personnel.

[0037] This invention also provides a composite anion exchange membrane, which is prepared using the above-described preparation method.

[0038] The embodiments of the present invention provide the application of the composite anion exchange membrane prepared by the above preparation method or the above composite anion exchange membrane in the fields of capacitive deionization (C-MCDI), electrodialysis or fuel cells.

[0039] The technical solution of the present invention will now be described in detail with reference to specific embodiments and accompanying drawings.

[0040] Example 1 (1) Preparation of quaternization functional inorganic phase (Q-inorganic phase): Weigh 2.5 parts of graphene oxide with oxygen-containing active groups (particle size 3-4 μm, oxygen-containing active group content 25 wt%), add 70 parts of deionized water, and ultrasonically disperse for 45 minutes (power 250W) to form a homogeneous suspension; add 10 parts of the tertiary amine reagent N,N-dimethylethylenediamine (DMEDA) to the suspension, stir magnetically for 30 minutes, then heat to 65℃ and maintain the reaction temperature for 9 hours; cool to 30-35℃, and slowly add 6.5 parts of methyl iodine (CH3I) dropwise. Continue stirring for 7 hours to obtain crude product of quaternized functionalized graphene oxide (Q-inorganic phase); after the reaction is completed, centrifuge at 4000 r / min for 25 minutes and collect the precipitate; wash repeatedly with polar dispersion medium until the washing liquid is free of halide ions or sulfate ions (no precipitate is detected by silver nitrate solution or barium chloride solution), and then wash twice with anhydrous ethanol; place the precipitate in a vacuum drying oven and dry at 70℃ and 0.06-0.1 MPa for 15 hours, grind it into fine powder, and seal and store for later use.

[0041] (2) Rigid-functional monomer free radical polymerized base film: Weigh out 50 parts by weight of rigid monomer acrylonitrile, 40 parts by weight of functional monomer dimethylaminoethyl methacrylate (DMAEMA), 5 parts by weight of Q-inorganic phase, and 1.2 parts by weight of free radical initiator azobisisobutyronitrile (AIBN), and place them together in a 1000mL three-necked flask; add 165 parts by weight of polar organic solvent N,N-dimethylformamide (DMF) to the flask, set the temperature to 70℃ and the stirring speed to 400r / min, and purge with nitrogen for 30 minutes to remove oxygen (to avoid oxygen inhibiting free radical polymerization); under nitrogen protection, stir at a constant temperature for 10 hours to decompose the initiator and generate free radicals; add 0.5% by weight of defoamer polyether modified silicone oil to the polymerization system, cool to 35℃, and stir for 25 minutes to remove bubbles and dissolved gases generated during the reaction, and obtain a homogeneous and stable "rigid=functional copolymer / Q-inorganic phase" composite film solution.

[0042] (3) Degassing and coating of membrane solution: The composite film solution was transferred to a vacuum degassing machine, with a vacuum level set to -0.08 to -0.1 MPa and a temperature of 35°C. Degassing was performed for 2 hours, with gas released every 30 minutes during this period to thoroughly remove dissolved gases and trace amounts of residual bubbles from the polymerization reaction, thus preventing pinholes and cracks after film formation. A clean and dry 13cm × 13cm glass plate was taken, its surface was wiped with anhydrous ethanol and dried with nitrogen, and it was fixed on a horizontal coating stage to ensure that the substrate surface was flat and without tilt. 15 portions of the degassed film solution were transferred and evenly inverted onto one end of the substrate. Using a 260μm thick stainless steel coater, the solution was uniformly coated in the same direction at a speed of 6cm / s to form a continuous and uniform liquid film. After coating, the solution was allowed to stand for 10 minutes to level naturally, eliminating coating marks and allowing the solvent to diffuse slowly to ensure a uniform internal structure of the film layer.

