Preparation method of chitosan membrane, chitosan membrane and application thereof

Abstract

This invention provides a method for preparing a chitosan membrane, the chitosan membrane prepared by this method, and its applications. The method includes the following steps: S1: mixing chitosan, acid, C1-C6 monohydric alcohol, pore-forming agent, metal salt, and water to obtain a casting solution; S2: placing the casting solution on a carrier to obtain a carrier loaded with the chitosan membrane; S3: immersing the carrier loaded with the chitosan membrane sequentially in an alkaline solution and water to separate the chitosan membrane from the carrier. The chitosan membrane of this invention has a strong resistance to strong alkalis. When used as an anion exchange membrane material in fuel cells, it has advantages such as high specific power, rapid start-up, non-corrosiveness, low reaction temperature, and low oxidant requirement.

Description

Technical Field

[0001] This invention relates to the field of ion exchange membrane materials, specifically to a method for preparing a chitosan membrane, the chitosan membrane prepared by the method, and its applications. Technical Background

[0002] Fuel cells, with their high energy conversion efficiency and near-zero emissions, have become an important choice for future clean and sustainable energy. Proton exchange membrane fuel cells (PEMFCs) have a high degree of commercialization and are widely used in portable power sources, power batteries, and stationary power stations. PEMFCs offer advantages such as high specific power, rapid start-up, non-corrosiveness, low reaction temperature, and low oxidant requirements; however, they require precious metal catalysts, which are expensive, and impurities in the fuel can easily cause catalyst poisoning, leading to reduced battery efficiency. Anion exchange membrane fuel cells rely on anions (OH-) - Electrochemical reactions are conducted to generate electrical energy, which has lower requirements for electrode materials and does not require the use of precious metals, resulting in a significant cost advantage. However, the membrane material needs to have strong resistance to strong alkalis. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a method for preparing a chitosan membrane and the chitosan membrane obtained by this method. This invention is the first to employ concentration and solvent extraction methods to prepare chitosan blend membranes containing different metal ions. The chitosan membrane of this invention exhibits strong resistance to strong alkalis, and when used as an anion exchange membrane material in fuel cells, it offers advantages such as high specific power, rapid start-up, non-corrosiveness, low reaction temperature, and low oxidant requirements.

[0004] A first aspect of the present invention provides a method for preparing a chitosan membrane, comprising the following steps:

[0005] S1: Chitosan, acid, C1-C6 monohydric alcohol, pore-forming agent, metal salt and water are mixed to obtain casting solution, wherein the total mass of the casting solution is used as the basis for calculation.

[0006] S2: Place the casting solution on the carrier to obtain a carrier loaded with chitosan membrane;

[0007] S3: Immerse the carrier loaded with chitosan membrane in alkaline solution and water in sequence to separate the chitosan membrane from the carrier.

[0008] According to some embodiments of the present invention, the method further includes allowing the casting solution to stand and defoam before placing it on the carrier. In some embodiments, the standing time is 0.5h-3h, for example 1h or 2h.

[0009] According to some embodiments of the present invention, in S2, after the casting solution is placed on the carrier, it is subjected to heat treatment to evaporate the monohydric alcohols of C1-C6 and water in the casting solution, thereby obtaining a carrier loaded with chitosan membrane.

[0010] According to some embodiments of the present invention, the method further includes washing the chitosan membrane obtained in S3, preferably with water until neutral.

[0011] According to some embodiments of the present invention, the chitosan content is 0.5%-2.5% by weight of the total mass of the casting solution. According to some embodiments of the present invention, the chitosan content is 0.6%, 0.7%, 0.75%, 0.85%, 0.9%, 0.95%, 1.0%, 1.05%, 1.1%, 1.15%, 1.2%, 1.25%, 1.35%, 1.4%, 1.45%, 1.5%, 1.55%, 1.6%, 1.65%, 1.7%, 1.75%, 1.8%, 1.85%, 1.9%, 1.95%, 2.1%, 2.2%, 2.3%, 2.4%, and any value between these values, based on the total mass of the casting solution. In some embodiments, the chitosan content is 0.8%-2.0% by weight of the total mass of the casting solution.

[0012] According to some embodiments of the present invention, the acid content, based on the total mass of the casting solution, is 0.5%-5%, for example, 0.8%, 1.2%, 1.5%, 1.7%, 2.0%, 2.3%, 2.5%, 2.7%, 3.0%, 3.3%, 3.5%, 3.7%, 3.9%, 4.2%, 4.5%, 4.7%, and any value between therewith. In some embodiments, the acid content, based on the total mass of the casting solution, is 1%-4%.

