Polymer-based ion exchange membrane, method for preparing the same, and use thereof

Abstract

The application discloses a polymer-based ion exchange membrane and a preparation method and application thereof, and is characterized in that dimethylaminoethyl methacrylate (DMAEMA) and methyl methacrylate (MMA) are used as raw materials in a specific proportion (1:3), a high polymer is generated through a free radical polymerization reaction, and the high polymer is grafted into brominated polyphenyl ether through a Grubbs reaction, so that a series of anion exchange membranes are prepared. The ion exchange membrane prepared by the application has excellent ion exchange capacity, water content, swelling rate and conductivity, and has high social use value and application prospect.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, and in particular to a polymer-based ion exchange membrane, its preparation method, and its applications. Background Technology

[0002] Membrane technology is gradually showing its important role and bright prospects in daily life. In particular, as a new separation technology, it has been widely used in gas separation, material separation and water treatment processes. As a branch of membrane materials, ion exchange membranes are also widely used in energy and power, biopharmaceuticals and wastewater reuse due to their good ion conductivity and strong hydrophilicity.

[0003] An ion exchange membrane is a membrane-like exchange resin with selective permeability and containing active ion exchange groups. It consists of three parts: fixed groups, mobile ions on the groups, and a polymeric framework. Ion exchange membranes can be classified into cation exchange membranes and anion exchange membranes according to the type of charge, and also into heterogeneous, homogeneous, and semi-homogeneous ion exchange membranes according to their macroscopic structure. Heterogeneous ion exchange membranes are made from binders and fine powdered ion exchange resin through intensive refining, stretching, and hot pressing processes. They exhibit two structural states: powdered ion exchange resin with active groups and inert binders, resulting in a non-uniform and discontinuous chemical structure. Homogeneous ion exchange membranes introduce active groups into a polymer supported by an inert substrate, causing a chemical reaction that binds the membrane material to the active groups, forming a uniform chemical structure. They are characterized by low electrical resistance and excellent electrochemical performance. Semi-homogeneous ion exchange membranes introduce active groups into the polymer, but these groups cannot chemically bond, resulting in a macroscopic structure between heterogeneous and homogeneous ion exchange membranes.

[0004] However, existing homogeneous ion exchange membranes generally suffer from low ion exchange capacity and conductivity. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention provides a polymer-based ion exchange membrane, its preparation method, and its application.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing a polymer-based ion exchange membrane includes the following steps:

[0008] S1. Mix methyl methacrylate (MMA) and dimethyl aminoethyl methacrylate (DMAEMA) and dissolve them completely in anhydrous ethanol. Then add azobisisobutyronitrile (AIBN) as an initiator and react at 60-80°C for 12-24 hours under argon atmosphere to obtain a polymer solution.

[0009] S2. The polymer solution obtained in step S1 is rotary evaporated at 35-55°C. The resulting viscous polymer is repeatedly purified by dissolving in chloroform and precipitating in n-hexane. The purified polymer is placed in a vacuum drying oven and dried to obtain polymer D1M3.

[0010] S3. Add polymer D1M3 to an organic solvent and stir until completely dissolved to obtain a polymer D1M3 solution with a mass concentration of 5-12% for later use.

[0011] S4. Add the purified brominated polyphenylene ether (BPPO) to an organic solvent and stir until completely dissolved to obtain a BPPO solution with a mass concentration of 2-3% for later use.

[0012] S5. Add BPPO solution to polymer D1M3 solution, stir and react for 2-3 hours. Spread the resulting reaction solution evenly on a glass slide and dry. The resulting film is the target ion exchange membrane.

[0013] Preferably, in step S1, the molar ratio of MMA to DMAEMA is 1:3, and the amount of AIBN added is 1% of the total mass of the polymer monomers.

[0014] Preferably, in step S2, the temperature of the vacuum drying oven is controlled at 50-55°C, and the drying time is 48-50 hours.

[0015] Preferably, the organic solvent in steps S3 and S4 is N-methyl-2-pyrrolidone.