[0043] (4) Gradient drying and quaternization activation: The leveled liquid film, along with the substrate, is placed in a forced-air drying oven and dried using a gradient temperature drying process: the first stage is held at 60℃ for 3 hours; the second stage is held at 85℃ for 3 hours; the third stage is held at 150℃ for 2.5 hours, and dried under a vacuum of 0.06-0.1MPa; after drying, it is allowed to cool naturally to room temperature, and the initially formed composite film is gently peeled off. Prepare a 1 mol / L trimethylamine reagent and completely immerse the composite membrane in it. Staticly soak the membrane in a 30℃ constant temperature water bath for 15 hours. Then, repeatedly wash the membrane with deionized water, and check the pH value of the washing solution after each wash until the pH = 7.0-8.0, so as to completely remove the residual quaternization activating reagent. Place the washed membrane in a vacuum drying oven and dry it at 60℃ and 0.06-0.1MPa for 10 hours until the membrane quality is constant, thus obtaining a rigid-functional free radical copolymer composite anion exchange membrane containing a quaternized inorganic phase.

[0044] Example 2 The preparation method of this embodiment is the same as that of Example 1, except that the amount of Q-inorganic phase (Q-rGO) used in step (2) is 3 parts.

[0045] Example 3 The preparation method of this embodiment is the same as that of Example 1, except that the amount of Q-inorganic phase (Q-rGO) used in step (2) is 7 parts.

[0046] Example 4 The preparation method of this embodiment is the same as that of Example 1, except that the rigid monomer in step (2) is styrene (St).

[0047] Example 5 The preparation method of this embodiment is the same as that of Example 1, except that the rigid monomer in step (2) is acrylonitrile (AN) + styrene (St) (mass ratio 1:1).

[0048] Example 6 The preparation method of this embodiment is the same as that of Example 1, except that the functional monomer in step (2) is diethylaminoethyl methacrylate (DEAEMA).

[0049] Example 7 The preparation method of this embodiment is the same as that of Example 1, except that the functional monomer in step (2) is dimethylaminoethyl methacrylate (DMAEMA) + N,N-dimethylacrylamide (DMAA) (mass ratio 1:1).

[0050] Example 8 The preparation method of this embodiment is the same as that of Example 1, except that: in step (1), the inorganic substrate is silicon dioxide (SiO2) and the Q-inorganic phase is quaternized silicon dioxide (Q-SiO2).

[0051] Example 9 The preparation method of this embodiment is the same as that of Example 1, except that the free radical initiator in step (2) is azobisisoheptanenitrile (ABVN).

[0052] Example 10 The preparation method of this embodiment is the same as that of Example 1, except that the free radical polymerization temperature in step (2) is 65°C and the quaternization activating agent in step (4) is triethylamine (1.0 mol / L aqueous solution).

[0053] Example 11 The preparation method of this embodiment is the same as that of Example 1, except that the free radical polymerization temperature in step (2) is 75°C and the quaternization activating agent in step (4) is benzyl chloride (1.0 mol / L ethanol solution).

[0054] Example 12 The preparation method of this embodiment is the same as that of Example 1, except that in step (4), the soaking time in the trimethylamine reagent is 12h.

[0055] Example 13 The preparation method of this embodiment is the same as that of Example 1, except that in step (1), the inorganic phase used is titanium dioxide nanotubes, and quaternized functional titanium dioxide nanotubes are obtained.

[0056] Example 14 The preparation method of this embodiment is the same as that of Example 1, except that in step (4), a one-step drying process is used for drying, and the temperature is kept at 85°C for 9 hours.

[0057] Comparative Example 1 The preparation method of this comparative example is the same as that of Example 1, except that: Q-inorganic phase is not added in step (2), the amount of rigid monomer acrylonitrile (AN) is changed to 50 parts, and the amount of functional monomer dimethylaminoethyl methacrylate (DMAEMA) is changed to 50 parts.

[0058] Comparative Example 2 The preparation method of this comparative example is the same as that of Example 1, except that: no functional monomer is added in step (2), and the amount of rigid monomer acrylonitrile (AN) is changed to 95 parts.

[0059] Comparative Example 3 The preparation method of this comparative example is the same as that of Example 1, except that the quaternization activation treatment was not performed in step (4).

[0060] Comparative Example 4 The preparation method of this comparative example is the same as that of Example 1, except that: no rigid monomer is added in step (2), the amount of functional monomer dimethylaminoethyl methacrylate (DMAEMA) is changed to 95 parts, and the amount of Q-inorganic phase is 5 parts.

