Preparation method of temperature-resistant solvent-resistant monovalent anion selective composite ion exchange membrane

Abstract

The invention relates to the field of polymer materials, and discloses a preparation method of a temperature-resistant solvent-resistant monovalent anion selective composite ion exchange membrane, which comprises the following steps: step 1, preparing a charged substrate membrane; and 2, preparing the composite ion exchange membrane. The swelling property of the basement membrane is utilized, macromolecules of a skin layer formed by interfacial polymerization and macromolecular chain segments of the basement membrane are interpenetrated and entangled at an interface so as to improve the interfacial compatibility, and the interfacial compatibility stability is further improved by utilizing ionic or covalent cross-linking among active groups of interfacial polymers. The long-acting high-monovalent ion permeation selectivity sandwich structure composite ionic membrane can be constructed by utilizing the characteristics that'ion exchange transfer 'and'ion screening conduction' are realized by virtue of short-range low resistance and effective screening functions of a compact cross-linked thin skin layer and the mass transfer resistance of monovalent anions is reduced by virtue of a large-size ion channel (gt; 2nm) of a cross-linked network basement membrane.

Description

Technical Field

[0001] The present invention relates to the field of polymer macromolecular materials, and particularly to a preparation method of a temperature-resistant and solvent-resistant monovalent anion-selective composite ion exchange membrane, belonging to the field of membrane technology. Background Art

[0002] Ion exchange membranes (referred to as ion membranes for short) are the core materials of electrochemical separation technology and are widely used in fields such as electrodialysis, fuel cells, electrolytic water hydrogen production, desalination of organic solvents, and resource recovery. However, with the expansion of industrial scenarios to high-temperature and highly corrosive environments (such as chemical wastewater treatment, high-temperature electrochemical synthesis, and separation of organic solvents), the limitations of traditional ion exchange membranes have become increasingly prominent, specifically manifested as follows: 1) Insufficient high-temperature resistance: Existing membrane materials (such as polysulfone and polystyrene) are prone to thermal degradation or crosslinked network relaxation at high temperatures (>80 °C), resulting in a decrease in mechanical strength and dimensional deformation, making it difficult to meet the requirements of continuous high-temperature operation. 2) Defects in solvent resistance: In systems containing organic solvents (such as DMF, NMP, and acetone), the membrane materials swell or dissolve due to the "like dissolves like" principle, leading to a sharp drop in separation efficiency or even complete failure. 3) Contradiction in monovalent / multivalent anion selectivity: Although traditional modification methods (such as introducing quaternary ammonium groups) can improve ionic conductivity, it is difficult to precisely control the selective separation of monovalent anions (such as Cl - , NO3 - ) and multivalent ions (such as SO4 2- , PO4 3- ), which limits their application in high-value-added scenarios such as lithium extraction from salt lakes and precious metal recovery.

[0003] In view of this, "material-structure-process" collaborative innovation is proposed. By constructing a three-dimensional crosslinked network, designing functionalized side chains, and using an interfacial polymerization membrane-forming process, a new type of composite ion membrane is constructed to break through the bottleneck of existing technologies and promote the development of high-temperature electrochemical technologies: The high-temperature resistance property (>80 °C) can expand the application of the membrane in high-temperature environments; improve the separation efficiency in organic solvent systems: Solvent resistance (such as resistance to DMF, tetrahydrofuran, etc.) supports the recovery of valuable substances in chemical wastewater, reducing energy consumption and costs; achieve precise separation of high-value-added resources: Monovalent anion selectivity (Cl - / SO4 2- separation factor > 20) provides an efficient solution for high-concentration salt wastewater, lithium extraction from salt lakes, rare earth separation, etc. Ultimately, it promotes the transformation of ion membranes from laboratory research to industrial application and contributes to the sustainable development of fields such as new energy, environmental protection, and chemical engineering. Summary of the Invention

[0004] In order to solve the above technical problems existing in the prior art, the present invention provides a preparation method of a temperature-resistant and solvent-resistant monovalent anion-selective composite ion exchange membrane, comprising the following steps:

[0005] Step 1: Preparation of a charged substrate membrane

[0006] In a three-necked flask, polyphenylene oxide bromide and N-butylimidazole (N-But-Im) are mixed in a polar aprotic solvent at a certain molar ratio and stirred and refluxed at 50 - 100 °C for 10 - 60 h. After precipitation in ethanol and vacuum drying, imidazole-functionalized polyphenylene oxide bromide (BPPO-Im) is obtained;

