A method for preparing a monovalent anion-selective and solvent-resistant ion exchange membrane

Abstract

The application discloses a preparation method of a monovalent anion selective and solvent-resistant ion exchange membrane, which comprises the following steps: (1) preparing long-side-chain 3-(6-bromohexyl)-1-butylimidazole with an imidazole structure; (2) preparing polyarylether sulfone (PAES) containing amino groups; (3) respectively dissolving side-chain 3-(6-bromohexyl)-1-butylimidazole (BIm), silane coupling agent 3-chloropropyltrimethoxysilane (CPTMS) and main-chain polyarylether sulfone (PAES) and mixing them according to a certain feeding ratio to obtain a casting solution, and pouring the casting solution on a glass flat plate and drying at 60-100 DEG C to obtain the anion exchange membrane. The monovalent anion selective and solvent-resistant ion exchange membrane prepared by the application has low membrane surface resistance, low swelling rate, high organic solvent resistance and high selectivity.

Description

Technical Field

[0001] This invention relates to the field of polymer materials, specifically to a method for preparing a monovalent anion-selective and solvent-resistant ion exchange membrane. Background Technology

[0002] Membrane separation technology is characterized by low energy consumption, simple operation, and strong adaptability, and is widely used in wastewater treatment, seawater desalination, and gas separation. In industries such as petrochemicals, food processing, and biopharmaceuticals, the separation of chemical substances from organic solvents is frequently involved (J.Membr.Sci.2017,538,41–49). Traditional ion exchange membrane materials (such as polysulfone, polyethersulfone, and polystyrene) experience membrane swelling (or even dissolution) in aqueous environments containing organic solvents, leading to reduced separation performance. This significantly limits the application of electrodialysis technology in complex industrial environments (J.Membr.Sci.1997,123(1)143–14). Therefore, researching and developing high-performance solvent-resistant membranes to broaden the application of membrane technology in industrial fields is of great significance.

[0003] There are generally three methods to improve the solvent resistance of membranes: chemical crosslinking, organic-inorganic hybridization, and the construction of an intermediate layer. Nanoparticle materials such as silica have wide applications in the preparation of organic-inorganic hybrid membranes. Organic-inorganic hybrid membranes prepared using silane coupling agents as modifiers possess the chemical stability of inorganic SiO2 and the functional properties of organic polymers, while also constructing a three-dimensional crosslinked network structure within the membrane. This invention proposes to use polyarylene ether sulfone (PAES) as the main chain, adding side chains and silane coupling agents. The polymer charging gives the prepared membrane ion selectivity while simultaneously constructing a three-dimensional crosslinked network, enhancing dimensional stability and achieving long-term resistance to organic solvents. PAES has a rigid structure and excellent mechanical stability, thermal stability, and certain chemical stability. The addition of side chains and silane coupling agents further endows the PAES membrane with excellent monovalent ion selectivity, solvent resistance, heat resistance, and antifouling properties, thus enabling IEMs to be better applied in practical applications of organic solvent desalination. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a monovalent anion-selective and solvent-resistant ion exchange membrane.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing a monovalent anion-selective and solvent-resistant ion exchange membrane includes the following steps:

[0007] (1) A certain amount of 1,6-dibromohexane was placed in a round-bottom flask and dissolved in solvent; then a certain amount of butylimidazolium was added to a constant-pressure dropping funnel and dissolved in solvent to obtain a dilute solution; subsequently, the dilute butylimidazolium solution was added dropwise to the dilute 1,6-dibromohexane solution and heated and stirred. As the reaction proceeded, a white precipitate gradually appeared; after the reaction was completed, the precipitate was filtered and the filtrate was collected; the filtrate was concentrated by evaporating the solvent, and the concentrated liquid was dried in a vacuum drying oven to remove the residual solvent, resulting in a long side chain with an imidazole structure as shown in formula (I), named: 3-(6-bromohexyl)-1-butylimidazolium (BIm).