[0061] The performance of the composite anion exchange membranes prepared in Examples 1-14 and Comparative Examples 1-4 was tested, and the results are shown in Table 1. The swelling rate test method is as follows: Cut the composite anion exchange membrane into 2cm × 2cm square samples, place them in a vacuum drying oven (60℃, 0.08MPa) and dry them until the mass is constant, and record the mass of the dry membrane (m1); then completely immerse the dry membrane in deionized water (25℃ constant temperature) for 24 hours, remove it, blot the surface moisture with filter paper, and immediately record the mass of the wet membrane (m2); the swelling rate is calculated according to the formula: Swelling rate (mass) = (m2 - m1) / m1 × 100%; The test method for performance retention after 100 cycles was as follows: A composite anion exchange membrane was assembled into a C-MCDI single cell (membrane area 2cm × 2cm, carbon electrode, 0.1mol / L NaCl solution). The operating parameters were set as follows: 1.2V adsorption for 10min + short-circuit desorption for 10min constituted one cycle. The peak desorption current (I1) of the first cycle and the peak desorption current (I0) of the 100th cycle were measured. 100 The performance retention rate after 100 cycles is calculated using the formula: Performance retention rate after 100 cycles = I 100 / I1×100%; The method for testing alkali resistance stability is as follows: The composite anion exchange membrane is cut into 2cm × 2cm square samples, and the initial ion exchange capacity (IEC0) is tested. Then, the membrane is completely immersed in a 1mol / L KOH solution (at a constant temperature of 80℃) for 48 hours. After immersion, it is removed and repeatedly washed with deionized water until the pH of the washing solution reaches 7-8. It is then vacuum dried (60℃, 0.08MPa) until its mass is constant, and the ion exchange capacity (IEC0) after immersion is tested. 48 Alkali resistance stability (IEC retention rate) is calculated using the formula: IEC retention rate = IEC0 / IEC0 48 ×100%.

[0062] Table 1

[0063] Test data show that the Q-inorganic phase, acting as an "ion site supplement + physical reinforcement phase," directly determines the ion exchange capacity and structural stability of the membrane through its dosage and type. In Example 2, due to the low proportion of the Q-inorganic phase and insufficient total amount of surface quaternary ammonium groups, the synergistic effect with the polymer quaternary ammonium sites was limited, resulting in an IEC of only 1.57 mmol / g and weak physical reinforcement with a swelling rate of 16.8%. In contrast, Example 3, by increasing the content of the Q-inorganic phase, introduced more exchangeable quaternary ammonium groups (-N... + (CH3)3), increasing the IEC to 1.93 mmol / g, and leveraging the layered structure of graphene to provide physical support, inhibits the hydrophilic swelling of polymer segments, reducing the swelling rate to 12.2%. Simultaneously, the high conductivity of Q-rGO accelerates anion transport, resulting in a sheet resistivity as low as 3.4 Ω. cm 2The performance retention rate after 100 cycles reached 95.8%, and its alkali resistance was significantly better than that of Example 8, which used quaternized silica. This is because the high specific surface area and better interfacial compatibility of graphene make it less prone to hydrolysis and shedding of quaternary ammonium groups, while SiO2 particles tend to agglomerate, leading to interfacial defects and a slight decrease in IEC and cycle stability. Furthermore, compared to Example 1, Example 12 showed a shorter quaternization activation time, resulting in insufficient quaternization of the polymer tertiary amine groups. The IEC decreased from 1.82 mmol / g to 1.71 mmol / g, and the sheet resistivity decreased from 3.8 Ω. cm 2 Increased to 4.4Ω cm 2 This verified the crucial role of full quaternization in the formation of ion sites.

