A method for preparing a monovalent selective anion exchange membrane

Abstract

The present invention provides a method for preparing a monovalent selective anion exchange membrane. This method involves modifying the anion exchange membrane by combining immersion in a potassium sorbate solution with ultraviolet irradiation. The resulting monovalent selective anion exchange membrane exhibits high separation performance for monovalent and polyvalent anions. The preparation method provided by the present invention is simple to operate, economically feasible, provides stable results, is low-cost, and is easily scalable to industrial production, thus possessing broad application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of ion exchange membranes, in particular to a method for preparing a monovalent selective anion exchange membrane. Background Art

[0002] As an emerging separation technology, electrodialysis technology has been widely used in industry due to its advantages such as high efficiency, environmental protection and energy saving. As the core component of electrodialysis technology, ion exchange membranes are widely used in seawater desalination, environmental protection, resource recovery, energy production and other aspects, but at the same time, they are also required to have the ability to remove specific ions in wastewater, distinguish between monovalent and polyvalent ions in seawater desalination and brine salt removal. Conventional ion exchange membranes can only separate anions and cations, and have poor selective separation effects on ions with the same charge but different valences. In order to solve the above problems, the research on monovalent selective anion exchange membranes has become a hot topic in membrane separation technology. Early research work was mainly carried out from two aspects: first, increasing the thickness of the membrane to enhance the screening effect and block ions with a larger hydration radius; second, introducing a negatively charged layer on the membrane surface to achieve a screening effect by using electrostatic repulsion.

[0003] Chinese patent CN107998900A discloses a method for preparing an anion exchange membrane with monovalent and multivalent selective separation functions, which includes the following steps: weighing a certain amount of DAS (sodium 4,4'-diazidostilbene-2,2'-disulfonate) powder, dissolving it in pure water, and adjusting the pH of the solution to 2-8 with hydrochloric acid to obtain a DAS solution with a DAS concentration of 3.0-7.0 mg / mL; immersing one or both sides of the anion exchange membrane in the DAS solution to allow the DAS to penetrate into the surface layer of the anion exchange membrane; irradiating the treated anion exchange membrane with ultraviolet light to cause cross-linking between the DAS and the membrane surface structure, thereby fixing the DAS in the membrane surface structure; and immersing the cross-linked membrane in pure water to obtain an anion exchange membrane with monovalent and multivalent selective separation functions.

[0004] Chinese patent CN108176250A discloses a method for preparing a stable and anti-fouling monovalent selective anion exchange membrane. The method comprises modifying the anion exchange membrane with sulfonated graphene oxide, reducing the modified membrane, and electrostatically depositing a dopamine solution onto the membrane surface. This method yields a stable and anti-fouling monovalent selective anion exchange membrane. This method utilizes the adhesiveness and hydrophilicity of polydopamine and the monovalent anion channels constructed by the sulfonated reduced graphene oxide to improve the stability, anti-fouling properties, and monovalent selectivity of the anion exchange membrane.

[0005] Chinese patent CN106925357A discloses a method for preparing a monovalent selective anion exchange membrane, comprising the following steps: first, adding a mixed solution of NSBC (sodium N-benzenesulfonate benzyl chitosan) and NaCl to the feed chamber, adding NaCl solution to the concentrate chamber, and filling electrode chamber A and electrode chamber B with Na2SO4 solution; then, setting electric pulse parameters, applying power to perform electric pulse deposition to deposit NSBC onto the anion exchange membrane; after a certain deposition period, replacing the solution in the feed chamber with a mixed solution of HACC (2-hydroxypropyltrimethylammonium chloride chitosan) and NaCl, and reversing the current direction on both sides; continuing electric pulse deposition while maintaining the electric pulse parameters unchanged to deposit HACC onto the anion exchange membrane; and repeating the process to alternately deposit NSBC sugar and HACC onto the anion exchange membrane, thereby obtaining an anion exchange membrane with multiple layers of NSBC / HACC attached.

