High-selectivity monovalent cation exchange membrane and application thereof in electrodialysis separation of hydrogen and magnesium

Abstract

The invention discloses a high-selectivity monovalent cation exchange membrane and application thereof in electrodialysis separation of hydrogen and magnesium, and the high-selectivity monovalent cation exchange membrane is obtained by adding a Ti3C2Tx nanosheet into a sulfonated polyphenyl sulfone membrane solution to prepare a base membrane and then spraying a quaternized polyphenyl ether solution on the surface of the base membrane. The obtained monovalent cation exchange membrane has high hydrogen ion flux and high hydrogen and magnesium ion selectivity, and the manufacturing process of the membrane is simple and suitable for industrial production.

Description

Technical Field

[0001] The invention belongs to the field of ion exchange membrane preparation, and in particular relates to a highly selective monovalent cation exchange membrane and application thereof in electrodialysis separation of hydrogen and magnesium. Background Art

[0002] Monovalent cation exchange membranes are widely used in waste acid recovery, lithium resource extraction, and wastewater treatment. However, they generally have problems such as low selectivity and low ion flux. 1] The monovalent cation exchange membrane was prepared by in situ deposition of polyaniline on a sulfonated polysulfone-based membrane. The results showed that the membrane had a strong affinity for Na + / Mg 2+ 、Li + / Mg 2+ The selectivities were 4.1 and 1.75 respectively. Meanwhile, Na + He Li + Throughput as low as 4×10 -10 mol / (cm 2 ·s). Academic paper "Application of Monovalent Selective Electrodialysis in the Treatment of Acidic Heavy Metal Wastewater" [2] reported the preparation of monovalent cation exchange membranes by pyrrole impregnation modification on the surface of homogeneous cation exchange membranes. The results showed that the membranes were sensitive to H + / Zn 2+ 、H + / Cd 2+ The selectivities are 27.18 and 33.26, respectively, showing good prospects in waste acid recovery applications. However, the membrane is prepared by impregnation modification on a commercial cationic membrane, and the preparation process is complex, making it difficult to scale up production.

[0003] Therefore, it is an inevitable trend to prepare monovalent cation exchange membranes with high selectivity, large ion flux and simple process.

[0004] Therefore, based on the current research status and in view of the deficiencies of the existing technology, the present invention proposes a highly selective monovalent cation exchange membrane and a preparation method thereof and its application in the electrodialysis separation of hydrogen and magnesium.

[0005] References:

[0006] [1]Xiao Pang, Yanyao Tao, Yanqing Xu, Jiefeng Pan, Jiangnan Shen, CongjieGao. Enhanced monovalent selectivity of cation exchange membranes via adjustable charge density on functional layers, Journal of Membrane Science, 2020, 595: 117544.

[0007] [2] Li Fuqin, Zhang Yingong, Zhu Min, Wang Shaozhou, Guo Yanfu. Application of monovalent selective electrodialysis in the treatment of acidic heavy metal wastewater. Water Treatment Technology, 2022, 3: 118-121. Summary of the Invention

[0008] To overcome the shortcomings of the prior art, the present invention primarily aims to provide a method for preparing a highly selective monovalent cation exchange membrane, which is simple and easy to operate. Another object is to provide a highly selective monovalent cation exchange membrane prepared by the above method, which has a large ion flux and high selectivity. A further object is to provide the use of the highly selective monovalent cation exchange membrane in electrodialysis separation of hydrogen and magnesium. The present invention addresses the problems of low selectivity and low ion flux in existing electrodialysis separations of hydrogen and magnesium.

[0009] The purpose of the present invention is achieved through the following technical solutions:

[0010] A method for preparing a highly selective monovalent cation exchange membrane comprises the following steps:

[0011] Step 1: Prepare quaternized polyphenylene ether solution:

[0012] The brominated polyphenylene ether is dissolved in an organic solvent A and stirred to obtain a brominated polyphenylene ether solution, a tertiary amine is added, and a quaternization reaction occurs between the tertiary amine and the brominated polyphenylene ether to obtain a reaction product; the reaction product is dropped into an organic solvent B to obtain a precipitate, and the precipitate is dried to obtain a solid, namely the quaternized polyphenylene ether; the quaternized polyphenylene ether is dissolved in the organic solvent A to obtain a quaternized polyphenylene ether solution;

