Preparation method of plant-based ion exchange membrane and application thereof in rare earth element recovery

Abstract

The application discloses a preparation method of a plant-based ion exchange membrane and application of the plant-based ion exchange membrane in rare earth element recovery, and relates to the technical field of ion exchange membranes. In the preparation of the plant-based ion exchange membrane, shell powder is sequentially reacted with N-[3-(trimethoxysilyl)propyl]ethylenediamine, dicyandiamide and 9-allyl-9H-carbazole to prepare functionalized shell powder; microcrystalline cellulose is sequentially reacted with thionyl chloride, carbazole and sulfamic acid to prepare functionalized microcrystalline cellulose; 2,7-bis(trifluoromethyl)-9H-carbazole is reacted with p-bromobenzaldehyde to prepare a functional monomer; and the functionalized microcrystalline cellulose, N-(4-benzaldehyde)-carbazole, functionalized shell powder, N,N-dimethylformamide and the functional monomer are reacted to prepare a plant-based ion exchange membrane. The plant-based ion exchange membrane prepared by the application has good antibacterial, corrosion-resistant and heat-stable capabilities.

Description

Technical Field

[0001] This invention relates to the field of ion exchange membrane technology, specifically to a method for preparing a plant-based ion exchange membrane and its application in rare earth element recovery. Background Technology

[0002] With the continuous expansion of rare earth applications and the sustained growth in demand, people have gradually realized that as a non-renewable resource, the long-term supply of rare earths in large quantities is becoming increasingly difficult. Therefore, people are using recycling to achieve effective reuse of resources and conserve natural resources. Ion exchange membranes are a common method for rare earth element recovery. Ion exchange membranes are composed of a polymer matrix, in which ionic groups are fixed on the polymer backbone. Based on the charge of the ionic groups, ion exchange membranes are divided into anion exchange membranes and cation exchange membranes. Among them, cation exchange membranes are commonly used for rare earth element recovery. In diffusion dialysis and electrodialysis technologies, cation exchange membranes can selectively allow cations to pass through while blocking anions and other impurities, thereby achieving the purification and recovery of rare earth elements.

[0003] The most widely used extraction process for ion-adsorption rare earth minerals is in-situ leaching. Although the leaching process is simple and the rare earth leaching rate is high, it suffers from the problem of high acidity in the leachate. Long-term exposure to this environment may cause irreversible damage to the membrane. Furthermore, bacteria such as Escherichia coli and Staphylococcus aureus in the environment can attach to the membrane surface and cause the secretion of extracellular polymers, forming a dense biofilm. This biofilm covers the membrane surface and blocks the membrane pores, hindering ion permeation. Moreover, the biofilm may cause irreversible fouling on the membrane surface, requiring membrane replacement or deep cleaning to restore performance. Therefore, this application introduces a plant-based ion exchange membrane with antibacterial and corrosion-resistant capabilities. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a plant-based ion exchange membrane and a lithium-ion battery, so as to solve the problems existing in the prior art.

[0005] A method for preparing a plant-based ion exchange membrane, wherein the method comprises reacting functionalized microcrystalline cellulose, N-(4-benzaldehyde)-carbazole, functionalized shell powder, N,N-dimethylformamide and functional monomers, forming a mold, and obtaining the membrane.

[0006] The functionalized microcrystalline cellulose is prepared by reacting microcrystalline cellulose sequentially with thionyl chloride, carbazole and aminosulfonic acid.

[0007] The functionalized shell powder is prepared by reacting shell powder sequentially with N-[3-(trimethoxysilyl)propyl]ethylenediamine, dicyandiamide and 9-allyl-9H-carbazole;

[0008] The functional monomer is prepared by reacting 2,7-bis(trifluoromethyl)-9H-carbazole with p-bromobenzaldehyde.

[0009] As an optimization, the preparation method of the plant-based ion exchange membrane mainly includes the following preparation steps:

[0010] (1) Modified shell powder, 9-allyl-9H-carbazole and acetone are mixed at a mass ratio of 1:0.08-0.12:14-16 and stirred at 45-55℃ and 200-300r / min for 38-42h. After filtration, the mixture is washed with acetone 3-5 times and vacuum dried at -10-0℃ for 22-26h to obtain functionalized shell powder.

[0011] (2) Pre-modified microcrystalline cellulose, dimethyl sulfoxide and carbazole are mixed at a mass ratio of 1:25-35:0.18-0.22 and stirred at 85-95℃ and 200-300r / min for 11-13h. The mixture is poured into deionized water, allowed to stand for 20-30min, filtered, washed with acetone 3-5 times, and vacuum dried at 45-55℃ for 11-13h to obtain modified microcrystalline cellulose.