[0008]

[0009] (2) A certain amount of three monomers, 4,4'-difluorodiphenyl sulfone, 2,2'-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, and hexafluorobisphenol A, were dissolved in NMP. Potassium carbonate was used as a salt-forming agent. The reaction was carried out at 145°C for 4 hours under nitrogen protection, and then the temperature was raised to 165°C for another 3 hours. After the reaction was completed, the mixture was cooled to room temperature and poured into isopropanol. The mixture was stirred continuously to obtain a yellow-green precipitate. After washing with deionized water several times, the precipitate was dried in a vacuum drying oven to obtain a random copolymer of polyarylether sulfone (PAES) containing amino groups, as shown in formula (III), with a molecular weight of 30,000 to 60,000.

[0010]

[0011] (3) Preparation of anion exchange membrane: Weigh a certain amount of side chain (I), crosslinking agent 3-chloropropyltrimethoxysilane (II) and PAES (III), and dissolve them in polar solvents respectively; first, mix the side chain and PAES according to a certain feeding ratio, and after sufficient reaction, add the crosslinking agent to the mixture and mix thoroughly. Heat and stir to obtain a clear and transparent casting solution. After cooling to room temperature and vacuum degassing, cast it onto a clean glass plate and vacuum dry at 60-100℃ for 12-36 hours to obtain an anion exchange membrane PAES-BIm-CPTMS with both monovalent anion selectivity and solvent resistance. Its chemical structure is shown in formula (IV):

[0012]

[0013] This invention introduces imidazole side chains and crosslinking agent 3-chloropropyltrimethoxysilane, and controls the ratio of side chains to crosslinking agents. The crosslinking agent is tightly wrapped with the main chain to form a three-dimensional network structure. The side chains charge the polymer and generate new chemical bonds during the crosslinking process, thereby enabling the membrane to have solvent resistance and selectivity while ensuring low membrane surface resistance.

[0014] Furthermore, the reaction temperature in step (1) is 30-70℃ and the reaction time is 12-36 hours, preferably 40℃ and 24 hours.

[0015] Furthermore, the solvent mentioned in step (1) is one or more of acetonitrile, acetone, and tetrahydrofuran, preferably acetone.

[0016] Furthermore, the weakly polar solvent mentioned in step (1) is one or more of diethyl ether, ethyl acetate, and n-hexane, preferably with alternating washing with diethyl ether and ethyl acetate.

[0017] Furthermore, in step (2), the molar ratio of 2,2'-bis(3-amino-4-hydroxyphenyl)hexafluoropropane to hexafluorobisphenol A in the polyarylene sulfone PAES is 7:3.

[0018] Furthermore, in step (3), the PAES functionalization temperature is 30-90℃ and the reaction time is 6-48 hours, preferably 80℃ for 12 hours and then 60℃ for 8 hours.

[0019] Furthermore, the polar solvent mentioned in step (3) is N-methylpyrrolidone.

[0020] Furthermore, the vacuum drying temperature in step (3) is 80°C and the time is 24 hours.

[0021] Beneficial effects:

[0022] This invention prepares a series of cross-linked polyarylene ether sulfone-based anion exchange membranes (AEMs) for electrodialysis. The optimized AEMs exhibit high IEC (internal electrochemical resistance), low membrane surface resistivity, and high transport number. The abundant ion exchange groups in the AEMs can establish suitable ion channels to reduce ion transport resistance. The optimized AEMs demonstrate low water absorption and swelling rates in water and various organic solvents, achieving good dimensional stability. Furthermore, due to their three-dimensional cross-linked network structure, the long side chains are tightly entangled with the main chain, reducing ether bond vibrations in the main chain, resulting in a more stable, dense structure and stronger resistance to organic solvents. The organic solvent resistance of the AEMs was evaluated. First, prolonged immersion in various organic solvents showed no dissolution or morphological change. Then, selectivity tests were performed on the AEMs treated with different organic solvents. The selectivity showed no significant decrease, and the current efficiency was high with low energy consumption, both superior to commercial AMX membranes, demonstrating excellent organic solvent resistance and practical application value. Attached Figure Description

[0023] Figure 1 This is a physical image of the AEMs obtained in Embodiment 4 of the present invention.