[0013] Step 2: Preparation of sulfonated polyphenylene sulfone / Ti3C2T x Membrane solution:

[0014] Dissolve sulfonated polyphenylene sulfone in organic solvent C, then add Ti3C2T x Nanosheets are stirred evenly to prepare sulfonated polyphenylsulfone / Ti3C2T x membrane solution;

[0015] Step 3: Prepare basement membrane:

[0016] Sulfonated polyphenylene sulfone / Ti3C2T x The membrane liquid is coated on a glass plate to form a film and then dried by heat treatment to obtain a base membrane;

[0017] Step 4: Preparation of highly selective monovalent cation exchange membrane:

[0018] The quaternized polyphenylene ether solution of step 1 is sprayed on the base membrane of step 3 and then heat-treated and dried to obtain a highly selective monovalent cation exchange membrane.

[0019] Preferably, the organic solvent A and the organic solvent C are independently selected from 1-methyl-2-pyrrolidone, dimethylformamide or dimethyl sulfoxide; and the organic solvent B is petroleum ether or ethyl acetate.

[0020] Preferably, in step 1: the degree of bromination of the brominated polyphenylene ether is 17.5-40.0%, the mass fraction of the brominated polyphenylene ether solution is 15-20%; the tertiary amine is trimethylamine, N,N-dimethyloctylamine or N,N-dimethylhexadecylamine, the mass ratio of tertiary amine to brominated polyphenylene ether is 0.4-1.2:1, the quaternization reaction time is 24-96 hours, and the reaction temperature is 25-60°C.

[0021] Preferably, in step 1, the mass fraction of the quaternized polyphenylene ether solution is 1-2%.

[0022] Preferably, the Ti3C2T x The nanosheets are single-layer or few-layer nanosheets prepared with reference to the literature (Science, 2016, 6304(353): 1137-1140) and the literature (Journal of Membrane Science, 2020, 593: 117431.).

[0023] Preferably, in step 2: the sulfonation degree of the sulfonated polyphenylene sulfone is 20-30%, and the sulfonated polyphenylene sulfone is in the sulfonated polyphenylene sulfone / Ti3C2T x The mass fraction of Ti3C2T in the membrane solution is 7.0-16.0%. x The mass ratio of the nanosheets to the sulfonated polyphenylene sulfone is 0-0.01:1.

[0024] Preferably, in step 3, the heat treatment temperature is 60-90° C., and the drying time is 6-10 hours.

[0025] Preferably, in step 4, the quaternized polyphenylene ether solution and the sulfonated polyphenylene sulfone / Ti3C2T x The volume ratio of membrane liquid is 1:5~20.

[0026] Preferably, in step 4, the heat treatment temperature is 60-90° C., and the drying time is 1-2 hours.

[0027] The highly selective monovalent cation exchange membrane prepared by the above steps of the present invention can be used in electrodialysis separation of hydrogen and magnesium, and the application method can be carried out by the following steps:

[0028] (1) The highly selective monovalent cation exchange membrane and the commercial anion exchange membrane are alternately installed in an electrodialysis membrane stack, forming an anode chamber and a cathode chamber on both sides of the membrane stack, and a repeating unit with alternating desalination chambers and concentrating chambers between the anode chamber and the cathode chamber. Together with a pump, a DC power supply, solution tanks (electrode solution tank, desalination chamber tank, concentrating chamber tank), and piping, an electrodialysis hydrogen and magnesium separation device is constructed.

[0029] (2) In the device of step (1), the electrode liquid tank, the desalination chamber tank, and the concentration chamber tank are respectively injected with the electrode liquid, the desalination liquid, and the concentrate liquid, and the pump is turned on to pump each solution into the corresponding compartment in the membrane stack for circulation; the DC power supply is turned on and a constant current or voltage is set to separate the hydrogen-magnesium solution.

[0030] (3) Record the initial current and voltage of the device in step (1), and then record the current or voltage value of the DC power supply at regular intervals. At the same time, sample the solutions in the desalination chamber and the concentration chamber and analyze the ion concentration.

