An acid-resistant anion exchange membrane, a preparation method and application thereof

Abstract

The application discloses an acid-resistant anion exchange membrane, a preparation method and application thereof, and relates to the technical field of ion exchange membranes. The acid-resistant anion exchange membrane is prepared by the following steps: taking N-allyl benzylamine as a monomer, copolymerizing the monomer with a crosslinking agent in a solvent, coating the copolymer on a base film, and further crosslinking the copolymer in a hot press through a Friedel-Crafts reaction. The anion exchange membrane prepared through the above technical means is suitable for use in nitric acid (salt) system electrodialysis for acid concentration or acid production, and has the advantages of good acid resistance, low surface resistance, stable long-term performance and long service life.

Description

Technical Field

[0001] This invention belongs to the field of polymer material synthesis, specifically relating to an acid-barrier anion exchange membrane, its preparation method, and its application. Background Technology

[0002] Electrodialysis is a mature technology in membrane separation engineering. Due to its advantages of energy saving, pollution-free operation, high-efficiency separation, and good stability, it has become an irreplaceable separation technology, widely used in chemical, light industry, metallurgy, papermaking, and pharmaceutical industries. It is particularly valued for its application in pure water preparation and waste treatment, such as acid and alkali recovery, electroplating wastewater treatment, and the recovery of beneficial substances from wastewater. However, in the separation and purification of nitrate (salt) systems, the acidity and strong oxidizing properties of nitric acid can shorten membrane life and cause poor performance stability, significantly limiting the application of electrodialysis technology in nitrate (salt) system separation.

[0003] Anion exchange membranes are one of the key materials in electrodialysis technology, largely determining the current efficiency and energy consumption of the separation process. Their selectivity is one of the most critical performance characteristics of the membrane. An ideal anion exchange membrane allows only anions to pass through, but ordinary anion exchange membranes generally suffer from hydrogen ion leakage. Therefore, acid-resistant anion exchange membranes have emerged.

[0004] Chinese patent (CN 111992259 A) discloses a method for preparing an acid-barrier anion exchange membrane. The method involves copolymerizing a monomer with both active vinyl and epoxy groups with a functional monomer containing unsaturated double bonds, followed by liquid membrane scraping and solvent evaporation to obtain the acid-barrier anion exchange membrane. However, due to the presence of residual double bonds in the structure, the membrane's density and oxidation resistance need to be further improved. Summary of the Invention

[0005] To address the aforementioned problems in the existing technology, the present invention aims to provide an acid-barrier anion exchange membrane and its preparation method. Considering the proton transport mechanism in the membrane, the present invention selects monomers containing weak base groups to maximize the reduction of water content without reducing the ion exchange capacity of the membrane. At the same time, the membrane is subjected to secondary cross-linking to increase the membrane density and enhance the acid-barrier effect. It has advantages such as stable membrane structure, strong acid resistance, and strong oxidation resistance.

[0006] The acid-barrier anion exchange membrane of this invention is used for the concentration or production of nitric acid in nitrate (salt) systems via electrodialysis. It features good acid barrier effect, low surface resistivity, long-term stable performance, and long lifespan, making it suitable for use in nitrate (salt) systems to concentrate or produce acid.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] This invention provides a method for preparing an acid-barrier anion exchange membrane. The method uses N-allylbenzylamine as a monomer, which is copolymerized with a crosslinking agent in a solvent. The copolymer is then coated onto a base membrane and further crosslinked in a hot press via a Friedel-Crafts reaction to obtain an anion exchange membrane with excellent acid-barrier properties and resistance to acids, alkalis, and oxidation.

[0009] A method for preparing an acid-barrier anion exchange membrane, comprising the following steps:

[0010] S1: N-allylbenzylamine, crosslinking agent and solvent are mixed, and an initiator is added to carry out a copolymerization reaction to obtain a preliminary casting solution;

[0011] S2: Add Friedel-Crafts reaction catalyst to the initial casting solution to obtain the final casting solution;

[0012] S3: The base membrane is immersed in the final casting solution and then hot-pressed to obtain an acid-resistant anion exchange membrane.

