Quaternized polymer and aperture-adjustable self-polymerization microporous anion selective membrane prepared from quaternized polymer

Abstract

The invention discloses a quaternized polymer and an aperture-adjustable self-polymerization microporous anion selective membrane prepared from the quaternized polymer. The quaternized polymer is formed by cross-linking an ether-free aromatic ring main chain and a halogenated compound containing double bonds and then quaternizing. Compared with the prior art, the main chain of the polymer provided by the invention contains a three-dimensional structural unit and a linear structural unit, and winding and stacking between molecular chains are regulated and controlled by regulating and controlling the proportion of the three-dimensional structural unit and the linear structural unit. In addition, a cross-linking agent is added into the structure to enhance the stability of the membrane, and the self-polymerization microporous membrane with the adjustable aperture is formed. Micropores in the membrane construct a confinement ion channel, the ion transmission capacity is enhanced, meanwhile, the anion selectivity of the membrane is improved through the size effect of the micropores, the membrane with the corresponding separation performance can be obtained by adjusting the size of the pore diameter, the membrane has good chemical stability in a strong alkali system, the preparation method is simple, the cost is low, and the method is suitable for industrial production. And the method has a wide application prospect in separation of monovalent and divalent anions in the electrodialysis process.

Description

Technical Field

[0001] This invention belongs to the field of anion exchange membrane separation technology, and specifically relates to a quaternized polymer and a self-polymerized microporous selective membrane with adjustable pore size prepared therefrom. Background Technology

[0002] Electrodialysis technology, with ion exchange membranes at its core, has become a key technology in emerging separation fields due to its significant advantages of high efficiency, environmental friendliness, and energy saving, playing an important role in various industries such as chemical synthesis, food processing, and environmental protection. Traditional ion exchange membrane-based electrodialysis systems have demonstrated excellent performance in separating oppositely charged ions (cations and anions).

[0003] As industrial production becomes more refined, ion exchange membranes face higher separation requirements. For example, in seawater desalination and brine salinization processes, it is necessary to achieve Cl... - With SO4 2- Precise separation is required; the wastewater generated in the alkaline decomposition process for tungsten extraction needs to be treated with WO4. 2- With OH - High-efficiency separation is crucial for alkali recovery. The alumina production process generates a large amount of red mud waste, and each ton of waste residue discharged via wet methods will be accompanied by 3-4 tons of alkaline waste liquid. The treatment of this waste liquid places stringent demands on membrane separation performance. Traditional ion exchange membranes can only achieve basic separation of anions and cations. In scenarios involving the selective separation of ions with the same charge but different valence states, they are insufficient to meet the refined requirements of industrial production, and their separation effect is significantly limited.

[0004] Currently, commercially available monovalent anion-selective ion exchange membranes are only mastered by a few countries such as the United States and Japan, and related research in China remains relatively weak. In the field of preparing monovalent anion-selective separation membranes, existing technologies mostly focus on surface modification of commercial ion exchange membranes. Patent CN 105646924 B discloses a selective separation membrane prepared by composited with a negatively charged thin layer on the surface of a positively charged base membrane, achieving the separation of monovalent anions (such as F...). - Cl - ,Br - I - NO3 - (etc.) and high-valence anions (such as SO42-) 2- CO3 2- PO4 3- Selective separation of ions (e.g., ions, etc.). The results show that this type of modified membrane exhibits significant selective separation effect in the separation of the above ion systems. However, this surface modification preparation process has a key drawback: during long-term operation, the surface modification layer is prone to peeling off, leading to a significant decrease in the separation performance of the membrane, making it difficult to meet the long-term application requirements of industrial scenarios.

[0005] The Journal of Membrane Science (Elsevier, 550 (2018) 427-435) reports a modification technique: by constructing a sulfonated dopamine layer on the surface of a commercial anion exchange membrane to form a negatively charged surface structure, and applying it to Cl... - With SO4 2- The modified membrane exhibits good selectivity in the separation of target ions, but it has obvious technical limitations: the modification steps are complex, making it unsuitable for large-scale preparation, and the thickness of the modified layer is difficult to control precisely.