[0006] As can be seen, modification methods for monovalent selective anion exchange membranes mostly focus on membrane substrate doping and surface modification. Surface modification through impregnation is a simple, cost-effective method for improving membrane selective separation performance. However, the separation performance and cost of existing monovalent selective anion exchange membranes are unsatisfactory, necessitating the urgent need to develop cost-effective monovalent selective anion exchange membranes. Summary of the Invention

[0007] To solve the above problems, the present invention provides a method for preparing a monovalent selective anion exchange membrane modified with potassium sorbate. The preparation process is simple to operate and low in cost. The prepared anion exchange membrane has a negatively charged layer, which can enhance the selectivity for monovalent and polyvalent ions. The preparation method of the monovalent selective anion exchange membrane of the present invention comprises the following steps:

[0008] (1) Soak the anion exchange membrane to be modified in deionized water for 12 h at room temperature to allow it to fully expand and remove surface impurities;

[0009] (2) immersing the anion exchange membrane treated in step (1) in a potassium sorbate solution, heating it in a constant temperature water bath at 30-50° C. for 3 h, and then taking it out;

[0010] (3) immersing the anion exchange membrane obtained in step (2) in a sodium chloride solution and irradiating it with ultraviolet light for 45 minutes, then adjusting the irradiated surface of the anion exchange membrane and continuing to irradiate it for 45 minutes to cross-link the potassium sorbate attached to the anion exchange membrane and fix the negatively charged groups to the surface of the anion exchange membrane;

[0011] (4) The anion exchange membrane after the reaction in step (3) is taken out, washed with deionized water to remove the sodium chloride and excess potassium sorbate on the anion exchange membrane, and then immersed in deionized water for storage to obtain a monovalent selective anion exchange membrane.

[0012] Furthermore, the temperature of the constant temperature water bath in step (2) is 40°C.

[0013] Furthermore, the concentration of the potassium sorbate solution in step (2) is 0.1 mol / L.

[0014] Furthermore, the concentration of the sodium chloride solution in step (3) is 0.1 mol / L.

[0015] Furthermore, the wavelength of the ultraviolet light in step (3) is 275-320 nm.

[0016] The present invention also provides a monovalent selective anion exchange membrane prepared according to the method.

[0017] In the technical solution of the present invention, potassium sorbate (potassium 2,4-hexadienoate) will dissociate in the solution to produce K + With C6H7O2 - , of which C6H7O2 - Under the action of electrostatics, it will spontaneously combine with the positively charged anion exchange membrane. After irradiation with ultraviolet light, the carbon-carbon double bond in potassium sorbate will cross-link with the material on the membrane, thereby achieving the purpose of increasing the density of the membrane and at the same time - Fixed to the membrane surface, the anion exchange membrane has a negatively charged layer, which enhances the membrane's selectivity for monovalent and multivalent ions.

[0018] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0019] The monovalent selective anion exchange membrane of the present invention is prepared by a method combining immersion in a potassium sorbate solution and modification by ultraviolet irradiation. The preparation process is simple to operate, economically feasible, has stable effects, low costs, and is easy to implement industrial production. The exchange membrane obtained by the preparation process of the present invention has high separation performance for monovalent and polyvalent anions, high selectivity, and good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a diagram of a four-compartment electrodialysis device made by the present invention;

[0021] Figure 2 This is a diagram showing the electrodialysis effect of the monovalent selective anion exchange membrane obtained in Example 1 of the present invention;

[0022] Figure 3The effect of potassium sorbate solution concentration on monovalent selective anion exchange membrane;

[0023] Figure 4 The effect of sodium chloride solution concentration on monovalent selective anion exchange membrane. DETAILED DESCRIPTION

[0024] The present invention provides a method for preparing a monovalent selective anion exchange membrane modified with potassium sorbate, comprising the following steps:

[0025] (1) Soak the anion exchange membrane to be modified in deionized water for 12 h at room temperature to allow it to fully expand and remove surface impurities;

[0026] (2) immersing the anion exchange membrane treated in step (1) in a potassium sorbate solution, heating it in a constant temperature water bath at 30-50° C. for 3 h, and then taking it out;

[0027] (3) immersing the anion exchange membrane obtained in step (2) in a sodium chloride solution and irradiating it with ultraviolet light for 45 minutes, then adjusting the irradiated surface of the anion exchange membrane and continuing to irradiate it for 45 minutes to cross-link the potassium sorbate attached to the anion exchange membrane and fix the negatively charged groups to the surface of the anion exchange membrane;

[0028] (4) The anion exchange membrane after the reaction in step (3) is taken out, washed with deionized water to remove the sodium chloride and excess potassium sorbate on the anion exchange membrane, and then immersed in deionized water for storage to obtain a monovalent selective anion exchange membrane.

[0029] Furthermore, the temperature of the constant temperature water bath in step (2) is 40°C.

[0030] Furthermore, the concentration of the potassium sorbate solution in step (2) is 0.1 mol / L.

