阅读说明：本技术 阴离子交换膜的制备方法以及阴离子交换膜 (Method for producing anion exchange membranes and anion exchange membranes ) 是由 徐铜文 葛亮 阿福 赵璋 于 2020-07-01 设计创作，主要内容包括：本发明公开了一种阴离子交换膜的制备方法,包括：使用1mg/L～2mg/L的多元酰氯溶液对基膜的表面进行改性,其中,所述基膜包括季铵基团以及羟基；持续3min～5min后,擦干所述基膜的表面的液体,得到处理后的所述基膜；将处理后的所述基膜在40℃～60℃下加热30min～60min,得到阴离子交换膜。本发明还公开了一种阴离子交换膜。本发明通过对侧链含有季铵基团以及羟基的基膜采用多元酰氯溶液进行改性,未反应的酰氯基团经水解后得到羧基,通过季铵基团提供阴离子传输通道,利用羧基对高价阴离子的排斥作用,降低高价阴离子的通量,提高低价阴离子的通量,进而,提高对低价阴离子的通量与选择性,制备的阴离子交换膜具有高通量、高选择性、高极限电流密度以及低面电阻等优势。(The invention discloses a preparation method of an anion exchange membrane, which comprises the following steps: modifying the surface of a basement membrane by using 1-2 mg/L polybasic acyl chloride solution, wherein the basement membrane comprises quaternary ammonium groups and hydroxyl groups; after lasting for 3min to 5min, wiping off the liquid on the surface of the basement membrane to obtain the processed basement membrane; and heating the treated base membrane at 40-60 ℃ for 30-60 min to obtain the anion exchange membrane. The invention also discloses an anion exchange membrane. According to the invention, the base membrane containing quaternary ammonium groups and hydroxyl groups on the side chain is modified by adopting a polybasic acyl chloride solution, unreacted acyl chloride groups are hydrolyzed to obtain carboxyl groups, an anion transmission channel is provided by the quaternary ammonium groups, the flux of high-valence anions is reduced and the flux of low-valence anions is improved by utilizing the repulsion action of the carboxyl groups on the high-valence anions, and further, the flux and selectivity on the low-valence anions are improved, and the prepared anion exchange membrane has the advantages of high flux, high selectivity, high limiting current density, low surface resistance and the like.)

1. The preparation method of the anion exchange membrane is characterized by comprising the following steps:

modifying the surface of a basement membrane by using a polybasic acyl chloride solution, wherein the basement membrane comprises quaternary ammonium groups and hydroxyl groups;

after lasting for 3min to 5min, wiping off the liquid on the surface of the basement membrane to obtain the processed basement membrane;

and heating the treated base membrane at 40-60 ℃ for 30-60 min to obtain the anion exchange membrane.

2. The method of preparing an anion exchange membrane according to claim 1, wherein the step of modifying the surface of the base membrane with a polyacyl chloride solution comprises:

infiltrating polyacyl chloride solution on the surface of the basement membrane to modify the basement membrane; alternatively, the first and second electrodes may be,

and soaking the basement membrane in a polyacyl chloride solution to modify the basement membrane.

3. The method of preparing an anion exchange membrane according to claim 1, wherein the step of preparing the base membrane comprises:

dissolving 5-20% of quaternized polymer in 80-95% of a first organic solvent by mass to obtain a first solution, wherein the first organic solvent comprises at least one of dimethyl sulfoxide, N-methylpyrrolidone and N, N-dimethylformamide;

processing the first solution into the base film.

4. The method of making an anion exchange membrane of claim 3, wherein the step of processing the first solution into the base membrane comprises:

dropping the first solution on a flat plate;

and heating the flat plate at 50-60 ℃ for 10-12 h to obtain the base film.

5. The method of claim 1, wherein the quaternized polymer is prepared by the steps of:

dissolving 10-20% of halomethylated polymer in 77-89% of a second organic solvent by mass to obtain a second solution, wherein the second organic solvent comprises at least one of dimethyl sulfoxide, N-methylpyrrolidone and N, N-dimethylformamide;

adding 1-3% by mass of N-methyldiethanolamine into the second solution, and reacting at 50-60 ℃ for 12-24 h to obtain a third solution;

adding 10-20 mL of toluene into the third solution, and collecting the precipitated precipitate;

washing the precipitate with diethyl ether to obtain the quaternized polymer.

6. The method of claim 5, wherein the halomethylated polymer comprises at least one of halomethyl polyphenylene ether, halomethyl polyethersulfone, halomethyl polystyrene, and halomethyl polyetherketone, wherein the halomethyl comprises at least one of chloromethyl, bromomethyl, and iodomethyl groups.

7. The method of claim 1, wherein the solution of polyacyl chloride comprises at least one of a solution of trimesoyl chloride in n-hexane, a solution of terephthaloyl chloride in n-hexane, and a solution of isophthaloyl chloride in n-hexane.

