Quaternization synergistic metal coordination chitosan-based anion exchange membrane and preparation method thereof

Abstract

The invention discloses a quaternization synergistic metal coordination chitosan-based anion exchange membrane and a preparation method thereof. The quaternization and metal coordination chitosan membrane is obtained by dissolving and uniformly mixing chitosan, quaternization chitosan and water-soluble transition metal salt, pouring and drying to form the membrane. According to the method, rich hydroxyl groups and amino groups in chitosan are coordinated with metal ions, so that not only is a firm network structure formed, but also OH <-> exchange capacity is provided by formed transition metal coordination cations. Meanwhile, due to the introduction of the quaternized chitosan, cation active sites are increased, and an ion transmission channel is expanded through steric hindrance and an electrostatic repulsion effect. According to the synergistic strategy, the ionic conductivity and the mechanical strength of the chitosan membrane are synchronously improved, and a new strategy is provided for developing a high-performance anion exchange membrane.

Description

Technical Field

[0001] This invention belongs to the field of new energy materials technology, specifically relating to a quaternized synergistic metal coordination chitosan-based anion exchange membrane and its preparation method. Background Technology

[0002] In recent years, ion exchange membranes have been widely used in water electrolysis for hydrogen production, fuel cells, and electrochemical synthesis due to their excellent ion conductivity and high selectivity. Anion exchange membranes, in particular, offer a cost advantage over traditional proton exchange membranes because they can be used with non-precious metal catalysts in alkaline environments. However, the development of anion exchange membranes currently faces two major challenges: First, mainstream anion exchange membranes require complex organic synthesis methods to construct polymer chains. This process typically involves multiple chemical modifications, expensive raw materials, and harsh reaction conditions, resulting in high production costs and poor environmental friendliness, thus limiting the feasibility of large-scale industrialization. Second, the cationic groups on the main chain are prone to decomposition reactions in strongly alkaline environments, leading to insufficient long-term durability of the membrane material. Therefore, simplifying the material structure, achieving a green manufacturing process, and simultaneously ensuring its ion conductivity and performance stability in alkaline environments have become the core challenges in the development of anion exchange membrane manufacturing technology.

[0003] Chitosan, as a natural alkaline polyelectrolyte, is a potential anion exchange membrane material due to its excellent film-forming properties, biodegradability, and abundant active sites (hydroxyl and amino groups). However, its low intrinsic ionic conductivity and poor mechanical strength in aqueous solutions remain to be overcome.

[0004] To address these issues, a common strategy is to design an ion exchange membrane with well-structured ion transport channels. Patent CN105733004A discloses a method for preparing a fully interpenetrating quaternized chitosan anion exchange membrane, which exhibits excellent mechanical properties and good alkali resistance. Patent CN119215696A discloses a method for preparing an alkaline anion exchange membrane through in-situ crosslinking, employing a dual-framework strategy and introducing quaternary ammonium salt groups to effectively improve its ionic conductivity. While these patents have achieved good results in improving the performance of chitosan-based anion exchange membranes, they cannot simultaneously achieve high mechanical strength and high ionic conductivity. Therefore, developing a high-performance chitosan-based anion exchange membrane is essential. Summary of the Invention

[0005] To address the challenge of simultaneously achieving high ionic conductivity and high mechanical strength in chitosan-based anion exchange membranes, this invention provides a quaternization-synergistic metal-coordinated chitosan-based anion exchange membrane and its preparation method. This chitosan-based anion exchange membrane achieves a simultaneous increase in both ionic conductivity and mechanical strength due to the synergistic effect of quaternization and coordination crosslinking with transition metal ions.

[0006] To achieve the above objectives, according to one aspect of the present invention, a quaternized co-coordinated metal-based chitosan-based anion exchange membrane is provided. This anion exchange membrane is obtained by dissolving and mixing chitosan and quaternized chitosan, followed by coordination crosslinking with a water-soluble transition metal salt, wherein the chitosan comprises 50-77 parts by weight and the quaternized chitosan comprises 23-50 parts by weight. The introduction of quaternized chitosan not only increases the number of cationic active sites but also expands the ion transport channels through steric hindrance and electrostatic repulsion effects; simultaneously, the abundant hydroxyl and amino groups in chitosan coordinate with transition metal ions, forming not only a robust network structure but also providing OH groups through the transition metal coordinating cations. - Exchange capacity.