[0006] Currently, research and applications of selective separation membranes for monovalent and divalent anions are mainly focused on neutral solution systems. These systems have relatively low requirements for membrane chemical stability, while there are few research reports on systems containing alkaline wastewater. Selective separation of hydroxide ions and oxygen-containing anions is required in alkaline wastewater, and even commercially available selective separation membranes for monovalent and divalent anions (ACS) still cannot meet the requirements in terms of alkali resistance and separation performance. Summary of the Invention

[0007] The present invention addresses many technical pain points existing in the prior art by proposing a quaternized polymer and a self-polymerizing microporous anion-selective membrane with tunable pore size prepared therefrom.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: a quaternized polymer, wherein the structural formula of the quaternized polymer is as shown in Formula 1:

[0009]

[0010] Among them: Ar1 and Ar2, one of which is a three-dimensional structural unit of etherless aromatic hydrocarbon, and the other is a linear structural unit of etherless aromatic hydrocarbon.

[0011] Furthermore, Ar1 is m-terphenyl, tetraphenylmethane, 1,3,5-triphenylbenzene, fluorene, or 9,9-dimethylfluorene; and Ar2 is biphenyl, p-terphenyl, p-tetraphenyl, 1,2-diphenylethane, or 1,6-diphenylhexane.

[0012] Furthermore, the crosslinking agent is 4-vinylbenzyl chloride, 6-bromo-hexene, or 4-bromo-1-butene.

[0013] A method for preparing the above-mentioned quaternized polymer includes the following steps:

[0014] (1) Dissolve etherless aromatic hydrocarbons with three-dimensional structural units and linear structural units in dichloromethane under ice bath, then add ketone compounds, add trifluoroacetic acid and trifluoromethanesulfonic acid dropwise under ice bath, continue to reverse the mixture in ice bath until the polymer can no longer flow freely, pour into sodium hydroxide solution to precipitate, stir, wash the precipitate repeatedly with deionized water, filter, dry, and obtain the polymer backbone;

[0015] (2) The polymer backbone is dissolved in a solvent, and a catalyst K2CO3 and a primary halogenated compound containing double bonds are added. The mixture is stirred at room temperature to carry out a cross-linking reaction. The above homogeneous solution is precipitated in acetone, washed, filtered, and dried to obtain the cross-linked polymer.

[0016] (3) Dissolve the cross-linked polymer in N-methylpyrrolidone, add haloalkanes, stir at high temperature, carry out the Menshoukin reaction, precipitate the above homogeneous solution in ethyl acetate, wash, filter, and dry to obtain the quaternized polymer.

[0017] Furthermore, in step (1), the molar ratio of the etherless aromatic hydrocarbon of the three-dimensional structural unit to the etherless aromatic hydrocarbon of the linear structural unit is 1:9 to 9:1;

[0018] The molar ratio of the etherless aromatic hydrocarbon to the ketone compound in the three-dimensional structural unit is 1:(1.1 to 1.3).

[0019] The molar ratio of the ether-free aromatic hydrocarbon to trifluoroacetic acid in the three-dimensional structural unit is 1:(1~1.5).

[0020] The molar ratio of trifluoroacetic acid to trifluoromethanesulfonic acid is 1:(7-12).

[0021] The ketone compound is: N-methylpiperidinone or 4-acetylpyridine;

[0022] The molecular weight of the polymer backbone is greater than 60,000 Da;

[0023] The ice bath temperature is 0–5 °C.

[0024] Furthermore, the molar ratio of the polymer backbone to the crosslinking agent in step (2) is 1:(0.1~1).

[0025] The solvent is N-methylpyrrolidone, sulfoxide, or N,N-dimethylformamide;

[0026] The double-bonded primary halogenated compound is 4-vinylbenzyl chloride, 6-bromo-hexene, or 4-bromo-1-butene;

[0027] The stirring time is 12–24 hours.

[0028] The stirring temperature is 60–100 °C.

[0029] Furthermore, in step (3), the haloalkane is a haloalkane such as iodomethane, bromoethane, bromobutane, or bromohexane;

[0030] The molar ratio of the crosslinked polymer to the halohydrocarbon is 1:(0.1 to 1.2).

[0031] A self-polymerized microporous anion-selective membrane with tunable pore size is prepared by solvent evaporation using the aforementioned quaternized polymer as raw material.

[0032] Furthermore, the solvent is dimethyl sulfoxide, N,N-dimethylformamide or N,N-dimethylacetamide, and the quaternized polymer is dissolved in the solvent to prepare a casting solution with a concentration of 10wt% to 40wt%.

[0033] Furthermore, the microporous anion-selective membrane can separate monovalent and divalent anions during the electrodialysis process; the monovalent and divalent anions are: Cl... - SO4 2- ,Br - SO4 2- F - SO4 2- NO3 - SO4 2- OH - / WO4 2- OH - SO4 2- Cl - / CO3 2- or OH - / MoO4 2 .