[0064] The combination of rigid-functional monomers and polymerization parameters balance ion conduction and anti-swelling properties by regulating the polymer network structure. Example 4 (rigid monomer St) showed a slight decrease in IEC compared to Example 1 (rigid monomer AN). Because the polarity of the benzene ring is weaker than that of the cyano group, its effect on improving the dispersibility of quaternary ammonium groups is limited. The benzene ring has a planar conjugated rigid structure with greater steric hindrance, which can form physical crosslinking points through steric hindrance and π-π stacking, more effectively limiting the hydrophilic swelling and disordered movement of polymer segments. On the one hand, the rigid framework of the benzene ring can reduce the flexibility of polymer segments, reducing the segment extension caused by the hydration of hydrophilic groups in aqueous solution; on the other hand… On the one hand, the π-π stacking effect between adjacent benzene rings enhances the intermolecular forces, making the polymer network denser. Therefore, although its swelling ratio (14.3%) is slightly higher than that of Example 1 (13.6%), it is still in the low swelling range, demonstrating the inhibitory effect of the rigid structure of the benzene ring on swelling and ensuring the structural stability and performance reliability of the membrane. Example 5 achieves synergy, with the cyano group improving the dispersion of ion sites and the benzene ring strengthening rigidity, resulting in an IEC of 1.79 mmol / g and a swelling ratio of 13.1%, demonstrating superior overall performance. Regarding functional monomers, in Example 7, because the density of the tertiary amine group in DMAA is slightly higher than that in DMAEMA, the ion sites are more densely packed after synergy, achieving an IEC of 1.84 mmol / g and a sheet resistivity of 3.7 Ω. cm 2 The cycle stability was 94.5%, superior to the single DMAEMA system (Example 1). Among the polymerization parameters, the substitution of the initiator type (Example 9 vs. Example 1) had a relatively small impact on performance (IEC 1.80 vs. 1.82 mmol / g), as both can efficiently initiate free radical polymerization; however, the decrease in polymerization temperature (Example 10 vs. Example 1) resulted in a slight decrease in the degree of polymerization and insufficient polymer network density, with an IEC of 1.73 mmol / g and a sheet resistivity of 4.3 Ω. cm 2 This verifies the importance of appropriate polymerization temperature for network structure.

[0065] Example 13 uses titanium dioxide nanotubes as the Q-inorganic phase, with an IEC of 1.65 mmol / g and a sheet resistivity of 4.9 Ω. cm², swelling rate 15.7%, overall performance inferior to Example 1. The core mechanism is as follows: Titanium dioxide nanotubes have a large aspect ratio, which makes them prone to aggregation in the polymer matrix, disrupting the continuity of ion transport channels and resulting in a higher sheet resistivity than in Example 1. At the same time, the hydroxyl density on the nanotube surface is lower than that of graphene oxide, and the quaternization modification efficiency is only 40%~50%, which is lower than 70%~80% of graphene oxide, resulting in insufficient total ion sites and a 9.3% reduction in IEC compared to Example 1. In addition, the interfacial compatibility between nanotubes and polymer chains is poor, and stable hydrogen bonds or covalent interactions cannot be formed. During cycling and alkali immersion, interfacial peeling is prone to occur, resulting in a significantly lower performance retention rate (88.7%) and alkali resistance stability (87.9%) after 100 cycles compared to Example 1. This further verifies the key role of "single high-efficiency Q-inorganic phase (such as Q-graphene oxide) + suitable particle size (50~200nm)" in membrane performance. However, due to aggregation and compatibility defects, the nanotube morphology is not suitable for the "rigid-functional monomer synergistic polymerization" system of this invention.

[0066] Example 14 employed a one-step drying process (holding at 85°C for 9 hours), resulting in a significant decrease in performance compared to Example 1: IEC decreased from 1.82 mmol / g to 1.52 mmol / g, and sheet resistivity decreased from 3.8 Ω. cm² increased to 5.3Ω The swelling ratio increased from 13.6% to 18.1% in cm². This is because gradient drying (Example 1), through a step-by-step design of "low-temperature slow drying (60°C) → medium-temperature setting (85°C) → high-temperature densification (150°C)," can remove the solvent in the membrane in stages, avoiding the disordered shrinkage of polymer chains and pore collapse caused by rapid solvent evaporation, and ensuring the regularity of ion channels and the uniform distribution of quaternary ammonium groups. In contrast, in one-step drying (85°C), the rapid escape of solvent will form micropores and stress concentration in the membrane, which will reduce the ion transport path and decrease the binding stability of quaternary ammonium groups and polymers, resulting in a 16.5% decrease in IEC. At the same time, disordered polymer chains are prone to excessive hydrophilic swelling in aqueous solution, with the swelling ratio increasing by 33.1% compared to Example 1, further distorting ion channels and increasing sheet resistivity. This result verifies that the gradient drying process is a necessary condition to ensure the synergistic effect of "high conductivity and low swelling" in the membrane, and one-step drying cannot achieve the densification and structural stability of the polymer network.