[0012] (3) Mix 2,7-bis(trifluoromethyl)-9H-carbazole, p-bromobenzaldehyde and NN dimethylformamide in a molar ratio of 1:1:14-16, stir for 25-35 min at 200-300 r / min, 55-65 °C under nitrogen protection, cool to room temperature, and vacuum dry at -10-0 °C for 22-26 h to obtain the functional monomer;

[0013] (4) The casting solution is evenly coated on a clean and dry glass plate with a thickness of 450-550 μm. It is dried at 75-85℃ for 5-7 h, scraped off, placed in a zeolite mixture, and left to stand for 20-30 min. It is then taken out, washed with deionized water 5-7 times, and vacuum dried at -10-0℃ for 22-26 h to obtain an ion exchange membrane.

[0014] As an optimization, the modified shell powder in step (1) is prepared by mixing pre-modified shell powder and 0.8 mol / L dilute hydrochloric acid at a mass ratio of 1:4-6, and then microwaved at 200-300 r / min, 45-55℃, and 400W microwave power for 8-12 minutes to obtain a pre-modified shell powder mixture. Dicyandiamide and deionized water are then mixed at a mass ratio of 1:4-6 to obtain a dicyandiamide solution. The pre-modified shell powder mixture and the dicyandiamide solution are then mixed at a mass ratio of 1:0.18-0.22, and the pH is adjusted to 1 with 0.8 mol / L dilute hydrochloric acid. The mixture is then microwaved at 200-300 r / min, 95-105℃, and 400W microwave power for 13-17 minutes. The mixture is then poured into ethanol, allowed to stand for 18-22 minutes, filtered, washed 3-5 times with ethanol, and then vacuum dried at -10-0℃ for 22-26 hours.

[0015] As an optimization, the reaction mechanism is as follows:

[0016]

[0017] As an optimization, the pre-modified shell powder is prepared by mixing 200-mesh shell powder, N-[3-(trimethoxysilyl)propyl]ethylenediamine and isopropanol in a mass ratio of 1:0.14-0.16:14-16, adjusting the pH to 3.8-4.2 with 0.1 mol / L acetic acid aqueous solution, stirring at 85-95℃ and 200-300 r / min for 5-7 h, filtering, washing with deionized water 3-5 times, and drying at 90-100℃ for 2-4 h.

[0018] As an optimization, the pre-modified microcrystalline cellulose in step (2) is prepared by mixing microcrystalline cellulose and N,N-dimethylformamide at a mass ratio of 1:20-30, stirring at 250-350 r / min and 85-95°C for 8-12 min, uniformly adding 0.17-0.18 times the volume of N,N-dimethylformamide thionyl chloride within 8-12 min, continuing to stir for 2-3 h, pouring into deionized water, stirring at 300-400 r / min for 10-20 min, filtering, washing with deionized water 6-8 times, and vacuum drying at 45-55°C for 11-13 h.

[0019] As an optimization, the casting solution in step (4) is prepared by mixing functionalized microcrystalline cellulose, N-(4-benzaldehyde)-carbazole, functionalized shell powder, N,N-dimethylformamide, functional monomers and ferric chloride in a mass ratio of 10-14:2-3:3-5:140-160:1:1, stirring at 75-85°C and 200-300 r / min for 10-14 min, and centrifuging at 8-12°C and 7000-9000 r / min for 8-12 min.

[0020] As an optimization, the functionalized microcrystalline cellulose is prepared by mixing aminosulfonic acid, N,N-dimethylformamide and modified microcrystalline cellulose at a mass ratio of 1:4-6:0.18-0.22, stirring at 75-85℃ and 200-300 r / min for 1-2 h, pouring into deionized water, letting stand for 20-30 min, filtering, washing with acetone 3-5 times, and vacuum drying at 45-55℃ for 11-13 h.

[0021] As an optimization, the zeolite mixture in step (4) is prepared by mixing zeolite and deionized water at a mass ratio of 1:5 to 7.

[0022] The application of a plant-based ion exchange membrane prepared by the method according to any one of claims 1 to 8 in the recovery of rare earth elements.

[0023] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0024] In preparing the plant-based ion exchange membrane, this invention involves reacting shell powder sequentially with N-[3-(trimethoxysilyl)propyl]ethylenediamine, dicyandiamide, and 9-allyl-9H-carbazole to obtain functionalized shell powder; reacting microcrystalline cellulose sequentially with thionyl chloride, carbazole, and aminosulfonic acid to obtain functionalized microcrystalline cellulose; reacting 2,7-bis(trifluoromethyl)-9H-carbazole with p-bromobenzaldehyde to obtain a functional monomer; and reacting the functionalized microcrystalline cellulose, N-(4-benzaldehyde)-carbazole, functionalized shell powder, N,N-dimethylformamide, and the functional monomer to form a mold, thereby obtaining the plant-based ion exchange membrane.

