Vinylcarbazole-based anion exchange membranes, their preparation methods, and applications

Abstract

This application provides a vinylcarbazole-based anion exchange membrane, its preparation method, and its application, belonging to the field of anion separation membrane technology. The vinylcarbazole-based anion exchange membrane is prepared by copolymerization of vinylcarbazole, piperidinone, and terphenyl monomers, possessing a poly(vinylcarbazole-arylpiperidine) backbone structure. By controlling the content of vinylcarbazole monomer, this application can effectively regulate the interchain spacing of the polymer within the membrane and construct densely interconnected ion channels. Utilizing precise interchain spacing sieving, the Donnan repulsion effect, and the synergistic effect of charge-assisted hopping conduction at the nitrogen center of carbazole, this vinylcarbazole-based anion exchange membrane simultaneously achieves high proton flux and high metal ion rejection rate during diffusion dialysis. The membrane exhibits excellent performance in HCl / FeCl2 and H2SO4 / FeSO4 mixed acid / metal ion systems, and possesses good anti-swelling and durability, making it effective for the recovery of industrial waste acids, such as those used in metal processing.

Description

Technical Field

[0001] This invention relates to the field of membrane separation materials technology, specifically to a vinylcarbazole-based anion exchange membrane, its preparation method and application, and particularly to the application of this anion exchange membrane in diffusion dialysis for the recovery of industrial waste acid containing metal ions. Background Technology

[0002] With the rapid evolution of modern manufacturing industries (such as aerospace, shipbuilding, heavy machinery, and construction), the demand for high-quality corrosion-resistant metal materials is increasing daily. In metal processing, pickling is widely used to remove oxide layers and impurities from metal surfaces. This process inevitably generates massive amounts of waste acid liquid rich in high concentrations of free acids (such as sulfuric acid and hydrochloric acid) and heavy metal ions (such as ferrous ions). Direct discharge without proper treatment will trigger a severe ecological crisis and cause enormous resource waste. Therefore, achieving efficient recovery and reuse of acid from waste liquid is a crucial step for the metal processing industry towards green and sustainable development. Traditional acid recovery methods (such as spray roasting or high-temperature hydrolysis) often rely on extreme heat treatment conditions of 700°C to 1000°C. This not only leads to huge energy consumption and high costs for exhaust gas treatment but also easily causes severe equipment corrosion, making it unsuitable for the large-scale low-carbon production needs of modern industry.

[0003] To address the aforementioned pain points, novel environmentally friendly technologies centered on membrane separation have emerged. Among them, diffusion dialysis, driven by spontaneous concentration gradients, boasts significant advantages such as extremely low energy consumption, simple equipment construction, low operation and maintenance costs, and easy integration with existing production lines. Within this separation system, the anion exchange membrane, as the core component for material exchange, directly influences the overall efficiency of the acid recovery process through its microstructure and separation characteristics.

[0004] Currently, researchers are primarily focused on optimizing the overall performance of anion exchange membranes by modifying the polymer backbone or grafting cationic active groups (such as imidazole salts and quaternary ammonium salts). For example, some studies have employed a one-step crosslinking and quaternization strategy to construct anion exchange membranes with asymmetric structures, aiming to accelerate proton conduction and block metal ions. Other literature reports the use of small-molecule crosslinking agents to crosslink brominated polyphenylene ether membranes, attempting to construct denser ion channels by compressing the stacking of polymer chains. In addition, there are attempts to construct nanochannels by introducing multifunctional molecules or blending, all with the aim of increasing the ion exchange capacity of the membrane and suppressing water absorption and swelling.

[0005] However, existing modification methods still face insurmountable technical bottlenecks: most separation membranes are often caught in a dilemma where high proton permeation flux, excellent separation selectivity, and high mechanical strength are mutually constrained. Particularly noteworthy is the persistent challenge of precisely controlling the interchain spacing within the polymer to efficiently sieve multivalent metal ions. Existing crosslinking control methods lack precision and are prone to inconsistencies: excessive crosslinking severely compresses the free volume, causing a sharp drop in proton flux; while insufficient crosslinking leads to excessive membrane swelling, rendering the size sieving mechanism for multivalent ions ineffective. This significantly limits their application performance in complex industrial waste acid systems.