8. An anion exchange membrane prepared by the method for preparing the anion exchange membrane according to any one of claims 1 to 7.

Technical Field

The invention relates to the technical field of membrane separation, in particular to a preparation method of an anion exchange membrane and the anion exchange membrane.

Background

The membrane technology has the characteristics of high separation capacity and high selectivity, and has wide application prospects in the fields of water treatment, acid-base production, seawater desalination and the like.

Membrane technology is relatively low cost and can be easily integrated with other industrial processes for targeted applications. In recent years, electrodialysis has been the focus of research on the removal of selective ions (monovalent anion/cation fractionation) from brackish water. However, in the electrodialysis process, the existence of membrane fouling has been a serious problem, and the membrane fouling is easily caused by the uneven distribution of charges on the membrane surface, and the membrane fouling causes the problem of the reduction of the separation performance of the membrane.

The above is only for the purpose of assisting understanding of the technical aspects of the present invention, and does not represent an admission that the above is prior art.

Disclosure of Invention

The embodiment of the invention mainly aims to provide a preparation method of an anion exchange membrane, and aims to solve the technical problem that the separation performance of the membrane is reduced due to membrane pollution in the prior art.

In order to solve the above problems, an embodiment of the present invention provides a method for preparing an anion exchange membrane, including the following steps:

modifying the surface of a basement membrane by using polyacyl chloride solution, wherein the basement membrane comprises quaternary ammonium groups and hydroxyl groups;

after lasting for 3min to 5min, wiping off the liquid on the surface of the basement membrane to obtain the processed basement membrane;

and heating the treated base membrane at 40-60 ℃ for 30-60 min to obtain the anion exchange membrane.

Optionally, the step of modifying the surface of the base film with the polyacyl chloride solution comprises:

soaking 1-2 mg/L of polyacyl chloride solution on the surface of the basement membrane to modify the basement membrane; alternatively, the first and second electrodes may be,

and soaking the basement membrane in 1-2 mg/L polyacyl chloride solution to modify the basement membrane.

Optionally, the base film is prepared by:

dissolving 5-20% of quaternized polymer in 80-95% of a first organic solvent by mass to obtain a first solution, wherein the first organic solvent comprises at least one of dimethyl sulfoxide, N-methylpyrrolidone and N, N-dimethylformamide;

processing the first solution into the base film.

Optionally, the step of processing the first solution into the base film comprises:

dropping the first solution on a flat plate;

and heating the flat plate at 50-60 ℃ for 10-12 h to obtain the base film.

Alternatively, the quaternized polymer is prepared by the steps of:

dissolving 10-20% of halomethylated polymer in 77-89% of a second organic solvent by mass to obtain a second solution, wherein the second organic solvent comprises at least one of dimethyl sulfoxide, N-methylpyrrolidone and N, N-dimethylformamide;

adding 1-3% by mass of N-methyldiethanolamine into the second solution, and reacting at 50-60 ℃ for 12-24 h to obtain a third solution;

adding 10-20 mL of toluene into the third solution, and collecting the precipitated precipitate;

washing the precipitate with diethyl ether to obtain the quaternized polymer.

Optionally, the halomethylated polymer comprises at least one of halomethyl polyphenylene ether, halomethyl polyethersulfone, halomethyl polystyrene, and halomethyl polyetherketone, wherein the halomethyl comprises at least one of chloromethyl, bromomethyl, and iodomethyl.

Optionally, the poly-acid chloride solution comprises at least one of a solution of trimesoyl chloride in n-hexane, a solution of terephthaloyl chloride in n-hexane, and a solution of isophthaloyl chloride in n-hexane.

In addition, in order to solve the above problems, embodiments of the present invention further provide an anion exchange membrane, which is prepared by the above method for preparing an anion exchange membrane.

According to the preparation method of the anion exchange membrane provided by the embodiment of the invention, the base membrane containing quaternary ammonium groups and hydroxyl groups on the side chain is modified by adopting a polybasic acyl chloride solution, unreacted acyl chloride groups are hydrolyzed to obtain carboxyl groups, an anion transmission channel is provided by the quaternary ammonium groups, the charge distribution in the membrane surface is adjusted by utilizing the repulsion effect of the carboxyl groups on high-valence anions, the flux of the high-valence anions is further reduced, the flux and the selectivity of the low-valence anions are further improved, and the prepared anion exchange membrane has the advantages of high flux, high selectivity, high limiting current density, low surface resistance and the like.

