High-temperature-resistant high-concentration alkali ion solvated microporous membrane as well as preparation method and application thereof

Abstract

The invention discloses a high-temperature-resistant and high-concentration alkali-resistant ion solvated microporous membrane and a preparation method and application thereof, and relates to the technical field of separation membranes. Uniformly distributed microporous structures are introduced into a polymer membrane through a controllable super-crosslinking reaction, so that an ion transmission channel is effectively expanded, and the ion flux of the membrane is remarkably improved; meanwhile, stable oxindole / OH <-> complex ion pairs are constructed in situ, and a continuous ion solvation micropore channel is formed; the channel not only provides abundant transmission sites for OH, but also constructs a selective transmission path penetrating through the membrane thickness direction, so that excellent ion selectivity and chemical stability can still be maintained under the conditions of high-concentration alkali liquor and high temperature.

Description

Technical Field

[0001] This invention relates to the field of separation membrane technology, specifically to a high-temperature, high-concentration alkali-resistant ion-solventized microporous membrane, its preparation method, and its application. Background Technology

[0002] High-temperature, high-concentration alkaline wastewater is a typical type of wastewater generated during continuous production processes in industries such as metallurgy, metal surface treatment, and textile dyeing and printing. For example, in textile dyeing, mercerizing cotton fabrics, and the alkaline extraction of cellulose from agricultural straw, the wastewater generated by these processes has a temperature of 25–75 °C, containing high levels of OH-. - The concentration is as high as 5 mol L. -1 Membrane separation technology has made significant progress in alkali recovery; however, the stability of membrane materials under extreme conditions such as high temperature and high alkali concentration still faces major challenges, and currently only a very small number of membranes can meet these requirements. To date, most anion exchange membranes developed lack sufficient chemical stability in high-temperature, high-concentration alkali environments, mainly due to the presence of OH groups. - Nucleophilic substitution or Hofmann elimination reactions of quaternary ammonium groups in the membrane can trigger membrane material degradation, which greatly reduces the stability of anion exchange membranes in high-temperature, high-concentration alkali environments, thereby affecting their performance stability and service life.

[0003] The ion-solvation membrane achieves OH by absorbing electrolytes from the hydroxide aqueous solution. - In terms of chemical stability, compared to traditional quaternized hydrocarbon polymers, ion-solventized membranes exhibit superior alkali resistance due to the absence of quaternary ammonium groups. Regarding structural stability, the channels formed by traditional microphase separation structures are prone to swelling, reducing ion selectivity. Hypercrosslinked polymers, however, demonstrate unique advantages in anti-swelling properties. They construct permanent rigid microporous structures through Friedel-Crafts reactions. This rigid network microporous structure, with its excellent pore connectivity and extremely low swelling degree, provides favorable conditions for ion-selective transport.

[0004] The journal *Angewandte Chemie International Edition* (2024, e202407372) reports a method for the hypercrosslinking preparation of microporous anion exchange membranes. This method effectively overcomes the swelling problem of microphase-separated ion exchange membranes and achieves the desired Cl... - The high transport rate of ions and Na + / Cl - It exhibits high ion selectivity, but the membrane contains quaternary ammonium groups, making it prone to degradation in high-concentration alkaline solutions.

[0005] Nature Energy (2024, 401-410) reports on poly(oxyindole-biphenyl)-based ion-solvation membranes with highly stable oxyindole / KOH complex ion pairs for use in water electrolysis devices. These ion-solvation membranes exhibit good alkaline stability at 80 °C; however, as dense membranes with a non-porous structure, ion transport channels rely solely on ion exchange, which is detrimental to improving ion transport rates.