[0067] Comparative Example 1 (without Q-inorganic phase) lacks "inorganic phase quaternary ammonium sites + physical enhancement," relying solely on polymer quaternary ammonium groups. Its IEC is only 1.45 mmol / g, and the inorganic phase inhibits swelling. The membrane exhibits excessive chain stretching in aqueous solution, resulting in a swelling rate of 19.3%. Ion channel distortion leads to a sheet resistivity of 5.7 Ω. cm 2 After 100 cycles, the quaternary ammonium groups easily hydrolyze and detach, resulting in a performance retention rate of only 82.6%. Comparative Example 2 (non-functional monomer), lacking quaternizable tertiary amine groups, relies solely on a small number of quaternary ammonium sites in Q-rGO, achieving an IEC of only 0.82 mmol / g and a sheet resistivity of 8.9 Ω. cm 2 Although the rigid monomer AN ensured a low swelling ratio (12.5%), its extremely poor ion conductivity highlighted the core role of the functional monomer. Comparative Example 3 (unactivated by quaternization) contained only trace quaternary ammonium sites in the Q-inorganic phase, with an IEC of only 0.35 mmol / g and a sheet resistivity of 12.6 Ω. cm 2 This demonstrates that quaternization activation is a necessary step in forming effective anion exchange sites. Comparative Example 4 (without rigid monomers) suffers from excessive polymer chain flexibility due to the lack of rigid support from cyano / benzene rings, resulting in a swelling rate as high as 23.7%. The loose membrane structure leads to easy shedding of quaternary ammonium groups, resulting in a performance retention rate of only 75.9% after 100 cycles and an alkali resistance stability of 74.3%. This fully validates the innovation of the "rigid-functional monomer + Q-inorganic phase" ternary system. By constructing a dense network through free radical polymerization, the rigid monomer inhibits swelling, and the functional monomer and Q-inorganic phase synergistically provide high-density ion sites, solving the pain point of traditional anion exchange membranes where "high IEC and low swelling, and long-term stability are difficult to achieve simultaneously."

[0068] The capacitive deionization (C-MCDI) desorption current performance of the anion exchange membrane prepared in Example 3 was tested. The test method was as follows: the composite anion exchange membrane of Example 3 was assembled into a C-MCDI single cell (carbon electrodes on both sides of the membrane, with an electrode area of ​​2 cm × 2 cm). 0.1 mol / L NaCl solution was used as the treatment solution, and the flow rate was controlled at 5 mL / min. The operating voltage was set to 1.2 V (adsorption stage) and short-circuit (desorption stage). Each cycle included "adsorption 10 min + desorption 10 min". The current change during the desorption stage was monitored in real time using an electrochemical workstation. Five consecutive cycles were tested, and the current response curve during the desorption process was recorded. The results are as follows: Figure 1 As shown. From Figure 1As can be seen from the curve, the desorption current peak value is stable (approximately -20 mA) and the rising and falling trends are highly consistent within each cycle, corresponding to the best-performing Example 3 (7 parts of Q-rGO). This is because the high proportion of Q-rGO in Example 3 provides a high IEC of 1.93 mmol / g, and the "polymer quaternary ammonium sites + inorganic phase quaternary ammonium sites" form a dual anion adsorption center, ensuring sufficient ion exchange capacity; at the same time, the low swelling network (swelling rate of 12.2%) constructed by the rigid AN monomer keeps the ion channels always regular, and the high conductivity of Q-rGO accelerates the desorption and migration of anions. Therefore, the desorption current does not decrease significantly within 5 consecutive cycles, demonstrating the synergy between the high capacity and cycling stability of the membrane.