Drawings

FIG. 1 is a representation of a base film in an embodiment of the present invention;

FIG. 2 is a nuclear magnetic resonance hydrogen spectrum of a brominated polyphenylene ether according to an example of the present invention;

FIG. 3 is a nuclear magnetic resonance hydrogen spectrum of a quaternized polyphenylene ether of an embodiment of the invention;

FIG. 4 is an infrared spectrum of a quaternized polyphenylene ether and a brominated polyphenylene ether prepared in examples 1 to 3 of the present invention;

FIG. 5 is a pictorial view of an anion exchange membrane of an embodiment of the present invention;

FIG. 6 is a scanning electron micrograph of a base film in an example of the present invention;

FIG. 7 is an atomic force microscope view of a base film in an example of the present method;

FIG. 8 is an atomic force microscope image of an anion exchange membrane according to an embodiment of the present invention;

FIG. 9 is a schematic diagram of a device for testing a limiting current density according to an embodiment of the present invention;

FIG. 10 is a schematic view of an electrodialysis testing apparatus according to an embodiment of the present invention;

FIG. 11 is a current density-voltage curve for a base membrane and anion exchange membrane in an example of the invention;

FIG. 12 shows the stability test results of the selectivity of the anion exchange membrane for chloride/sulfate ions in the examples of the present invention.

The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.

Detailed Description

It should be understood that the detailed description and specific examples, while indicating the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

In this example, the base membrane was chemically modified with a polybasic acid chloride due to the large number of hydroxyl groups on the base membrane, resulting in an anion exchange membrane having a large number of ester groups. After acyl chloride on the anion exchange membrane is hydrolyzed, a large number of negatively charged carboxyl groups are generated, and the anion exchange membrane has stronger electrostatic repulsion action on high-valence anions such as sulfate ions, carbonate ions and the like, so that the flux of the high-valence anions is greatly reduced; due to the reduction of the flux of the high-valence anions and the constant electric field, the flux of low-valence anions such as chloride ions and hydroxyl ions is greatly increased, and meanwhile, the selectivity of the low-valence anions is improved.

The basement membrane can be prepared by taking polysulfone, polyphenyl ether, aromatic polyamide, polyether sulfone, polyether ketone, polystyrene, polytetrafluoroethylene, polypropylene, polyacrylonitrile, polyvinyl alcohol, polybenzimidazole, polyimide and the like as a main chain structure, but a large number of quaternary ammonium groups and hydroxyl groups are arranged on the side chain of the basement membrane. Wherein the quaternary ammonium groups form anion channels; hydroxyl groups are used as chemically modified groups to prepare the base membrane into a functionalized active membrane.

Optionally, the base film is stored in deionized water.

And modifying the surface of the basement membrane by using a polybasic acyl chloride solution. Optionally, the polyacyl chloride solution is soaked on the surface of the basement membrane to modify the basement membrane. Optionally, the polyacyl chloride solution is dripped on the surface of the basement membrane to enable the basement membrane to be completely immersed by the polyacyl chloride solution, and the polyacyl chloride solution is supplemented at the position where the basement membrane is not immersed. Alternatively, the base film may be soaked in a polyacyl chloride solution to modify the base film. Optionally, the concentration of the polyacyl chloride solution is 1 mg/L-2 mg/L.

And continuously acting the polybasic acyl chloride solution on the base membrane for 3-5 min to allow hydroxyl on the base membrane to react with the polybasic acyl chloride so as to modify the base membrane, and wiping off the residual polybasic acyl chloride solution on the surface of the base membrane to obtain the treated base membrane. And heating the treated base membrane at 40-60 ℃ for 30-60 min to ensure that the polybasic acyl chloride and the carboxyl on the base membrane completely react to obtain the anion exchange membrane. Alternatively, the treated base film may be heated in an oven.

Optionally, the anion exchange membrane is stored in deionized water.

As an alternative embodiment, the preparation of the base film comprises: dissolving 5-20% of quaternized polymer in 80-95% of first organic solvent by mass to obtain first solution, wherein the first organic solvent comprises at least one of dimethyl sulfoxide, N-methylpyrrolidone and N, N-dimethylformamide.

The quaternary ammonium polymer has a large number of quaternary ammonium groups and can be well dissolved in a strong polar solvent. The quaternary ammonium group is a branched structure of the quaternary ammonium polymer.

After the first solution is obtained, the first solution is processed into a base film. The base membrane is prepared by a simple and easily-obtained method, so that the preparation cost of the anion exchange membrane can be greatly reduced, and the method is suitable for industrial production.

Referring to fig. 1, the base film was brown, and the surface was smooth and a homogeneous film without significant bubbles.

As an alternative embodiment, the first solution is dropped on a flat plate to uniformly distribute the first solution on the flat plate, and the flat plate on which the first solution is dropped is heated at 50 to 60 ℃ for 10 to 12 hours to volatilize the first organic solvent in the first solution to obtain the base film. The basement membrane was a brown, homogeneous film with smooth surface and no apparent bubble particles.