[0031] The highly selective monovalent cation exchange membrane provided by the present invention, its preparation method, and its application in electrodialysis separation of hydrogen and magnesium have the following outstanding effects compared with the prior art:

[0032] (1) Ti3C2T x Nanosheets have good hydrophilicity and are naturally negatively charged. At the same time, they have functional groups such as -OH, -O and -F on their surfaces, which have the ability to construct efficient hydrogen ion transmission channels. Therefore, doping Ti3C2T in the base film x The nanosheets can increase the hydrogen ion flux of the membrane by 15.41%.

[0033] (2) Ti3C2T x The nanosheets, with their unique layered structure, are dispersed within the base membrane, regulating the pore size distribution within the membrane and acting as a sieving agent for cations with varying hydrated ion radii. Consequently, the membrane's magnesium hydrogen ion selectivity is increased by at least 6.40%.

[0034] (3) The present invention coats the surface of the base membrane with a positively charged quaternized polyphenylene ether modified layer, which can repel multivalent cations (electrostatic repulsion effect). In addition, the longer the carbon chain of the grafted tertiary amine during the polyphenylene ether quaternization reaction, the greater the repulsion of multivalent cations through the hydration energy effect. Therefore, compared with the base membrane, the selectivity of the monovalent cation exchange membrane with the quaternized polyphenylene ether modified layer for hydrogen magnesium ions can be increased by 20.42 to 45.27 times.

[0035] (4) The manufacturing process of the highly selective monovalent cation exchange membrane of the present invention is simple and easy to operate, and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly and vividly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0037] Figure 1 Schematic diagram of a device for separating hydrogen and magnesium using highly selective monovalent cation exchange membrane electrodialysis according to an embodiment of the present invention. DETAILED DESCRIPTION

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0039] Ti3C2T used in the following examples x The preparation steps of the nanosheets are as follows: 1.6 g of LiF was slowly added to 20 mL of HCl and stirred to obtain a mixed solution; 1 g of Ti3AlC2 powder was slowly added to the mixed solution, heated in a water bath at 35 ° C, stirred, and reacted for 48 hours to obtain Ti3C2T x The suspension was washed three times by centrifugation with a 1 mol / L hydrochloric acid solution (at a speed of 3500 rpm for 8 min), and then washed with deionized water at the same speed and time until the pH was ≥ 5; the suspension was shaken by hand to peel the layers, and then centrifuged at a speed of 4500 rpm to obtain single-layer and few-layer Ti3C2T x The suspension was placed in a vacuum freeze dryer (-50 ° C) and freeze-dried to obtain Ti3C2T x Nanosheets.

[0040] Example 1

[0041] A method for preparing a highly selective monovalent cation exchange membrane comprises the following steps:

[0042] Step 1, preparing a quaternized polyphenylene ether solution: dissolving 2g of brominated polyphenylene ether (degree of bromination is 17.5%) in 1-methyl-2-pyrrolidone to obtain a brominated polyphenylene ether solution with a mass fraction of 20%, then adding 2.94g of trimethylamine ethanol solution (trimethylamine mass fraction is 30%), stirring and reacting at room temperature of 25°C for 48 hours; slowly dripping the reaction product into petroleum ether to precipitate and wash away impurities, and drying to obtain a precipitate, which is a solid quaternized polyphenylene ether; dissolving 0.2g of quaternized polyphenylene ether in 1-methyl-2-pyrrolidone to obtain a quaternized polyphenylene ether solution with a mass fraction of 1%.

[0043] Step 2: Preparation of sulfonated polyphenylene sulfone / Ti3C2T x Membrane solution: 0.75g sulfonated polyphenylene sulfone (sulfonation degree is 30%) was added to 9.2g 1-methyl-2-pyrrolidone solution to obtain a sulfonated polyphenylene sulfone membrane solution with a mass fraction of 7.5%; then 0.00375g Ti3C2T x Nanosheets, obtained sulfonated polyphenylsulfone / Ti3C2T x Membrane liquid.

[0044] Step 3: Prepare the basement membrane: Take 5 mL of the sulfonated polyphenylene sulfone / Ti3C2T x The membrane liquid was dropped onto a 5 cm × 10 cm glass plate, formed into a film by the salivation method, and dried in a far-infrared oven at 60° C. for 9 hours to obtain a base membrane.