[0006] Patent CN 110903449A discloses a method for preparing an indigo aromatic copolymer. This method involves a hydroxyalkylation polycondensation reaction of indigo, methylpiperidone, and aromatic hydrocarbons under a strong acid catalysis to synthesize an indigo aromatic copolymer containing quaternary ammonium cations. This copolymer is then further used to prepare an anion exchange membrane, which can be used in electrochemical devices such as fuel cells, energy storage batteries, and water electrolysis. However, this membrane relies on quaternary ammonium groups as cation transport sites. While achieving ion transport, this also introduces stability concerns: on the one hand, the quaternized structure is prone to water absorption and swelling, affecting the membrane's dimensional stability; on the other hand, under high temperature and high-concentration alkaline conditions, the quaternary ammonium groups are susceptible to Hoffmann degradation or nucleophilic substitution reactions, leading to chemical structural damage and thus limiting its durability during long-term operation.

[0007] Patent CN 119039574A discloses a self-porous polymer based on indole-2,3-dione, and its application in the preparation of ion-solubilized membranes and alkaline water electrolysis for hydrogen production. This patent describes the copolymerization of a rigid, twisted aromatic monomer with indole-2,3-dione via superacid catalysis to form a self-porous polymer membrane. The membrane is then treated in a KOH solution to obtain a self-porous ion-solubilized membrane, which is used as an electrode diaphragm material in an alkaline electrolyzer. However, the microporous structure of this ion-solubilized membrane mainly relies on the non-covalent entanglement between polymer chains and lacks a chemical cross-linking network. Therefore, it has weak resistance to swelling in strongly alkaline environments and limited structural stability. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a method for preparing an ion-solventized microporous membrane that is resistant to high temperature and high concentration of alkali. The membrane does not contain easily degradable quaternary ammonium groups, which fundamentally avoids the problem of functional group degradation in alkaline environment and significantly improves the chemical stability of the membrane during long-term operation. At the same time, by introducing a hypercrosslinking reaction to construct a highly stable covalent three-dimensional network structure, the swelling behavior of polymer chains is effectively suppressed, thus making it suitable for the treatment of high temperature and high concentration of alkaline wastewater.

[0009] The technical problem to be solved by this invention is achieved by the following technical solution:

[0010] The first objective of this invention is to provide a method for preparing an ion-solventized microporous membrane, comprising the following steps:

[0011] S1. Indigo-aromatic copolymers are synthesized from aromatic hydrocarbons and indigo through a superacid catalytic reaction.

[0012] S2. Prepare a polymer film from the indigo-aromatic copolymer;

[0013] S3. The polymer membrane forms a supercrosslinked microporous membrane through a supercrosslinking reaction;

[0014] S4. Immerse the hypercrosslinked microporous membrane in an alkaline solution to obtain an ion-solventized microporous membrane.

[0015] Furthermore, the aromatic hydrocarbons include, but are not limited to, at least one of biphenyl, para-terphenyl, meta-terphenyl, and tetraphenyl.

[0016] Furthermore, the molar ratio of the aromatic hydrocarbon to indigo is 1:(1 to 1.3).

[0017] Furthermore, the catalyst for the superacid catalytic reaction is a mixed acid of trifluoroacetic acid and trifluoromethanesulfonic acid. Even further, the molar ratio of the aromatic hydrocarbon to trifluoroacetic acid is 1:(1~1.5); the molar ratio of trifluoroacetic acid to trifluoromethanesulfonic acid is 1:(7~12).

[0018] Furthermore, the reaction solvent for the superacid catalytic reaction includes, but is not limited to, at least one of dichloromethane, trichloromethane, and tetrahydrofuran.

[0019] Furthermore, the polymer film is prepared using at least one solution film-forming method, such as solution casting, blade coating, or spin coating, using at least one of N-methylpyrrolidone, dimethyl sulfoxide, and N,N-dimethylformamide as a solvent. For example, solution casting is used, with a glass plate as a carrier, and the film is peeled off from the glass plate after drying.

[0020] Furthermore, the reaction solvent for the hypercrosslinking reaction includes, but is not limited to, at least one of 1,2-dichloroethane, N,N-dimethylformamide, and carbon tetrachloride.