[0016] Preferably, in step S4, the degree of bromination of the purified brominated polyphenylene ether is 23%.

[0017] Preferably, in step S5, the volume ratio of the polymer D1M3 solution to the BPPO solution is (0.2–0.75):4. The specific reaction formula between polymer D1M3 and brominated polyphenylene ether is as follows: Figure 1 As shown.

[0018] Preferably, in step S5, the glass slide temperature is 60–80°C and the drying time is 3–8 hours.

[0019] The ion exchange membrane prepared by the above method can be applied in fields such as energy and power, biopharmaceuticals, and wastewater reuse.

[0020] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0021] This invention uses dimethylaminoethyl methacrylate (DMAEMA) and methyl methacrylate (MMA) in a specific ratio (1:3) as raw materials to generate a polymer via free radical polymerization. The polymer is then grafted onto brominated polyphenylene ether via the Mensøe-Glaucon reaction to obtain a series of anion exchange membranes. Experimental results in the examples show that when the volume ratio of polymer D1M3 solution to BPPO solution is 0.75:4, the resulting anion exchange capacity (IEC) of the anion exchange membrane is 2.5 mmol / g. -1 The water content is 26.9%, the swelling rate is 10.0%, and the electrical conductivity is 23.5 mS / cm. -1 It has high social value and application prospects. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 The specific reaction formula is for polymer D1M3 and brominated polyphenylene ether;

[0024] Figure 2 This is a diagram showing the anion exchange capacity of the ion exchange membranes prepared in Examples 2-4 of this invention;

[0025] Figure 3 The water content diagrams are for the ion exchange membranes prepared in Examples 1-4 of this invention.

[0026] Figure 4 Linear swelling ratio diagrams of the ion exchange membranes prepared in Examples 1-4 of this invention;

[0027] Figure 5 The conductivity diagrams are for the ion exchange membranes prepared in Examples 1-4 of this invention.

[0028] Figure 6 The infrared spectra of the ion exchange membranes prepared in Examples 1-4 of this invention are shown below.

[0029] Figure 7 Scanning electron microscope (SEM) images of the ion exchange membranes prepared in Examples 1-4 of this invention (a. Surface morphology of M2; b. Cross-sectional morphology of M2; c. Surface morphology of M3; d. Cross-sectional morphology of M3; e. Surface morphology of M4; f. Cross-sectional morphology of M4). Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1

[0032] In this embodiment, the ion exchange membrane is prepared according to the following steps:

[0033] S1. Mix 2.00 mL of methyl methacrylate (MMA) and 6.28 mL of dimethylaminoethyl methacrylate (DMAEMA), add 120.96 mL of anhydrous ethanol to fully dissolve them, then add 1% (by mass) of azobisisobutyronitrile (AIBN) and react at 70 °C for 24 h under argon atmosphere to obtain a polymer solution.

[0034] S2. The polymer solution obtained in step S1 was rotary evaporated at 50°C. The resulting viscous polymer was dissolved in chloroform and purified repeatedly by precipitation with n-hexane. The purified polymer was placed in a vacuum drying oven and dried at 50°C for 48 hours to obtain the final product, named polymer D1M3.

[0035] S3. Take 4.0680g of polymer D1M3 and add it to 35.62mL of N-methyl-2-pyrrolidone. Stir until completely dissolved to obtain a polymer D1M3 solution with a mass concentration of 10% for later use.

[0036] S4. Take 3.0000g of purified brominated polyphenylene ether (BPPO, bromination degree 23%) and add it to 26.32mL of N-methyl-2-pyrrolidone. Stir until completely dissolved to obtain BPPO solution for later use.

[0037] S5. Add 4.00 mL of BPPO solution to 0 mL of polymer D1M3 solution and stir for 2 h. Spread the prepared solution evenly on a glass slide at 80 °C and dry for 3 h. The resulting film is the target ion exchange membrane, named M1.

[0038] Example 2

[0039] In this embodiment, the ion exchange membrane was prepared using the same process as in Example 1, except that the volume of the polymer D1M3 solution in step S5 was 0.25 mL, and the resulting ion exchange membrane was named M2.