[0007] The thickness of the chitosan-based anion exchange membrane ranges from 10 to 200 µm.

[0008] The chitosan-based anion exchange membrane has a tensile strength exceeding 20 MPa and an ionic conductivity exceeding 30 mS / cm at room temperature. -1 .

[0009] A second aspect of the present invention provides a method for preparing a quaternized synergistic metal-coordinated chitosan-based anion exchange membrane, comprising the following steps.

[0010] First, chitosan powder is added to a three-necked flask containing isopropanol. After stirring and dispersing evenly, a quaternizing agent is added, and the molar ratio of chitosan structural units to the quaternizing agent is controlled at 1:2~4. The temperature is raised to 60~90℃, and after reacting for 3~6 hours, a homogeneous solution is obtained. After cooling to room temperature, the product is precipitated with anhydrous ethanol, washed, and dried to obtain quaternized chitosan with a degree of quaternization of 10~20%.

[0011] Chitosan, quaternized chitosan powder, and a water-soluble transition metal salt were then dissolved in a protic acid aqueous solution, with the mass ratio of chitosan to quaternized chitosan controlled at 1:0.25~1, and the molar ratio of chitosan structural units to the water-soluble transition metal salt controlled at 1:0.02~0.05. After stirring at room temperature for 2~6 hours, the insoluble matter was removed by centrifugation to obtain the precursor solution of the quaternized synergistic metal-coordinated chitosan-based anion exchange membrane.

[0012] Finally, the precursor solution prepared above was poured into a polytetrafluoroethylene mold and dried at 60~80℃. The membrane was then peeled off from the polytetrafluoroethylene mold and soaked in potassium hydroxide to remove impurity ions, thus obtaining a quaternized synergistic metal coordination chitosan-based anion exchange membrane.

[0013] The chitosan powder has a viscosity of 100-200 mPa·s and a degree of deacetylation of 95% or higher.

[0014] The quaternizing agent is one of 2,3-epoxypropyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrimethylammonium chloride, and (2,3-epoxypropyl)[2-(methacryloyloxy)ethyl]dimethylammonium chloride.

[0015] The water-soluble transition metal salt is one of nickel sulfate hexahydrate, copper sulfate pentahydrate, zinc sulfate heptahydrate, and cobalt nitrate hexahydrate.

[0016] The protic acid is one of hydrochloric acid, sulfuric acid, and acetic acid.

[0017] Compared with the prior art, the beneficial effects of the present invention include at least the following:

[0018] (1) The introduction of quaternized chitosan not only increases the number of cationic active sites, but also broadens the OH groups due to the steric hindrance and electrostatic repulsion effect of the quaternary ammonium groups. - The transport channels enhance the ionic conductivity of the membrane.

[0019] (2) Chitosan structural units contain a large number of hydroxyl and amino groups, which can coordinate with transition metal ions to form a stable cross-linked network structure, which can significantly improve the mechanical properties and chemical stability of anion exchange membranes.

[0020] (3) Transition metal ion coordinated chitosan can form continuous OH groups within the membrane. - Migration channels, via transition metal coordination cations to OH - Exchange reaction, promoting OH - The directional movement of the membrane further improves its ionic conductivity.

[0021] (4) Chitosan itself has good biodegradability and environmental friendliness. The preparation process is simple and the production cost is much lower than that of commercial anion exchange membranes. It has broad application prospects. Attached Figure Description

[0022] Figure 1 (A) Scanning electron microscope image and (B) elemental distribution of the quaternized synergistic metal-coordinated chitosan-based anion exchange membrane described in Example 1.

[0023] Figure 2The ionic conductivity at different temperatures for Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3.

[0024] Figure 3 The stress-strain curves are for Example 1, Comparative Example 1, and Comparative Example 2.