[0034] The beneficial effects of this invention are as follows:

[0035] Compared with existing technologies, the tunable-pore-size self-polymerized microporous anion-selective membrane prepared in this invention is a covalently cross-linked homogeneous membrane, avoiding the defects of easy detachment and poor alkali resistance of monovalent anion-selective separation membranes prepared by surface modification processes. This invention, starting from the design of different polymer molecular configurations and the control of the polymer membrane microporous structure, prepares a tunable-pore-size self-polymerized microporous anion-selective membrane. The polymer backbone provided by this invention contains three-dimensional structural units and linear structural units. By controlling the ratio between these two units, the entanglement and stacking between molecular chains are controlled, thereby forming a microporous structure. Furthermore, an appropriate amount of cross-linking agent is added to the structure to enhance the membrane's stability. The micropores within the membrane construct "confined" ion channels, enhancing ion transport capacity, while the size effect of the micropores improves the membrane's ion selectivity. Moreover, this membrane exhibits good chemical stability in strongly alkaline systems, and its preparation method is simple and low-cost, showing broad application prospects in the separation of anions in electrodialysis. Attached Figure Description

[0036] Figure 1 This is a scanning electron microscope image of the microporous anion-selective membrane prepared in Example 1.

[0037] Figure 2 This is a radar chart comparing the basic property parameters of the microporous anion-selective membrane of Example 1 with those of a commercial ACS membrane.

[0038] Figure 3 The pore size distribution curve of the microporous anion-selective membrane in Example 1 was obtained based on the N2 adsorption-desorption isotherm.

[0039] Figure 4 Example 1 shows a microporous anion-selective membrane at 1 mol L⁻¹ −1 NaOH / 0.1 mol L −1 Stability of the Na2WO4 mixture after 50 cycles.

[0040] Figure 5 The changes in mechanical properties of the commercial ACS, microporous anion-selective membrane, and microporous anion-selective membrane after alkaline cycling test in Example 1 are shown.

[0041] Figure 6 The pore size distribution curve of the microporous anion-selective membrane was obtained from the N2 adsorption-desorption isotherm in Example 2.

[0042] Figure 7 The pore size distribution curve of the microporous anion-selective membrane was obtained in Example 3 based on the N2 adsorption-desorption isotherm. Detailed Implementation

[0043] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0044] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification, claims and accompanying drawings of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product or device.

[0045] A method for preparing a pore size-tunable self-polymer microporous anion-selective membrane involves first preparing a polymer backbone by reacting an ether-free aromatic hydrocarbon with a ketone compound via superacid catalysis, then performing a crosslinking reaction with a crosslinking reagent to obtain a crosslinked polymer, followed by a quaternization reaction with a haloalkane to obtain a quaternized polymer, and finally obtaining a pore size-tunable self-polymer microporous anion-selective membrane by solvent evaporation.

[0046] Specifically, the following steps are included:

[0047] Step 1: Preparation of the polymer backbone

[0048] Etherless aromatic hydrocarbons with both three-dimensional and linear structural units were dissolved in dichloromethane in an ice bath. Then, ketone compounds were added, followed by the dropwise addition of trifluoroacetic acid and trifluoromethanesulfonic acid in an ice bath. The mixture was continuously reacted in the ice bath until the polymer could no longer flow freely. The solution was then poured into a sodium hydroxide solution to precipitate the polymer. The mixture was stirred, and the precipitate was repeatedly washed with deionized water. After filtration and drying, the polymer backbone was obtained.

[0049] Step 2: Crosslinking reaction

[0050] The polymer backbone is dissolved in a solvent, and a catalyst K₂CO₃ and a primary halogenated compound containing double bonds are added. The mixture is stirred at room temperature to carry out a crosslinking reaction. The homogeneous solution is then precipitated in acetone, washed, filtered, and dried to obtain the crosslinked polymer.

[0051] Step 3: Quaternization

[0052] The crosslinked polymer was dissolved in N-methylpyrrolidone, and a haloalkane was added. The mixture was stirred at high temperature to carry out the Mensøe-Glaucon reaction. The homogeneous solution was then precipitated in ethyl acetate, washed, filtered, and dried to obtain the quaternized polymer.

[0053] Step 4: Preparation of self-aggregating microporous anion-selective membranes with tunable pore size

[0054] Quaternized polymers were used to prepare casting solutions with dimethyl sulfoxide as solvent. A self-polymerized microporous anion-selective membrane with adjustable pore size was obtained by solvent evaporation.

[0055] Preferably, the three-dimensional structural unit in step 1 is one of m-terphenyl, tetraphenylmethane, 1,3,5-triphenylbenzene, and fluorene 9,9-dimethylfluorene.