[0013] According to some embodiments of the present invention, the pore-forming agent has a mass content of 0.5%-10% based on the total mass of the casting solution, for example, 1.5%, 2.0%, 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, 7.5%, 8.5%, 9.0%, and any value between therewith. In some embodiments, the pore-forming agent has a mass content of 1%-8% based on the total mass of the casting solution.

[0014] According to some embodiments of the present invention, the mass content of the C1-C6 monohydric alcohols is 10%-50% based on the total mass of the casting solution, for example, 15%, 20%, 25%, 27%, 32%, 35%, 37%, 42%, 45%, and any value between therewith. In some embodiments, the mass content of the C1-C6 monohydric alcohols is 30%-40% based on the total mass of the casting solution.

[0015] According to some embodiments of the present invention, the mass content of the metal salt, based on the total mass of the casting solution, is 0.01-30%, for example, 0.03, 0.05, 0.1, 0.25, 0.50, 0.75, 1.0, 2.0, 5.0, 10, 15, 20, 25, 29%, and any value between therewith. In some embodiments, the mass content of the metal salt, based on the total mass of the casting solution, is 0.1%-10%. In some embodiments, the mass content of the metal salt, based on the total mass of the casting solution, is 0.1%-1%.

[0016] According to some embodiments of the present invention, the water content is 50%-70% by mass of the total casting solution, for example 52%, 54%, 57%, 60%, 62%, 64%, 67%, 69% and any value therebetween. In some embodiments, the water content is 55%-65% by mass of the total casting solution.

[0017] In some embodiments, the casting solution comprises 0.9wt%-1.5wt% chitosan, 3wt%-4wt% acid, 1wt%-2wt% porogen, 30wt%-40wt% C1-C6 monohydric alcohol, and 55wt%-65wt% water. In some embodiments, the casting solution comprises 0.8wt%-1.2wt% chitosan, 3.5wt%-4.5wt% acid, 1.5wt%-2.0wt% porogen, 30wt%-34wt% C1-C6 monohydric alcohol, and 60wt%-64wt% water.

[0018] According to some embodiments of the present invention, in S1, the mixing time is 4h-32h, for example 5h, 7h, 9h, 10h, 12h, 14h, 15h, 17h, 18h, 22h, 24h, 25h, 27h, 29h, 31h, and any value between them. In some embodiments, the mixing time is 8h-20h.

[0019] According to some embodiments of the present invention, the metal salt is composed of a metal ion and an acid radical ion. According to some embodiments of the present invention, the metal ion is selected from Mg. 2+ Ca 2+ Ba 2+ V 3+ V 2+ Cr 3+ Mo 5+ Mn 2+ Fe 3+ Fe 2+ Co 2 + Ni 2+Cu 2+ Zn 2+ Cd 2+ Al 3+ Ti 4+ or Zr 4+ At least one of the following. According to some embodiments of the present invention, the anion is selected from Cl... - ClO4 - ClO3 - ,ClO - NO3 - NO2 - SO4 2- HSO4 - SO3 2- HSO3 - S2O3 2- PO4 3- HPO4 2- H2PO4 - C2O4 2- COO - CH3COO - CF3COO - CH3SO3 - or CF3SO3 - At least one of the following. In some embodiments, the metal salt is selected from at least one of CuCl2, FeCl3, MgCl2, NiCl2, ZrCl4, or CaCl2.

[0020] According to some embodiments of the present invention, the porogen is selected from one or more of ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, polyethylene glycol monomethyl ether, polyethylene glycol dimethyl ether, polyvinyl alcohol, and polyvinylpyrrolidone. In some embodiments, the porogen is selected from polyethylene glycol. In some embodiments, the porogen is selected from polyethylene glycol with a molecular weight of 200-600, such as PEG200, PEG400, or PEG600.

[0021] According to some embodiments of the present invention, the degree of deacetylation of the chitosan is not less than 55%, preferably greater than 70%, for example, 75%, 80%, 85%, 90%, 95%, and any value between therewith. In some embodiments, the molecular weight of the chitosan is 1 × 10⁻⁶. 5 -2×10 6 Preferably 3×10 5 -7×10 5 .

[0022] According to some embodiments of the present invention, in S1, the volume ratio of the casting solution to the surface area of ​​the carrier is (5-30) mL:100 cm².2 For example, 7mL:100cm 2 9mL:100cm 2 12mL:100cm 2 14mL:100cm 2 17mL:100cm 2 19mL:100cm 2 21mL:100cm 2 23mL:100cm 2 27mL:100cm 2 Or any value in between. In some embodiments, the volume ratio of the casting solution to the surface area of ​​the carrier is (7.5-25) mL:100 cm². 2 In some embodiments, the volume ratio of the casting solution to the surface area of ​​the carrier is (15-22.5) mL:100 cm². 2 .