[0040] Example 3

[0041] In this embodiment, the ion exchange membrane was prepared using the same process as in Example 1, except that the volume of the polymer D1M3 solution in step S5 was 0.50 mL, and the resulting ion exchange membrane was named M3.

[0042] Example 4

[0043] In this embodiment, the ion exchange membrane was prepared using the same process as in Example 1, except that the volume of the polymer D1M3 solution in step S5 was 0.75 mL, and the resulting ion exchange membrane was named M4.

[0044] The ion exchange membranes prepared in Examples 1-4 were subjected to the following performance characterization tests:

[0045] 1. Ion exchange capacity (IEC)

[0046] Weigh a small amount of membrane sample and place it in a 60℃ oven at constant weight for 24 hours, then weigh it again and immerse it in 1 mol L... -1 Soak in NaCl solution for 24 hours, rinse and soak with plenty of deionized water for 24 hours, then soak in 0.5 mol L... -1 In Na2SO4 solution for 24 hours, use 0.01 mol -1 Titration with AgNO3 solution, using potassium dichromate as an indicator, resulted in a color change from bright yellow to brownish-yellow. The volume of AgNO3 consumed was V. AgNO3 The mass of the membrane sample after constant weight is denoted as W1. The formula for calculating the anion exchange capacity is shown in equation (1), where C AgNO3 The molar concentration of AgNO3:

[0047]

[0048] from Figure 2 The trend shows that the ion exchange capacity of ion exchange membranes M2, M3, and M4 increases sequentially, specifically in the following order: IEC M2 (1.2mmol g -1 ) <IEC M3 (1.4 mmol g) -1 ) <IEC M4 (2.5mmol g -1 This is because the tertiary amine groups in polymer D1M3 react with BPPO groups to generate quaternary amine groups. Quaternary amine groups carry a positive charge, thus accelerating the transfer rate between ions. As the amount of polymer D1M3 solution added increases, more quaternary amine groups are grafted, and therefore the ion exchange capacity shows an upward trend.

[0049] 2. Water content (WU) and swelling ratio (SR)

[0050] Water content refers to the amount of water inherent in the ion exchange membrane that is combined with the active functional groups; linear swelling rate refers to the percentage of the volume of the expanded portion of the membrane after it is immersed in water, relative to the original volume.

[0051] Cut a 20mm × 20mm sample membrane and dry it in a 60℃ oven for 24 hours to maintain constant weight. Measure the side length L1 and weight W2 of the sample membrane. Then immerse the membrane in deionized water for 24 hours. After that, remove the sample membrane and gently wipe off the water droplets remaining on it. Press the membrane down and measure its side length L2 and weight W3.

[0052] The formula for calculating water content is shown in equation (2):

[0053]

[0054] The formula for calculating the swelling ratio is shown in equation (3):

[0055]

[0056] from Figure 3 It can be seen that the water content of ion exchange membranes M2, M3, and M4 increases sequentially, in the following order: WU M2 (2.0%) <WU M3 (10.1%) <WU M4 (26.9%). This phenomenon occurs because the tertiary amine group in polymer D1M3 reacts with the bromomethyl group in BPPO to form a quaternary amine group. The quaternary amine group is hydrophilic. The more polymer D1M3 solution is added, the more hydrophilic the quaternary amine group and the membrane will become, and thus the water content of the ion exchange membrane will increase as shown in the figure above.

[0057] from Figure 4 It can be seen that the linear swelling ratios of ion exchange membranes M2, M3, and M4 show an increasing trend, specifically: SR M2 (2.0%) <SR M3 (8.0%) <SR M4 (10.0%). The reason for the sequential increase is that a quaternary ammonium group is obtained by grafting between the tertiary amine group and the bromomethyl group. The linear swelling rate is related to the hydrophilicity of the membrane, and the hydrophilicity of the membrane is related to the quaternary ammonium group. Therefore, the increase of the amount of polymer will increase the linear swelling rate of the membrane.