[0024] Table 1 shows the physicochemical properties of the anionic AEMs prepared in Examples 1–6 of this invention. Detailed Implementation

[0025] To further illustrate the technical solution of the present invention, the preferred embodiments of the present invention are described below in conjunction with specific examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the claims of the present invention.

[0026] Example 1:

[0027] Preparation of polyarylene ether sulfone: 10.18 g (40 mmol) of 4,4'-difluorodiphenyl sulfone, 10.25 g (28 mmol) of 2,2'-bis(3-amino-4-hydroxyphenyl)hexafluoropropane and 4.03 g (12 mmol) of 2,2'-bis(4-hydroxyphenyl)hexafluoropropane were added to a 250 mL round-bottom flask. NMP was used as the solvent (120 mL), and 11.20 g of K₂CO₃ was added as a catalyst. The reaction was carried out at 145 °C for 4 hours under a nitrogen atmosphere, followed by a further reaction at 165 °C for 3 hours. The solution was cooled to room temperature and poured into 800 mL of isopropanol, and stirred to obtain a yellow-green flocculent polymer. After repeated washing with deionized water, the polymer was vacuum dried at 80°C for 24 hours to obtain 17.54 g of amino-containing polyarylene ether sulfone (PAES-NH2,2,2'-bis(3-amino-4-hydroxyphenyl)hexafluoropropane in a molar fraction of 70%), with a molecular weight of 56,600.

[0028] Preparation of the side chain: 50 mL of acetone was placed in a 250 mL round-bottom three-necked flask. Under a nitrogen atmosphere, 40 mmol (9.677 g) of 1,6-dibromohexane was added and stirred to dissolve. Then, 40 mmol (4.964 g) of butylimidazole was added dropwise. The mixture was heated to 40 °C and stirred for 24 hours. As the reaction proceeded, a white precipitate gradually appeared. After the reaction was completed, the precipitate was filtered, and the filtrate was collected. The filtrate was evaporated by rotary evaporation to obtain a small amount of solid and concentrated liquid. The solid was extracted with diethyl ether and ethyl acetate and washed alternately to obtain a pale yellow homogeneous solution. The solution was dried under vacuum at 60 °C for 12 hours to obtain 9.7 g of 3-(6-bromohexyl)-1-butylimidazole with an imidazole side chain.

[0029] Preparation of polyarylene ether sulfone (PAES) membrane: 2.80 g of PAES polymer was dissolved in 60 mL of NMP solvent and magnetically stirred at 80 °C until completely dissolved. Then, 0.73 g of imidazole side chain was added and stirred for 12 hours. 2.36 g of 3-chloropropyltrimethoxysilane and 0.008 g of potassium iodide were added at 60 °C and stirred for 8 hours. After cooling to room temperature, the casting solution was degassed and poured onto a clean glass plate with an effective size of 8 cm × 8 cm (width × length). The plate was vacuum dried at 80 °C for 24 hours to remove residual solvent, resulting in a colored PAES film with a thickness of 151 μm.

[0030] Experimental testing using national standard methods showed that the ion exchange capacity of the prepared solvent-resistant anion exchange membrane was 2.3 mmol·g. -1 The surface resistivity is 47.58 Ω·cm. 2 The ion transport number is 0.83, the tensile strength is 31.7 MPa, the water swelling rate is 4.3%, and the swelling rate in 60% DMSO aqueous solution is 5.9%. Electrodialysis (initial solution in the concentration chamber: 0.5 M NaCl solution; the solvent used in the solution is a mixed solvent: 20% DMSO + 80% water) showed a Cl... - SO4 2- The selectivity was 3.7. Performance comparisons with commercial ion exchange membranes are shown in Table 1. (For specific test methods, please refer to the literature reports: Journal of Membrane Science 574(2019)181–195; Journal of Membrane Science 577(2019)153–164).

[0031] Example 2:

[0032] Preparation of polyarylene ether sulfone: Polyarylene ether sulfone was prepared using the same preparation process as in Example 1.

[0033] Side chain preparation: The side chain was prepared using the same preparation process as in Example 1.

