Preparation method and application of a double cross-linking network anion exchange membrane

Abstract

This invention discloses a method for preparing a double-crosslinked network anion exchange membrane and its application. The method for preparing the double-crosslinked network anion exchange membrane includes the following steps: (1) dissolving polyvinylidene fluoride in DFM to obtain a transparent solution A; (2) dissolving p-vinylbenzyltrimethylammonium chloride in solution A to obtain solution B; (3) dissolving 1-vinylimidazolium in solution B to obtain solution C; (4) dissolving benzoyl peroxide in solution C to obtain solution D; (5) heating solution D and then adding 1,4-p-dichlorobenzyl to obtain solution E; (6) heating solution E and then spreading the resulting brown transparent solution onto a clean glass plate and drying it to obtain the double-crosslinked network anion exchange membrane. This invention provides the application of the prepared double-crosslinked network anion exchange membrane in electrodialysis desalination. The preparation process of this invention is simple, achieves good desalination performance of the anion exchange membrane, and improves the stability and mechanical strength of the membrane.

Description

Technical Field

[0001] This invention relates to a method for preparing a double cross-linked network anion exchange membrane and its application in electrodialysis desalination. Background Technology

[0002] Freshwater scarcity is a widespread problem facing nearly half the world's population, and the situation is worsening. Seawater desalination may be a permanent solution to the freshwater shortage in severely water-scarce cities. With continuous advancements in technology, membrane technology has emerged, effectively addressing water pollution and significantly impacting the development of my country's water treatment industry. Using membrane technology to treat water resources can substantially improve water quality and reduce the content of harmful substances, making it a crucial water treatment technology for future development in my country. Continuously optimizing water treatment technologies is vital for improving water resource utilization efficiency and alleviating water scarcity. Membrane technology is a critical technology in the water treatment process, effectively improving treatment results, and its development prospects are very promising.

[0003] Polyvinylidene fluoride (PVDF) is a highly non-reactive thermoplastic fluoropolymer. Compared to perfluorinated compounds, it has better plasticity, is soluble in organic solvents, and is easy to process. It is soluble in highly polar solvents such as dimethylacetamide and possesses excellent properties such as anti-aging, chemical resistance, weather resistance, and UV radiation resistance. It can be used as an engineering plastic for manufacturing sealing rings, corrosion-resistant equipment, capacitors, coatings, insulating materials, and ion exchange membrane materials. Currently, electrodialysis technology is used for seawater desalination. Electrodialysis is a relatively mature technology in membrane separation and is widely used in brackish water desalination, being one of the main methods for seawater desalination worldwide. Electrodialysis also features low energy consumption, small footprint, simple operation, and no phase change during desalination. However, traditional electrodialysis membranes often cannot achieve high desalination efficiency due to swelling and water migration.

[0004] In summary, we have developed a double-crosslinked network anion exchange membrane with high desalination efficiency, which possesses the excellent properties of polyvinylidene fluoride (PVDF) material, to provide a solution for the problem of seawater desalination using novel electrodialysis methods.

[0005] Technical content

[0006] To address the aforementioned problems in the existing technology, this invention provides a method for preparing an anion exchange membrane with a double cross-linked network. This preparation process is simple, and by enabling the anion exchange membrane to have better component dispersion and a more stable ion exchange structure, it achieves good desalination performance and improves the membrane's stability and mechanical strength.

[0007] The second problem to be solved by the present invention is to provide the application of the anion exchange membrane in electrodialysis desalination.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a method for preparing a double cross-linked network anion exchange membrane, comprising the following steps:

[0010] (1) Dissolve a certain mass of polyvinylidene fluoride in N,N-dimethylformamide and stir thoroughly at 60-70°C to obtain a transparent solution A;

[0011] (2) According to the mass ratio of vinylbenzyltrimethylammonium chloride to polyvinylidene fluoride of 1:2 to 3.5, p-vinylbenzyltrimethylammonium chloride is dissolved in solution A at 60 to 70°C to obtain solution B;

[0012] (3) Dissolve 1-vinylimidazole in solution B at 60-70℃ according to the mass ratio of polyvinylidene fluoride to 1-vinylimidazole of 2:1 to 1:1 to obtain solution C;

[0013] (4) According to the mass ratio of polyvinylidene fluoride to benzoyl peroxide of 40:1 to 50:1, benzoyl peroxide is dissolved in solution C at 60 to 70°C to obtain solution D;

[0014] (5) Heat solution D to 80-90℃ and react for 8-12 hours. Then cool it down to 40-50℃ and add 1,4-dichlorobenzyl chloride that has been dissolved in a certain amount of N,N-dimethylformamide. The mass ratio of polyvinylidene fluoride to 1,4-dichlorobenzyl chloride is 14-30:1. Stir thoroughly to obtain solution E.