[0031] Furthermore, the concentration of the sodium chloride solution in step (3) is 0.1 mol / L.

[0032] Furthermore, the wavelength of the ultraviolet rays in step (3) is 275-320 nm.

[0033] The present invention also provides a monovalent selective anion exchange membrane prepared according to the method.

[0034] The preparation method of the monovalent selective anion exchange membrane provided by the present invention is further described below with reference to examples.

[0035] Example 1

[0036] Solution preparation:

[0037] 1. Potassium sorbate solution: Dissolve potassium sorbate in deionized water to prepare potassium sorbate solution. Prepare potassium sorbate solutions with concentrations of 0.05 mol / L, 0.10 mol / L, 0.15 mol / L, 0.20 mol / L, and 0.25 mol / L, respectively.

[0038] 2. Sodium chloride solution: Dissolve sodium chloride in deionized water to prepare sodium chloride solution. Prepare sodium chloride solutions with concentrations of 0.05 mol / L, 0.10 mol / L, 0.20 mol / L, 0.30 mol / L, and 0.40 mol / L respectively.

[0039] 3. Sodium sulfate solution: Dissolve sodium sulfate in deionized water to prepare sodium sulfate solution with a concentration of 0.2 mol / L.

[0040] 4. Sodium chloride and sodium sulfate mixed solution: Sodium chloride and sodium sulfate were dissolved in deionized water to prepare a sodium chloride and sodium sulfate mixed solution with a concentration of 0.25 mol / L.

[0041] Preparation of monovalent selective anion exchange membrane:

[0042] (1) The anion exchange membrane to be modified (manufacturer: Shandong Tianwei Membrane Technology Co., Ltd., model: EDAIS-70nw) was soaked in deionized water for 12 h at room temperature to fully expand and remove surface impurities;

[0043] (2) Immerse the anion exchange membrane prepared in step (1) in a 0.1 mol / L potassium sorbate solution, heat in a 40°C constant temperature water bath for 3 h, and then remove;

[0044] (3) immersing the anion exchange membrane obtained in step (2) in a 0.1 mol / L sodium chloride solution and irradiating it with ultraviolet light for 90 minutes to cross-link the carbon-carbon double bonds in potassium sorbate with the substances on the membrane;

[0045] (4) The anion exchange membrane after the reaction in step (3) is taken out, washed with deionized water, and then immersed in deionized water to remove impurities such as sodium chloride and unsuccessfully reacted potassium sorbate, thereby obtaining a monovalent selective anion exchange membrane.

[0046] Electrodialysis experiment:

[0047] The membranes were installed in a homemade four-compartment electrodialysis device, e.g. Figure 1 As shown, the anode plate material of the electrodialysis device is titanium coated with ruthenium, the cathode plate material is stainless steel, AEM is the patented modified anion exchange membrane, CEM is the cation exchange membrane (manufacturer: Shandong Tianwei Membrane Technology Co., Ltd., model: EDCIS-70nw), and the effective area of ​​the membrane is 7×9 cm 2The four compartments from left to right are the polar chamber, concentrated chamber, dilute chamber, and polar chamber. The polar liquid in the two polar chambers is Na2SO4 with a concentration of 0.2 mol / L; the solution in the concentrated chamber is NaCl with a concentration of 0.05 mol / L; the solution in the dilute chamber is a mixture of Na2SO4 and NaCl, both with a concentration of 0.25 mol / L. The volume of the solution in each compartment is 500 mL, the operation time of the electrodialysis device is 120 min, and the current density is 10 mA / cm 2 , measure Cl in the fresh water chamber every 20 minutes - 、SO4 2- The concentration was tested seven times, and the results were as follows Figure 2 As shown, the specific calculation formula is as follows:

[0048] Unit price selectivity is calculated by the following formula;

[0049]

[0050] Where: t i ——Transfer number of ion i through the membrane; z i ——the charge of ion i; J i ——The flux of ion i through the membrane (mol / m 2 ·S);c i ——Concentration of ion i in the dilute chamber (mol / L).

[0051] Example 2

[0052] Same as Example 1, except that the concentration of potassium sorbate solution in step (2) is 0.05 mol / L. Then, electrodialysis experiment is carried out on the modified anion exchange membrane to measure Cl-, SO4 and 2- The concentration was calculated and analyzed, and the results were as follows Figure 3 shown.