[0023] According to some embodiments of the present invention, the carrier is selected from one or more of glass plates, ceramic plates, or organic polymer plates.

[0024] According to some embodiments of the present invention, the acid is selected from one or more of hydrochloric acid, sulfuric acid, nitric acid, formic acid, acetic acid, and trifluoroacetic acid.

[0025] According to some embodiments of the present invention, the C1-C6 monohydric alcohol is selected from one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol and tert-butanol.

[0026] According to some embodiments of the present invention, the alkaline solution is one or more selected from sodium hydroxide solution, potassium hydroxide solution, potassium carbonate solution, sodium carbonate solution, potassium phosphate solution, and sodium phosphate solution. In some embodiments, the mass concentration of the alkaline solution is 0.1%-10%.

[0027] According to some embodiments of the present invention, the method for preparing the chitosan membrane includes the following specific steps:

[0028] (1) Mix C1-C6 monohydric alcohol, acid, metal salt, water, pore-forming agent and chitosan to obtain casting solution;

[0029] (2) Allow the casting solution to stand in an ultrasonic instrument to defoam;

[0030] (3) Pour the defoamed casting solution onto the carrier and stretch it to the same size as the carrier. Then heat and dry it until all the solvent has evaporated completely to obtain a carrier loaded with chitosan membrane.

[0031] (4) Immerse the membrane from (3) in a sodium hydroxide solution, preferably a 10% sodium hydroxide solution, for 0.5h-3h, for example, 1h or 2h, and then transfer it to distilled water for soaking. After the membrane separates from the glass plate, wash it until it is neutral, and store it in a wet state to obtain the chitosan membrane.

[0032] The method of the present invention ensures that there is no solvent residue in the membrane before the membrane is immersed in alkaline solution for extraction, and that the membrane structure is uniform, thus guaranteeing the uniform extraction of the pore-forming agent and the unobstructed pores resulting from the fully and regularly arranged pore-forming agent.

[0033] A second aspect of the present invention provides a chitosan membrane prepared by the preparation method described in the first aspect.

[0034] According to some embodiments of the present invention, the average pore size of the chitosan membrane is 0.005 μm-5 μm.

[0035] The third aspect of the present invention provides the application of chitosan membranes prepared according to the preparation method of the first aspect or the chitosan membranes of the second aspect in anion exchange membrane materials.

[0036] Chitosan is derived from chitin by removing acetyl groups under strong alkaline conditions. It inherently possesses the ability to withstand strong alkalis and is abundant in nature, providing a sustainable material source. The chitosan membrane of this invention exhibits strong resistance to strong alkalis. When used as an anion exchange membrane material in fuel cells, it offers advantages such as high specific power, rapid start-up, non-corrosiveness, low reaction temperature, and low oxidant requirements. Detailed Implementation

[0037] The present invention will be further described below through specific embodiments, but the scope of the present invention is not limited thereto.

[0038] Measurement of anionic conductivity

[0039] Measuring instrument: EIS (electrochemical impedance spectroscopy)

[0040] Measurement environment: In a humidity-controlled room, room temperature

[0041] Test steps:

[0042] 1. Immerse the chitosan membrane in 3 mol / L NaOH for 24 h.

[0043] 2. Wash with water to remove excess NaOH.

[0044] 3. Measurements were performed using a bioelectrochemical station with a frequency ranging from 100 kHz to 1 Hz.

[0045] 4. Record the true axis value R (resistance obtained from EIS test) at the high-frequency intercept.

[0046] Calculation formula:

[0047]

[0048] σ—Conductivity of hydroxide ions

[0049] L – Length of the chitosan membrane

[0050] R – Resistance obtained from EIS testing (true axial value at the high-frequency intercept)

[0051] S—Cross-sectional area of ​​the membrane

[0052] Examples 1-27, Comparative Examples 1-3

[0053] According to a certain ratio (see Table 1), solvents 95% ethanol (34% by mass), water, acetic acid (2% by mass), metal salts of varying mass content, pore-forming agent PEG400 of varying mass content, and chitosan (95% deacetylation, 2% by mass) were mixed and stirred for 20 hours to obtain a chitosan membrane solution, i.e., casting solution. This solution was allowed to stand in an ultrasonic instrument for one hour to defoam. The drying platform was pre-calibrated horizontally, and 20 mL of the casting solution was weighed and poured onto a clean glass plate (10×10 cm) to extend it to the same size as the carrier. Then, it was dried at 50℃ for 24 hours on a graphite constant-temperature drying tray until all solvents (95% ethanol and water) had completely evaporated. The membrane was then immersed in a 10% sodium hydroxide solution for 1 hour, followed by immersion in distilled water until it separated from the glass plate. It was then washed until neutral and stored in a moist state to obtain the chitosan membrane.