[0025] Figure 4 The polarization curves are for the membrane electrode devices assembled in Example 1, Comparative Example 1, and Comparative Example 2. Detailed Implementation

[0026] To make the inventive purpose, technical solution and beneficial technical effects of this application clearer, the following detailed description is provided in conjunction with embodiments.

[0027] Example 1

[0028] In this embodiment, a quaternized synergistic nickel-coordinated chitosan-based anion exchange membrane is provided, which is prepared by the following steps.

[0029] (1) Take 4 g (25 mmol structural unit) of chitosan powder and 36 mL of isopropanol and add them to a three-necked flask. Stir and disperse evenly. Then add 15.1 g (100 mmol) of 2,3-epoxypropyltrimethylammonium chloride, heat to 80℃, and react for 6 hours to obtain a uniform solution. After cooling to room temperature, the product is precipitated with anhydrous ethanol, washed and dried to obtain quaternized chitosan powder with a degree of quaternization of 20%.

[0030] (2) Dissolve 0.5 g of acetic acid in 100 g of deionized water, add 0.081 g (0.3 mmol) of nickel sulfate hexahydrate, and stir for 10 minutes to dissolve completely. Add 0.7 g of chitosan powder and 0.3 g of quaternized chitosan powder to the above solution, stir for 6 hours, and centrifuge to remove insoluble matter to obtain the precursor solution of quaternized synergistic nickel-coordinated chitosan-based anion exchange membrane.

[0031] (3) Pour the above precursor solution into a polytetrafluoroethylene mold, dry it at 60°C, cool it and peel the membrane off from the polytetrafluoroethylene mold, and then soak it in potassium hydroxide to remove impurity ions, thus obtaining a quaternized synergistic nickel-coordinated chitosan-based anion exchange membrane.

[0032] The applicant performed scanning electron microscopy and elemental distribution observations on the obtained quaternized synergistic nickel-coordinated chitosan-based anion exchange membrane, such as... Figure 1 As shown, the quaternized synergistic nickel-coordinated chitosan-based anion exchange membrane described in Example 1 has a smooth and defect-free surface with uniform nickel element distribution, indicating that nickel ions are uniformly coordinated between chitosan molecular chains.

[0033] The applicant further tested the ionic conductivity and mechanical strength of the quaternized synergistic nickel-coordinated chitosan-based anion exchange membrane described in this embodiment. At room temperature, the ionic conductivity of the quaternized synergistic nickel-coordinated chitosan-based anion exchange membrane reached 37 mS / cm. -1 At 80℃, it can reach 73 mS cm. -1 ( Figure 2 The tensile strength reached 101.6 MPa, and the elongation at break was 10.8%. Figure 3 ).

[0034] Simultaneously, the quaternized synergistic nickel-coordinated chitosan-based anion exchange membrane obtained in this embodiment and the self-supporting NiFeCu and NiMo catalysts were assembled into a membrane electrode device. At 80°C, with an electrolyte of 1M KOH, and a voltage of 2.0 V, the current density reached 1.34 A cm⁻¹. -1 ( Figure 4 This indicates that the hydrogen production efficiency is high.

[0035] Example 2

[0036] In this embodiment, a quaternized synergistic nickel-coordinated chitosan-based anion exchange membrane is provided, which is prepared by the following steps.

[0037] (1) Take 4 g (25 mmol structural unit) of chitosan powder and 36 mL of isopropanol and add them to a three-necked flask. Stir and disperse evenly. Then add 14 g (75 mmol) of 3-chloro-2-hydroxypropyltrimethylammonium chloride. Heat to 70℃ and react for 5 hours to obtain a uniform solution. After cooling to room temperature, the product is precipitated with anhydrous ethanol, washed and dried to obtain quaternized chitosan powder with a degree of quaternization of 16%.

[0038] (2) Dissolve 0.5 g of hydrochloric acid in 100 g of deionized water, add 0.081 g (0.3 mmol) of nickel sulfate hexahydrate, and stir for 10 minutes to dissolve completely. Add 0.5 g of chitosan powder and 0.5 g of quaternized chitosan powder to the above solution, stir for 2 hours, and centrifuge to remove insoluble matter to obtain the precursor solution of quaternized synergistic nickel-coordinated chitosan-based anion exchange membrane.