[0006] On the other hand, some existing technologies attempt to synthesize anion exchange membranes using m-bromotriphenyl monomers. However, their meta-bonded configuration inevitably leads to random kinks in the polymer backbone, and this disordered chain segment conformation severely hinders the precise control of interchain spacing and polymer free volume. Furthermore, such materials are highly dependent on subsequent bromine atom substitution reactions to introduce ionizing groups, which not only easily leads to uneven distribution of functional sites, but also poses a serious challenge to their long-term chemical stability under strong acidic extreme environments.

[0007] In summary, there is an urgent need in this field to develop a novel anion exchange membrane material that can not only achieve precise control of interchain spacing, but also break through traditional performance limitations and possess high proton transport flux, excellent metal ion retention capacity, and outstanding acid resistance. Summary of the Invention

[0008] To address the technical bottleneck in existing technologies where anion exchange membranes struggle to simultaneously achieve high proton permeation flux, excellent multivalent metal ion rejection rate, and low hydration swelling rate in diffusion dialysis acid recovery applications, this application provides a vinylcarbazole-based anion exchange membrane, its preparation method, and its application.

[0009] This application achieves precise control over the free volume and micro-chain spacing within the polymer by introducing electron-rich vinylcarbazole groups into the polymer backbone, thereby constructing a dense and highly interconnected ion transport network. This precisely constructed confined space, on the one hand, enables the transport of multivalent heavy metal ions (such as Fe) through significant steric hindrance. 2+ On the one hand, it achieves efficient interception of protons (H+); on the other hand, the charge-assisted hopping conduction mechanism of the nitrogen atom on the carbazole ring facilitates the transfer of protons (H+). + This opens up a high-speed penetration path. In addition, the introduction of vinylcarbazole units significantly enhances the interaction forces between polymer chains, effectively suppressing excessive swelling of the membrane material in an aqueous environment, and endowing the separation membrane with excellent structural stability and service life.

[0010] This application provides a method for preparing a vinylcarbazole-based anion exchange membrane, comprising the following steps: S1. Dissolve the monomers p-terphenyl, vinylcarbazole and N-methyl-4-piperidinone in dichloromethane and mix thoroughly to obtain a reaction solution; S2. Under ice-water bath cooling, trifluoroacetic acid and trifluoromethanesulfonic acid are added to the reaction solution to carry out a polymerization reaction. After the reaction, the resulting system is poured into precipitation solvent A to precipitate the product. After washing and drying, the precursor copolymer is obtained. S3. Dissolve the precursor copolymer in solvent B, add iodomethane to carry out quaternization reaction, and after the reaction is complete, precipitate the product in precipitant C, wash and dry to obtain the quaternized polymer; S4. Dissolve the quaternized polymer in solvent D, remove impurities by centrifugation or filtration to obtain a casting solution; then, coat the casting solution onto a substrate, dry and cure it to form a film, and peel it off to obtain a vinylcarbazole-based anion exchange membrane.

[0011] Further, in step S1, the molar concentration of N-methyl-4-piperidinone in dichloromethane is 1.1 mol / L-1.4 mol / L.

[0012] Further, in step S1, the molar ratio of the three monomers—vinylcarbazole, p-terphenyl, and N-methyl-4-piperidinone—is (0.05~0.2): (0.8~0.95): 1.1.

[0013] Further, in step S2, the molar ratio of p-terphenyl, trifluoromethanesulfonic acid, and trifluoroacetic acid is 1: (12~16): (1.3~1.7).

[0014] Furthermore, in step S2, the precipitation solvent A is water or ethanol.

[0015] Further, in step S3, the mass ratio of the precursor copolymer to iodomethane is 1:(2-2.5); the quaternization reaction time is 18 to 28 hours, and the reaction temperature is 20℃-30℃; the solvent B is dimethyl sulfoxide or N-methylpyrrolidone; and the precipitant C is diethyl ether or ethyl acetate.

[0016] Further, in step S4, the solvent D is dimethyl sulfoxide or N-methylpyrrolidone; the drying and curing temperature is 60°C to 80°C, and the time is 4 to 12 hours.

[0017] This application also provides a vinylcarbazole-based anion exchange membrane, prepared by the aforementioned method. The vinylcarbazole-based anion exchange membrane is formed by copolymerization of polymeric monomers, including vinylcarbazole, N-methyl-4-piperidinone, and p-terphenyl. The vinylcarbazole-based anion exchange membrane has a poly(vinylcarbazole-arylpiperidine) backbone structure.