[0013] In this invention, the crosslinking agent in S1 is selected from one or more of polyvinylbenzenes, preferably one or more of divinylbenzene, trivinylbenzene, divinyltoluene, and divinylethylbenzene.

[0014] In this invention, the solvent in S1 is selected from one or more of dipolar aprotic solvents, preferably one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), and N-methylpyrrolidone (NMP).

[0015] In this invention, the initiator in S1 is selected from one or more of oil-soluble azo radical initiators, oil-soluble peroxide radical initiators, and oil-soluble redox initiation systems, preferably one or more of azobisisoheptanenitrile, azobisisobutyronitrile (AIBN), benzoyl peroxide, lauryl peroxide, and N,N-dibutylaniline.

[0016] In this invention, the amount of crosslinking agent added in S1 is 4-10 wt% of the mass of N-allylbenzylamine.

[0017] In this invention, the amount of initiator added in S1 is 0.2-2 wt% of the total mass of N-allylbenzylamine and crosslinking agent.

[0018] In this invention, the amount of solvent added in S1 is 2-5 times the total mass of N-allylbenzylamine and crosslinking agent;

[0019] In this invention, the copolymerization reaction described in S1 is carried out at a temperature of 60-100℃ for a time of 6-10 hours.

[0020] In this invention, the Friedel-Crafts reaction catalyst described in S2 is an acidic catalyst, preferably a Lewis acid of aprotic acid, and more preferably ferric chloride and / or aluminum chloride.

[0021] In this invention, the amount of Friedel-Crafts reaction catalyst added in S2 is 0.2-1.5 wt% of the total mass of N-allylbenzylamine and crosslinking agent in S1.

[0022] In this invention, the base film in S3 is selected from any one of nylon mesh, PET mesh, and PP mesh;

[0023] Preferably, the base film has a mesh size of 180-250.

[0024] In this invention, the immersion time in step S3 is 5-10 minutes. The immersion operation is a conventional method in the field, which usually involves immersing the base film in the casting solution for a certain period of time. The specific operating parameters can be selected as needed.

[0025] In this invention, the hot pressing reaction described in S3 is carried out at a temperature of 30-100℃ for a time of 2-12 hours.

[0026] The hot-pressing reaction is carried out at a pressure of 0.1-0.4 MPaG.

[0027] The present invention also provides an acid-barrier anion exchange membrane prepared by the above method.

[0028] The present invention also provides the application of the acid-barrier anion exchange membrane prepared by the above method, which is suitable for fields such as nitrate (salt) system electrodialysis and bipolar membrane electrodialysis, and is especially suitable for the concentration or production of nitrate in nitrate (salt) system electrodialysis.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] The acid-barrier anion exchange membrane prepared by the method of this invention minimizes water content without reducing the membrane's ion exchange capacity. Simultaneously, secondary cross-linking increases the membrane's density and enhances its acid-barrier effect. This acid-barrier anion exchange membrane exhibits stable structure, strong acid and oxygen resistance, and is suitable for use in nitrate (salt) systems for acid concentration or production. Detailed Implementation

[0031] The technical solutions of the present invention are illustrated by the following examples; however, these examples do not limit the present invention.

[0032] The main raw material sources in the embodiments and comparative examples of this invention are as follows. Unless otherwise specified, other raw materials and reagents were obtained through commercially available channels:

[0033] reagents factory Specification N-allylbenzylamine Aladdin ＞97.0％ N,N-Dimethylformamide Inokai 99.9％ N,N-Dimethylacetamide Inokai 99.9％ N-Methylpyrrolidone Inokai 98％ Divinylbenzene Merck 80％ Anhydrous aluminum chloride Aladdin 99％ Anhydrous ferric chloride Aladdin 98％ AIBN Inokai 98％ Trivinylbenzene Inokai 98％ PP mesh Shanghai Yongheng Wire Mesh Manufacturing Co., Ltd. 200 mesh Acrylamide Inokai 99％

[0034] Example 1:

[0035] The steps for preparing an acid-barrier anion exchange membrane are as follows:

[0036] S1 Synthetic Preliminary Casting Solution

[0037] 640g of N,N-dimethylformamide was added to the reactor, followed by 200g of N-allylbenzylamine and 17.5g of divinylbenzene under stirring. Then 2.14g of AIBN was added and stirred to dissolve. The copolymerization reaction was carried out at 80°C for 8 hours to obtain the preliminary casting solution.