[0021] Furthermore, the catalyst for the hypercrosslinking reaction includes, but is not limited to, at least one of ferric chloride, tin dichloride, aluminum trichloride, boron fluoride, and ferric bromide.

[0022] Furthermore, the crosslinking agent for the hypercrosslinking reaction includes, but is not limited to, at least one of dimethylformaldehyde, dichloromethyl ether, dichloroxylene, and 4,4'-bis(chloromethyl)biphenyl.

[0023] Furthermore, the molar ratio of the reaction solvent to the catalyst and crosslinking agent is (5~20):1:(0.5~3), preferably 5:1:1. In the presence of the catalyst and crosslinking agent, ion-solventized microporous membranes with multi-scale pore structures that meet the differentiated functional requirements of membranes are prepared.

[0024] Furthermore, the reaction temperature of the hypercrosslinking reaction is 25~80 °C.

[0025] Furthermore, the alkaline solution includes, but is not limited to, one of sodium hydroxide, potassium hydroxide, lithium hydroxide, and calcium hydroxide solutions.

[0026] Furthermore, the concentration of the alkaline solution is 1~10 mol L. -1 .

[0027] Furthermore, the soaking temperature of the alkaline solution is 20~80 ℃, and the soaking time is 7~10 days.

[0028] A second objective of this invention is to provide an ion-solventized microporous membrane prepared by the aforementioned preparation method.

[0029] A third objective of this invention is to provide the ion-solventized microporous membrane in OH... - Applications in the separation of multivalent anions.

[0030] Furthermore, the OH - Polyvalent anions include, but are not limited to, OH-. - / WO4 2- OH - / MoO4 2-- OH - SO4 2-- OH - / CO3 2- At least one of them.

[0031] Furthermore, the OH - The separation of multivalent anions is performed using electrodialysis.

[0032] The beneficial effects of this invention are:

[0033] 1. This invention provides an ion-solventized microporous membrane with high-efficiency OH⁻ selective transport capability under high temperature and high concentration alkaline environment. Its core principle is to achieve synergistic optimization of the structural stability and ion transport performance of the membrane material under harsh alkaline conditions through a dual strategy of "hypercrosslinking" and "ion solvation".

[0034] 2. This invention introduces a uniformly distributed microporous structure into the polymer membrane through a controllable hypercrosslinking reaction, effectively expanding ion transport channels and significantly improving the ion flux of the membrane; simultaneously, it constructs a stable oxyindole / OH structure in situ. - Complexing ion pairs and forming continuous ion-solubilized microporous channels; these channels not only provide OH- - It provides abundant transport sites and constructs selective transport pathways that run through the film thickness direction, thereby maintaining excellent ion selectivity and chemical stability even under high concentration alkaline solutions and high temperature conditions. Attached Figure Description

[0035] Figure 1 The 1H NMR spectrum of the indigo-biphenyl copolymer prepared in Example 1;

[0036] Figure 2 Infrared spectra of the polymer membrane and the hypercrosslinked microporous membrane prepared in Example 1;

[0037] Figure 3 The image shows the X-ray photoelectron spectroscopy (XPS) spectrum of the ion-solventized microporous membrane prepared in Example 1.

[0038] Figure 4 The pore size distribution diagram is shown for the ion-solventized microporous membrane prepared in Example 1.

[0039] Figure 5 The ion-solventized microporous membrane prepared in Example 8 underwent 20 electrodialysis cycles at 50°C. - Graph showing the changes in ion flux and selectivity. Detailed Implementation

[0040] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific embodiments and illustrations.

[0041] Example 1

[0042] 1. Preparation of ion-solventized microporous membranes

[0043] Step 1: Preparation of indigo-biphenyl copolymer

[0044] 15.4 g of biphenyl and 16.2 g of indigo were added to 20 mL of dichloromethane and stirred at 0–5 °C for 30 min. Then, a mixed solution of 30 mL of trifluoroacetic acid and 70 mL of trifluoromethanesulfonic acid was added dropwise, and the reaction was continued at 0–5 °C for 8 hours. The reaction solution was slowly poured into methanol, and a precipitate formed. The precipitate was filtered, washed with methanol, and dried at 80 °C for 24 hours to obtain the indigo-biphenyl copolymer.