[0018] Furthermore, in the anion exchange membrane, the molar amount of the vinylcarbazole monomer unit accounts for 2% to 10% of the total molar amount of the vinylcarbazole and p-terphenyl monomer units.

[0019] The vinylcarbazole-based anion exchange membrane can be applied to the recovery of industrial waste acids, such as those used in metal processing.

[0020] The beneficial effects of this application are as follows: 1. This application proposes a method for preparing a vinylcarbazole-based anion exchange membrane. By adjusting the proportion of vinylcarbazole monomers (the molar amount of vinylcarbazole monomer units accounts for 2% to 10% of the total molar amount of vinylcarbazole and p-terphenyl monomer units), sub-nanometer precise control of the polymer chain spacing within the membrane is achieved. In diffusion dialysis operation, this membrane exhibits not only extremely high proton permeation flux (UH)... + It also possesses superior proton / metal ion sieving selectivity (S), effectively overcoming the industry challenge of achieving both high throughput and high selectivity.

[0021] 2. In this application, the strong interaction between multiple aromatic rings and functional groups in the polymerization system endows the polymer network with excellent rigidity and cohesive energy, enabling it to exhibit extremely low swelling rate and long-term operational stability in a strongly acidic environment, fully meeting the requirements for large-scale application in harsh industrial environments.

[0022] 3. The superacid-catalyzed copolymerization and subsequent light-shielded quaternization process employed in this application are simple to operate, have mild reaction conditions, and exhibit excellent batch-to-batch reproducibility. The overall synthetic route does not require complex and demanding post-processing equipment, making it highly feasible for industrial-scale production and providing a high-performance candidate material for industrial waste acid recovery technology.

[0023] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0025] Figure 1 For PT in this application x -Vc y A route diagram for membrane synthesis.

[0026] Figure 2 PT prepared in Example 1 0.98 -Vc 0.02 SEM image of the membrane surface.

[0027] Figure 3 PT prepared in Example 1 0.98 -Vc 0.02 SEM image of the membrane cross-section.

[0028] Figure 4 PT prepared in Example 2 0.96 -Vc 0.04 SEM image of the membrane surface.

[0029] Figure 5 PT prepared in Example 2 0.96 -Vc 0.04 SEM image of the membrane cross-section.

[0030] Figure 6 The synthesis route of the PT1-Vc0 membrane in Comparative Example 1 is shown.

[0031] Figure 7 SEM image of the PT1-Vc0 membrane surface prepared for Comparative Example 1.

[0032] Figure 8 SEM image of the cross-section of the PT1-Vc0 membrane prepared for Comparative Example 1.

[0033] Figure 9 The image shows the X-ray diffraction (XRD) patterns and interchain spacing comparisons of the anion exchange membranes prepared in Comparative Example 1 and Examples 1, 3, and 5.

[0034] Figure 10 This is a schematic diagram of the diffusion dialysis device in the embodiment.

[0035] Figure 11 This is a diagram showing the diffusion dialysis results of hydrogen ions and metal ions in the examples.

[0036] Figure 12 The diagram shows the separation results of diffusion dialysis in the examples. Detailed Implementation

[0037] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0039] This application provides a method for preparing a vinylcarbazole-based anion exchange membrane, comprising the following steps: S1. Dissolve the monomers p-terphenyl, vinylcarbazole and N-methyl-4-piperidinone in dichloromethane and mix thoroughly to obtain a reaction solution; The molar concentration of N-methyl-4-piperidinone in dichloromethane is 1.1 mol / L-1.4 mol / L.

[0040] The molar ratio of the three monomers vinylcarbazole, p-terphenyl, and N-methyl-4-piperidinone in the system is (0.05~0.2): (0.8~0.95): 1.1.

[0041] S2. Under ice-water bath cooling, trifluoroacetic acid and trifluoromethanesulfonic acid are slowly added dropwise to the reaction solution as a catalytic system. After polymerization at a constant temperature for 2-5 hours, the dark, viscous reactant is poured into precipitation solvent A (water or ethanol) for phase inversion precipitation. The solid product is collected and repeatedly washed with deionized water until the washing solution is neutral. After drying in a vacuum oven, the precursor copolymer is finally obtained.

[0042] At this stage, the molar ratio of terphenyl, trifluoromethanesulfonic acid, and trifluoroacetic acid is 1: (12~16): (1.3~1.7).