[0056] Preferably, the linear structural unit in step 1 is one of biphenyl, p-terphenyl, p-tetraphenyl, 1,2-diphenylethane, and 1,6-diphenylhexane.

[0057] Preferably, the molar ratio of the three-dimensional structural unit to the linear structural unit in step 1 is 1:9-9:1;

[0058] Preferably, the molecular weight of the polymer backbone in step 1 is greater than 60,000 Da;

[0059] Preferably, the ketone compound in step 1 is one of N-methylpiperidinone and 4-acetylpyridine.

[0060] Preferably, the molar ratio of the three-dimensional structural unit to the ketone compound in step 1 is 1:1.1 to 1:1.3.

[0061] Preferably, the ice bath temperature in step 1 is 0-5℃.

[0062] Preferably, the molar ratio of the three-dimensional structural unit to trifluoroacetic acid in step 1 is 1:1 to 1:1.5.

[0063] Preferably, the molar ratio of trifluoroacetic acid to trifluoromethanesulfonic acid in step 1 is 1:7 to 1:12.

[0064] Preferably, the crosslinking agent mentioned in step 2 is one of 4-vinylbenzyl chloride, 6-bromo-hexene, and 4-bromo-1-butene.

[0065] Preferably, the molar ratio of the polymer backbone to the crosslinking agent in step 2 is 1:0.1-1:1.

[0066] Preferably, the solvent in step 2 is any one of N-methylpyrrolidone, sulfoxide, and N,N-dimethylformamide.

[0067] Preferably, the stirring time in step 2 is 12-24 hours.

[0068] Preferably, the stirring temperature in step 2 is 60-100 ℃.

[0069] Preferably, the haloalkane described in step 3 has the structure of one of iodomethane, bromoethane, bromobutane, or bromohexane.

[0070] Preferably, the molar ratio of the crosslinked polymer to the haloalkane in step 3 is 1:0.1 to 1:1.2.

[0071] Preferably, the organic solvent in step 4 is any one of dimethyl sulfoxide, N,N-dimethylformamide, and N,N-dimethylacetamide;

[0072] Preferably, the concentration of the casting solution in step 4 is 10wt%-40wt%;

[0073] Preferably, the casting process in step 4 is as follows: the casting solution is applied to a glass plate or polyethylene terephthalate (PET) substrate by solution casting or by blade coating at a temperature of 50-100 °C and then dried.

[0074] Preferably, the thickness of the membrane in step 4 is 30-150 μm.

[0075] Preferably, the pore size range of the tunable microporous polymer membrane in step 4 is 0.1-1 nm.

[0076] The second objective of this invention is to provide a self-polymerized microporous anion-selective membrane with tunable pore size obtained according to the aforementioned preparation method.

[0077] The third objective of this invention is to provide a self-aggregating microporous anion-selective membrane with adjustable pore size for use in the electrodialysis process to separate monovalent and divalent anions;

[0078] Preferably, the monovalent or divalent anion is: Cl - SO4 2- ,Br - SO4 2- F - SO4 2- NO3 - SO4 2- OH - / WO4 2- OH - SO4 2- Cl - / CO3 2- OH - / MoO4 2- One of them.

[0079] Example 1

[0080] 1. Preparation of a self-polymerizing microporous polymer membrane with adjustable pore size

[0081] Step 1: Preparation of polymer backbone (5:5)

[0082] 4.6 g of m-terphenyl and 4.6 g of p-terphenyl were dissolved in 4 mL of dichloromethane in an ice bath. Then, 4.97 g of N-methyl-4-piperidinone was added. 1.6 mL of trifluoroacetic acid and 20 mL of trifluoromethanesulfonic acid were added dropwise in an ice bath. The mixture was allowed to react for 9 hours in an ice bath until the polymer could no longer flow freely. The solution was then poured into 1000 mL of 2 mol / L sodium hydroxide solution to precipitate the polymer. The mixture was stirred for 36 hours. The precipitate was repeatedly washed with deionized water, filtered, and dried at 60 °C to obtain the polymer backbone.

[0083] Step 2: Crosslinking reaction

[0084] 2.6 g of polymer backbone was dissolved in 18 mL of DMSO, and 0.33 g of K2CO3 and 0.122 g of 4-vinylbenzyl chloride were added. The mixture was stirred at room temperature for 24 hours to carry out the crosslinking reaction and prepare the crosslinked polymer.

[0085] Step 3: Quaternization reaction

[0086] The cross-linked polymer was dissolved in N-methylpyrrolidone, and 2.25 mL (excess) of iodomethane was added. The mixture was stirred at 80 °C for 12 hours in the dark. The homogeneous solution was then precipitated in acetone, washed with water, and dried.