[0045] Step 2: Preparation of polymer film

[0046] 0.6 g of the indigo-biphenyl copolymer prepared in step 1 was dissolved in 10 mL of N-methylpyrrolidone and filtered through a 0.45 μm nylon injection filter. The filtrate was then cast onto a clean glass plate and dried at 55 °C for 24 hours. After cooling the membrane to room temperature, it was immersed in deionized water until it automatically peeled off. Finally, the membrane was dried at 80 °C for 24 hours to obtain the polymer membrane.

[0047] Step 3: Preparation of hypercrosslinked microporous membranes

[0048] The polymer membrane prepared in step 2 was immersed in a mixed solution consisting of 100 mL of 1,2-dichloroethane, 48.75 g of ferric chloride and 22.8 g of dimethylformaldehyde, and reacted at 80 °C for 30 min. The membrane was then washed with ethanol and deionized water in sequence to obtain a hypercrosslinked microporous membrane.

[0049] Step 4: Preparation of ion-solventized microporous membranes

[0050] The hypercrosslinked microporous membrane prepared in step 3 was immersed in a solution with a concentration of 6 mol·L⁻¹. -1 The ion-solventized microporous membrane was obtained by treating the membrane in NaOH solution at 80 °C for 7 days.

[0051] Step 5: Preparation of non-hypercrosslinked ion-solventized dense film

[0052] The polymer membrane prepared in step 2 was immersed in a solution with a concentration of 6 mol·L⁻¹. -1 In a NaOH solution, the film was treated at 80 °C for 7 days to obtain an ion-solventized dense film without hypercrosslinking.

[0053] Figure 1 The image shows the 1H NMR spectrum of the indigo-biphenyl copolymer prepared in this embodiment. Figure 1 It can be seen that the characteristic peak at 10.82 ppm belongs to the proton on the NH bond in the indigo structure, and the peak in the range of 6.96~7.58 ppm corresponds to the proton on the aromatic ring, thus confirming the successful preparation of the indigo-biphenyl copolymer.

[0054] Figure 2 Infrared spectra of the polymer membrane and the hypercrosslinked microporous membrane prepared in this embodiment. Figure 2 It can be seen that 1604 and 1460 cm -1 The absorption peaks at 1710 cm⁻¹ are attributed to C=C bonds on aromatic rings in the polymer membrane and the hypercrosslinked microporous membrane, respectively, indicating the presence of aromatic structures in the membranes. -1 The characteristic peaks at 2962 and 2923 cm⁻¹ correspond to the stretching vibration peaks of the C=O bond. Compared with polymer membranes, the infrared spectra of hypercrosslinked microporous membranes show peaks at 2962 and 2923 cm⁻¹.-1 A characteristic peak of -CH2- tensile vibration appeared at the wavenumber. These results indicate that the dimethylformaldehyde crosslinking agent successfully introduced -CH2- bonds between polymer chains, thus confirming the successful preparation of the hypercrosslinked microporous membrane.

[0055] Figure 3 This is an XPS image of the ion-solventized microporous membrane prepared in this embodiment. From... Figure 3 It can be seen that the characteristic peaks of the hypercrosslinked microporous membrane in the N 1s and O 1s high-resolution XPS spectra all show a shift toward the direction of lower binding energy, indicating that there is an ion pair interaction between deprotonated indole and NaOH.

[0056] Figure 4 This is a pore size distribution diagram of the ion-solventized microporous membrane prepared in this embodiment. From... Figure 4 It can be seen that the pore size distribution of the multi-scale micropores ranges from 0.4 to 0.85 nm.