[0058] 3. Hydroxide conductivity

[0059] Hydroxide conductivity is an important indicator for evaluating ion exchange membranes, as it effectively reflects their performance. The Mensøein reaction between tertiary amine groups and bromomethyl groups in polymers generates numerous quaternary amine active sites, thus enabling rapid conduction with anions.

[0060] Cut out a rectangular sample membrane of 10mm × 40mm using a knife, and immerse it in 1mol L... -1 Immerse the membrane in NaOH solution for 12 hours, then carefully remove it and repeatedly rinse the surface with deionized water to ensure that the OH groups on the membrane surface are washed away. - The chemical resistance of the ion exchange membrane, after being rinsed with deionized water, was measured under alternating current. The membrane resistance was denoted as R, the distance between the electrodes as D, the membrane thickness as T, and the width as W.

[0061] OH of membrane samples - The formula for calculating conductivity (σ) is shown in equation (4):

[0062]

[0063] like Figure 5 It can be seen that the higher the amount of polymer D1M3, the higher the OH content. - The conductivity also increases accordingly. This is mainly because as the amount of polymer added increases, the hydrophilicity of the membrane becomes stronger, enabling it to absorb more water molecules. Therefore, the hydroxide ion conductivity shows an upward trend, specifically: σ M1 (1.3mS cm -1 )<σ M2 (2.8mS cm -1 )<σ M3 (18.4mS cm -1 )<σ M4 (23.5mScm -1 ).

[0064] 4. Infrared spectroscopy characterization

[0065] Four membranes, M1, M2, M3, and M4, were dried at 60℃ for 24 hours. Fine powder was carefully scraped from the surface and extracted for infrared spectroscopy measurement. A small amount of the fine powder scraped from each membrane was mixed with potassium bromide and pressed into a pellet. Finally, the infrared spectra of the four membranes were measured.

[0066] like Figure 6 As shown, the four membranes are at 1601 cm⁻¹ -1 and 1470cm -1 A skeletal vibrational peak of the benzene ring appeared at 2850 cm⁻¹. -1 A stretching vibration peak of CH on saturated alkanes appeared at 2920 cm⁻¹. -1 A stretching vibration peak of CH on the benzene ring appeared at 3500 cm⁻¹. Four films showed peaks at 3500 cm⁻¹. -1 Characteristic peaks were present at all locations, with M2, M3, and M4 becoming increasingly prominent. This is due to the membrane absorbing water during the test. At 1680 cm⁻¹... -1Strong absorption peaks are observed at M2, M3, and M4, but no peak is observed at M1. This is because of the quaternary ammonium group produced after the reaction between the bromomethyl group in the base film and the tertiary amine group in the polymer.

[0067] 5. Scanning Electron Microscope (SEM)

[0068] M2, M3, and M4 were dried at 60℃ for 24 hours. Then, the surface and cross-section of the films were cut out, adhered to the sample stage, uniformly sputtered with gold, and subjected to SEM analysis. Finally, the surface and cross-section of M1, M2, M3, and M4 were photographed, and the final images were saved. The results are as follows: Figure 7 As shown.

[0069] from Figure 7 (a) to Figure 7 (f) Surface and cross-sectional SEM images show that the ion exchange membrane has a dense membrane morphology; from Figure 7 (a) Figure 7 (b) Figure 7 (e) and Figure 7 (f) The surface of the membrane is relatively rough, which is due to the tearing during the cutting process. Figure 7 (c) and Figure 7 (d) The surface and cross-section are intact and smooth, indicating that the surface and cross-section of the membrane are relatively uniform and flat.