[0053] Example 3

[0054] Same as Example 1, except that the concentration of potassium sorbate solution in step (2) is 0.1 mol / L. Then, the modified anion exchange membrane is subjected to electrodialysis experiment to measure Cl-, SO4 and 2- The concentration was calculated and analyzed, and the results were as follows Figure 3 shown.

[0055] Example 4

[0056] Same as Example 1, except that the concentration of potassium sorbate solution in step (2) is 0.15 mol / L. Then, electrodialysis experiment is carried out on the modified anion exchange membrane to measure Cl-, SO4 and 2- The concentration was calculated and analyzed, and the results were as follows Figure 3shown.

[0057] Example 5

[0058] Same as Example 1, except that the concentration of potassium sorbate solution in step (2) is 0.2 mol / L. Then, electrodialysis experiment is carried out on the modified anion exchange membrane to measure Cl-, SO4 and 2- The concentration was calculated and analyzed, and the results were as follows Figure 3 shown.

[0059] Example 6

[0060] Same as Example 1, except that the concentration of potassium sorbate solution in step (2) is 0.25 mol / L. Then, electrodialysis experiment is carried out on the modified anion exchange membrane to measure Cl-, SO4 and 2- The concentration was calculated and analyzed, and the results were as follows Figure 3 shown.

[0061] Example 7

[0062] Same as Example 1, except that the concentration of sodium chloride in step (3) is 0.0 mol / L. Then, an electrodialysis experiment is performed on the modified anion exchange membrane to measure the Cl-, SO4 and 2- The concentration was calculated and analyzed, and the results were as follows Figure 4 shown.

[0063] Example 8

[0064] Same as Example 1, except that the concentration of sodium chloride in step (3) is 0.1 mol / L. Then, an electrodialysis experiment is performed on the modified anion exchange membrane to measure the Cl-, SO4 and 2- The concentration was calculated and analyzed, and the results were as follows Figure 4 shown.

[0065] Example 9

[0066] Same as Example 1, except that the concentration of sodium chloride in step (3) is 0.2 mol / L. Then, an electrodialysis experiment is carried out on the modified anion exchange membrane to measure the Cl-, SO4 and 2- The concentration was calculated and analyzed, and the results were as follows Figure 4 shown.

[0067] Example 10

[0068] Same as Example 1, except that the concentration of sodium chloride in step (3) is 0.3 mol / L. Then, an electrodialysis experiment is carried out on the modified anion exchange membrane to measure the Cl-, SO4 and 2-The concentration was calculated and analyzed, and the results were as follows Figure 4 shown.

[0069] Example 11

[0070] Same as Example 1, except that the concentration of sodium chloride in step (3) is 0.4 mol / L. Then, an electrodialysis experiment is carried out on the modified anion exchange membrane to measure the Cl-, SO4 and 2- The concentration was calculated and analyzed, and the results were as follows Figure 4 shown.

[0071] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A method for preparing a monovalent selective anion exchange membrane, characterized in that: The following steps are involved: (1) Soak the anion exchange membrane to be modified in deionized water for 12 h at room temperature to allow it to fully expand and remove surface impurities; (2) immersing the anion exchange membrane treated in step (1) in a potassium sorbate solution, heating it in a constant temperature water bath at 30-50° C. for 3 h, and then taking it out; (3) immersing the anion exchange membrane obtained in step (2) in a sodium chloride solution and irradiating it with ultraviolet light for 45 minutes, then adjusting the irradiated surface of the anion exchange membrane and continuing to irradiate it for 45 minutes to cross-link the potassium sorbate attached to the anion exchange membrane and fix the negatively charged groups to the surface of the anion exchange membrane; (4) taking out the anion exchange membrane after the reaction in step (3), washing it with deionized water to remove the sodium chloride and excess potassium sorbate on the anion exchange membrane, and then immersing it in deionized water for storage to obtain a monovalent selective anion exchange membrane; The concentration of the potassium sorbate solution in step (2) is 0.1 mol / L.

2. The method for preparing a monovalent selective anion exchange membrane according to claim 1, wherein: The temperature of the constant temperature water bath in step (2) is 40°C.

3. The method for preparing a monovalent selective anion exchange membrane according to claim 1, wherein: The concentration of the sodium chloride solution in step (3) is 0.1 mol / L.

4. The method for preparing a monovalent selective anion exchange membrane according to claim 1, wherein: The wavelength of the ultraviolet rays in step (3) is 275-320 nm.

5. A monovalent selective anion exchange membrane, characterized in that Prepared by the method according to any one of claims 1 to 4.

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