[0057] 2. Applications of ion-solventized microporous membranes

[0058] The ion-solventized microporous membrane and the non-hypercrosslinked ion-solventized dense membrane prepared in this embodiment were placed in an electrodialysis apparatus with a current density of 10 mA·cm⁻¹. -2 At a temperature of 20 ℃, 100 mL of a solution with a concentration of 4 mol·L⁻¹ was added to the dilution chamber. -1 The NaOH solution has a concentration of 0.4 mol·L⁻¹. -1 A mixed solution consisting of Na₂WO₄ solution was added to a concentration chamber in 100 mL of a solution with a concentration of 0.01 mol·L⁻¹. -1 NaOH solution.

[0059] The results show that the ion-solventized microporous membrane prepared in this embodiment is effective against OH-. - The ion flux is 6.6 mol·m -2 ·h -1 The separation factor was 2869; the non-hypercrosslinked ion-solventized dense membrane was effective against OH. - The ion flux is 3.8 mol·m -2 ·h -1 The separation factor was 2100. Compared with the non-hypercrosslinked ion-solventized dense membrane, the ion-solventized microporous membrane showed better resistance to OH-. - The ion flux increased by 73.7%, and the separation factor increased by 36.6%.

[0060] Example 2

[0061] Ion-solventized microporous membranes and non-hypercrosslinked ion-solventized dense membranes were prepared according to the method of Example 1, except that the hypercrosslinking reaction time in step 3 was 20 min.

[0062] Following the method of Example 1, the ion-solventized microporous membrane and the non-hypercrosslinked ion-solventized dense membrane prepared in this example were applied to electrodialysis to separate NaOH from a NaOH / Na2WO4 mixed solution.

[0063] The results show that the ion-solventized microporous membrane prepared in this embodiment is effective against OH-. - The ion flux is 6.0 mol·m -2 ·h -1 The separation factor is 2750; the non-hypercrosslinked ion-solventized dense membrane is effective against OH. - The ion flux is only 3.8 mol·m -2 ·h -1 The separation factor was 2100. Compared with the non-hypercrosslinked ion-solventized dense membrane, the ion-solventized microporous membrane showed better resistance to OH-. - The ion flux increased by 57.9% and the separation factor increased by 31.0%.

[0064] Example 3

[0065] Ion-solventized microporous membranes and non-hypercrosslinked ion-solventized dense membranes were prepared according to the method of Example 1, except that the hypercrosslinking reaction time in step 3 was 10 min.

[0066] Following the method of Example 1, the ion-solventized microporous membrane and the non-hypercrosslinked ion-solventized dense membrane prepared in this example were applied to electrodialysis to separate NaOH from a NaOH / Na2WO4 mixed solution.

[0067] The results show that the ion-solventized microporous membrane prepared in this embodiment is effective against OH-. - The ion flux is 4.6 mol·m -2 ·h -1 The separation factor is 2466; the non-hypercrosslinked ion-solventized dense membrane is effective against OH. - The ion flux is only 3.8 mol·m -2 ·h -1 The separation factor was 2100. Compared with the non-hypercrosslinked ion-solventized dense membrane, the ion-solventized microporous membrane showed better resistance to OH-. - The ion flux increased by 21.1%, and the separation factor increased by 17.4%.

[0068] Example 4

[0069] Ion-solventized microporous membranes and non-hypercrosslinked ion-solventized dense membranes were prepared according to the method in Example 1.

[0070] The ion-solventized microporous membrane and the non-hypercrosslinked ion-solventized dense membrane prepared in this example were applied to the electrodialysis separation of NaOH in a NaOH / Na2WO4 mixed solution, following the method of Example 1. The difference was that 100 mL of a solution with a concentration of 6 mol·L⁻¹ was added to the dilution chamber. -1 The NaOH solution has a concentration of 0.4 mol·L⁻¹. -1 A mixed solution consisting of Na₂WO₄ solution was added to a concentration chamber in 100 mL of a solution with a concentration of 0.01 mol·L⁻¹. -1 NaOH solution.