[0034] Preparation of polyarylene ether sulfone (PAES) membrane: 2.80 g of PAES polymer was dissolved in 60 mL of NMP solvent and magnetically stirred at 80 °C until completely dissolved. Then, 1.46 g of imidazole side chain was added and stirred for 12 hours. 1.96 g of 3-chloropropyltrimethoxysilane and 0.006 g of potassium iodide were added at 60 °C and stirred for 8 hours. After cooling to room temperature, the casting solution was degassed and poured onto a clean glass plate with an effective size of 8 cm × 8 cm (width × length). The plate was vacuum dried at 80 °C for 24 hours to remove residual solvent, resulting in a colored PAES film with a thickness of 152 μm.

[0035] Experimental testing using national standard methods showed that the ion exchange capacity of the prepared solvent-resistant anion exchange membrane was 2.2 mmol·g. -1 The surface resistivity is 37.38 Ω·cm. 2 The ion transport number is 0.85, the tensile strength is 29.7 MPa, the water swelling rate is 4.7%, and the swelling rate in 60% DMSO aqueous solution is 6.1%. Electrodialysis (initial solution in the concentration chamber: 0.5 M NaCl solution; the solvent used in the solution is a mixed solvent: 20% DMSO + 80% water) showed a Cl... - SO4 2-The selectivity was 4.3. Performance comparisons with commercial ion exchange membranes are shown in Table 1. (For specific test methods, please refer to the literature reports: Journal of Membrane Science 574(2019)181–195; Journal of Membrane Science 577(2019)153–164).

[0036] Example 3:

[0037] Preparation of polyarylene ether sulfone: Polyarylene ether sulfone was prepared using the same preparation process as in Example 1.

[0038] Side chain preparation: The side chain was prepared using the same preparation process as in Example 1.

[0039] Preparation of polyarylene ether sulfone (PAES) membrane: 2.80 g of PAES polymer was dissolved in 60 mL of NMP solvent and magnetically stirred at 80 °C until completely dissolved. Then, 2.17 g of imidazole side chain was added and stirred for 12 hours. 1.57 g of 3-chloropropyltrimethoxysilane and 0.005 g of potassium iodide were added at 60 °C and stirred for 8 hours. After cooling to room temperature, the casting solution was degassed and poured onto a clean glass plate with an effective size of 8 cm × 8 cm (width × length). The plate was vacuum dried at 80 °C for 24 hours to remove residual solvent, resulting in a colored PAES film with a thickness of 150 μm.

[0040] Experimental testing using national standard methods showed that the ion exchange capacity of the prepared solvent-resistant anion exchange membrane was 1.9 mmol·g. -1 The surface resistivity is 16.77 Ω·cm. 2 The ion transport number is 0.87, the tensile strength is 24.7 MPa, the water swelling rate is 5.3%, and the swelling rate in 60% DMSO aqueous solution is 7.1%. Electrodialysis (initial solution in the concentration chamber: 0.5 M NaCl solution; the solvent used in the solution is a mixed solvent: 20% DMSO + 80% water) showed a Cl... - SO4 2- The selectivity was 7.1. Performance comparisons with commercial ion exchange membranes are shown in Table 1. (For specific test methods, please refer to the literature reports: Journal of Membrane Science 574(2019)181–195; Journal of Membrane Science 577(2019)153–164).

[0041] Example 4:

[0042] Preparation of polyarylene ether sulfone: Polyarylene ether sulfone was prepared using the same preparation process as in Example 1.

[0043] Side chain preparation: The side chain was prepared using the same preparation process as in Example 1.

[0044] Preparation of polyarylene ether sulfone (PAES) membrane: 2.80 g of PAES polymer was dissolved in 60 mL of NMP solvent and magnetically stirred at 80 °C until completely dissolved. Then, 2.89 g of imidazole side chain was added and stirred for 12 hours. 1.17 g of 3-chloropropyltrimethoxysilane and 0.004 g of potassium iodide were added at 60 °C and stirred for 8 hours. After cooling to room temperature, the casting solution was degassed and poured onto a clean glass plate with an effective size of 8 cm × 8 cm (width × length). The plate was vacuum dried at 80 °C for 24 hours to remove residual solvent, resulting in a colored PAES film with a thickness of 151 μm.