[0007] At room temperature, BPPO-Im is dissolved in an organic solvent, and a certain amount of N-(trimethoxysilylpropyl)imidazole (Im-3C-3OCH3) is added. After stirring for a certain period of time under certain temperature conditions and standing for defoaming, a casting solution is obtained. The mass-volume concentration of polyarylether sulfone in the casting solution is 3 - 8%; the obtained casting solution is poured onto a glass plate and in-situ reaction and drying are carried out at 40 - 200 °C for 12 - 96 h. After cooling, the film is peeled off from the glass plate in water, and a crosslinked anion exchange substrate membrane (cBPPO-Im) with a thickness of 50–100 μm is obtained; Step 2: Preparation of a composite ion exchange membrane

[0008] The crosslinked anion exchange substrate membrane (cBPPO-Im) is immersed in an aqueous solution containing a water-soluble basic monomer (B-nC-3Pip), where n = 0, 1, 2, 3, for a certain period of time to allow the monomer molecules to be absorbed and dispersed on the surface and inner surface of the substrate membrane. Then, the excess solution is removed with flowing air, and then it is immersed in an organic solvent containing an oil-soluble monomer, 1,3,5-tris(bromomethyl)benzene (TBMB). After curing at a certain temperature, a composite ion exchange membrane (cBPPO-Im-Pip) with a thin-layer interface modification and a thickness of 80–180 μm is obtained.

[0009] Furthermore, the molar ratio in Step 1 is 2.5 - 3.5:1, and most preferably 2:1; the reflux reaction temperature is 50 - 100 °C.

[0010] Furthermore, the polar aprotic solvent in Step 1 is at least one of N,N'-dimethylformamide, N,N'-dimethylacetamide, and N-methylpyrrolidone.

[0011] Furthermore, the molar ratio of N-But-Im to Im-3C-3OCH3 in Step 1 is most preferably 4:1.

[0012] Furthermore, when the casting solution in Step 1 is poured onto the glass plate, it is further preferably 180 °C and 48 h.

[0013] Furthermore, the thickness of the crosslinked anion exchange substrate membrane (cBPPO-Im) in Step 1 is preferably 60 μm.

[0014] Further, the concentration of the water-soluble basic monomer aqueous solution in step two is 1–5 wt%, and the most preferred is 3%.

[0015] Further, the concentration of the oil-soluble monomer organic solvent in step two is 0.5–3 wt%, and the most preferred is 2%.

[0016] Further, the curing temperature in step two is 40–100 °C, and the thickness of the obtained composite ion exchange membrane is preferably 150 μm.

[0017] Compared with the prior art, the advantages of the present invention are as follows:

[0018] (1) Utilizing the swelling property of the base membrane, the polymers of the interfacial polymerization forming the skin layer and the polymer chain segments of the base membrane are interpenetrated and entangled at the interface to improve the interfacial compatibility, and the ionic or covalent cross-linking between the active groups of the interfacial polymer is further used to increase the interfacial compatibility stability.

[0019] (2) Utilizing the short-range low resistance and effective sieving function of the dense cross-linked thin skin layer to achieve "ion exchange transfer" and "ion sieving conduction", and the characteristic of the cross-linked network base membrane with large-size ion channels (>2 nm) to reduce the mass transfer resistance of monovalent anions, a long-lasting high monovalent ion permeation selectivity "sandwich" structure composite ion membrane can be constructed. Description of the Drawings

[0020] Figure 1 is the process flow chart for the preparation of the composite ion membrane in Example 1.

[0021] Figure 2 is the composite ion exchange membrane prepared in Example 2;

[0022] Figure 3 is the possible structural formula diagram of the prepared composite ion exchange membrane. Detailed Embodiments

[0023] To further illustrate the technical solution of the present invention, the preferred implementation schemes of the present invention are described below in combination with specific examples.

[0024] The preparation method of the heat-resistant and solvent-resistant monovalent anion-selective composite ion exchange membrane of the present invention includes the following steps:

[0025] Step 1: Preparation of the charged base membrane

[0026] In a three-necked flask, brominated polyphenylene ether shown in formula (I) and N-butylimidazole N-But-Im shown in formula (II) are mixed in a certain molar ratio in a polar aprotic solvent, and stirred and refluxed at 50–100 °C for 10–60 h. After precipitation in ethanol and vacuum drying, imidazole-functionalized brominated polyphenylene ether BPPO-Im is obtained, and its structure is shown in formula (III);

[0027]

[0028] The molar ratio of the feedstock described in Step 1 is 2.5 - 3.5:1, and the most preferred is 2:1.

[0029] The reflux reaction temperature described in Step 1 is 50 - 100 °C, and the reaction time is 10 - 60 h. Further preferably, it is 80 °C for 48 h.