[0069] The solution conductivity cyclic stability of the anion exchange membrane prepared in Example 3 was tested in a C-MCDI system. The test method was as follows: using a... Figure 1 The same C-MCDI single cell and operating parameters (0.1 mol / L NaCl solution, flow rate 5 mL / min, adsorption / short-circuit desorption 1.2 V, 10 min / cycle) were used. During the adsorption / desorption process in each cycle, the conductivity change of the treated solution (Cl in the solution during the adsorption stage) was monitored in real time using a conductivity meter. - Cl is adsorbed onto the membrane, and its conductivity decreases; during the desorption phase... - (After being released back into the solution, the conductivity rebounded); five consecutive tests were conducted, and the fluctuation curve of the solution conductivity in each cycle was recorded. The results are as follows: Figure 2 As shown. From Figure 2 As can be seen from the curve, the conductivity fluctuates within each cycle with a final value stabilizing at 0.96-1.08 mS / cm, corresponding to Example 3. This is because the "Q-rGO enhanced + AN rigid network" system in Example 3 ensures rapid adsorption-desorption of anions through high IEC and avoids channel distortion with low swelling ratio. Therefore, in each cycle, solution anions can stably migrate through the membrane, and the "decrease (adsorption) - increase (desorption)" amplitude of conductivity does not change significantly. Furthermore, the interfacial hydrogen bonding between Q-rGO and the polymer inhibits the detachment of the inorganic phase, further maintaining ion transport efficiency and verifying the long-term operational stability of the membrane.

[0070] The mechanical properties of the composite anion exchange membranes prepared in Examples 1, 2, 1, and 4 were tested, and the results are as follows: Figure 3 As shown, from Figure 3As can be seen, Example 1 has the largest slope and a fracture stress of nearly 40 MPa, corresponding to the "AN+DMAEMA+Q-rGO" system; in Example 2, the amount of Q-rGO is 3 parts, and the fracture stress is slightly reduced due to the weakening of physical reinforcement; in Comparative Example 4, there is no rigid monomer, the chain segments are loose, and the fracture stress is the lowest; in Comparative Example 1, there is no Q-inorganic phase, and due to the lack of physical reinforcement, the fracture stress is lower than that of Example 1 but higher than that of Comparative Example 4. Mechanistically, the cyano groups of AN construct a rigid framework, and the Q-rGO sheets strengthen stress transfer, and the two synergistically improve mechanical strength; without the Q-inorganic phase, the physical reinforcement is lost, and without the rigid monomer, the framework support is lacking. Therefore, the stress-strain behavior of different systems is significantly different, highlighting the synergistic reinforcement effect of "rigid monomer + Q-inorganic phase".

[0071] 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.

[0072] 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 method for preparing a composite anion exchange membrane, characterized in that, Includes the following steps: (1) Add a rigid monomer containing a strong polar group, a functional monomer containing a tertiary amine group, a quaternized functional inorganic phase and a free radical initiator to a polar organic solvent, carry out free radical polymerization under inert gas protection, add an antifoaming agent after the reaction is completed, cool down and stir to obtain a homogeneous and stable "rigid-functional copolymer / quaternized functional inorganic phase" composite film liquid; (2) After degassing the composite film liquid obtained in step (1), it is coated onto the surface of the substrate. After coating, it is allowed to stand and level naturally. (3) After drying the leveled liquid film, a composite membrane is obtained. The composite membrane is then subjected to quaternization activation treatment to obtain a rigid-functional free radical copolymer composite anion exchange membrane containing a quaternized inorganic phase.

2. The method for preparing the composite anion exchange membrane according to claim 1, characterized in that, In step (1), the rigid monomer includes at least one of acrylonitrile, styrene, or methacrylonitrile; And / or, in step (1), the functional monomer containing a tertiary amine group includes at least one of dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, or N,N-dimethylacrylamide; And / or, in step (1), the quaternized functional inorganic phase includes at least one of quaternized graphene oxide, quaternized silicon dioxide, quaternized titanium dioxide, or quaternized montmorillonite; the particle size of the quaternized functional inorganic phase is 50~200nm; And / or, in step (1), the free radical initiator includes at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide or di-tert-butyl peroxide; And / or, in step (1), the polar organic solvent includes at least one of N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, or N,N-dimethylacetamide.

3. The method for preparing the composite anion exchange membrane according to claim 1 or 2, characterized in that, In step (1), the mass ratio of the polar organic solvent, rigid monomer, functional monomer containing tertiary amine group, quaternized functional inorganic phase and free radical initiator is: (150~180): (45~55): (35~45): (3~8): (0.8~1.5). And / or, in step (1), the temperature of the free radical polymerization is 65~75℃, the time of the free radical polymerization is 8~12 hours, the free radical polymerization is carried out under stirring, and the stirring speed is 350~450r / min. And / or, in step (1), the defoamer includes at least one of polyether-modified silicone oil, organosilicon defoamer, or polyoxyethylene polyoxypropylene ether, and the amount of the defoamer added is 0.3% to 0.6% of the total mass of the system; And / or, in step (1), the temperature is lowered to 30~35℃ and the stirring time is 25~35min.