[0071] The results show that the ion-solventized microporous membrane prepared in this embodiment is effective against OH-. - The ion flux is 7.3 mol·m -2 ·h -1 The separation factor is 3047; the non-hypercrosslinked ion-solventized dense membrane is effective against OH. - The ion flux was only 4.1 mol·m -2 ·h -1 The separation factor was 2178. Compared with the non-hypercrosslinked ion-solventized dense membrane, the ion-solventized microporous membrane showed better resistance to OH-. - The ion flux increased by 78.0%, and the separation factor increased by 39.9%.

[0072] Example 5

[0073] Ion-solventized microporous membranes and non-hypercrosslinked ion-solventized dense membranes were prepared according to the method in Example 1.

[0074] The ion-solventized microporous membrane and the non-hypercrosslinked ion-solventized dense membrane prepared in this example were applied to the electrodialysis separation of NaOH in a NaOH / Na2WO4 mixed solution, following the method of Example 1. The difference was that 100 mL of a solution with a concentration of 8 mol·L⁻¹ was added to the dilution chamber. -1 The NaOH solution has a concentration of 0.4 mol·L⁻¹. -1 A mixed solution consisting of Na₂WO₄ solution was added to a concentration chamber in 100 mL of a solution with a concentration of 0.01 mol·L⁻¹. -1 NaOH solution.

[0075] The results show that the ion-solventized microporous membrane prepared in this embodiment is effective against OH-. - The ion flux is 7.8 mol·m -2 ·h -1 The separation factor is 3350; the non-hypercrosslinked ion-solventized dense membrane is effective against OH. - The ion flux was only 4.3 mol·m -2 ·h -1The separation factor was 2200. Compared with the non-hypercrosslinked ion-solventized dense membrane, the ion-solventized microporous membrane showed better resistance to OH-. - The ion flux increased by 81.4%, and the separation factor increased by 52.3%.

[0076] Example 6

[0077] Ion-solventized microporous membranes and non-hypercrosslinked ion-solventized dense membranes were prepared according to the method in Example 1.

[0078] The ion-solventized microporous membrane and the non-hypercrosslinked ion-solventized dense membrane prepared in this example were applied to the electrodialysis separation of NaOH in a NaOH / Na2WO4 mixed solution, following the method of Example 1. The difference was that 100 mL of a solution with a concentration of 10 mol·L⁻¹ was added to the dilution chamber. -1 The NaOH solution has a concentration of 0.4 mol·L⁻¹. -1 A mixed solution consisting of Na₂WO₄ solution was added to a concentration chamber in 100 mL of a solution with a concentration of 0.01 mol·L⁻¹. -1 NaOH solution.

[0079] The results show that the ion-solventized microporous membrane prepared in this embodiment is effective against OH-. - The ion flux was 8.9 mol·m -2 ·h -1 The separation factor is 3780; the non-hypercrosslinked ion-solventized dense membrane is effective against OH. - The ion flux was only 4.4 mol·m -2 ·h -1 The separation factor was 2300. Compared with the non-hypercrosslinked ion-solventized dense membrane, the ion-solventized microporous membrane showed better resistance to OH-. - The ion flux increased by 102.3%, and the separation factor increased by 64.3%.

[0080] Example 7

[0081] Ion-solventized microporous membranes were prepared according to the method in Example 1.

[0082] The ion-solventized microporous membrane prepared in this example was applied to the electrodialysis separation of NaOH in a NaOH / Na2WO4 mixed solution according to the method of Example 1, except that the electrodialysis process was carried out at 40 °C.

[0083] The results show that the ion-solventized microporous membrane prepared in this embodiment exhibits good resistance to OH- at 40 °C. - The ion flux is 7.7 mol·m -2 ·h -1 The separation factor was 2467; compared with Example 1, the separation factor for OH was 2467. -The ion flux increased by 16.7%, while the separation factor decreased slightly.

[0084] Example 8

[0085] Ion-solventized microporous membranes were prepared according to the method in Example 1.