[0030] The polar aprotic solvent described in Step 1 is at least one of N,N'-dimethylformamide, N,N'-dimethylacetamide, and N-methylpyrrolidone.

[0031] At room temperature, BPPO-Im is dissolved in an organic solvent, and a certain amount of N-(trimethoxysilylpropyl)imidazole Im-3C-3OCH3 as shown in formula (IV) is added. It is stirred for a certain period of time under certain temperature conditions and then left to stand for defoaming to obtain a casting solution. The mass-volume concentration of polyarylethersulfone in the casting solution is 3 - 8%; the obtained casting solution is poured onto a glass plate and kept at 40 - 200 °C for 12 - 96 h to achieve in-situ reaction and drying. After cooling, the film is peeled off from the glass plate in water, and the crosslinked anion exchange substrate membrane cBPPO-Im is obtained. Its structure is as shown in formula (V), and the thickness is 50 - 100 μm;

[0032]

[0033] For the main chain BPPO-Im, modifier N-But-Im, and modifier Im-3C-3OCH3 described in Step 1, the mass ratio of the feedstock materials is 0.4 - 1.00:1. As a further preference, the molar ratio of N-But-Im to Im-3C-3OCH3 is 0.5 - 5:1; the reaction temperature is 20 - 100 °C, and the reaction time is 24 h. Further preferably, it is 80 °C.

[0034] The molar ratio of the two small molecule modifiers N-But-Im and Im-3C-3OCH3 described in Step 1 is most preferably 4:1.

[0035] The casting solution described in Step 1 is poured onto a glass plate and kept at 40 - 200 °C for 12 - 96 h to achieve in-situ reaction and drying. Further preferably, it is 180 °C for 48 h.

[0036] The crosslinked anion exchange substrate membrane cBPPO-Im described in Step 1 has a thickness of 50 - 100 μm, and the most preferred is 60 μm.

[0037] Step 2: Preparation of the composite ion exchange membrane

[0038] The cross-linked anionic exchange substrate membrane cBPPO-Im was immersed in an aqueous solution containing a water-soluble basic monomer B-nC-3Pip (n = 0, 1, 2, 3; as shown in formula (VI)) at a certain concentration (1–5 wt%), and soaked for a certain time so that the monomer molecules were absorbed and dispersed on the surface and inner surface of the substrate membrane. Then, the excess solution was removed with flowing air, and then it was immersed in an organic solvent containing an oil-soluble monomer 1,3,5-tris(bromomethyl)benzene TBMB (0.5–3 wt%, as shown in formula (VII)). After curing at a certain temperature, the composite ion membrane cBPPO-Im-Pip with a thin-layer interface modification was obtained, with a thickness of 80–180 μm. One of its possible structural formulas is as Figure 3 shown.

[0039]

[0040] The concentration of the water-soluble basic monomer described in step two is 1–5 wt%, and the most preferred is 3%.

[0041] The concentration of the oil-soluble monomer described in step two is 0.5–3 wt%, and the most preferred is 2%.

[0042] The certain curing temperature described in step two is 40–100 °C, and the thickness of the obtained composite ion membrane is 80–180 μm. The most preferred temperature is 80 °C and the most preferred thickness is 150 μm.

[0043] Example 1

[0044] As Figure 1 shown, the preparation method of the temperature- and solvent-resistant monovalent anion-selective composite ion exchange membrane of the present invention includes the following steps:

[0045] 1) Preparation of the charged substrate membrane:

[0046] In a three-necked flask, polyphenylene oxide bromide (BPPO) and N-butylimidazole (N-But-Im) were dissolved in N-methylpyrrolidone (NMP) according to a certain molar ratio, and stirred and refluxed at 80 °C for 48 h. After precipitation in ethanol and vacuum drying, imidazole-functionalized polyphenylene oxide bromide (BPPO-Im) was obtained.

[0047] At room temperature, BPPO-Im was dissolved in NMP, and a certain amount of N-(trimethoxysilylpropyl)imidazole (Im-3C-3OCH3) was added (feeding ratio: molar ratio of N-But-Im to Im-3C-3OCH3 was 5:0). The mixture was stirred at 80 °C for 30 min and then left standing for 1 h to remove bubbles, obtaining a casting solution. The mass-volume concentration of BPPO-Im in the obtained casting solution was 5%. The obtained casting solution was poured into a glass plate groove and maintained at 180 °C for 48 h to achieve in-situ reaction and drying. After cooling, the film was peeled off from the glass plate in water, obtaining a crosslinked anionic exchange substrate membrane (cBPPO-Im-5 / 0) with a thickness of 61 μm.