[0025] First, shell powder is reacted sequentially with N-[3-(trimethoxysilyl)propyl]ethylenediamine, dicyandiamide, and 9-allyl-9H-carbazole to prepare functionalized shell powder. A biguanide structure is formed on the surface of the shell powder through the reaction of dicyandiamide with amino groups. Biguanides can specifically interact with the ribosomal RNA portion of bacteria, blocking the normal chain reaction required for protein synthesis. They can also interact with the circular structure of bacterial DNA, blocking its replication and repair processes, leading to DNA strand breaks and damage, affecting bacterial replication and reproduction, and enhancing the antibacterial effect of the material.

[0026] Secondly, microcrystalline cellulose was reacted sequentially with thionyl chloride, carbazole, and aminosulfonic acid to prepare functionalized microcrystalline cellulose; 2,7-bis(trifluoromethyl)-9H-carbazole was reacted with p-bromobenzaldehyde to prepare functional monomers; functionalized microcrystalline cellulose, N-(4-benzaldehyde)-carbazole, functionalized shell powder, N,N-dimethylformamide, and functional monomers were reacted and molded to prepare a plant-based ion exchange membrane; carbazole was introduced onto the surface of cellulose through the reaction of cellulose with thionyl chloride and carbazole, and then reacted with carbazole, N-(4-benzaldehyde)-carbazole, and functional monomers on the surface of functionalized shell powder to form polycarbazole. The functional monomers in polycarbazole are rich in trifluoromethyl groups. The carbon-fluorine bond is a very strong chemical bond with high bond energy and short bond length, which gives the resulting membrane high chemical stability and makes it difficult to be destroyed in chemical reactions. The high electronegativity of trifluoromethyl groups allows them to attract surrounding electrons, giving the carbon atoms a certain positive charge. Furthermore, the small radius of the fluorine atoms in the trifluoromethyl group means that when they replace other atoms in the compound, they have a smaller impact on the molecular volume, further enhancing the corrosion resistance of the membrane. By forming polycarbazole, the carbazole monomer, functionalized microcrystalline cellulose, and functionalized shell powder are crosslinked together, enhancing the thermal stability of the membrane. Moreover, polycarbazole, as a stable polymer with a benzene ring, can also enhance the thermal stability of the membrane. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1

[0029] A method for preparing a plant-based ion exchange membrane mainly includes the following preparation steps:

[0030] (1) 200 mesh shell powder, N-[3-(trimethoxysilyl)propyl]ethylenediamine and isopropanol were mixed in a mass ratio of 1:0.14:14, the pH was adjusted to 3.8 with 0.1 mol / L acetic acid aqueous solution, stirred at 85℃ and 200 r / min for 5 h, filtered, washed 3 times with deionized water, and dried at 90℃ for 2 h to obtain pre-modified shell powder;

[0031] Pre-modified shell powder and 0.8 mol / L dilute hydrochloric acid were mixed evenly at a mass ratio of 1:4, and microwaved at 200 r / min, 45℃, and 400 W for 8 min to obtain a pre-modified shell powder mixture. Dicyandiamide and deionized water were mixed evenly at a mass ratio of 1:4 to obtain a dicyandiamide solution. The pre-modified shell powder mixture and dicyandiamide solution were mixed at a mass ratio of 1:0.18, and the pH was adjusted to 1 with 0.8 mol / L dilute hydrochloric acid. The mixture was microwaved at 200 r / min, 95℃, and 400 W for 13 min, poured into ethanol, allowed to stand for 18 min, filtered, washed three times with ethanol, and vacuum dried at -10℃ for 22 h to obtain modified shell powder.

[0032] Modified shell powder, 9-allyl-9H-carbazole and acetone were mixed at a mass ratio of 1:0.08:14, stirred at 45℃ and 200r / min for 38h, filtered, washed three times with acetone, and vacuum dried at -10℃ for 22h to obtain functionalized shell powder.

[0033] (2) Microcrystalline cellulose and N,N-dimethylformamide were mixed at a mass ratio of 1:20 and stirred at 250 r / min and 85℃ for 8 min. Within 8 min, 0.17 times the volume of N,N-dimethylformamide thionyl chloride was added at a uniform rate and stirring was continued for 2 h. The mixture was then poured into deionized water and stirred at 300 r / min for 10 min. The mixture was filtered, washed 6 times with deionized water, and vacuum dried at 45℃ for 11 h to obtain pre-modified microcrystalline cellulose.