[0039] (3) Pour the above precursor solution into a polytetrafluoroethylene mold, dry it at 60°C, cool it and peel the membrane off from the polytetrafluoroethylene mold, and then soak it in potassium hydroxide to remove impurity ions, thus obtaining a quaternized synergistic nickel-coordinated chitosan-based anion exchange membrane.

[0040] The applicant further tested the ionic conductivity and mechanical strength of the nickel-coordinated quaternized chitosan-based anion exchange membrane described in this embodiment.

[0041] Example 3

[0042] In this embodiment, a quaternized synergistic copper-coordinated chitosan-based anion exchange membrane is provided, which is prepared by the following steps.

[0043] (1) Take 4 g (25 mmol structural unit) of chitosan powder and 36 mL of isopropanol and add them to a three-necked flask. Stir and disperse evenly. Then add 18.7 g (75 mmol) (2,3-epoxypropyl)[2-(methacryloyloxy)ethyl]dimethylammonium chloride. Heat to 90℃ and react for 3 hours to obtain a uniform solution. After cooling to room temperature, the product is precipitated with anhydrous ethanol, washed and dried to obtain quaternized chitosan powder with a degree of quaternization of 15%.

[0044] (2) Dissolve 0.5 g of sulfuric acid in 100 g of deionized water, add 0.046 g (0.3 mmol) of copper sulfate pentahydrate, and stir for 10 minutes to dissolve completely. Add 0.5 g of chitosan powder and 0.5 g of quaternized chitosan powder to the above solution, stir for 3 hours, and centrifuge to remove insoluble matter to obtain the precursor solution of quaternized synergistic copper-coordinated chitosan-based anion exchange membrane.

[0045] (3) Pour the above precursor solution into a polytetrafluoroethylene mold, dry it at 60°C, and after cooling, peel the membrane from the polytetrafluoroethylene mold. Then soak it in potassium hydroxide to remove impurity ions and obtain a quaternized synergistic copper-coordinated chitosan-based anion exchange membrane.

[0046] The applicant further tested the ionic conductivity and mechanical strength of the quaternized synergistic copper-coordinated chitosan-based anion exchange membrane described in this embodiment.

[0047] Example 4

[0048] In this embodiment, a quaternized synergistic zinc-coordinated chitosan-based anion exchange membrane is provided, which is prepared by the following steps.

[0049] (1) Take 4 g (25 mmol structural unit) of chitosan powder and 36 mL of isopropanol and add them to a three-necked flask. Stir and disperse evenly. Then add 7.5 g (50 mmol) of 2,3-epoxypropyltrimethylammonium chloride, heat to 70℃, and react for 3 hours to obtain a uniform solution. After cooling to room temperature, the product is precipitated with anhydrous ethanol, washed and dried to obtain quaternized chitosan powder with a degree of quaternization of 12%.

[0050] (2) Dissolve 0.5 g of hydrochloric acid in 100 g of deionized water, add 0.071 g (0.4 mmol) of zinc sulfate heptahydrate, and stir for 10 minutes to dissolve completely. Add 0.6 g of chitosan powder and 0.4 g of quaternized chitosan powder to the above solution, stir for 4 hours, and centrifuge to remove insoluble matter to obtain the precursor solution of quaternized synergistic zinc coordinated chitosan-based anion exchange membrane.

[0051] (3) Pour the above precursor solution into a polytetrafluoroethylene mold, dry it at 60°C, cool it and peel the membrane off from the polytetrafluoroethylene mold, and then soak it in potassium hydroxide to remove impurity ions, thus obtaining a quaternized synergistic zinc coordinated chitosan-based anion exchange membrane.

[0052] The applicant further tested the ionic conductivity and mechanical strength of the quaternized synergistic zinc-coordinated chitosan-based anion exchange membrane described in this embodiment.

[0053] Example 5

[0054] In this embodiment, a quaternized cobalt-coordinated chitosan-based anion exchange membrane is provided, which is prepared by the following steps.