[0048] 2) Preparation of composite ion membrane:

[0049] cBPPO-Im-SiO-4 / 1 was immersed in an aqueous solution containing 3 wt% water-soluble basic B-1C-3Pip monomer for a certain time to allow 1,3,5-tris(bromomethyl)benzene (TBMB) monomer molecules to be absorbed and dispersed on the surface and inner surface of the substrate membrane. Then, the excess solution was removed with flowing air, and then it was immersed in an organic solvent containing 2 wt% oil-soluble monomer (n-hexane). After heating and curing at 80 °C, a composite ion exchange membrane with a thin-layer interface modification (cBPPO-Im-4 / 1-Pip-1C) was finally obtained, with a thickness of 152 μm.

[0050] 3) Property performance test and evaluation:

[0051] The thickness, ion exchange capacity, swelling ratio, and tensile strength of the prepared composite ion membrane were tested by the national standard method. The surface resistance (25 °C, 0.5 M NaCl solution), transference number (25 °C), permselectivity (electrodialysis ion membrane test conditions: 0.05 M NaCl + 0.05 M Na2SO4 mixed brine solution containing 30 wt% DMAc; solution temperature was 70 °C), and ion flux of the composite ion membrane were tested by a self-made device. The results are shown in Table 1. (The test methods refer to the literature reports: Journal of Membrane Science 574 (2019) 181–195; Journal of Membrane Science 577 (2019) 153–164).

[0052] Example 2

[0053] 1) Preparation of charged substrate membrane:

[0054] The same preparation process as in Example 1 was adopted, with the difference that the molar ratio of N-But-Im to Im-3C-3OCH3 was 4:1.

[0055] 2) Preparation of composite ion membrane:

[0056] The same preparation process as in Example 1 was adopted. Finally, the composite ion membrane cBPPO-Im-4 / 1-Pip-1C was obtained.

[0057] 3) Property performance test and evaluation:

[0058] The same preparation process as in Example 1 was adopted.

[0059] The prepared composite ion exchange membrane is as Figure 2 shown.

[0060] Example 3

[0061] 1) Preparation of the charged substrate membrane:

[0062] The same preparation process as in Example 2 was adopted, except that the molar ratio of N-But-Im to Im-3C-3OCH3 was 3:2.

[0063] 2) Preparation of the composite ion membrane:

[0064] The same preparation process as in Example 1 was adopted. Finally, the composite ion membrane cBPPO-Im-3 / 2-Pip-1C was obtained.

[0065] 3) Property performance test and evaluation:

[0066] The same preparation process as in Example 1 was adopted.

[0067] Example 4

[0068] 1) Preparation of the charged substrate membrane:

[0069] The same preparation process as in Example 2 was adopted, except that the molar ratio of N-But-Im to Im-3C-3OCH3 was 2:3.

[0070] 2) Preparation of the composite ion membrane:

[0071] The same preparation process as in Example 1 was adopted. Finally, the composite ion membrane cBPPO-Im-2 / 3-Pip-1C was obtained.

[0072] 3) Property performance test and evaluation:

[0073] The same preparation process as in Example 1 was adopted.

[0074] Example 5

[0075] 1) Preparation of the charged substrate membrane:

[0076] The same preparation process as in Example 2 was adopted.

[0077] 2) Preparation of the composite ion membrane:

[0078] The same preparation process as in Example 1 was adopted, except that the basic monomer used was B-0C-3Pip. The composite ion membrane cBPPO-Im-4 / 1-Pip-1C was finally obtained.

[0079] 3) Property and performance test and evaluation:

[0080] The same preparation process as in Example 1 was adopted.

[0081] Example 6

[0082] 1) Preparation of charged substrate membrane:

[0083] The same preparation process as in Example 2 was adopted.

[0084] 2) Preparation of composite ion membrane:

[0085] The same preparation process as in Example 1 was adopted, except that the basic monomer used was B-1C-3Pip. The composite ion membrane cBPPO-Im-4 / 1-Pip-2C was finally obtained.

[0086] 3) Property and performance test and evaluation:

[0087] The same preparation process as in Example 1 was adopted.

[0088] Example 7

[0089] 1) Preparation of charged substrate membrane:

[0090] The same preparation process as in Example 2 was adopted.

[0091] 2) Preparation of composite ion membrane:

[0092] The same preparation process as in Example 1 was adopted, except that the basic monomer used was B-2C-3Pip. The composite ion membrane cBPPO-Im-4 / 1-Pip-3C was finally obtained.