[0045] Step 4: Prepare a highly selective monovalent cation exchange membrane: Take 0.5 mL of the quaternized polyphenylene ether solution of step 1 and spray it evenly on the base membrane of step 3, and dry it in a far-infrared oven at 70°C for 1.5 hours to obtain a highly selective monovalent cation exchange membrane, and soak it in 0.3 mol / L sodium sulfate solution for later use.

[0046] Application of the highly selective monovalent cation exchange membrane obtained in this embodiment in electrodialysis separation of hydrogen and magnesium: Figure 1 The device shown in the figure includes two anion exchange membranes (one on each side, left and right) and a monovalent cation exchange membrane (in the middle); the anion exchange membranes used are from AMVn, Asahi Glass Co., Ltd. of Japan, and the monovalent cation exchange membrane used is the highly selective monovalent cation exchange membrane prepared in this example. The effective area of a single membrane is S (20 cm 2); 200 mL of 0.3 mol / L sodium sulfate solution was introduced into the anode chamber and the cathode chamber and circulated between the anode and cathode chambers; 200 mL of a hydrogen-magnesium mixed solution (0.1 mol / L hydrogen chloride solution + 0.1 mol / L magnesium chloride solution) was introduced into the compartment on the left side of the monovalent cation exchange membrane (the desalination chamber); and 200 mL of a 0.01 mol / L potassium chloride solution was introduced into the compartment on the right side (the concentrating chamber); the DC power supply was adjusted to a constant current mode with a current density of 5 mA cm -2 Run stably for 1 hour, read the voltage of the DC power supply at regular intervals, and analyze the concentrations of hydrogen and magnesium ions in the solutions in the compartments on both sides of the monovalent cation exchange membrane. and selectivity The calculation formula is as follows:

[0047]

[0048] in, and are the M in the right compartment (concentration compartment) of the monovalent cation exchange membrane at time t and time 0, respectively. n+ concentration, Z is the ion charge number, V is the volume of the desalination chamber, t is the operation time, and S is the effective area of a single membrane.

[0049] The ion flux and selectivity of the highly selective monovalent cation exchange membrane prepared in this embodiment during the electrodialysis separation of hydrogen and magnesium are shown in Table 1. The hydrogen ion flux of this embodiment (6.14E-08 mol / (m 2 ·s)) and selectivity (48.88) were higher than those of the comparative example 1 (5.63E-08mol / (m 2 ·s)) and selectivity (1.74), indicating that Ti3C2T x The addition of and spraying of quaternized polyphenylene ether solution help to improve the separation of hydrogen and magnesium; the selectivity of this embodiment (48.88) is higher than the selectivity of Comparative Example 2 (2.25), indicating that spraying of quaternized polyphenylene ether solution helps to improve the separation of hydrogen and magnesium; in addition, the hydrogen ion flux and selectivity of this embodiment are higher than those of the commercial membrane CIMS in Comparative Example 3.

[0050] Example 2

[0051] A method for preparing a highly selective monovalent cation exchange membrane comprises the following steps:

[0052] Step 1, preparing a quaternized polyphenylene ether solution: dissolving 2g of brominated polyphenylene ether (bromination degree of ~17.5%) in 1-methyl-2-pyrrolidone to obtain a brominated polyphenylene ether solution with a mass fraction of ~20%, then adding 1.38g of N,N-dimethyl-n-octylamine (N,N-dimethyl-n-octylamine with a mass fraction of ~95%), stirring and reacting at room temperature of 50°C for 24 hours; slowly dripping the reaction product into petroleum ether to precipitate and wash away impurities, and drying the precipitate to obtain a solid quaternized polyphenylene ether; dissolving 0.2g of quaternized polyphenylene ether in 1-methyl-2-pyrrolidone to obtain a quaternized polyphenylene ether solution with a mass fraction of ~2%.

[0053] Step 2: Preparation of sulfonated polyphenylene sulfone / Ti3C2T x Membrane solution: 1.2 g of sulfonated polyphenylene sulfone (sulfonation degree is 30%) was added to 8.8 g of 1-methyl-2-pyrrolidone solution to obtain a sulfonated polyphenylene sulfone membrane solution with a mass fraction of 12%. Then, 0.00375 g of Ti3C2T x Nanosheets, obtained sulfonated polyphenylsulfone / Ti3C2T x Membrane liquid.