[0087] Step 4: Preparation of microporous polymer membranes with adjustable pore size

[0088] The quaternized polymer was used as a solvent to prepare a 25 wt% casting solution, which was then cast onto glass and dried on a flat plate heater to obtain a self-polymerized microporous anion-selective membrane with adjustable pore size.

[0089] Figure 1 The image shows a cross-sectional SEM image of the membrane, revealing a thickness of 75 μm.

[0090] Figure 2 The radar chart compares the basic properties of the microporous membrane and the commercial ACS membrane. The chart shows that the microporous membrane has a mechanical strength of 45 MPa, an elongation at break of 40%, and a sheet resistivity of 2.2 Ω cm⁻¹. 2 The membrane has an ion exchange capacity of 2.53 mmol / g, a water content of 35%, and a swelling rate of 7.8%, all of which are superior to commercial ACS membranes. Its migration number of 0.95 is comparable to that of commercial ACS membranes.

[0091] Figure 3 The pore size distribution of the tunable microporous anion-selective membrane obtained in this embodiment is shown in the N2 adsorption-desorption isotherm. The figure shows that the membrane pore size ranges from 0.47 to 0.55 nm, with a relatively narrow distribution and a concentrated pore size of 0.5 nm.

[0092] 2. The tunable pore size self-polymerized microporous anion-selective membrane prepared in this embodiment is applied to electrodialysis for the separation of Cl. - SO4 2- and Cl - SO4 2- Mixed system.

[0093] With Cl - SO4 2- As a separation system, the results show that the microporous membrane Cl prepared in this embodiment... - The flux is 3 mol m -2 h -1The selectivity is 20. Commercial ACS membranes, however, are selective for Cl... - The flux is 2.2 mol m -2 h -1 Cl - SO4 2- The selectivity was 2.5. In contrast, the microporous membrane prepared in this embodiment showed better selectivity for Cl... - Flux and Cl - SO4 2- The selectivity is superior to that of commercial ACS membranes.

[0094] With OH - / WO4 2- As a separation system, the results show that the membrane OH prepared in this example - The flux was 4.7 mol m -2 h -1 The selectivity is 250. Commercial ACS membranes, however, are selective for Cl... - The flux is 3.6 mol m -2 h -1 Cl - SO4 2- The selectivity is 80%. In contrast, the microporous membrane prepared in this embodiment is more resistant to OH-. - Flux and OH - / WO4 2- The selectivity is superior to that of commercial ACS membranes.

[0095] The stability of the microporous membrane prepared in this embodiment was evaluated after 50 consecutive cycles in a separation system of 1.0 mol / L NaOH and 0.1 mol / L Na2WO4. Figure 4 The results showed that OH ion flux and OH - / WO4 2- The selectivity remained unchanged, indicating that the membrane has long-term operational stability in high-concentration alkaline solutions.

[0096] Figure 5 The figure shows the changes in mechanical properties of the commercial ACS membrane, the microporous membrane, and the microporous membrane after alkali cycling. As can be seen from the figure, the tensile strength and elongation at break of the microporous membrane are superior to those of the commercial ACS membrane before and after alkali immersion.

[0097] The selective separation performance of the microporous anion-selective membrane prepared in this embodiment was evaluated by electrodialysis. - SO4 2-The electrodialysis conditions for separation of the mixed system are as follows: 100 mL of 0.1 mol / L NaCl / Na₂SO₄ in the desalination chamber, 100 mL of 0.01 mol / L KNO₃ in the concentration chamber, 0.3 mol / L Na₂SO₄ in the electrode chamber, and a current density of 10 mA / cm². 2 The running time was 1 hour, and the effective membrane area was 7.07 cm². 2 .

[0098] When OH - / WO4 2- The electrodialysis conditions for system separation were as follows: 100 mL of a mixed solution of 1.0 mol / L NaOH and 0.1 mol / L Na₂WO₄ in the desalination chamber, 0.01 mol / L NaOH in the concentration chamber, and 0.3 mol / L Na₂SO₄ in the electrode chamber; the current density was 10 mA / cm². 2 The time was 1 hour, and the effective membrane area was 7.07 cm². 2 .

[0099] The formula for calculating ion flux (J) is:

[0100]

[0101] Where J is the ion flux through the membrane, in mol / m³. -2 h -1 ;

[0102] C t C0 and C0 represent the ion concentrations in the concentration chamber at time t and the initial time, respectively, in mol / L.