[0045] Experimental testing using national standard methods showed that the ion exchange capacity of the prepared solvent-resistant anion exchange membrane was 1.8 mmol·g. -1 The surface resistivity is 6.38 Ω·cm. 2 The ion transport number is 0.89, the tensile strength is 24.2 MPa, the water swelling rate is 5.5%, and the swelling rate in 60% DMSO aqueous solution is 7.6%. Electrodialysis (initial solution in the concentration / dilute chamber: 0.5 M NaCl solution; the solvent used in the solution is a mixed solvent: 20% DMSO + 80% water) showed a Cl... - SO4 2- The selectivity was 19. Performance comparisons with commercial ion exchange membranes are shown in Table 1. (For specific test methods, please refer to the literature reports: Journal of Membrane Science 574(2019)181–195; Journal of Membrane Science 577(2019)153–164).

[0046] Example 5:

[0047] Preparation of polyarylene ether sulfone: Polyarylene ether sulfone was prepared using the same preparation process as in Example 1.

[0048] Side chain preparation: The side chain was prepared using the same preparation process as in Example 1.

[0049] Preparation of polyarylene ether sulfone (PAES) membrane: 2.80 g of PAES polymer was dissolved in 60 mL of NMP solvent and magnetically stirred at 80 °C until completely dissolved. Then, 3.62 g of imidazole side chain was added and stirred for 12 hours. 0.78 g of 3-chloropropyltrimethoxysilane and 0.003 g of potassium iodide were added at 60 °C and stirred for 8 hours. After cooling to room temperature, the casting solution was degassed and poured onto a clean glass plate with an effective size of 8 cm × 8 cm (width × length). The plate was vacuum dried at 80 °C for 24 hours to remove residual solvent, resulting in a colored PAES film with a thickness of 152 μm.

[0050] Experimental testing using national standard methods showed that the ion exchange capacity of the prepared solvent-resistant anion exchange membrane was 1.8 mmol·g. -1 The surface resistivity is 5.99 Ω·cm. 2 The ion transport number is 0.91, the tensile strength is 23.9 MPa, the water swelling rate is 5.6%, and the swelling rate in 60% DMSO aqueous solution is 7.7%. Electrodialysis (initial solution in the concentration / dilute chamber: 0.5 M NaCl solution; the solvent used in the solution is a mixed solvent: 20% DMSO + 80% water) showed a Cl... - SO4 2- The selectivity was 4.3. Performance comparisons with commercial ion exchange membranes are shown in Table 1. (For specific test methods, please refer to the literature reports: Journal of Membrane Science 574(2019)181–195; Journal of Membrane Science 577(2019)153–164).

[0051] Example 6:

[0052] Preparation of polyarylene ether sulfone: Polyarylene ether sulfone was prepared using the same preparation process as in Example 1.

[0053] Side chain preparation: The side chain was prepared using the same preparation process as in Example 1.

[0054] Preparation of polyarylene ether sulfone (PAES) membrane: 2.80 g of PAES polymer was dissolved in 60 mL of NMP solvent and magnetically stirred at 80 °C until completely dissolved. Then, 4.34 g of imidazole side chain was added and stirred for 12 hours. 0.39 g of 3-chloropropyltrimethoxysilane and 0.002 g of potassium iodide were added at 60 °C and stirred for 8 hours. After cooling to room temperature, the casting solution was degassed and poured onto a clean glass plate with an effective size of 8 cm × 8 cm (width × length). The plate was vacuum dried at 80 °C for 24 hours to remove residual solvent, resulting in a colored PAES film with a thickness of 155 μm.