[0055] (1) Take 4 g (25 mmol structural unit) of chitosan powder and 36 mL of isopropanol and add them to a three-necked flask. Stir and disperse evenly. Then add 9.4 g (50 mmol) of 3-chloro-2-hydroxypropyltrimethylammonium chloride. Heat to 60℃ and react for 4 hours to obtain a uniform solution. After cooling to room temperature, the product is precipitated with anhydrous ethanol, washed and dried to obtain quaternized chitosan powder with a degree of quaternization of 10%.

[0056] (2) Dissolve 0.5 g of acetic acid in 100 g of deionized water, add 0.090 g (0.5 mmol) of cobalt nitrate hexahydrate, and stir for 10 minutes to dissolve completely. Add 0.8 g of chitosan powder and 0.2 g of quaternized chitosan powder to the above solution, stir for 6 hours, and centrifuge to remove insoluble matter to obtain the precursor solution of quaternized cobalt-coordinated chitosan-based anion exchange membrane.

[0057] (3) Pour the above precursor solution into a polytetrafluoroethylene mold, dry it at 60°C, and after cooling, peel the membrane from the polytetrafluoroethylene mold. Then soak it in potassium hydroxide to remove impurity ions and obtain a quaternized cobalt-coordinated chitosan-based anion exchange membrane.

[0058] The applicant further tested the ionic conductivity and mechanical strength of the quaternized cobalt-coordinated chitosan-based anion exchange membrane described in this embodiment.

[0059] Comparative Example 1

[0060] In this comparative example, a chitosan anion exchange membrane is provided, which is prepared by the following steps.

[0061] (1) Dissolve 0.5 g of acetic acid in 100 g of deionized water, add 1.0 g of chitosan powder to the above solution, stir for 3 hours and centrifuge to remove insoluble matter to obtain the precursor solution of chitosan anion exchange membrane.

[0062] (2) Pour the above precursor solution into a polytetrafluoroethylene mold, dry it at 60°C, cool it and peel the membrane off from the polytetrafluoroethylene mold, and then soak it in potassium hydroxide to remove impurity ions to obtain a chitosan anion exchange membrane.

[0063] The applicant further tested the ionic conductivity and mechanical strength of the chitosan anion exchange membrane described in this comparative example, and assembled it with self-supporting NiFeCu and NiMo catalysts into a membrane electrode device.

[0064] Comparative Example 2

[0065] In this comparative example, a chitosan / quaternized chitosan composite anion exchange membrane is provided, which is prepared by the following steps.

[0066] (1) Take 4 g (25 mmol structural unit) of chitosan powder and 36 mL of isopropanol and add them to a three-necked flask. Stir and disperse evenly. Then add 15.1 g (100 mmol) of 2,3-epoxypropyltrimethylammonium chloride, heat to 80℃, and react for 6 hours to obtain a uniform solution. After cooling to room temperature, the product is precipitated with anhydrous ethanol, washed and dried to obtain quaternized chitosan powder with a degree of quaternization of 20%.

[0067] (2) Dissolve 0.5 g of hydrochloric acid in 100 g of deionized water, add 0.7 g of chitosan powder and 0.3 g of quaternized chitosan powder to the above solution, stir for 3 hours and centrifuge to remove insoluble matter to obtain the precursor solution of chitosan / quaternized chitosan composite anion exchange membrane.

[0068] (3) Pour the above precursor solution into a polytetrafluoroethylene mold, dry it at 60°C, cool it and peel the membrane off from the polytetrafluoroethylene mold, and then soak it in potassium hydroxide to remove impurity ions, thus obtaining a chitosan / quaternized chitosan composite anion exchange membrane.

[0069] The applicant further tested the ionic conductivity and mechanical strength of the chitosan / quaternized chitosan composite anion exchange membrane described in this comparative example, and assembled it with self-supporting NiFeCu and NiMo catalysts into a membrane electrode device.

[0070] Comparative Example 3

[0071] In this comparative example, a nickel-coordinated chitosan-based anion exchange membrane is provided, which is prepared by the following steps.