[0103] V is the volume of the solution in the concentration chamber, measured in cubic meters (m³). 3 ;

[0104] A represents the effective contact area between the membrane and the solution, measured in cm². 2 ;

[0105] t represents the electrodialysis operation time, in hours.

[0106] The formula for calculating selectivity (S) is:

[0107]

[0108] in, and Fluxes of monovalent and divalent anions (mol m) −2 h −1 ). and These represent the concentrations (mol / L) of monovalent and divalent anions in the desalination chamber during the experiment. −1 The monovalent anion is F. − Cl − ,Br − NO3 − or OH − The divalent anion is SO42-. 2− Or WO4 2− .

[0109] Example 2

[0110] 1. In this embodiment, the pore size adjustable microporous polymer membrane is prepared by the same method as in Example 1, except that 2.76 g of m-terphenyl and 6.44 g of p-terphenyl (3:7) are added in step 1.

[0111] 2. The microporous membrane prepared in this embodiment has a thickness of 77 μm, a mechanical strength of 35 MPa, an elongation at break of 45%, and a sheet resistivity of 2.5 Ω cm. 2 The membrane exhibited a swelling ratio of 10%, an ion exchange capacity of 2.46 mmol / g, and a water content of 30%, all superior to commercial ACS membranes. Its migration number of 0.94 was comparable to that of commercial ACS membranes. Compared to Example 1, the microporous membrane prepared in this example showed decreased tensile strength, increased elongation at break, and increased swelling ratio.

[0112] Figure 6 The pore size distribution of the tunable self-polymerized microporous anion-selective membrane prepared in this embodiment was obtained based on the N2 adsorption-desorption isotherm. The figure shows that the membrane's pore size ranges from 0.48 to 0.70 nm, and the distribution is relatively wide. Compared to Example 1, the pore size range of the microporous membrane prepared in this embodiment is increased.

[0113] 3. The microporous anion-selective membrane with adjustable pore size prepared in this embodiment is applied to electrodialysis for the separation of Cl. - SO4 2- and OH - / WO4 2- Mixed system.

[0114] With Cl - SO4 2- As a separation system, the results show that the membrane Cl prepared in this example - The flux is 3.5 mol m -2 h -1 The selectivity is 15. Compared to commercial ACS membranes, the membrane flux and selectivity prepared in this invention are superior. Compared to Example 1, the microporous membrane prepared in this example exhibits better performance for Cl... - Increased ion flux, Cl- SO4 2- Selectivity is reduced.

[0115] With OH - / WO4 2- As a separation system, the results show that the microporous membrane prepared in this example is effective against OH. - The flux is 5.0 molm. -2 h -1 The selectivity is 200. Compared with commercial ACS membranes, the membrane prepared in this invention has superior flux and selectivity. Compared with Example 1, the microporous membrane prepared in this example has better OH flux and selectivity. - Increased ion flux, OH - / WO4 2- Selectivity is reduced.

[0116] Example 3

[0117] 1. In this embodiment, a self-polymerized microporous membrane with adjustable pore size is prepared according to the same method as in Example 1, except that 6.44 g of m-terphenyl and 2.76 g of p-terphenyl (7:3) are added in step 1.

[0118] 2. The microporous membrane prepared in this embodiment has a thickness of 75 μm, a tensile strength of 55 MPa, an elongation at break of 28%, and a sheet resistivity of 2.5 Ω cm. 2 The swelling ratio was 6.5%, the ion exchange capacity was 2.58 mmol / g, and the water content was 32%, all of which were superior to commercial ACS membranes. The migration number was 0.96, which was comparable to that of commercial ACS membranes. Compared with Example 1, the microporous membrane prepared in this example showed increased tensile strength, decreased elongation at break, and reduced swelling ratio.

[0119] Figure 7 The pore size distribution of the tunable self-polymerized microporous anion-selective membrane obtained in this embodiment was obtained based on the N2 adsorption-desorption isotherm. The figure shows that the membrane's pore size ranges from 0.52 to 0.80 nm and has a relatively wide distribution. Compared to Example 1, the pore size range of the microporous membrane prepared in this embodiment is increased.

[0120] 2. The tunable pore size self-polymerized microporous anion-selective membrane prepared in this embodiment is applied to electrodialysis for the separation of Cl. - SO4 2- and OH - / WO4 2- Mixed system.