[0086] The ion-solventized microporous membrane prepared in this example was applied to the electrodialysis separation of NaOH in a NaOH / Na2WO4 mixed solution according to the method of Example 1, except that the electrodialysis process was carried out at 50 °C.

[0087] The results show that the ion-solventized microporous membrane prepared in this embodiment exhibits good resistance to OH- at 50 °C. - The ion flux was 9.4 mol·m -2 ·h -1 The separation factor was 1845; compared with Example 1, the separation factor for OH was 1845. - The ion flux increased by 42.4%, while the separation factor decreased slightly.

[0088] Figure 5 The changes in OH⁻ ion flux and selectivity of the ion-solventized microporous membrane prepared in this embodiment during 20 electrodialysis cycles at 50°C. Figure 5 It can be seen that the OH⁻ ion flux and selectivity remain almost unchanged, indicating that the ion-solventized microporous membrane has excellent cycling stability in the separation of high-temperature and high-concentration alkaline solutions.

[0089] Example 9

[0090] Ion-solventized microporous membranes were prepared according to the method in Example 1.

[0091] The ion-solventized microporous membrane prepared in this example was applied to the electrodialysis separation of NaOH in a NaOH / Na2WO4 mixed solution according to the method of Example 1, except that the electrodialysis process was carried out at 60 °C.

[0092] The results show that the ion-solventized microporous membrane prepared in this embodiment exhibits good resistance to OH- at 60 °C. - The ion flux was 10.7 mol·m -2 ·h -1 The separation factor was 913; compared with Example 1, the separation factor for OH was 913. - The ion flux increased by 62.1%, while the separation factor decreased by 68.2%.

[0093] Example 10

[0094] Ion-solventized microporous membranes were prepared according to the method in Example 1.

[0095] The ion-solventized microporous membrane prepared in this example was applied to the electrodialysis separation of NaOH in a NaOH / Na2SO4 mixed solution according to the method of Example 1, except that: 100 mL of a solution with a concentration of 4 mol·L⁻¹ was added to the dilution chamber. -1 The NaOH solution has a concentration of 0.4 mol·L⁻¹. -1 A mixed solution consisting of Na₂SO₄ solution was added to a concentration chamber in 100 mL of a solution with a concentration of 0.01 mol·L⁻¹. -1 NaOH solution.

[0096] The results show that the ion-solventized microporous membrane prepared in this embodiment is effective against OH-. - The ion flux is 7.1 mol·m -2 ·h -1 The separation factor was 1819; compared with Example 1, OH - Flux and selectivity are comparable.

[0097] Example 11

[0098] Ion-solventized microporous membranes were prepared according to the method in Example 1.

[0099] The ion-solventized microporous membrane prepared in this example was applied to the electrodialysis separation of NaOH in a NaOH / Na2MoO4 mixed solution according to the method of Example 1, except that: 100 mL of a solution with a concentration of 4 mol·L⁻¹ was added to the dilution chamber. -1 The NaOH solution has a concentration of 0.4 mol·L⁻¹. -1 A mixed solution consisting of Na₂MoO₄ solution was added to a concentration chamber in 100 mL of a solution with a concentration of 0.01 mol·L⁻¹. -1 NaOH solution.

[0100] The results show that the ion-solventized microporous membrane prepared in this embodiment is effective against OH-. - The ion flux is 6.8 mol·m -2 ·h -1 The separation factor was 2390; compared with Example 1, OH - Flux and selectivity are comparable.

[0101] Example 12

[0102] Ion-solventized microporous membranes were prepared according to the method in Example 1.

[0103] The ion-solventized microporous membrane prepared in this example was applied to the electrodialysis separation of NaOH in a NaOH / Na2CO3 mixed solution according to the method of Example 1, except that: 100 mL of a solution with a concentration of 4 mol·L⁻¹ was added to the dilution chamber. -1The NaOH solution has a concentration of 0.4 mol·L⁻¹. -1 A mixed solution consisting of Na₂CO₃ solution was added to a concentration chamber in 100 mL of a solution with a concentration of 0.01 mol·L⁻¹. -1 NaOH solution.