[0038] S2 Synthesis Final Casting Solution

[0039] Add the above preliminary casting solution to the immersion tank, add 2g of anhydrous ferric chloride while stirring, and stir to dissolve to obtain the final casting solution;

[0040] S3 fully immerses the PP mesh in the casting solution, removes it, and places it in a hot press. After hot pressing at 60℃ and 0.2MPaG for 8 hours, the membrane is removed to obtain an acid-resistant anion exchange membrane.

[0041] Example 2

[0042] The steps for preparing an acid-barrier anion exchange membrane are as follows:

[0043] S1 Synthetic Preliminary Casting Solution

[0044] 1000g N,N-dimethylacetamide was added to the reactor, followed by 200g N-allylbenzylamine and 20g trivinylbenzene under stirring. Then 4.2g benzoyl peroxide was added and stirred to dissolve. The copolymerization reaction was carried out at 60°C for 10 hours to obtain the preliminary casting solution.

[0045] S2 Synthesis Final Casting Solution

[0046] Add the above preliminary casting solution to the impregnation tank, add 3g of anhydrous aluminum chloride while stirring, and stir to dissolve to obtain the final casting solution;

[0047] S3 fully immerses the PP mesh in the final casting solution, removes it, and places it in a hot press at 100℃ and 0.4MPaG for 2 hours to obtain an acid-resistant anion exchange membrane.

[0048] Example 3

[0049] The steps for preparing an acid-barrier anion exchange membrane are as follows:

[0050] 420g of N-methylpyrrolidone was added to the reactor, followed by 200g of N-allylbenzylamine and 8g of divinylbenzene under stirring. Then 0.4g of AIBN was added and stirred to dissolve. The copolymerization reaction was carried out at 100°C for 6 hours to obtain the preliminary casting solution.

[0051] S2 Synthesis Final Casting Solution

[0052] Add the above preliminary casting solution to the immersion tank, add 0.4g of anhydrous ferric chloride while stirring, and stir to dissolve to obtain the final casting solution;

[0053] S3 fully immerses the PP base membrane in the final casting solution, removes it, and places it in a hot press at 30°C and 0.1 MPaG for 12 hours to obtain an acid-resistant anion exchange membrane.

[0054] Comparative Example 1

[0055] The anion exchange membrane was prepared by referring to the method of Example 1, except that N-allylbenzylamine was replaced with acrylamide, while other operations and conditions remained unchanged.

[0056] Comparative Example 2

[0057] The method of Example 1 is used, except that divinylbenzene is not added in S1, while other operations and conditions remain unchanged, to obtain an anion exchange membrane.

[0058] Comparative Example 3

[0059] The method is the same as in Example 1, except that step S2 is omitted and the preliminary casting solution of S1 is directly used in S3, while other operations and conditions remain unchanged, to obtain anion exchange membrane.

[0060] Comparative Example 4

[0061] The method of Example 1 is used, except that Friedel-Crafts reaction catalyst is added before the copolymerization reaction in step S1, step S2 is omitted, and other operations and conditions remain unchanged to obtain anion exchange membrane.

[0062] The performance of the prepared anion exchange membrane is then tested:

[0063] In Embodiments 1-3 and Comparative Examples 1-4 of this invention, the performance test parameters and corresponding test methods are as follows:

[0064] The test methods for membrane thickness, ion exchange capacity, and sheet resistivity are as described in HY / T-166.1-2013.