[0015] (6) Heat solution E to 70-90℃ and react for 6-8 hours. Spread the resulting brown transparent solution on a clean glass plate and dry it under vacuum at 60-90℃ for 12-24 hours to obtain a double cross-linked network anion exchange membrane.

[0016] Preferably, in step (1), 5 to 10 mL of N,N-dimethylformamide is required per gram of polyvinylidene fluoride.

[0017] Preferably, in step (5), the mass ratio of polyvinylidene fluoride to 1,4-dichlorobenzyl is 14 to 25:1.

[0018] Preferably, the thickness of the double cross-linked network anion exchange membrane is controlled at 170–190 μm.

[0019] This invention first prepares a polymer solution by dissolving polyvinylidene fluoride in an organic solvent. Then, by introducing p-vinylbenzyltrimethylammonium chloride and 1-vinylimidazole, a proton-carrying cross-linked polymer material is generated under the condition of an initiator. Furthermore, 1,4-dichlorobenzyl chloride with halogen group active sites is introduced to graft the tertiary amine group in 1-vinylimidazole, which is then further quaternized to facilitate ion conduction in the membrane, thus obtaining a modified semi-homogeneous polyvinylidene fluoride anion exchange membrane.

[0020] Secondly, the present invention provides the application of the aforementioned double cross-linked network anion exchange membrane in electrodialysis desalination.

[0021] Preferably, the salt is NaCl.

[0022] The double cross-linked network anion exchange membrane of the present invention can be used for seawater desalination.

[0023] Compared with existing materials and technologies, the present invention has the following advantages:

[0024] 1) The anion exchange membrane prepared by the preparation method proposed in this invention has low surface resistance and high ion exchange capacity.

[0025] 2) The anion exchange membrane prepared using the present invention uses polyvinylidene fluoride as the main skeleton and has excellent mechanical properties and membrane stability.

[0026] 3) The anion exchange membrane prepared by this invention has a simple preparation process and simple synthesis steps, and is easy to industrialize.

[0027] 4) The anion exchange membrane prepared by this invention has excellent performance in electrodialysis desalination, can effectively enhance ion transfer, and has good water permeability, making it suitable for electrodialysis desalination. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the electrodialysis desalination device used in an embodiment of the present invention. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions will be further described clearly and completely below through embodiments, but the scope of protection of this invention is not limited thereto. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0030] The semi-homogeneous anion exchange membrane prepared by the method of the present invention has good desalination performance. It achieves good desalination performance by improving the dispersion of components and a more stable ion exchange structure, and the preparation method is simple.

[0031] Example 1

[0032] (1) Weigh 20g of polyvinylidene fluoride and dissolve it in N,N-dimethylformamide, wherein each gram of polyvinylidene fluoride requires 5mL of N,N-dimethylformamide. Stir thoroughly at 65℃ to obtain a transparent solution A.

[0033] (2) Dissolve 6g of p-vinylbenzyltrimethylammonium chloride in solution A at 65℃ to obtain solution B;

[0034] (3) Dissolve 10g of 1-vinylimidazolium in solution B and stir vigorously at 65℃ for 15min to obtain solution C;

[0035] (4) Dissolve 0.5g of benzoyl peroxide in solution C by vigorous stirring at 65℃ to obtain solution D;

[0036] (5) Heat solution D to 85°C and react for 12 hours. Then cool it down to 50°C and add 0.7 g of 1,4-dichlorobenzyl that has been dissolved in 5 ml of N,N-dimethylformamide. Stir thoroughly to obtain solution E.

[0037] (6) Heat solution E to 80°C and react for 6 hours. Spread the resulting brown transparent solution onto a clean glass plate and vacuum dry at 80°C for 12 hours to obtain a semi-homogeneous anion exchange membrane with a thickness of 180 μm and high desalination performance. It is denoted as AEM-1.

[0038] Example 2

[0039] (1) Weigh 20g of polyvinylidene fluoride and dissolve it in N,N-dimethylformamide, wherein each gram of polyvinylidene fluoride requires 5mL of N,N-dimethylformamide. Stir thoroughly at 65℃ to obtain a transparent solution A.