[0054] Table 1

[0055]

[0056] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. An application of a chitosan membrane in anion exchange membrane materials, wherein, The method for preparing the chitosan membrane includes the following steps: S1: Chitosan, acid, C1-C6 monohydric alcohol, pore-forming agent, metal salt, and water are mixed to obtain a casting solution. Wherein, the metal salt is selected from FeCl3, and the chitosan content is 0.5%-2.5% by mass of the total mass of the casting solution; the acid content is 0.5%-5% by mass; the pore-forming agent content is 4% by mass; the C1-C6 monohydric alcohol content is 10%-50% by mass; and the metal salt content is 0.1%-1% by mass; or The metal salt is selected from FeCl3. Based on the total mass of the casting solution, the chitosan content is 0.5%-2.5%; the acid content is 0.5%-5%; the pore-forming agent content is 0%; the C1-C6 monohydric alcohol content is 10%-50%; and the metal salt content is 0.25%. The metal salt is selected from NiCl2. Based on the total mass of the casting solution, the chitosan content is 0.5%-2.5%; the acid content is 0.5%-5%; the pore-forming agent content is 0%; the C1-C6 monohydric alcohol content is 10%-50%; and the metal salt content is 0.1%. The metal salt is selected from ZrCl4. Based on the total mass of the casting solution, the chitosan content is 0.5%-2.5%; the acid content is 0.5%-5%; the porogen content is 4%; the C1-C6 monohydric alcohol content is 10%-50%; and the metal salt content is 0.05%. S2: Place the casting solution on the carrier to obtain a carrier loaded with chitosan membrane; S3: Immerse the carrier loaded with chitosan membrane in alkaline solution and water in sequence to separate the chitosan membrane from the carrier.

2. The application according to claim 1, characterized in that, The chitosan content is 0.8%-2.0% based on the total mass of the casting solution.

3. The application according to claim 1, characterized in that, The acid content is 1%-4% by mass.

4. The application according to claim 1, characterized in that, The mass content of the C1-C6 monohydric alcohol is 30%-40%.

5. The application according to claim 1, characterized in that, In S1, the mixing time is 4h-32h.

6. The application according to claim 1, characterized in that, In S1, the mixing time is 8h-20h.

7. The application according to claim 1, characterized in that, The pore-forming agent is selected from one or more of ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, polyethylene glycol monomethyl ether, polyethylene glycol dimethyl ether, polyvinyl alcohol, and polyvinylpyrrolidone.

8. The application according to claim 1, characterized in that, The pore-forming agent is polyethylene glycol.

9. The application according to claim 1, characterized in that, The porogen is polyethylene glycol with a molecular weight of 200-600.

10. The application according to claim 1, characterized in that, In S1, the volume ratio of the casting solution to the surface area of ​​the carrier is (5-30) mL:100 cm². 2 .

11. The application according to claim 1, characterized in that, In S1, the volume ratio of the casting solution to the surface area of ​​the carrier is (7.5-25) mL:100 cm². 2 .

12. The application according to claim 1, characterized in that, In S1, the volume ratio of the casting solution to the surface area of ​​the carrier is (15-22.5) mL:100 cm². 2 .

13. The application according to claim 1, characterized in that, The degree of deacetylation of the chitosan is not less than 55%, and the molecular weight of the chitosan is 1×10⁻⁶. 5 -2×10 6 .

14. The application according to claim 1, characterized in that, The degree of deacetylation of the chitosan is greater than 70%.

15. The application according to claim 1, characterized in that, The molecular weight of the chitosan is 3 × 10⁻⁶. 5 -7×10 5 .

16. The application according to claim 1, characterized in that, The carrier is selected from one or more of glass plates, ceramic plates, or organic polymer plates; And / or the acid is selected from one or more of hydrochloric acid, sulfuric acid, nitric acid, formic acid, acetic acid, and trifluoroacetic acid; And / or the C1-C6 monohydric alcohol is selected from one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, and tert-butanol; And / or the alkaline solution is one or more of sodium hydroxide solution, potassium hydroxide solution, potassium carbonate solution, sodium carbonate solution, potassium phosphate solution, and sodium phosphate solution.

17. The application according to any one of claims 1-16, characterized in that, The average pore size of the chitosan membrane is 0.005 μm-5 μm.

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