[0054] Step 3: Prepare the basement membrane: Take 5 mL of the sulfonated polyphenylene sulfone / Ti3C2T x The membrane liquid was dropped onto a 5 cm × 10 cm glass plate, formed into a film by the salivation method, and dried in a far-infrared oven at 80° C. for 8 hours to obtain a base membrane.

[0055] Step 4: Prepare a highly selective monovalent cation exchange membrane: Take 0.5 mL of the quaternized polyphenylene ether solution of step 1 and spray it evenly on the base membrane of step 3, and dry it in a far-infrared oven at 60°C for 2 hours to obtain a highly selective monovalent cation exchange membrane, and soak it in 0.3 mol / L sodium sulfate solution for later use.

[0056] In this example, the ion flux and selectivity of the obtained highly selective monovalent cation exchange membrane in the electrodialysis separation of hydrogen and magnesium were tested in the same manner as in Example 1. The results are shown in Table 1. 2 ·s)) and selectivity (78.30) were higher than those of the comparative example 1 (5.63E-08mol / (m 2 ·s)) and selectivity (1.74), again indicating that Ti3C2T x The addition of and spraying of quaternized polyphenylene ether solution help to improve the separation of hydrogen and magnesium; the selectivity of this embodiment (78.30) is higher than the selectivity of Comparative Example 2 (2.25), indicating that spraying of quaternized polyphenylene ether solution helps to improve the separation of hydrogen and magnesium; in addition, the hydrogen ion flux and selectivity of this embodiment are higher than those of the commercial membrane CIMS in Comparative Example 3.

[0057] Example 3

[0058] A method for preparing a highly selective monovalent cation exchange membrane comprises the following steps:

[0059] Step 1, preparing a quaternized polyphenylene ether solution: dissolving 2g of brominated polyphenylene ether (degree of bromination: 30.0%) in 1-methyl-2-pyrrolidone to obtain a brominated polyphenylene ether solution with a mass fraction of 20%, then adding 2.36g of N,N-dimethylhexadecylamine (N,N-dimethylhexadecylamine with a mass fraction of 98%), and stirring at 60°C for 96 hours; slowly dripping the reaction product into petroleum ether to precipitate and wash away impurities, and drying the precipitate to obtain a solid quaternized polyphenylene ether; dissolving 0.2g of quaternized polyphenylene ether in 1-methyl-2-pyrrolidone to obtain a quaternized polyphenylene ether solution with a mass fraction of 1%.

[0060] Step 2: Preparation of sulfonated polyphenylene sulfone / Ti3C2T x Membrane solution: 1.6 g of sulfonated polyphenylene sulfone (sulfonation degree is 20%) was added to 8.4 g of 1-methyl-2-pyrrolidone solution to obtain a sulfonated polyphenylene sulfone membrane solution with a mass fraction of 16%; then 0.016 g of Ti3C2T x Nanosheets, obtained sulfonated polyphenylsulfone / Ti3C2T x Membrane liquid.

[0061] Step 3: Prepare the basement membrane: Take 5 mL of the sulfonated polyphenylene sulfone / Ti3C2T x The membrane liquid was dropped onto a 5 cm × 10 cm glass plate, formed into a film by the salivation method, and dried in a far-infrared oven at 90° C. for 6 hours to obtain a base membrane.

[0062] Step 4: Prepare a highly selective monovalent cation exchange membrane: Take 0.5 mL of the quaternized polyphenylene ether solution of step 1 and spray it evenly on the base membrane of step 3, and dry it in a far-infrared oven at 90°C for 1 hour to obtain a highly selective monovalent cation exchange membrane, and soak it in 0.3 mol / L sodium sulfate solution for later use.

[0063] In this example, the ion flux and selectivity of the obtained highly selective monovalent cation exchange membrane in the electrodialysis separation of hydrogen and magnesium were tested in the same manner as in Example 1. The results are shown in Table 1. 2 ·s)) and selectivity (101.85) were higher than those of the comparative example 1 (5.63E-08mol / (m 2 ·s)) and selectivity (1.74), indicating that Ti3C2T x The addition of nanosheets and the spraying of quaternized polyphenylene ether solution help to improve the separation of hydrogen and magnesium; at the same time, the hydrogen ion flux of this embodiment (6.67E-08mol / (m 2·s)) and selectivity (101.85) were higher than those of the comparative example 2 (6.52E-08mol / (m 2 ·s)) and selectivity (2.25), indicating that spraying of quaternized polyphenylene ether solution helps to improve hydrogen-magnesium separation; compared with Comparative Example 3, the hydrogen ion flux and selectivity of this embodiment are also advantageous.