[0043] S3. The obtained precursor copolymer was completely dissolved in solvent B (dimethyl sulfoxide or N-methylpyrrolidone); then, quaternizing agent iodomethane was added at a copolymer to iodomethane mass ratio of 1:(2-2.5). The reaction system was placed at 20℃-30℃ in the dark for 18-28 hours. After the reaction was completed, the mixture was slowly added dropwise to precipitant C (diethyl ether or ethyl acetate) to completely precipitate the target product. After washing with precipitant C, filtration and drying were performed to obtain the quaternized polymer.

[0044] S4. Dissolve the obtained quaternized polymer in solvent D (selected from N-methylpyrrolidone or dimethyl sulfoxide), remove trace amounts of undissolved impurities by high-speed centrifugation, and collect the clear casting solution.

[0045] The casting liquid is evenly spread on the surface of a clean glass substrate using a casting and coating method, and then placed in an oven at 60~80℃ for 4~12 hours for constant temperature solvent evaporation and molding.

[0046] Finally, the glass plate with the cured film was immersed in deionized water to allow the membrane to peel off naturally, thus successfully preparing the vinylcarbazole-based anion exchange membrane.

[0047] The vinylcarbazole-based anion exchange membrane prepared by the aforementioned method is formed by copolymerization of polymeric monomers. The polymeric monomers include vinylcarbazole, N-methyl-4-piperidinone, and p-terphenyl; the vinylcarbazole-based anion exchange membrane has a poly(vinylcarbazole-arylpiperidine) backbone structure.

[0048] In anion exchange membranes, the molar amount of vinylcarbazole monomer units accounts for 2% to 10% of the total molar amount of vinylcarbazole and p-terphenyl monomer units.

[0049] This vinylcarbazole-based anion exchange membrane is used for the separation and acid recovery of mixed waste acid systems containing metallic impurities (particularly suitable for mixed solutions of HCl / FeCl2 and H2SO4 / FeSO4).

[0050] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0051] Example 1 Please see Figure 1 As shown, this embodiment provides a method for preparing a vinylcarbazole-based anion exchange membrane, wherein the molar content of vinylcarbazole (Vc) in this embodiment is 2%. The anion exchange membrane in this application constructs a dense cross-linked network through a double polymerization reaction. Figure 1 In this context, the variable (10-z) represents the number of vinylcarbazole structural units that participate in both vinyl addition polymerization and condensation polymerization via the carbazole ring. These units constitute an effective crosslinking bridge connecting the aliphatic chain and the aromatic backbone. The variable z represents the number of pendant carbazole units that undergo only vinyl polymerization without aromatic ring condensation. Furthermore, the variables n and (90-n) represent the p-terphenyl-piperidinone polymerization segments in the crosslinked and linear non-crosslinked regions of the backbone, respectively.

[0052] In this application, by changing the initial feed ratio of vinylcarbazole, the effective cross-linking nodes (i.e., the relative proportion of (10-z)) can be precisely controlled, thereby optimizing the free volume, interchain spacing and spatial sieving performance of the anion exchange membrane.

[0053] The specific steps are as follows: S1. Add 9.8 mmol of p-terphenyl, 0.2 mmol of vinylcarbazole, and 11 mmol of N-methyl-4-piperidinone to a pre-dried round-bottom flask, and then add 8.5 mL of dichloromethane as a solvent to obtain the reaction solution.

[0054] S2. Place the reaction solution in an ice-water bath at 0°C and mechanically stir for 10 minutes. Then, slowly add 1 mL of trifluoroacetic acid (TFA) and 8 mL of trifluoromethanesulfonic acid (TFSA) dropwise to the system. After the addition is complete, maintain the temperature at 0°C and continue the reaction for 2 hours. The system gradually becomes viscous, indicating that the polycondensation reaction has been successfully completed.

[0055] The resulting reaction solution was poured into 100 mL of deionized water to precipitate the copolymer, and saturated potassium carbonate solution was added dropwise to neutralize the system until no more bubbles were generated. The polymer was obtained by vacuum filtration, thoroughly washed with excess deionized water, and finally dried in a vacuum environment at 60°C for 12 hours, yielding a white fibrous copolymer PT. 0.98 -Vc 0.02 .

[0056] S3. Weigh 1.0 g of the above PT 0.98 -Vc 0.02 The copolymer was uniformly dispersed in 10 mL of dimethyl sulfoxide. 1.0 mL of iodomethane reagent was added, and the mixture was stirred at 25°C in the dark for 24 hours to complete quaternization. After the reaction was complete, the solution was poured into 200 mL of ethyl acetate to precipitate the quaternized product. The solid was collected by filtration, washed with ethyl acetate, and air-dried at room temperature.