[0034] Pre-modified microcrystalline cellulose, dimethyl sulfoxide and carbazole were mixed at a mass ratio of 1:25:0.18 and stirred at 85℃ and 200r / min for 11h. The mixture was then poured into deionized water, allowed to stand for 20min, filtered, washed three times with acetone, and vacuum dried at 45℃ for 11h to obtain modified microcrystalline cellulose.

[0035] Aminosulfonic acid, N,N-dimethylformamide and modified microcrystalline cellulose were mixed at a mass ratio of 1:4:0.18 and stirred at 75℃ and 200r / min for 1h. The mixture was then poured into deionized water, allowed to stand for 20min, filtered, washed three times with acetone, and vacuum dried at 55℃ for 11h to obtain functionalized microcrystalline cellulose.

[0036] (3) 2,7-bis(trifluoromethyl)-9H-carbazole, p-bromobenzaldehyde and NN dimethylformamide were mixed in a molar ratio of 1:1:14 and stirred for 25 min at 200 r / min, 55 °C and nitrogen protection. The mixture was then cooled to room temperature and dried under vacuum at -10 °C for 22 h to obtain the functional monomer.

[0037] (4) Zeolite and deionized water were mixed at a mass ratio of 1:5 to prepare a zeolite mixture; functionalized microcrystalline cellulose, N-(4-benzaldehyde)-carbazole, functionalized shell powder, N,N-dimethylformamide, functional monomers and ferric chloride were mixed at a mass ratio of 10:2:3:140:1:1, stirred at 75℃ and 200r / min for 10min, and centrifuged at 8℃ and 7000r / min for 8min to prepare a casting solution; the casting solution was evenly coated on a clean and dry glass plate with a thickness of 450μm, dried at 75℃ for 5h, scraped off, placed in the zeolite mixture, stood for 20min, removed, washed 5 times with deionized water, and vacuum dried at -10℃ for 22h to prepare an ion exchange membrane.

[0038] Example 2

[0039] A method for preparing a plant-based ion exchange membrane mainly includes the following preparation steps:

[0040] (1) 200 mesh shell powder, N-[3-(trimethoxysilyl)propyl]ethylenediamine and isopropanol were mixed in a mass ratio of 1:0.15:15, the pH was adjusted to 4 with 0.1 mol / L acetic acid aqueous solution, stirred at 90℃ and 250 r / min for 6 h, filtered, washed 4 times with deionized water, and dried at 95℃ for 3 h to obtain pre-modified shell powder;

[0041] Pre-modified shell powder and 0.8 mol / L dilute hydrochloric acid were mixed evenly at a mass ratio of 1:5, and microwaved for 10 min at 250 r / min, 50℃, and 400 W to obtain a pre-modified shell powder mixture. Dicyandiamide and deionized water were mixed evenly at a mass ratio of 1:5 to obtain a dicyandiamide solution. The pre-modified shell powder mixture and dicyandiamide solution were mixed at a mass ratio of 1:0.2, and the pH was adjusted to 1 with 0.8 mol / L dilute hydrochloric acid. The mixture was microwaved for 14 min at 250 r / min, 100℃, and 400 W, poured into ethanol, allowed to stand for 20 min, filtered, washed 4 times with ethanol, and vacuum dried at -5℃ for 24 h to obtain modified shell powder.

[0042] Modified shell powder, 9-allyl-9H-carbazole and acetone were mixed at a mass ratio of 1:0.1:15, stirred at 50℃ and 250r / min for 40h, filtered, washed 4 times with acetone, and vacuum dried at -5℃ for 24h to obtain functionalized shell powder.

[0043] (2) Microcrystalline cellulose and N,N-dimethylformamide were mixed at a mass ratio of 1:25 and stirred at 300 r / min and 90 °C for 10 min. Within 10 min, 0.175 times the volume of N,N-dimethylformamide thionyl chloride was added at a uniform rate and stirring was continued for 2.5 h. The mixture was then poured into deionized water and stirred at 350 r / min for 15 min. The mixture was filtered, washed 7 times with deionized water, and vacuum dried at 50 °C for 12 h to obtain pre-modified microcrystalline cellulose.

[0044] Pre-modified microcrystalline cellulose, dimethyl sulfoxide and carbazole were mixed at a mass ratio of 1:30:0.2 and stirred at 90℃ and 250r / min for 12h. The mixture was poured into deionized water, allowed to stand for 25min, filtered, washed 4 times with acetone, and dried under vacuum at 50℃ for 12h to obtain modified microcrystalline cellulose.