[0055] Experimental testing using national standard methods showed that the ion exchange capacity of the prepared solvent-resistant anion exchange membrane was 1.6 mmol·g. -1 The surface resistivity is 4.78 Ω·cm. 2 The ion transport number is 0.93, the tensile strength is 23.2 MPa, the water swelling rate is 6.3%, and the swelling rate in 60% DMSO aqueous solution is 7.9%. Electrodialysis (initial solution in the concentration / dilute chamber: 0.5 M NaCl solution; the solvent used in the solution is a mixed solvent: 20% DMSO + 80% water) showed a Cl... - SO4 2-The selectivity was 3.2. Performance comparisons with commercial ion exchange membranes are shown in Table 1. (For specific test methods, please refer to the literature reports: Journal of Membrane Science 574(2019)181–195; Journal of Membrane Science 577(2019)153–164).

[0056]

[0057] Table 1. Physicochemical properties of AEMs prepared in Examples 1–6.

Claims

1. A method for preparing a monovalent anion-selective and solvent-resistant ion exchange membrane, comprising the following steps: (1) A certain amount of 1,6-dibromohexane was placed in a round-bottom flask and dissolved in solvent; then a certain amount of butylimidazole was added to a constant-pressure dropping funnel and dissolved in solvent to obtain a dilute solution; subsequently, the dilute butylimidazole solution was added dropwise to the dilute 1,6-dibromohexane solution and heated and stirred. As the reaction proceeded, a white precipitate gradually appeared; after the reaction was completed, the precipitate was filtered and the filtrate was collected; the filtrate was concentrated by evaporating the solvent, and the concentrated liquid was dried in a vacuum drying oven to remove the residual solvent, resulting in a long side chain with an imidazole structure as shown in formula (I), named 3-(6-bromohexyl)-1-butylimidazole BIM: (2) A certain amount of three monomers, 4,4'-difluorodiphenyl sulfone, 2,2'-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, and hexafluorobisphenol A, were dissolved in NMP. Potassium carbonate was used as a salt-forming agent. The reaction was carried out at 145°C for 4 hours under nitrogen protection, and then the temperature was raised to 165°C for another 3 hours. After the reaction was completed, the mixture was cooled to room temperature and poured into isopropanol. The mixture was stirred continuously to obtain a yellow-green precipitate. After washing with deionized water several times, the precipitate was dried in a vacuum drying oven to obtain a random copolymer of polyarylether sulfone (PAES) containing amino groups, as shown in formula (III), with a molecular weight of 30,000 to 60,000. (3) Preparation of anion exchange membrane: Weigh a certain amount of long side chain (I), crosslinking agent 3-chloropropyltrimethoxysilane CPTMS (II) and PAES (III), and dissolve them in polar solvents respectively; first, mix the long side chain and PAES according to a certain feeding ratio, and after the reaction is complete, add the crosslinking agent to the mixture and mix thoroughly. Heat and stir to obtain a clear and transparent casting solution. After cooling to room temperature and vacuum degassing, cast it onto a clean glass plate and vacuum dry at 60-100℃ for 12-36 hours to obtain anion exchange membrane PAES-BIm-CPTMS with both monovalent anion selectivity and solvent resistance. Its chemical structure is shown in formula (IV): The reaction temperature in step (1) is 30-70℃, and the reaction time is 12-36 hours; The solvent mentioned in step (1) is one or more of acetonitrile, acetone, and tetrahydrofuran.

2. The method for preparing a monovalent anion-selective and solvent-resistant ion exchange membrane as described in claim 1, characterized in that: In step (2), the molar ratio of 2,2'-bis(3-amino-4-hydroxyphenyl)hexafluoropropane to hexafluorobisphenol A in the polyarylene ether sulfone (PAES) is 7:

3.

3. The method for preparing a monovalent anion-selective and solvent-resistant ion exchange membrane as described in claim 1, characterized in that: In step (3), the PAES functionalization temperature is 30-90℃ and the reaction time is 6-48 hours.

4. The method for preparing a monovalent anion-selective and solvent-resistant ion exchange membrane as described in claim 1, characterized in that: The polar solvent mentioned in step (3) is N-methylpyrrolidone.

5. The method for preparing a monovalent anion-selective and solvent-resistant ion exchange membrane as described in claim 1, characterized in that: The vacuum drying temperature in step (3) is 80°C and the time is 24 hours.

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