4. The method for preparing the composite anion exchange membrane according to claim 1, characterized in that, In step (1), the preparation method of the quaternized functional inorganic phase includes the following steps: (a) Disperse the inorganic substrate containing oxygen-containing active groups in a polar dispersion medium, ultrasonically disperse it for 40-50 minutes at a power of 200-300W, add a tertiary amine reagent and magnetically stir for 30-50 minutes, then heat it to 60-70℃ and keep it at that temperature for 8-10 hours. (b) After the heat preservation reaction is completed, cool down to 30~35℃, add quaternization reagent to the system and continue stirring for 6~8 hours. After the reaction is completed, centrifuge at 4000~4500r / min for 20~25 minutes, collect the precipitate, wash repeatedly with polar dispersion medium until the washing solution is free of halogen ions or sulfate ions, and then wash with anhydrous ethanol at least twice. (c) Place the precipitate in a vacuum drying oven and dry it at 60~80℃ and 0.06~0.1MPa for 12~16 hours. Grind it into a fine powder and store it in a sealed container for later use.

5. The method for preparing the composite anion exchange membrane according to claim 4, characterized in that, The inorganic substrate containing oxygen-containing active groups includes at least one of graphene oxide, silicon dioxide, titanium dioxide, and montmorillonite, with a particle size of 1-5 μm. The oxygen-containing active groups include at least one of hydroxyl, epoxy, or carboxyl groups, and the content of the oxygen-containing active groups is 20-30 wt%. The polar dispersion medium includes at least one of deionized water, anhydrous ethanol, or ethylene glycol; The tertiary amine reagent includes at least one of N,N-dimethylethylenediamine, N,N-dimethylpropylenediamine, or triethylenetetramine; The quaternizing agent includes at least one of methyl iodide, methyl bromide, or dimethyl sulfate; The mass ratio of the inorganic substrate, polar dispersion medium, tertiary amine reagent and quaternizing reagent is (2~3):(60~80):(8~12):(5~8).

6. The method for preparing the composite anion exchange membrane according to claim 1, characterized in that, In step (2), the degassing process includes: transferring the composite membrane liquid to a vacuum degassing machine, setting the vacuum degree to -0.08~-0.1MPa and the temperature to 30~35℃, and degassing for 2~3 hours, during which the gas is released once every 20~40 minutes; And / or, in step (2), the coating specifically includes: after pretreating the substrate, the degassed composite film liquid is evenly poured onto one end of the substrate, and a 200~280μm thickness coater is used to uniformly coat the film in the same direction at a speed of 5-8cm / s to form a continuous and uniform liquid film.

7. The method for preparing the composite anion exchange membrane according to claim 1, characterized in that, In step (3), the drying process is gradient drying, which specifically involves: first stage of holding at 55~65℃ for 3~4 hours; second stage of holding at 80~90℃ for 2.5~3.5 hours; third stage of holding at 100~110℃ for 2~3 hours, and drying under a vacuum of 0.06~0.1MPa.

8. The method for preparing the composite anion exchange membrane according to claim 1 or 7, characterized in that, In step (3), the quaternization activation treatment includes: immersing the composite membrane in the quaternization activation reagent, and after soaking, repeatedly washing the membrane with deionized water, detecting the pH value of the washing solution after each washing until pH=7.0~8.0, and placing the washed membrane in a vacuum drying oven for drying. The concentration of the quaternization activating agent is 0.8~1.2 mol / L, and the quaternization activating agent includes an aqueous solution and / or an ethanolic solution of at least one of trimethylamine, triethylamine, benzyl chloride or dimethyl sulfate; the drying treatment is to dry at 55~65℃ and 0.06~0.1MPa for 8~12 hours.

9. A composite anion exchange membrane, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the composite anion exchange membrane prepared by the preparation method according to any one of claims 1 to 8 or the composite anion exchange membrane according to claim 9 in the fields of capacitive deionization, electrodialysis or fuel cells.

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