[0045] Aminosulfonic acid, N,N-dimethylformamide and modified microcrystalline cellulose were mixed at a mass ratio of 1:5:0.2 and stirred at 80℃ and 250r / min for 1.5h. The mixture was then poured into deionized water, allowed to stand for 25min, filtered, washed 4 times with acetone, and vacuum dried at 50℃ for 12h to obtain functionalized microcrystalline cellulose.

[0046] (3) 2,7-bis(trifluoromethyl)-9H-carbazole, p-bromobenzaldehyde and NN dimethylformamide were mixed in a molar ratio of 1:1:15 and stirred for 30 min at 250 r / min, 60 °C and nitrogen protection. The mixture was then cooled to room temperature and dried under vacuum at -5 °C for 24 h to obtain the functional monomer.

[0047] (4) Zeolite and deionized water were mixed at a mass ratio of 1:6 to prepare a zeolite mixture; functionalized microcrystalline cellulose, N-(4-benzaldehyde)-carbazole, functionalized shell powder, N,N-dimethylformamide, functional monomers and ferric chloride were mixed at a mass ratio of 12:2.5:4:150:1:1, stirred at 80℃ and 250r / min for 12min, and centrifuged at 10℃ and 8000r / min for 10min to prepare a casting solution; the casting solution was evenly coated on a clean and dry glass plate with a thickness of 500μm, dried at 80℃ for 6h, scraped off, placed in the zeolite mixture, stood for 25min, removed, washed 6 times with deionized water, and vacuum dried at -5℃ for 24h to prepare an ion exchange membrane.

[0048] Example 3

[0049] A method for preparing a plant-based ion exchange membrane mainly includes the following preparation steps:

[0050] (1) 200 mesh shell powder, N-[3-(trimethoxysilyl)propyl]ethylenediamine and isopropanol were mixed in a mass ratio of 1:0.16:16, the pH was adjusted to 4.2 with 0.1 mol / L acetic acid aqueous solution, stirred at 95℃ and 300 r / min for 7 h, filtered, washed 5 times with deionized water, and dried at 100℃ for 4 h to obtain pre-modified shell powder;

[0051] Pre-modified shell powder and 0.8 mol / L dilute hydrochloric acid were mixed evenly at a mass ratio of 1:6, and microwaved at 300 r / min, 55℃, and 400 W for 12 min to obtain a pre-modified shell powder mixture. Dicyandiamide and deionized water were mixed evenly at a mass ratio of 1:6 to obtain a dicyandiamide solution. The pre-modified shell powder mixture and dicyandiamide solution were mixed at a mass ratio of 1:0.22, and the pH was adjusted to 1 with 0.8 mol / L dilute hydrochloric acid. The mixture was microwaved at 300 r / min, 105℃, and 400 W for 17 min, poured into ethanol, allowed to stand for 22 min, filtered, washed 5 times with ethanol, and vacuum dried at 0℃ for 26 h to obtain modified shell powder.

[0052] Modified shell powder, 9-allyl-9H-carbazole and acetone were mixed at a mass ratio of 1:0.12:16, stirred at 55℃ and 300r / min for 42h, filtered, washed 5 times with acetone, and vacuum dried at 0℃ for 26h to obtain functionalized shell powder.

[0053] (2) Microcrystalline cellulose and N,N-dimethylformamide were mixed at a mass ratio of 1:30 and stirred at 350 r / min and 95℃ for 12 min. Within 12 min, 0.18 times the volume of N,N-dimethylformamide thionyl chloride was added at a uniform rate, and stirring was continued for 3 h. The mixture was then poured into deionized water and stirred at 400 r / min for 20 min. The mixture was filtered, washed 8 times with deionized water, and vacuum dried at 55℃ for 13 h to obtain pre-modified microcrystalline cellulose.

[0054] Pre-modified microcrystalline cellulose, dimethyl sulfoxide and carbazole were mixed at a mass ratio of 1:35:0.22 and stirred at 95℃ and 300r / min for 13h. The mixture was poured into deionized water, allowed to stand for 30min, filtered, washed 5 times with acetone, and vacuum dried at 55℃ for 13h to obtain modified microcrystalline cellulose.

[0055] Aminosulfonic acid, N,N-dimethylformamide and modified microcrystalline cellulose were mixed at a mass ratio of 1:6:0.22 and stirred at 85℃ and 300r / min for 2h. The mixture was then poured into deionized water, allowed to stand for 30min, filtered, washed 5 times with acetone, and vacuum dried at 55℃ for 13h to obtain functionalized microcrystalline cellulose.