Optionally, the flat plate may be glass, a rectangular area may be formed on the cleaned glass by using adhesive tape, the glass plate is placed on the heating table, the first solution is dropped on the glass plate by using a dropper, so that the rectangular area is uniformly dispersed by the first solution, and then the heating plate is opened for drying, so as to obtain the base film.

Optionally, the flat plate to which the first solution is added may be placed in an oven for heating, and after the solvent is volatilized, the base film is obtained.

As an alternative embodiment, the quaternized polymer can be obtained by the following steps: dissolving 10-20% of halomethylated polymer in 77-89% of second organic solvent by mass to obtain a second solution, wherein the second organic solvent comprises at least one of dimethyl sulfoxide, N-methylpyrrolidone and N, N-dimethylformamide.

Adding 1-3% by mass of N-methyldiethanolamine into the second solution, reacting at 50-60 ℃ for 12-24 h to obtain a third solution, carrying out substitution reaction on amino groups on the N-methyldiethanolamine and halogen groups on the halomethylated polymer to generate a quaternized polymer, adding 10-20 mL of toluene into the third solution, separating out off-white precipitate of the quaternized polymer due to low solubility in the toluene, and washing the precipitate by using ether to obtain the quaternized polymer.

As an alternative embodiment, the halomethylated polymer comprises at least one of halomethyl polyphenylene ether, halomethyl polyethersulfone, halomethyl polystyrene, and halomethyl polyetherketone, wherein the halomethyl comprises at least one of chloromethyl, bromomethyl, and iodomethyl groups.

The halomethylated polymer is preferably bromomethylated polyphenylene ether. The reaction activity of the bromomethylated polyphenyl ether is relatively high, and side reactions are less.

Taking a halomethylated polymer as an example of brominated polyphenylene ether, after the brominated polyphenylene ether is sufficiently reacted with N-methyldiethanolamine, a nuclear magnetic resonance spectrum (refer to FIG. 2) of the brominated polyphenylene ether and a nuclear magnetic resonance spectrum (refer to FIG. 2) of a quaternized polyphenylene ether are comparedFIG. 3) shows that-CH of polyphenylene ether is brominated₂The chemical shift of H in Br group is 4.5ppm, while in the nuclear magnetic resonance spectrum of the quaternary ammonium polyphenyl ether, no peak with the chemical shift of 4.5ppm exists, which indicates that bromine group in the brominated polyphenyl ether is converted into quaternary ammonium group.

Further, the conversion of brominated polyphenylene ether to quaternized polyphenylene ether can be further confirmed by Fourier infrared spectroscopy. In the IR spectrum of the quaternized polyphenylene ether, with reference to FIG. 4, C-Br was at 738cm^-1The vibration peak of (A) disappeared and 1660cm appeared^-1The peak of (A) indicates the presence of a quaternary ammonium group, and the peak appears at 3468-3103cm^-1The large broad peak of (a) indicates the introduction of a hydroxyl group, and the disappearance and appearance of the above characteristic peak indicates that the brominated polyphenylene ether has been converted into a quaternized polyphenylene ether.

As an alternative embodiment, the poly (acid chloride) solution comprises at least one of trimesoyl chloride in hexane, terephthaloyl chloride in hexane and isophthaloyl chloride in hexane.

The polybasic acyl chloride has a plurality of acyl chloride groups, and after the polybasic acyl chloride reacts with hydroxyl in the basement membrane to generate an ester group, residual unreacted acyl chloride is hydrolyzed to obtain carboxyl, and carboxylate ions are formed in an aqueous solution, so that the polybasic acyl chloride has a strong repelling effect on high-valence anions and further has high selectivity on low-valence anions.

In one embodiment, the anion exchange membrane prepared by the preparation method of the anion exchange membrane is also provided. The anion exchange membrane is provided with positively charged quaternary ammonium groups and negatively charged carboxylic acid groups, wherein the quaternary ammonium groups provide anion transmission channels, the carboxylic acid groups repel each other due to negative charges, the flux of high-valence anions is reduced, and under the action of the same electric field, the flux of low-valence anions is improved, and the selectivity of the low-valence anions is improved.

Optionally, the ratio of the flux of the anion exchange membrane to the monovalent anion to the flux of the divalent anion is (15.4-59.46): 1.

In this embodiment, a base film containing a quaternary ammonium group and a hydroxyl group in a side chain is modified with a polybasic acid chloride solution to generate an ester group, unreacted acid chloride groups are hydrolyzed to obtain carboxyl groups, an anion transmission channel is provided by the quaternary ammonium groups, and the flux of high-valent anions is reduced and the flux of low-valent anions and selectivity of the low-valent anions are improved by using the repulsion of the carboxyl groups to the high-valent anions.