[0057] S4. Take 0.5 g of the dried quaternized polymer, dissolve it in 8 mL of dimethyl sulfoxide, and filter it through a 0.45 μm microporous membrane to remove undissolved impurities, thus obtaining the casting solution.

[0058] A clear casting solution was uniformly cast onto a clean glass substrate, and the solvent was slowly evaporated in a 60°C oven. After drying and curing, the solution was peeled off the glass substrate with water to obtain a uniform and transparent anion exchange membrane PT. 0.98 -Vc 0.02 The surface and cross-sectional microstructures (SEM images) of the membrane are shown below. Figure 2 , Figure 3 As shown.

[0059] Depend on Figure 2 As can be seen from the microstructure of the membrane surface shown, the PT prepared in this embodiment... 0.98 -Vc 0.02The anion exchange membrane surface was smooth, dense, and uniform, with no obvious cracks, pinholes, or particulate agglomerates observed, indicating that the quaternized copolymer possesses excellent film-forming properties. Further integration... Figure 3 As can be seen from the cross-sectional morphology diagram, the film exhibits a highly dense and uniform solid structure in the thickness direction, with no obvious micropores or phase separation phenomena inside.

[0060] Example 2 This embodiment provides a method for preparing a vinylcarbazole-based anion exchange membrane. In this embodiment, the molar content of vinylcarbazole (Vc) is 4%, and the steps are as follows: S1. 9.6 mmol of p-terphenyl, 0.4 mmol of vinylcarbazole, and 11 mmol of N-methyl-4-piperidinone were added to a pre-dried round-bottom flask, followed by the addition of 8.5 mL of dichloromethane as a solvent. Subsequent procedures were the same as steps S1 and S2 in Example 1, and the white fibrous copolymer PT was collected. 0.96 -Vc 0.04 .

[0061] S3. Same as step S3 in Example 1, using PT 0.96 -Vc 0.04 The copolymer is quaternized.

[0062] S4. Following the same procedure as in Example 1, the anion exchange membrane PT is prepared. 0.96 -Vc 0.04 The surface and cross-sectional microstructures (SEM images) of the membrane are shown below. Figure 4 , Figure 5 As shown.

[0063] Depend on Figure 4 As can be seen from the microstructure of the membrane surface shown, the PT prepared in this embodiment... 0.96 -Vc 0.04 The anion exchange membrane surface was smooth, dense, and uniform, with no obvious cracks, pinholes, or particulate agglomerates observed, indicating that the quaternized copolymer possesses excellent film-forming properties. Further integration... Figure 5 As can be seen from the cross-sectional morphology diagram, the film exhibits a highly dense and uniform solid structure in the thickness direction, with no obvious micropores or phase separation phenomena inside.

[0064] Example 3 This embodiment provides a method for preparing a vinylcarbazole-based anion exchange membrane. In this embodiment, the molar content of vinylcarbazole (Vc) is 6%, and the steps are as follows: S1. 9.4 mmol of p-terphenyl, 0.6 mmol of vinylcarbazole, and 11 mmol of N-methyl-4-piperidinone were added to a pre-dried round-bottom flask, followed by the addition of 8.5 mL of dichloromethane as a solvent. Subsequent procedures were the same as steps S1 and S2 in Example 1, and the white fibrous copolymer PT was collected. 0.94 -Vc 0.06 .

[0065] S3. Same as step S3 in Example 1, using PT 0.94 -Vc 0.06 The copolymer is quaternized.

[0066] S4. Following the same procedure as in Example 1, the anion exchange membrane PT is prepared. 0.94 -Vc 0.06 .

[0067] Example 4 This embodiment provides a method for preparing a vinylcarbazole-based anion exchange membrane. In this embodiment, the molar content of vinylcarbazole (Vc) is 8%, and the steps are as follows: S1. 9.2 mmol of p-terphenyl, 0.8 mmol of vinylcarbazole, and 11 mmol of N-methyl-4-piperidinone were added to a pre-dried round-bottom flask, followed by the addition of 8.5 mL of dichloromethane as a solvent. Subsequent procedures were the same as steps S1 and S2 in Example 1, and the white fibrous copolymer PT was collected. 0.92 -Vc 0.08 .