[0104] The results show that the ion-solventized microporous membrane prepared in this embodiment is effective against OH-. - The ion flux was 6.9 mol·m -2 ·h -1 The separation factor was 2026; compared with Example 1, OH - Flux and selectivity are comparable.

[0105] In summary, the ion-solventized microporous membrane obtained by the preparation method provided by this invention can be used for electrodialysis separation of OH under high temperature and high concentration alkaline conditions. - And multivalent anions, compared with non-hypercrosslinked ion-solventized dense films, OH - Ion flux and selectivity have been significantly and simultaneously improved.

[0106] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an ion-solventized microporous membrane, characterized in that, Includes the following steps: S1. Indigo-aromatic copolymers are synthesized from aromatic hydrocarbons and indigo through a superacid catalytic reaction. S2. Prepare a polymer film from the indigo-aromatic copolymer; S3. The polymer membrane forms a supercrosslinked microporous membrane through a supercrosslinking reaction; S4. Immerse the hypercrosslinked microporous membrane in an alkaline solution to obtain an ion-solventized microporous membrane.

2. The preparation method according to claim 1, characterized in that: The aromatic hydrocarbon is at least one of biphenyl, para-terphenyl, meta-terphenyl, and tetraphenyl.

3. The preparation method according to claim 1, characterized in that: The molar ratio of the aromatic hydrocarbon to indigo is 1:(1-1.3).

4. The preparation method according to claim 1, characterized in that: The catalyst for the superacid catalytic reaction is a mixture of trifluoroacetic acid and trifluoromethanesulfonic acid; Preferably, the molar ratio of the aromatic hydrocarbon to trifluoroacetic acid is 1:(1~1.5); Preferably, the molar ratio of trifluoroacetic acid to trifluoromethanesulfonic acid is 1:(7~12). Preferably, the reaction solvent for the superacid catalytic reaction is at least one of dichloromethane, trichloromethane, and tetrahydrofuran.

5. The preparation method according to claim 1, characterized in that: The polymer film is prepared by at least one of solution casting, blade coating, and spin coating, using at least one of N-methylpyrrolidone, dimethyl sulfoxide, and N,N-dimethylformamide as a solvent.

6. The preparation method according to claim 1, characterized in that: The reaction solvent for the hypercrosslinking reaction is at least one of 1,2-dichloroethane, N,N-dimethylformamide, and carbon tetrachloride. Preferably, the catalyst for the hypercrosslinking reaction is at least one selected from ferric chloride, tin dichloride, aluminum trichloride, boron fluoride, and ferric bromide. Preferably, the crosslinking agent for the hypercrosslinking reaction is at least one selected from dimethylformaldehyde, dichloromethyl ether, dichloroxylene, and 4,4'-bis(chloromethyl)biphenyl; Preferably, the molar ratio of the reaction solvent to the catalyst and crosslinking agent is (5~20): 1: (0.5~3); Preferably, the reaction temperature of the hypercrosslinking reaction is 25~80 °C.

7. The preparation method according to claim 1, characterized in that: The alkaline solution is one of sodium hydroxide, potassium hydroxide, lithium hydroxide, and calcium hydroxide solutions; Preferably, the concentration of the alkaline solution is 1~10 mol L. -1 ; Preferably, the soaking temperature of the alkaline solution is 20~80 ℃, and the soaking time is 7~10 days.

8. An ion-solventized microporous membrane prepared by the preparation method according to any one of claims 1 to 7.

9. The ion-solventized microporous membrane according to claim 8 in OH - Applications in the separation of multivalent anions.

10. The application according to claim 9, characterized in that: The OH - Polyvalent anions include OH- - / WO4 2- OH - / MoO4 2-- OH - SO4 2-- OH - / CO3 2- At least one of them; Preferably, the OH - The separation of multivalent anions is performed using electrodialysis.

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