[0072] (1) Dissolve 0.5 g of acetic acid in 100 g of deionized water, add 0.081 g (0.3 mmol) of nickel sulfate hexahydrate, and stir for 10 minutes to dissolve it completely. Add 1.0 g of chitosan powder to the above solution, stir for 6 hours, and centrifuge to remove insoluble matter to obtain the precursor solution of nickel-coordinated chitosan-based anion exchange membrane.

[0073] (2) Pour the above precursor solution into a polytetrafluoroethylene mold, dry it at 60°C, cool it and peel the membrane off from the polytetrafluoroethylene mold, and then soak it in potassium hydroxide to remove impurity ions to obtain a nickel-coordinated chitosan anion exchange membrane.

[0074] The applicant further tested the nickel-coordinated chitosan-based anion exchange membrane of this comparative example for ionic conductivity and mechanical strength.

[0075] Verification Implementation Examples

[0076] The anion exchange membranes described in the examples and comparative examples were tested for mechanical properties, ionic conductivity, and swelling degree.

[0077] Table 1. Tensile strength, ionic conductivity at 80°C, and swelling degree of the Examples and Comparative Examples Indicator Sample Tensile strength (MPa) <![CDATA[Ionic conductivity at 80 °C (mS cm -1 ).]]> Swelling degree (%) Example 1 101.6 73.3 34.6 Example 2 87.6 70.2 37.1 Example 3 96.9 67.8 38.4 Example 4 80.1 64.1 45.5 Example 5 73.6 61.5 49.3 Comparative Example 1 60.6 18.3 58.8 Comparative Example 2 45.5 50.5 71.8 Comparative Example 3 142.6 40.2 23.4

[0078] Table 1 compares the tensile strength, ionic conductivity at 80℃, and swelling degree data of five examples (quaternization-metal coordination chitosan-based anion exchange membranes) with three comparative examples (membranes with single components or single modification strategies), clearly demonstrating the optimizing effect of the "quaternization-metal coordination" synergistic modification strategy on the overall performance of chitosan-based anion exchange membranes. The hydroxyl and amino groups in the chitosan molecular chain interact with transition metal ions (Ni... 2+ Cu 2+ Zn 2+ Co 2+ Stable coordination bonds are formed, constructing a cross-linked network that restricts molecular chain slippage, thereby significantly improving tensile strength. Coordination effect: Ni 2+ >Cu 2+ >Zn 2+ >Co 2+ This may be because Ni 2+ With a coordination number of 6, it can link 2-3 molecular chains, resulting in a dense cross-linked structure. (Cu) 2+ With Zn 2+With a coordination number of 4, the crosslinking density is higher than that of Ni. 2+ Low, while Co 2+ The coordination bond is weaker, and the coordination ability is weaker than that of Ni. 2+ Quaternized chitosan provides additional cationic active sites, while the steric hindrance and electrostatic repulsion of the quaternary ammonium groups expand ion transport channels and reduce OH- ions. - Migration resistance. Transition metal coordination cations also possess OH groups. - The exchange capacity also forms continuous ion migration channels, promoting OH- - Directional movement. This synergistic effect is also reflected in the change in swelling degree. The "cross-linking constraint" of metal coordination and the "hydrophilicity" of quaternization are balanced, so that the swelling degree is controlled within a reasonable range.

[0079] The ionic conductivity of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 was evaluated, and the results are as follows: Figure 2 As shown, the ionic conductivity increases with increasing temperature; in Example 1, the ionic conductivity reaches as high as 73 mS / cm at 80°C. -1 Comparative Examples 1, 2, and 3, however, only showed 18 mS / cm at 80°C. -1 50 mS cm -1 and 40 mS cm -1 These data strongly demonstrate that the quaternized synergistic metal-coordinated chitosan-based anion exchange membrane prepared in this invention has higher ionic conductivity.

[0080] The mechanical properties of Example 1, Comparative Example 1, and Comparative Example 2 were evaluated. Figure 3 The stress-strain curves were shown, with Example 1 exhibiting a tensile strength as high as 101.6 MPa, while Comparative Examples 1 and 2 only showed 60.6 MPa and 45.5 MPa, respectively. These data strongly demonstrate that the quaternized synergistic metal-coordinated chitosan-based anion exchange membrane prepared in this invention forms a robust network structure due to the coordination effect of transition metal ions, resulting in superior mechanical properties.