[0070] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a polymer-based ion exchange membrane, characterized in that, Includes the following steps: S1. Mix 2.00 mL of methyl methacrylate (MMA) and 6.28 mL of dimethylaminoethyl methacrylate (DMAEMA), add 120.96 mL of anhydrous ethanol to dissolve them completely, then add 1% (by mass) of azobisisobutyronitrile (AIBN) and react at 70°C for 24 h under argon atmosphere to obtain a polymer solution. S2. The polymer solution obtained in step S1 is rotary evaporated at 50°C. The resulting viscous polymer is dissolved in chloroform and purified by repeated purification with n-hexane precipitation. The purified polymer is placed in a vacuum drying oven and dried at 50°C for 48 hours to obtain the final product, named polymer D1M3. S3. Take 4.0680 g of polymer D1M3 and add it to 35.62 mL of N-methyl-2-pyrrolidone. Stir until completely dissolved to obtain a polymer D1M3 solution with a mass concentration of 10% for later use. S4. Take 3.0000 g of purified brominated polyphenylene ether with a bromination degree of 23% and add it to 26.32 mL of N-methyl-2-pyrrolidone. Stir until completely dissolved to obtain BPPO solution for later use. S5. Add 4.00 mL of BPPO solution to 0.25 mL of polymer D1M3 solution and stir for 2 h. Spread the prepared solution evenly on a glass slide at 80℃ and dry for 3 h. The resulting film is the target ion exchange membrane.

2. A polymer-based ion exchange membrane prepared by the preparation method of claim 1.

3. A method for preparing a polymer-based ion exchange membrane, characterized in that, Includes the following steps: S1. Mix 2.00 mL of methyl methacrylate (MMA) and 6.28 mL of dimethylaminoethyl methacrylate (DMAEMA), add 120.96 mL of anhydrous ethanol to dissolve them completely, then add 1% (by mass) of azobisisobutyronitrile (AIBN) and react at 70°C for 24 h under argon atmosphere to obtain a polymer solution. S2. The polymer solution obtained in step S1 is rotary evaporated at 50°C. The resulting viscous polymer is dissolved in chloroform and purified by repeated purification with n-hexane precipitation. The purified polymer is placed in a vacuum drying oven and dried at 50°C for 48 hours to obtain the final product, named polymer D1M3. S3. Take 4.0680 g of polymer D1M3 and add it to 35.62 mL of N-methyl-2-pyrrolidone. Stir until completely dissolved to obtain a polymer D1M3 solution with a mass concentration of 10% for later use. S4. Take 3.0000 g of purified brominated polyphenylene ether with a bromination degree of 23% and add it to 26.32 mL of N-methyl-2-pyrrolidone. Stir until completely dissolved to obtain BPPO solution for later use. S5. Add 4.00 mL of BPPO solution to 0.50 mL of polymer D1M3 solution and stir for 2 h. Spread the prepared solution evenly on a glass slide at 80℃ and dry for 3 h. The resulting film is the target ion exchange membrane.

4. A polymer-based ion exchange membrane prepared by the preparation method of claim 3.

5. A method for preparing a polymer-based ion exchange membrane, characterized in that, Includes the following steps: S1. Mix 2.00 mL of methyl methacrylate (MMA) and 6.28 mL of dimethylaminoethyl methacrylate (DMAEMA), add 120.96 mL of anhydrous ethanol to dissolve them completely, then add 1% (by mass) of azobisisobutyronitrile (AIBN) and react at 70°C for 24 h under argon atmosphere to obtain a polymer solution. S2. The polymer solution obtained in step S1 is rotary evaporated at 50°C. The resulting viscous polymer is dissolved in chloroform and purified by repeated purification with n-hexane precipitation. The purified polymer is placed in a vacuum drying oven and dried at 50°C for 48 hours to obtain the final product, named polymer D1M3. S3. Take 4.0680 g of polymer D1M3 and add it to 35.62 mL of N-methyl-2-pyrrolidone. Stir until completely dissolved to obtain a polymer D1M3 solution with a mass concentration of 10% for later use. S4. Take 3.0000 g of purified brominated polyphenylene ether with a bromination degree of 23% and add it to 26.32 mL of N-methyl-2-pyrrolidone. Stir until completely dissolved to obtain BPPO solution for later use. S5. Add 4.00 mL of BPPO solution to 0.75 mL of polymer D1M3 solution and stir for 2 h. Spread the prepared solution evenly on a glass slide at 80℃ and dry for 3 h. The resulting film is the target ion exchange membrane.

6. A polymer-based ion exchange membrane prepared by the preparation method of claim 5.

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