[0121] With Cl - SO4 2- As a separation system, the results show that the microporous membrane prepared in this embodiment is effective for the separation of Cl. - The flux is 3.8 molm.-2 h -1 The selectivity is 10. Compared with commercial ACS membranes, the membrane prepared in this invention is more selective for Cl... - Flux and Cl - SO4 2- The selectivity is superior to that of commercial ACS membranes. Compared to Example 1, the microporous membrane prepared in this example exhibits better selectivity for Cl... - Increased ion flux, Cl - SO4 2- Selectivity is reduced.

[0122] With OH - / WO4 2- As a separation system, the results show that the microporous membrane prepared in this example is effective against OH. - The flux is 5.3 mol m -2 h -1 The selectivity is 180. Compared with commercial ACS membranes, the membrane prepared in this invention has superior flux and selectivity. Compared with Example 1, the microporous membrane prepared in this example has better OH flux and selectivity. - Increased ion flux, OH - / WO4 2- Selectivity is reduced.

[0123] Examples 1-3 demonstrate that when the ratio of three-dimensional structural units to linear structural units tends to be equal, the pore size distribution range of the membrane is narrow, concentrated at 0.5 nm. Furthermore, the wider the pore size distribution range, the more the ratio of three-dimensional to linear structural units increases or decreases. A narrow pore size range results in low ion flux and high selectivity; a wide pore size range results in high ion flux and low selectivity.

[0124] Preferably, the ratio of the three-dimensional structural unit to the linear structural unit is 5:5.

[0125] Example 4

[0126] 1. In this embodiment, the microporous membrane is prepared using the same method as in Example 1, except that no crosslinking agent is added in step 2.

[0127] 2. The uncrosslinked polymer membrane prepared in this embodiment has a pore size range of 0.5-0.9 nm, a thickness of 70-80 μm, a mechanical strength of 35 MPa, and an elongation at break of 45%. The swelling ratio of the membrane is 21%. Compared with the crosslinked membrane prepared in Example 1, the tensile strength of the membrane is reduced, the swelling ratio is increased, and the stability of the membrane is reduced.

[0128] 3. The tunable pore size self-polymerizing microporous anion-selective membrane prepared in this embodiment is applied to electrodialysis for the separation of Cl. - SO4 2- and OH- / WO4 2- Mixed system.

[0129] With Cl - SO4 2- As a separation system, the results show that the microporous membrane Cl prepared in this embodiment... - The flux is 4.0 molm. -2 h -1 The selectivity is 5. Compared with the membrane prepared in Example 1, Cl - The flux increased and the selectivity decreased, but both were better than commercial membranes.

[0130] With OH - / WO4 2- As a separation system, the results show that the microporous membrane OH prepared in this example - The flux is 6.1 molm. -2 h -1 The selectivity was 80%. Compared to the membrane prepared in Example 1, OH... - The flux increases, but the selectivity decreases, but both are superior to commercial membranes.

[0131] Example 5

[0132] 1. In this embodiment, a self-polymerized microporous anion-selective membrane with adjustable pore size is prepared according to the same method as in Example 1, except that 2.25 mL (excess) of bromhexane is added in step 3.

[0133] 2. The tunable pore size self-polymer microporous anion-selective membrane prepared in this embodiment has a pore size range of 0.48-0.55 nm, a membrane thickness of 70-80 μm, and a sheet resistivity of 2.2 Ω cm. 2 The tensile strength was 43 MPa, and the elongation at break was 42%. The swelling ratio of the membrane was 7.5%, and the water content of the membrane was 28%. The tensile strength and swelling ratio of the microporous membrane prepared in this embodiment are comparable to those of the microporous membrane prepared in Example 1, while the water content of the membrane is reduced.

[0134] 3. The tunable pore size self-polymerizing microporous anion-selective membrane prepared in this embodiment is applied to electrodialysis for the separation of Cl. - SO4 2- and OH - / WO4 2- Mixed system.

[0135] With Cl - SO4 2- As a separation system, the results show that the microporous membrane Cl prepared in this embodiment... - The flux is 3.5 molm. -2 h -1The selectivity was 5, which is better than that of commercial membranes and comparable to the membrane separation performance prepared in Example 1.

[0136] With OH - / WO4 2- As a separation system, the results show that the microporous membrane OH prepared in this example - The flux is 4.5 molm. -2 h -1 The selectivity was 80%. Both were superior to commercial membranes and comparable to the membrane separation performance prepared in Example 1.

[0137] Based on the above analysis, it can be concluded that the microporous membrane prepared in this embodiment is only a preferred embodiment. This membrane can be used for electrodialysis to separate monovalent and divalent anions. Compared with commercial ACS membranes, the flux and selectivity of monovalent ions are simultaneously improved. Furthermore, the membrane exhibits high tensile strength and low swelling ratio, indicating that the microporous membrane can effectively improve the separation performance of monovalent and divalent ions.