[0040] (2) Dissolve 7g of p-vinylbenzyltrimethylammonium chloride in solution A at 65℃ to obtain solution B;

[0041] (3) Dissolve 10g of 1-vinylimidazolium in solution B and stir vigorously at 65℃ for 15min to obtain solution C;

[0042] (4) Dissolve 0.5g of benzoyl peroxide in solution C by vigorous stirring at 65℃ to obtain solution D;

[0043] (5) Heat solution D to 85°C and react for 12 hours. Then cool it down to 50°C and add 0.9 g of 1,4-dichlorobenzyl that has been dissolved in 5 ml of N,N-dimethylformamide. Stir thoroughly to obtain solution E.

[0044] (6) Heat solution E to 80°C and react for 6 hours. Spread the resulting brown transparent solution onto a clean glass plate and vacuum dry at 80°C for 12 hours to obtain a semi-homogeneous anion exchange membrane with a thickness of 178 μm and high desalination performance. It is denoted as AEM-2.

[0045] Example 3

[0046] (1) Weigh 20g of polyvinylidene fluoride and dissolve it in N,N-dimethylformamide, wherein each gram of polyvinylidene fluoride requires 5mL of N,N-dimethylformamide. Stir thoroughly at 65℃ to obtain a transparent solution A.

[0047] (2) Dissolve 8g of p-vinylbenzyltrimethylammonium chloride in solution A at 65℃ to obtain solution B;

[0048] (3) Dissolve 10g of 1-vinylimidazolium in solution B and stir vigorously at 65℃ for 15min to obtain solution C;

[0049] (4) Dissolve 0.5g of benzoyl peroxide in solution C by vigorous stirring at 65℃ to obtain solution D;

[0050] (5) Heat solution D to 85°C and react for 12 hours. Then cool it down to 50°C and add 1.1 g of 1,4-dichlorobenzyl that has been dissolved in 5 ml of N,N-dimethylformamide. Stir thoroughly to obtain solution E.

[0051] (6) Heat solution E to 80°C and react for 6 hours. Spread the resulting brown transparent solution onto a clean glass plate and vacuum dry at 80°C for 12 hours to obtain a semi-homogeneous anion exchange membrane with a thickness of 182 μm and high desalination performance. It is denoted as AEM-3.

[0052] Example 4

[0053] (1) Weigh 20g of polyvinylidene fluoride and dissolve it in N,N-dimethylformamide, wherein each gram of polyvinylidene fluoride requires 5mL of N,N-dimethylformamide. Stir thoroughly at 65℃ to obtain a transparent solution A.

[0054] (2) Dissolve 9g of p-vinylbenzyltrimethylammonium chloride in solution A at 65℃ to obtain solution B;

[0055] (3) Dissolve 10g of 1-vinylimidazolium in solution B and stir vigorously at 65℃ for 15min to obtain solution C;

[0056] (4) Dissolve 0.5g of benzoyl peroxide in solution C by vigorous stirring at 65℃ to obtain solution D;

[0057] (5) Heat solution D to 85°C and react for 12 hours. Then cool it down to 50°C and add 1.4 g of 1,4-dichlorobenzyl that has been dissolved in 5 ml of N,N-dimethylformamide. Stir thoroughly to obtain solution E.

[0058] (6) Heat solution E to 80°C and react for 6 hours. Spread the resulting brown transparent solution onto a clean glass plate and vacuum dry at 80°C for 12 hours to obtain a semi-homogeneous anion exchange membrane with a thickness of 184 μm and high desalination performance. It is denoted as AEM-4.

[0059] The performance of the prepared anion exchange membrane was then tested:

[0060] Test 1: Membrane thickness, membrane surface resistance, and ion exchange capacity data are shown in Table 1.

[0061] Table 1. Types and properties of ion exchange membranes used.

[0062] Membrane types Thickness (μm) <![CDATA[Sheet resistance (Ω·cm 2 )]]> <![CDATA[Ion exchange capacity (mmol·g –1 )]]> AMX 170 3.53 1.28 AEM-1 180 2.86 1.32 AEM-2 178 2.35 1.34 AEM-3 182 2.76 1.30 AEM-4 184 2.84 1.34