[0056] (3) 2,7-bis(trifluoromethyl)-9H-carbazole, p-bromobenzaldehyde and NN dimethylformamide were mixed in a molar ratio of 1:1:16 and stirred for 35 min at 300 r / min, 65 °C and nitrogen protection. The mixture was then cooled to room temperature and dried under vacuum at 0 °C for 26 h to obtain the functional monomer.

[0057] (4) Zeolite and deionized water were mixed at a mass ratio of 1:7 to prepare a zeolite mixture; functionalized microcrystalline cellulose, N-(4-benzaldehyde)-carbazole, functionalized shell powder, N,N-dimethylformamide, functional monomers and ferric chloride were mixed at a mass ratio of 14:3:5:160:1:1, stirred at 85℃ and 300r / min for 14min, and centrifuged at 12℃ and 9000r / min for 12min to prepare a casting solution; the casting solution was evenly coated on a clean and dry glass plate with a thickness of 550μm, dried at 85℃ for 7h, scraped off, placed in the zeolite mixture, stood for 30min, taken out, washed 7 times with deionized water, and vacuum dried at 0℃ for 26h to prepare an ion exchange membrane.

[0058] Comparative Example 1

[0059] A method for preparing a plant-based ion exchange membrane mainly includes the following preparation steps:

[0060] The preparation method of the plant-based ion exchange membrane in Comparative Example 1 differs from that in Example 2 only in that the shell powder is not modified. The remaining steps are the same as in Example 2.

[0061] Comparative Example 2

[0062] A method for preparing a plant-based ion exchange membrane mainly includes the following preparation steps:

[0063] The preparation method of the plant-based ion exchange membrane in Comparative Example 2 differs from that in Example 2 in that steps (3) and (4) are omitted. Step (4) is modified as follows: Zeolite and deionized water are mixed at a mass ratio of 1:6 to obtain a zeolite mixture; functionalized microcrystalline cellulose, N-(4-benzaldehyde)-carbazole, functionalized shell powder, N,N-dimethylformamide, and ferric chloride are mixed at a mass ratio of 12:2.5:4:150:1, stirred at 80°C and 250 r / min for 12 min, and centrifuged at 10°C and 8000 r / min for 10 min to obtain a casting solution; the casting solution is evenly coated on a clean, dry glass plate with a thickness of 500 μm, dried at 80°C for 6 h, scraped off, placed in the zeolite mixture, allowed to stand for 25 min, removed, washed 6 times with deionized water, and vacuum dried at -5°C for 24 h to obtain the ion exchange membrane. The remaining steps are the same as in Example 2.

[0064] Comparative Example 3

[0065] A method for preparing a plant-based ion exchange membrane mainly includes the following preparation steps:

[0066] The preparation method of the plant-based ion exchange membrane in Comparative Example 3 differs from that in Example 2 in that steps (3) and (4) are omitted. Step (4) is modified as follows: Zeolite and deionized water are mixed at a mass ratio of 1:6 to obtain a zeolite mixture; functionalized microcrystalline cellulose, functionalized shell powder, and N,N-dimethylformamide are mixed at a mass ratio of 12:4:150, stirred at 80°C and 250 r / min for 12 min, and centrifuged at 10°C and 8000 r / min for 10 min to obtain a casting solution; the casting solution is evenly coated on a clean, dry glass plate with a thickness of 500 μm, dried at 80°C for 6 h, scraped off, placed in the zeolite mixture, allowed to stand for 25 min, removed, washed 6 times with deionized water, and vacuum dried at -5°C for 24 h to obtain the ion exchange membrane. The remaining steps are the same as in Example 2.

[0067] Test Example 1

[0068] Ion exchange capacity test

[0069] Test method: Samples of each embodiment and comparative example were cut into 5 cm diameter and 200 μm thick specimens. The dry weight of the membranes was recorded. The membranes were then immersed in a 10% hydrochloric acid aqueous solution for 24 h, followed by immersion in deionized water for 48 h. Next, the membranes were immersed in a 1 mol / L sodium chloride aqueous solution for 24 h. A sodium hydroxide aqueous solution was then prepared. Using phenolphthalein as an indicator, the hydrogen ion content in the sodium chloride aqueous solution after immersion was determined by molar titration. The ion exchange capacity was calculated as: ion exchange capacity = sodium hydroxide aqueous solution concentration × sodium hydroxide aqueous solution volume / membrane dry weight. The results are shown in Table 1.

[0070] Table 1

[0071] Ion exchange capacity Example 1 1.78meq. / g Example 2 1.80meq. / g Example 3 1.76meq. / g Comparative Example 1 1.75 meq. / g Comparative Example 2 1.79meq. / g Comparative Example 3 1.76meq. / g

[0072] A comparison of the experimental data in Table 1 shows that the plant-based ion exchange membrane prepared in this invention has a good ion exchange capacity.