[0093] 3) Property and performance test and evaluation:

[0094] The same preparation process as in Example 1 was adopted.

[0095] Example 8

[0096] 1) Preparation of charged substrate membrane:

[0097] The same preparation process as in Example 2 was adopted.

[0098] 2) Preparation of composite ion membrane:

[0099] Using the same preparation process as in Example 1, except that the basic monomer used is B-3C-3Pip. The final composite ion membrane obtained is cBPPO-Im-4 / 1-Pip-4C.

[0100] 3) Property and performance test and evaluation:

[0101] Using the same preparation process as in Example 1.

[0102]

[0103]

[0104] Table 1.

Claims

1. A preparation method of a temperature- and solvent-resistant monovalent anion-selective composite ion exchange membrane, comprising the following steps: Step 1: Preparation of a charged substrate membrane In a three-necked flask, polyphenylene ether bromide and N-butylimidazole (N-But-Im) are reacted at a certain molar ratio in a polar aprotic solvent by stirring and refluxing at 50-100 °C for 10-60 h. After precipitation in ethanol and vacuum drying, imidazole-functionalized polyphenylene ether bromide (BPPO-Im) is obtained; At room temperature, BPPO-Im is dissolved in an organic solvent, a certain amount of N-(trimethoxysilylpropyl)imidazole (Im-3C-3OCH3) is added, and the mixture is stirred for a certain period of time at a certain temperature and then left to stand for degassing to obtain a casting solution. The mass-volume concentration of polyarylethersulfone in the casting solution is 3-8%; the obtained casting solution is poured onto a glass plate and kept at 40-200 °C for 12-96 h for in-situ reaction and drying. After cooling, the film is peeled off from the glass plate in water to obtain a crosslinked anion exchange substrate membrane (cBPPO-Im) with a thickness of 50-100 μm; Step 2: Preparation of the composite ion exchange membrane The crosslinked anion exchange substrate membrane (cBPPO-Im) is immersed in an aqueous solution containing a water-soluble basic monomer (B-nC-3Pip), where n = 0, 1, 2, 3, for a certain time so that the monomer molecules are absorbed and dispersed on the surface and inner surface of the substrate membrane. Then, the excess solution is removed with flowing air, and then the membrane is immersed in an organic solvent containing an oil-soluble monomer, 1,3,5-tris(bromomethyl)benzene (TBMB). After curing at a certain temperature, a composite ion exchange membrane (cBPPO-Im-Pip) with a thin-layer interface modification is obtained, with a thickness of 80-180 μm.

2. The preparation method of the temperature- and solvent-resistant monovalent anion-selective composite ion exchange membrane according to claim 1, characterized in that: The molar ratio in Step 1 is 2.5-3.5:1, and the most preferred is 2:1; the reflux reaction temperature is 50-100 °C.

3. The preparation method of the temperature- and solvent-resistant monovalent anion-selective composite ion exchange membrane according to claim 1, characterized in that: The polar aprotic solvent in Step 1 is at least one of N,N'-dimethylformamide, N,N'-dimethylacetamide, and N-methylpyrrolidone.

4. The preparation method of the temperature- and solvent-resistant monovalent anion-selective composite ion exchange membrane according to claim 1, characterized in that: The most preferred molar ratio of N-But-Im to Im-3C-3OCH3 in Step 1 is 4:

1.

5. The preparation method of the temperature-resistant and solvent-resistant monovalent anion-selective composite ion exchange membrane according to claim 1, characterized in that: Pouring the casting solution onto the glass plate in Step 1 is further preferably at 180 °C for 48 h.

6. The preparation method of the temperature- and solvent-resistant monovalent anion-selective composite ion exchange membrane according to claim 1, characterized in that: The thickness of the crosslinked anion exchange substrate membrane (cBPPO-Im) in Step 1 is preferably 60 μm.

7. The preparation method of the temperature-resistant and solvent-resistant monovalent anion-selective composite ion exchange membrane according to claim 1, characterized in that: The concentration of the aqueous solution containing the water-soluble basic monomer in Step 2 is 1-5 wt%, and the most preferred is 3%.

8. The preparation method of the temperature- and solvent-resistant monovalent anion-selective composite ion exchange membrane according to claim 1, characterized in that: The concentration of the organic solvent containing the oil-soluble monomer in Step 2 is 0.5-3 wt%, and the most preferred is 2%.

9. The preparation method of the temperature- and solvent-resistant monovalent anion-selective composite ion exchange membrane according to claim 1, characterized in that: The curing temperature in Step 2 is 40-100 °C, and the thickness of the obtained composite ion exchange membrane is preferably 150 μm.

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