[0068] S3. Same as step S3 in Example 1, using PT 0.92 -Vc 0.08 The copolymer is quaternized.

[0069] S4. Following the same procedure as in Example 1, the anion exchange membrane PT is prepared. 0.92 -Vc 0.08 .

[0070] Example 5 This embodiment provides a method for preparing a vinylcarbazole-based anion exchange membrane. In this embodiment, the molar content of vinylcarbazole (Vc) is 10%, and the steps are as follows: S1. 9.0 mmol of p-terphenyl, 1.0 mmol of vinylcarbazole, and 11 mmol of N-methyl-4-piperidinone were added together to a pre-dried round-bottom flask, followed by the addition of 8.5 mL of dichloromethane as a solvent. Subsequent procedures were the same as steps S1 and S2 in Example 1, and the white fibrous copolymer PT was collected. 0.9 -Vc 0.1 .

[0071] S3. Same as step S3 in Example 1, using PT 0.9 -Vc 0.1 The copolymer is quaternized.

[0072] S4. Following the same procedure as in Example 1, the anion exchange membrane PT is prepared. 0.9 -Vc 0.1 .

[0073] Comparative Example 1 Please see Figure 6 As shown, Comparative Example 1 provides the preparation of a reference control membrane without the addition of vinylcarbazole (i.e., Vc content is 0).

[0074] Step S1: Mix 10 mmol of p-terphenyl and 11 mmol of N-methyl-4-piperidinone in a dry reaction flask and dissolve in 8.5 mL of dichloromethane. Place the solution in an ice bath at 0°C and stir for 10 minutes. Slowly add 1 mL of trifluoroacetic acid and 8 mL of trifluoromethanesulfonic acid. Incubate the reaction at 0°C for 2 hours until the system becomes viscous. Then pour in 100 mL of deionized water to precipitate the polymer. Neutralize with saturated potassium carbonate solution until no more bubbles are expelled. Filter the precipitate and wash it several times with pure water. Dry it under vacuum at 60°C for 12 hours to obtain a white fibrous, Vc-free copolymer PT1-Vc0.

[0075] Step S2: Disperse 1.0 g of the above PT1-Vc0 product into 10 mL of dimethyl sulfoxide, and add 1.0 mL of iodomethane. Maintain the reaction at 25°C in the dark with stirring for 24 hours. After the reaction is complete, pour the precipitate into 200 mL of ethyl acetate, filter, wash, and dry at room temperature to obtain the quaternized comparative compound.

[0076] Step S3: Dissolve 0.5 g of the quaternized comparative compound in 8 mL of dimethyl sulfoxide and pass it through a 0.45 μm microfiltration membrane to remove impurities. Spread the casting solution evenly on a glass plate and allow it to dry at 60 °C. After the solvent has evaporated, peel it off to obtain a uniform and transparent comparative anion exchange membrane PT1-Vc0.

[0077] The surface and cross-sectional microstructures (SEM images) of the membrane are as follows: Figure 7 , Figure 8 As shown.

[0078] Depend on Figure 7 The microstructure of the membrane surface shown indicates that the PT1-Vc0 anion exchange membrane prepared in this embodiment has a smooth, dense, and uniform surface, with no obvious cracks, pinholes, or particulate agglomerates observed, indicating that this quaternized copolymer has excellent film-forming properties. Further combining... Figure 8As can be seen from the cross-sectional morphology diagram, the film exhibits a highly dense and uniform solid structure in the thickness direction, with no obvious micropores or phase separation phenomena inside.

[0079] To further verify the microscopic mechanism by which vinylcarbazole functionalization regulates the polymer crosslinking network and spatial sieving effect, X-ray diffraction (XRD) was used to characterize the anion exchange membranes prepared in Examples 1, 3, 5, and Comparative Example 1. The comparative spectra are shown below. Figure 9 As shown.

[0080] As can be seen, with the gradual increase of the vinylcarbazole monomer content in the polymerization system, a clear trend of increasing interchain spacing can be observed. This objective change in interchain spacing strongly confirms that this application has successfully achieved sub-nanometer-level precise control of the free volume and micropore size within the membrane through the dual polymerization and cross-linking effects of Vc monomers. This specific interchain spacing size can utilize the steric hindrance effect to extremely effectively contain polyvalent metal ions with large hydration radii (such as Fe). 2+ The membrane blocks the protons from entering; at the same time, the spacing is still sufficient to protect the smaller protons (H). + With the aid of carbazole nitrogen centers, rapid jump-through with low resistance is achieved. The microscopic XRD structural data and macroscopic diffusion-dialysis separation performance provide perfect logical corroboration.