[0081] Membrane electrode devices were assembled using Examples 1, 1, and 2, and their performance was evaluated. Figure 4 As shown, at 80°C, with an electrolyte of 1M KOH, and a voltage of 2.0 V, the current density in Example 1 reached as high as 1.34 A cm⁻¹. -1 Comparative Example 1 and Comparative Example 2, however, only had 0.91 A cm⁻¹. -1 and 0.61 A cm -1 These data strongly demonstrate that the quaternized synergistic metal-coordinated chitosan-based anion exchange membrane prepared in this invention possesses excellent device performance.

[0082] The present invention has been described by the above-described embodiments; however, these embodiments are merely examples for implementing the present invention. It must be noted that the disclosed embodiments do not limit the scope of the present invention. Conversely, modifications and equivalents contained within the spirit and scope of the claims are included within the scope of the present invention.

Claims

1. A quaternized synergistic metal-coordinated chitosan-based anion exchange membrane, characterized in that, The anion exchange membrane is prepared by dissolving and mixing chitosan and quaternized chitosan, followed by coordination crosslinking with a water-soluble transition metal salt, wherein chitosan comprises 50–77 parts by weight and quaternized chitosan comprises 23–50 parts by weight. The membrane has a thickness of 10–200 µm, a tensile strength exceeding 20 MPa, and an ionic conductivity exceeding 30 mS / cm at room temperature. -1 The quaternized synergistic metal-coordinated chitosan-based anion exchange membrane is prepared by the following method: (1) Chitosan powder is added to a three-necked flask containing isopropanol. After stirring and dispersing evenly, a quaternizing agent is added. The molar ratio of chitosan structural units to quaternizing agent is controlled to be 1:2~4. The temperature is raised to 60~90℃ and reacted for 3~6 hours to obtain a uniform solution. After cooling to room temperature, the product is precipitated with anhydrous ethanol, washed, and dried to obtain quaternized chitosan with a degree of quaternization of 10~20%. (2) Chitosan, quaternized chitosan powder, and water-soluble transition metal salt are dissolved in a protic acid aqueous solution, and the mass ratio of chitosan to quaternized chitosan is controlled to be 1:0.25~1, and the molar ratio of chitosan structural units to water-soluble transition metal salt is 1:0.02~0.

05. After stirring at room temperature for 2~6 hours, the insoluble matter is removed by centrifugation to obtain the precursor solution of quaternized synergistic metal coordination chitosan-based anion exchange membrane; (3) Pour the precursor solution obtained in step (2) into a polytetrafluoroethylene mold, dry it at 60~80℃, peel the membrane from the polytetrafluoroethylene mold, and then soak it in potassium hydroxide to remove impurity ions, so as to obtain a quaternized synergistic metal coordination chitosan-based anion exchange membrane.

2. The quaternized synergistic metal-coordinated chitosan-based anion exchange membrane and its preparation method according to claim 1, characterized in that, The chitosan has a viscosity of 100-200 mPa·s and a degree of deacetylation of over 95%.

3. The quaternized synergistic metal-coordinated chitosan-based anion exchange membrane and its preparation method according to claim 1, characterized in that, In step (1), the quaternizing agent is one of 2,3-epoxypropyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrimethylammonium chloride, or (2,3-epoxypropyl)[2-(methacryloyloxy)ethyl]dimethylammonium chloride.

4. The quaternized synergistic metal-coordinated chitosan-based anion exchange membrane and its preparation method according to claim 1, characterized in that, In step (2), the water-soluble transition metal salt is one of nickel sulfate hexahydrate, copper sulfate pentahydrate, zinc sulfate heptahydrate, and cobalt nitrate hexahydrate.

5. The quaternized synergistic metal-coordinated chitosan-based anion exchange membrane and its preparation method according to claim 1, characterized in that, In step (2), the protic acid is one of hydrochloric acid, sulfuric acid, or acetic acid.

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