[0065] Test 1: Acid / Oxidation Resistance Test

[0066] The membrane materials prepared in the above embodiments and comparative examples were immersed in 4 mol / L nitric acid for 96 h. The membrane thickness, ion exchange capacity, and sheet resistance were measured before and after the immersion. The results are shown in Table 1.

[0067] Table 1

[0068]

[0069] Test 2: Acid Barrier Performance Test

[0070] The concentration limit test method in standard T / CAEPI 19-2019 was used to concentrate 1 mol / L nitric acid as an evaluation system for membrane acid barrier performance. The results are shown in Table 2.

[0071] Table 2

[0072]

Claims

1. A method for preparing an acid-resistant anion exchange membrane, characterized by the steps of The method comprises the following steps: S1: mixing N-allyl benzylamine, a crosslinking agent and a solvent, adding an initiator, and performing a copolymerization reaction to obtain a preliminary casting solution; S2: adding a Friedel-Crafts reaction catalyst to the preliminary casting solution to obtain a final casting solution; S3: immersing a base film in the final casting solution, and then performing a hot-pressing reaction to obtain an acid-resistant anion exchange membrane.

2. The production method according to claim 1, characterized by, The crosslinking agent in S1 is selected from one or more of polyvinylbenzene; and / or The solvent in S1 is selected from one or more of a dipolar aprotic solvent; and / or The initiator in S1 is selected from one or more of an oil-soluble azo radical initiator, an oil-soluble peroxide radical initiator, and an oil-soluble redox initiation system.

3. The preparation method according to claim 2, characterized in that, The crosslinking agent is selected from one or more of divinylbenzene, trivinylbenzene, divinyltoluene and divinyl ethylbenzene.

4. The production method according to claim 2, characterized by, The solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone.

5. The preparation method according to claim 2, characterized in that, The initiator is selected from one or more of azobis isonitrile, azobis isobutyronitrile, benzoyl peroxide, lauryl amine peroxide and N,N-dibutyl aniline.

6. The method of claim 1, wherein, The crosslinking agent in S1 is added in an amount of 4-10wt% of the mass of N-allyl benzylamine; and / or The initiator in S1 is added in an amount of 0.2-2wt% of the total mass of N-allyl benzylamine and the crosslinking agent; and / or The solvent in S1 is added in an amount of 2-5 times the total mass of N-allyl benzylamine and the crosslinking agent.

7. The preparation method according to claim 1, characterized in that, The copolymerization reaction in S1 is performed at a temperature of 60-100℃ for 6-10h.

8. The method of claim 1, wherein, The Friedel-Crafts reaction catalyst in S2 is an acidic catalyst; and / or The Friedel-Crafts reaction catalyst in S2 is added in an amount of 0.2-1.5wt% of the total mass of N-allyl benzylamine and the crosslinking agent in S1.

9. The production method according to claim 8, characterized by, The Friedel-Crafts reaction catalyst is a Lewis acid of a non-protic acid.

10. The method of claim 9, wherein, The Friedel-Crafts reaction catalyst is iron chloride and / or aluminum chloride.

11. The method of claim 1, wherein, The base film in S3 is selected from any one of nylon mesh cloth, PET mesh cloth and PP mesh cloth.

12. The method of claim 1, wherein, The base film in S3 has a mesh number of 180-250.

13. The method of claim 1, wherein, The immersion in S3 is performed for 5-10min.

14. The method of claim 1, wherein, The hot-pressing reaction in S3 is performed at a temperature of 30-100℃ for 2-12h; and / or The hot-pressing reaction in S3 is performed at a pressure of 0.1-0.4MPaG.

15. An acid-resistant anion exchange membrane prepared by the method in any one of claims 1-14.

16. Use of the acid-resistant anion exchange membrane prepared by the method in any one of claims 1-14 or the acid-resistant anion exchange membrane in claim 15 in the field of nitric acid and nitrate system electrodialysis and bipolar membrane electrodialysis.

17. Use according to claim 16, characterized in that, The acid-resistant anion exchange membrane is suitable for use in concentrating or producing nitric acid in a nitric acid and nitrate system electrodialysis.

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