[0073] Test Example 2

[0074] Corrosion resistance test

[0075] Test method: The films prepared in each example and comparative example were made into samples with a radius of 5 cm and a thickness of 200 μm. The samples were weighed, and then immersed in a 1M sodium hydroxide aqueous solution at 80℃ for 2 hours. They were washed 5 times with deionized water and then freeze-dried under vacuum at -5℃. The mass loss rate was tested, where the mass loss rate = [(initial mass - mass after alkali corrosion) / initial mass] × 100%. The results are shown in Table 2.

[0076] Table 2

[0077]

[0078]

[0079] A comparison of the experimental data in Table 2 shows that the plant-based ion exchange membrane prepared by this invention has good corrosion resistance.

[0080] A comparison of the experimental data from Examples 1, 2, and 3 and Comparative Example 2 in Table 2 reveals that Examples 1, 2, and 3 exhibit low mass loss rates. The difference between Comparative Example 2 and the Examples lies in the absence of added functional monomers. This indicates that the introduction of trifluoromethyl groups onto the membrane via polycarbazole polymerization is achieved. The carbon-fluorine bond of trifluoromethyl groups is a very strong chemical bond with high bond energy and short bond length, resulting in a membrane with high chemical stability that is difficult to break down during chemical reactions. Furthermore, the high electronegativity of trifluoromethyl groups allows it to attract surrounding electrons, giving the carbon atoms a certain positive charge. Additionally, the small radius of the fluorine atoms in the trifluoromethyl group minimizes the impact on molecular volume when they replace other atoms in the compound, further enhancing the membrane's stability and corrosion resistance.

[0081] Test Example 3

[0082] Antibacterial test

[0083] Test method: The membranes prepared in each example and comparative example were pulverized to 80 mesh, and 1g was tested according to GB / T31402-2015, where the selected bacterial species were Staphylococcus aureus and Escherichia coli. The results are shown in Table 3.

[0084] Table 3

[0085]

[0086]

[0087] A comparison of the experimental data in Table 3 shows that the plant-based ion exchange membrane prepared in this invention has good antibacterial ability.

[0088] A comparison of the experimental data from Examples 1, 2, and 3 and Comparative Example 1 in Table 3 reveals that Examples 1, 2, and 3 exhibit high antibacterial rates. The difference between Comparative Example 1 and the Examples lies in the absence of modification of the shell powder. This indicates that the biguanide structure formed on the surface of the shell powder through the reaction of dicyandiamide and amino groups can specifically interact with the ribosomal RNA portion of bacteria, blocking the normal chain reaction required for protein synthesis. It can also interact with the circular structure of bacterial DNA, blocking its replication and repair processes, leading to breakage and damage of the bacterial DNA chain, affecting bacterial replication and reproduction, and increasing the antibacterial rate of the material.

[0089] Test Example 4

[0090] Thermal stability test

[0091] Test method: The membranes prepared in each embodiment and comparative example were made into samples with a radius of 5 cm and a thickness of 200 μm. The thermal stability of the samples was characterized by thermogravimetric analysis. The membrane samples were heated from 30 °C to 300 °C under nitrogen protection using a simultaneous thermal analyzer at a heating rate of 10 °C / min. The mass loss rate was measured, where the mass loss rate = [(initial mass - mass at 400 °C) / initial mass] × 100%. The results are shown in Table 4.

[0092] Table 4

[0093] Quality loss rate Example 1 25.8％ Example 2 25.5％ Example 3 25.7％ Comparative Example 1 25.6％ Comparative Example 2 31.3％ Comparative Example 3 48.8％

[0094] A comparison of the experimental data in Table 4 shows that the plant-based ion exchange membrane prepared in this invention has good thermal stability.

[0095] A comparison of the experimental data of Examples 1, 2, 3 and Comparative Example 3 in Table 4 reveals that Examples 1, 2, and 3 have low mass loss rates. The difference between Comparative Example 3 and the Examples is that polycarbazole was not formed. This indicates that by forming polycarbazole, the materials are cross-linked, which enhances the thermal stability of the membrane. Furthermore, polycarbazole, as a stable polymer with benzene rings, can also enhance the thermal stability of the membrane.