[0081] Testing of the application of diffusion dialysis for acid recovery: The diffusion dialysis performance of the membrane was evaluated using a dual-chamber diffusion cell (each with a capacity of 40 mL). A schematic diagram of the dual-chamber diffusion cell is shown below. Figure 10 As shown.

[0082] Before the test, the membrane was placed in a solution containing 1.1 mol·L⁻¹ -1 Acid with 0.18 mol·L -1 Pretreatment in a mixed salt solution (such as HCl / FeCl2) for 24 hours to stabilize it was then performed. Subsequently, an effective area of ​​0.0001767 m² was obtained. 2 The pretreatment membrane is according to Figure 10 The device is clamped between the two chambers as shown in the diagram. 40 mL of an acid / salt mixture (acid concentration of 1.1 mol·L⁻¹) is added to the feed side. -1 The concentration of the salt solution is 0.18 mol·L⁻¹. -1 40 mL of deionized water was injected into the dialysis side. The test was conducted at 25°C for 45 minutes. After the test, 5 mL of the dialysis solution was collected for analysis: using 0.05 mol·L⁻¹... -1 The concentration of acid in NaOH solution was determined by titration using a mixed indicator of methyl red and bromocresol green; metal ions were detected by inductively coupled plasma spectrometry. The concentration of hydrogen ions was then calculated using the following formula. ) and metal ions ( The dialysis coefficient.

[0083] .

[0084] In the formula, U (m·h) -1 The ) represents the dialysis coefficient, and M (mol) represents the target substance (H) that diffuses into the dialysis solution. + The amount of the substance (or metal ions), A (m²) is the effective area of ​​the membrane, t (h) is the diffusion time, and ΔC (mol·L⁻¹) is the diffusion rate. -1 This represents the concentration difference across the membrane. The specific formula for calculating this concentration difference (ΔC) is shown below.

[0085] .

[0086] In the formula, and These represent the concentrations of the feed solution at the initial time and at time t, respectively. Let be the concentration of the dialysate at time t. The membrane selectivity (S) can be calculated. and The ratio is obtained by the following formula.

[0087] .

[0088] In the formula, and They represent hydrogen ions (H+, H+, ...) + ) and metal ions ( ) transmission rate.

[0089] Test results are as follows Figure 11 , Figure 12 As shown in Table 1.

[0090] Table 1 As can be seen, compared with the baseline blank group (i.e., the PT1-Vc0 membrane in Comparative Example 1) without vinylcarbazole functionalization, the series of modified anion exchange membranes prepared in this application (Examples 1 to 5) all exhibit superior overall performance in simulated waste liquid separation. This is mainly attributed to the fact that this application successfully optimized and customized the micro-chain spacing within the polymer by precisely controlling the introduction of a specific ratio of Vc monomer.

[0091] Proton dialysis coefficient (UH) + The selectivity and selectivity show a pattern of first increasing and then decreasing with the increase of the proportion of vitamin C.

[0092] Specifically, the UH of the unmodified PT1-Vc0 membrane + It is 5.23 × 10 -3 m·h -1 .

[0093] In contrast, the introduction of an appropriate amount of vitamin C resulted in a significant jump in proton conductivity, at PT. 0.94 -Vc 0.06 The membrane concentration reached 18.21 × 10⁻⁶. -3 m·h -1 However, when the vitamin C content increases further (e.g., PT...), 0.9 -Vc 0.1 The excessively dense rigid network and cross-linked structure significantly compress the free volume available for ion transport, leading to UH + Reduced to 9.20 × 10 -3 m·h -1 .

[0094] Regarding metal ion retention, Fe 2+ The dialysis coefficient is several orders of magnitude lower than that of the proton. Its value initially ranges from 4.35 × 10⁻⁶ for the base membrane. -6 m·h -1 Growth to PT 0.96 -Vc 0.04 14.10 × 10 -6 m·h -1 As the membrane structure becomes denser, in PT 0.9 -Vc 0.1 The concentration in the medium decreased to 5.71 × 10⁻⁶. -6 m·h -1 .