[0063] Test 2: To evaluate the desalination performance of the prepared anion exchange membrane, a current density (I = 15 mA·cm⁻¹) was used. -2 An electrochemical experiment was conducted to remove NaCl. The electrodialysis desalination apparatus used in the experiment contained four compartments, and the effective area of ​​the ion-exchange membrane being tested was 19.625 cm². 2 Test equipment such as Figure 1 As shown. The cation exchange membrane (CEM) used in the electrodialysis device was a CEM-Type-II cation exchange membrane manufactured by Fuji Electric Corporation of Japan, while the anion exchange membrane used as the control group was an AMX type anion exchange membrane manufactured by Astom Corporation of Japan. During the test, 90 mL of 0.5 mol / L solution was added to the concentrate compartment (CC) and the dilute compartment (DC) of the device, respectively. -1 NaCl solution. Meanwhile, the solution in the electrode chamber is 0.3 mol / L. -1 Na₂SO₄ solution was used, and a pump was used to circulate the solution at a set flow rate. Each compartment was circulated for at least 0.5 hours before testing to remove air bubbles. During the experiment, CC and DC were stirred with mechanical stirrers to ensure uniform solution concentration in each compartment. The ionic conductivity of the NaCl solution in the concentrated and dilute compartments was recorded every 30 minutes, along with the voltage across the electrodialysis apparatus. The NaCl removal rate (%) during the electrodialysis desalination process was calculated. The results are shown in Table 2. The results indicate that the desalination performance of the anion exchange membranes prepared in Examples 1-4 of this invention is no less than that of the commercial AMX membrane, and the desalination performance of the anion exchange membranes prepared in Examples 2-4 even exceeds that of the commercial AMX membrane.

[0064] Table 2. NaCl removal rate in the desalination system at different time periods.

[0065]

[0066]

[0067] At current density (I = 15 mA·cm) -2 After an electrochemical experiment to remove NaCl was conducted for 360 min, the final concentration and dilute solution volumes of the prepared anion exchange membrane and the commercial AMX membrane after 360 min of desalination were compared. The remaining solution in the corresponding concentration and dilute compartments was extracted using a pipette, and the corresponding volumes were measured using a graduated cylinder. The results are shown in Table 3. The results indicate that the anion exchange membranes prepared in Examples 1-4 of this invention have water permeability performance comparable to that of the commercial AMX membrane.

[0068] Table 3. Volume of final concentration / dilute chamber solution for different samples using AMX

[0069] Sample number Final volume of the concentration chamber (ml) Final volume of the dilute chamber (ml) AMX 84.5 75.1 AEM-1 85.6 74.1 AEM-2 84.8 74.9 AEM-3 82.1 77.5 AEM-4 83.6 76.8

[0070] The present invention has been specifically demonstrated and described through the above preferred embodiments. However, those skilled in the art should understand that various changes in form and detail may be made to the present invention without departing from the spirit and scope of the invention as defined in the appended claims, and all such changes shall be within the scope of protection of the present invention.

Claims

1. A method for preparing a double cross-linked network anion exchange membrane, characterized in that: The preparation method includes the following steps: (1) Dissolve a certain mass of polyvinylidene fluoride in N,N-dimethylformamide and stir thoroughly at 60-70°C to obtain a transparent solution A; (2) According to the mass ratio of vinylbenzyltrimethylammonium chloride to polyvinylidene fluoride of 1:2 to 3.5, p-vinylbenzyltrimethylammonium chloride is dissolved in solution A at 60 to 70°C to obtain solution B; (3) Dissolve 1-vinylimidazole in solution B at 60-70℃ according to the mass ratio of polyvinylidene fluoride to 1-vinylimidazole of 2:1 to 1:1 to obtain solution C; (4) According to the mass ratio of polyvinylidene fluoride to benzoyl peroxide of 40:1 to 50:1, benzoyl peroxide is dissolved in solution C at 60 to 70°C to obtain solution D; (5) Heat solution D to 80-90℃ and react for 8-12 hours. Then cool it down to 40-50℃ and add 1,4-dichlorobenzyl chloride that has been dissolved in a certain amount of N,N-dimethylformamide. The mass ratio of polyvinylidene fluoride to 1,4-dichlorobenzyl chloride is 14-30:

1. Stir thoroughly to obtain solution E. (6) Heat solution E to 70-90℃ and react for 6-8 hours. Spread the resulting brown transparent solution on a clean glass plate and dry it under vacuum at 60-90℃ for 12-24 hours to obtain a double cross-linked network anion exchange membrane.

2. The preparation method according to claim 1, characterized in that: In step (1), 5 to 10 mL of N,N-dimethylformamide is required per gram of polyvinylidene fluoride.

3. The preparation method according to claim 1, characterized in that: In step (5), the mass ratio of polyvinylidene fluoride to 1,4-dichlorobenzyl is 14 to 25:

1.

4. The preparation method according to claim 1, characterized in that: The thickness of the double cross-linked network anion exchange membrane is controlled at 170–190 μm.

5. The application of the double cross-linked network anion exchange membrane prepared by the preparation method according to any one of claims 1-4 in electrodialysis desalination.

6. The application as described in claim 5, characterized in that: The salt is NaCl.

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