[0096] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a plant-based ion exchange membrane, characterized in that, The preparation method of the plant-based ion exchange membrane mainly includes the following preparation steps: (1) Mix pre-modified shell powder and 0.8 mol / L dilute hydrochloric acid at a mass ratio of 1:4~6 until homogeneous, and microwave at 200~300 r / min, 45~55℃, and 400W microwave power for 8~12 min to obtain a pre-modified shell powder mixture. Mix dicyandiamide and deionized water at a mass ratio of 1:4~6 until homogeneous to obtain a dicyandiamide solution. Mix the pre-modified shell powder mixture and the dicyandiamide solution at a mass ratio of 1:0.18~0.22, adjust the pH to 1 with 0.8 mol / L dilute hydrochloric acid, and microwave at 200~300 r / min, 95~105W microwave power for 8~12 min to obtain a pre-modified shell powder mixture. Microwave at 400W for 13-17 minutes, pour into ethanol, let stand for 18-22 minutes, filter, wash with ethanol 3-5 times, and vacuum dry at -10-0℃ for 22-26 hours to obtain modified shell powder; mix modified shell powder, 9-allyl-9H-carbazole and acetone at a mass ratio of 1:0.08-0.12:14-16, stir at 45-55℃ and 200-300 r / min for 38-42 hours, filter, wash with acetone 3-5 times, and vacuum dry at -10-0℃ for 22-26 hours to obtain functionalized shell powder; (2) Mix pre-modified microcrystalline cellulose, dimethyl sulfoxide and carbazole at a mass ratio of 1:25~35:0.18~0.22, stir at 85~95℃ and 200~300r / min for 11~13h, pour into deionized water, let stand for 20~30min, filter, wash with acetone 3~5 times, and vacuum dry at 45~55℃ for 11~13h to obtain modified microcrystalline cellulose; (3) Mix 2,7-bis(trifluoromethyl)-9H-carbazole, p-bromobenzaldehyde and NN dimethylformamide in a molar ratio of 1:1:14~16, stir for 25~35 min at 200~300 r / min, 55~65℃ under nitrogen protection, cool to room temperature, and vacuum dry at -10~0℃ for 22~26 h to obtain the functional monomer; (4) The casting solution is evenly coated on a clean and dry glass plate with a thickness of 450~550μm. It is dried at 75~85℃ for 5~7h, scraped off, placed in zeolite mixture, and left to stand for 20~30min. It is then taken out, washed with deionized water 5~7 times, and vacuum dried at -10~0℃ for 22~26h to obtain an ion exchange membrane.

2. The method for preparing a plant-based ion exchange membrane according to claim 1, characterized in that, The pre-modified shell powder in step (1) is prepared by mixing 200-mesh shell powder, N-[3-(trimethoxysilyl)propyl]ethylenediamine and isopropanol in a mass ratio of 1:0.14~0.16:14~16, adjusting the pH to 3.8~4.2 with 0.1mol / L acetic acid aqueous solution, stirring at 85~95℃ and 200~300r / min for 5~7h, filtering, washing with deionized water 3~5 times, and drying at 90~100℃ for 2~4h.

3. The method for preparing a plant-based ion exchange membrane according to claim 1, characterized in that, The pre-modified microcrystalline cellulose in step (2) is prepared by mixing microcrystalline cellulose and N,N-dimethylformamide at a mass ratio of 1:20~30, stirring at 250~350 r / min and 85~95℃ for 8~12 min, adding 0.17~0.18 times the volume of N,N-dimethylformamide thionyl chloride at a uniform rate within 8~12 min, continuing to stir for 2~3 h, pouring into deionized water, stirring at 300~400 r / min for 10~20 min, filtering, washing with deionized water 6~8 times, and vacuum drying at 45~55℃ for 11~13 h.

4. The method for preparing a plant-based ion exchange membrane according to claim 1, characterized in that, The casting solution in step (4) is prepared by mixing functionalized microcrystalline cellulose, N-(4-benzaldehyde)-carbazole, functionalized shell powder, N,N-dimethylformamide, functional monomers and ferric chloride in a mass ratio of 10~14:2~3:3~5:140~160:1:1, stirring at 75~85℃ and 200~300r / min for 10~14min, and centrifuging at 8~12℃ and 7000~9000r / min for 8~12min.

5. The method for preparing a plant-based ion exchange membrane according to claim 4, characterized in that, The functionalized microcrystalline cellulose is prepared by mixing aminosulfonic acid, N,N-dimethylformamide and modified microcrystalline cellulose at a mass ratio of 1:4~6:0.18~0.22, stirring at 75~85℃ and 200~300r / min for 1~2h, pouring into deionized water, letting stand for 20~30min, filtering, washing with acetone 3~5 times, and vacuum drying at 45~55℃ for 11~13h.

6. The method for preparing a plant-based ion exchange membrane according to claim 1, characterized in that, The zeolite mixture in step (4) is prepared by mixing zeolite and deionized water at a mass ratio of 1:5~7.

7. The application of a plant-based ion exchange membrane prepared by the method according to any one of claims 1 to 6 in the recovery of rare earth elements.

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