[0095] Considering the differences in acid salt flux, the separation selectivity of the system (H + / Fe 2+ It exhibited an extremely excellent evolution trend, gradually increasing from 1202.4 for the basic membrane, and reaching PT... 0.92 -Vc 0.08 The value reached 4515.99 in the membrane, and then at PT. 0.9 -Vc 0.1 The concentration in the membrane dropped to 1612.58. This data demonstrates that high proton flux and high separation selectivity can be achieved by precisely controlling the Vc content.

[0096] Of particular note is that when the molar doping amount of Vc is controlled at 6% and 8% respectively (corresponding to Examples 3 and 4), the resulting membrane materials achieve high proton throughput while perfectly maintaining high selectivity for heavy metal ions, reaching the optimal equilibrium state of the system. The comparative analysis of the above measured data not only intuitively highlights the scientific nature of the microstructure design in this application, but also fully demonstrates the significant advancement and enormous application potential of this technical solution in the field of industrial waste acid recovery.

[0097] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for preparing a vinylcarbazole-based anion exchange membrane, characterized in that, Includes the following steps: S1. Dissolve the monomers p-terphenyl, vinylcarbazole and N-methyl-4-piperidinone in dichloromethane and mix thoroughly to obtain a reaction solution; S2. Under ice-water bath cooling, trifluoroacetic acid and trifluoromethanesulfonic acid are added to the reaction solution to carry out a polymerization reaction. After the reaction, the resulting system is poured into precipitation solvent A to precipitate the product. After washing and drying, the precursor copolymer is obtained. S3. Dissolve the precursor copolymer in solvent B, add iodomethane to carry out quaternization reaction, and after the reaction is complete, precipitate the product in precipitant C, wash and dry to obtain the quaternized polymer; S4. Dissolve the quaternized polymer in solvent D, remove impurities by centrifugation or filtration, and obtain a casting solution; Subsequently, the casting solution was coated onto the substrate, dried and cured to form a shape, and then peeled off to obtain a vinylcarbazole-based anion exchange membrane.

2. The method for preparing the vinylcarbazole-based anion exchange membrane according to claim 1, characterized in that, In step S1, the molar concentration of N-methyl-4-piperidinone in dichloromethane is 1.1 mol / L to 1.4 mol / L.

3. The method for preparing the vinylcarbazole-based anion exchange membrane according to claim 1, characterized in that, In step S1, the molar ratio of the three monomers—vinylcarbazole, p-terphenyl, and N-methyl-4-piperidinone—is (0.05~0.2):(0.8~0.95):1.

1.

4. The method for preparing the vinylcarbazole-based anion exchange membrane according to claim 1, characterized in that, In step S2, the molar ratio of p-terphenyl, trifluoromethanesulfonic acid, and trifluoroacetic acid is 1: (12~16): (1.3~1.7).

5. The method for preparing the vinylcarbazole-based anion exchange membrane according to claim 1, characterized in that, In step S2, the precipitation solvent A is water or ethanol.

6. The method for preparing the vinylcarbazole-based anion exchange membrane according to claim 1, characterized in that, In step S3, the mass ratio of the precursor copolymer to iodomethane is 1:(2-2.5); the quaternization reaction takes 18 to 28 hours and the reaction temperature is 20℃-30℃; the solvent B is dimethyl sulfoxide or N-methylpyrrolidone; and the precipitant C is diethyl ether or ethyl acetate.

7. The method for preparing the vinylcarbazole-based anion exchange membrane according to claim 1, characterized in that, In step S4, the solvent D is dimethyl sulfoxide or N-methylpyrrolidone; the drying and curing temperature is 60°C to 80°C, and the time is 4 to 12 hours.

8. A vinylcarbazole-based anion exchange membrane, characterized in that, The vinylcarbazole-based anion exchange membrane is prepared by the preparation method described in any one of claims 1-7, wherein the vinylcarbazole-based anion exchange membrane is formed by copolymerization of polymeric monomers, wherein the polymeric monomers include vinylcarbazole, N-methyl-4-piperidinone, and p-terphenyl; and the vinylcarbazole-based anion exchange membrane has a poly(vinylcarbazole-arylpiperidine) backbone structure.

9. The vinylcarbazole-based anion exchange membrane according to claim 8, characterized in that, In the anion exchange membrane, the molar amount of the vinylcarbazole monomer unit accounts for 2% to 10% of the total molar amount of the vinylcarbazole and p-terphenyl monomer units.

10. The application of a vinylcarbazole-based anion exchange membrane prepared by any one of claims 1-7 or as described in claims 8-9 in diffusion dialysis for the recovery of waste acid.

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