[0138] 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 quaternized polymer, characterized in that: The quaternized polymer has the structural formula shown in Formula 1: ， Among them: Ar1 and Ar2, one of which is a three-dimensional structural unit of etherless aromatic hydrocarbon, and the other is a linear structural unit of etherless aromatic hydrocarbon.

2. The quaternized polymer according to claim 1, characterized in that: Ar1 is m-terphenyl, tetraphenylmethane, 1,3,5-triphenylbenzene, fluorene, or 9,9-dimethylfluorene; Ar2 is biphenyl, p-terphenyl, p-tetraphenyl, 1,2-diphenylethane, or 1,6-diphenylhexane.

3. The quaternized polymer according to claim 1, characterized in that: The crosslinking agent is 4-vinylbenzyl chloride, 6-bromo-hexene, or 4-bromo-1-butene.

4. A method for preparing the quaternized polymer according to any one of claims 1 to 3, characterized in that: Includes the following steps: (1) Dissolve etherless aromatic hydrocarbons with three-dimensional structural units and linear structural units in dichloromethane under ice bath, then add ketone compounds, add trifluoroacetic acid and trifluoromethanesulfonic acid dropwise under ice bath, continue to reverse the mixture in ice bath until the polymer can no longer flow freely, pour into sodium hydroxide solution to precipitate, stir, wash the precipitate repeatedly with deionized water, filter, dry, and obtain the polymer backbone; (2) The polymer backbone is dissolved in a solvent, and a catalyst K2CO3 and a primary halogenated compound containing double bonds are added. The mixture is stirred at room temperature to carry out a cross-linking reaction. The above homogeneous solution is precipitated in acetone, washed, filtered, and dried to obtain the cross-linked polymer. (3) Dissolve the cross-linked polymer in N-methylpyrrolidone, add haloalkanes, stir at high temperature, carry out the Menshoukin reaction, precipitate the above homogeneous solution in ethyl acetate, wash, filter, and dry to obtain the quaternized polymer.

5. The preparation method according to claim 4, characterized in that: The molar ratio of the etherless aromatic hydrocarbons of the three-dimensional structural unit to the etherless aromatic hydrocarbons of the linear structural unit in step (1) is 1:9 to 9:

1. The molar ratio of the etherless aromatic hydrocarbon to the ketone compound in the three-dimensional structural unit is 1:(1.1 to 1.3). The molar ratio of the ether-free aromatic hydrocarbon to trifluoroacetic acid in the three-dimensional structural unit is 1:(1~1.5). The molar ratio of trifluoroacetic acid to trifluoromethanesulfonic acid is 1:(7-12). The ketone compound is: N-methylpiperidinone or 4-acetylpyridine; The molecular weight of the polymer backbone is greater than 60,000 Da; The ice bath temperature is 0–5 °C.

6. The preparation method according to claim 4, characterized in that: The molar ratio of the polymer backbone to the crosslinking agent in step (2) is 1:(0.1~1). The solvent is N-methylpyrrolidone, sulfoxide, or N,N-dimethylformamide; The double-bonded primary halogenated compound is 4-vinylbenzyl chloride, 6-bromo-hexene, or 4-bromo-1-butene; The stirring time is 12–24 hours. The stirring temperature is 60–100 °C.

7. The preparation method according to claim 4, characterized in that: The haloalkane in step (3) is a haloalkane such as iodomethane, bromoethane, bromobutane or bromohexane; The molar ratio of the crosslinked polymer to the halohydrocarbon is 1:(0.1 to 1.2).

8. A self-aggregating microporous anion-selective membrane with tunable pore size, characterized in that: It is prepared by solvent evaporation using the quaternized polymer according to any one of claims 1 to 3 as raw material.

9. The tunable pore size self-aggregating microporous anion-selective membrane according to claim 8, characterized in that: The solvent is dimethyl sulfoxide, N,N-dimethylformamide or N,N-dimethylacetamide. The quaternized polymer is dissolved in the solvent to prepare a casting solution with a concentration of 10wt% to 40wt%.

10. The tunable pore size self-aggregating microporous anion-selective membrane according to claim 8, characterized in that: The microporous anion-selective membrane can separate monovalent and divalent anions during the electrodialysis process; the monovalent and divalent anions are: Cl... - SO4 2- ,Br - SO4 2- F - SO4 2- NO3 - SO4 2- OH - / WO4 2- OH - SO4 2- Cl - / CO3 2- or OH - / MoO4 2 .

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