[0064] Example 4

[0065] In this example, a highly selective monovalent cation exchange membrane was prepared by the same method as in Example 1, except that the degree of bromination of the brominated polyphenylene ether in step 1 was ∼40.0%, and the mass fraction of the brominated polyphenylene ether solution was ∼15%.

[0066] In this example, the ion flux and selectivity of the obtained highly selective monovalent cation exchange membrane in the electrodialysis separation of hydrogen and magnesium were tested in the same manner as in Example 1. The results are shown in Table 1.

[0067] The hydrogen ion flux of this embodiment (5.90E-08mol / (m 2 ·s)) and selectivity (62.11) were higher than those of the comparative example 1 (5.63E-08mol / (m 2 ·s)) and selectivity (1.74), indicating that Ti3C2T x The addition of nanosheets and the spraying of a quaternized polyphenylene ether solution helped improve hydrogen-magnesium separation. Furthermore, the selectivity of this example (62.11) was higher than that of Comparative Example 2 (2.25), indicating that spraying a quaternized polyphenylene ether solution helped improve hydrogen-magnesium separation. Furthermore, the hydrogen ion flux and selectivity of this example were both higher than those of the commercial CIMS membrane in Comparative Example 3.

[0068] Example 5

[0069] In this example, a highly selective monovalent cation exchange membrane was prepared in the same manner as in Example 1, with the only difference being that the amount of the quaternized polyphenylene ether solution used in step 4 was 1 mL.

[0070] In this example, the ion flux and selectivity of the obtained highly selective monovalent cation exchange membrane in the electrodialysis separation of hydrogen and magnesium were tested in the same manner as in Example 1. The results are shown in Table 1.

[0071] The hydrogen ion flux of this embodiment (5.68E-08mol / (m 2 ·s)) and selectivity (70.24) were higher than those of the comparative example 1 (5.63E-08mol / (m 2 ·s)) and selectivity (1.74), indicating that Ti3C2T xThe addition of nanosheets and the spraying of quaternized polyphenylene ether solution help to improve the separation of hydrogen and magnesium; at the same time, the selectivity of this embodiment (70.24) is higher than the selectivity of Comparative Example 2 (2.25), indicating that the spraying of quaternized polyphenylene ether solution helps to improve the separation of hydrogen and magnesium; in addition, the hydrogen ion flux and selectivity of this embodiment are both higher than those of the commercial membrane CIMS in Comparative Example 3.

[0072] Example 6

[0073] In this example, a highly selective monovalent cation exchange membrane was prepared by the same method as in Example 1. The only difference was that the Ti3C2T x The amount of nanosheets added is 0, that is, the Ti3C2T x The content is 0 and the mass fraction of sulfonated polyphenylene sulfone is ~7.5%.

[0074] In this example, the ion flux and selectivity of the obtained highly selective monovalent cation exchange membrane in the electrodialysis separation of hydrogen and magnesium were tested in the same manner as in Example 1. The results are shown in Table 1. 2 ·s)) and selectivity (45.94) were higher than those of the comparative example 1 (5.63E-08mol / (m 2 ·s)) and selectivity (1.74), indicating that spraying of the quaternized polyphenylene ether solution helps to improve the separation of hydrogen and magnesium; at the same time, the selectivity of this embodiment (45.94) is higher than the selectivity of Comparative Example 2 (2.25), indicating that spraying of the quaternized polyphenylene ether solution helps to improve the separation of hydrogen and magnesium; in addition, the hydrogen ion flux and selectivity of this embodiment are both higher than those of the commercial membrane CIMS of Comparative Example 3.

[0075] Comparative Example 1 (pure sulfonated polyphenylene sulfone membrane)

[0076] The cation exchange membrane of Comparative Example 1 is not added with Ti3C2T x The preparation method of the pure sulfonated polyphenylene sulfone membrane without spraying the quaternized polyphenylene ether solution on the membrane surface comprises the following steps:

[0077] (1) 0.75 g of sulfonated polyphenylene sulfone (sulfonation degree is 30%) was added to 9.25 g of 1-methyl-2-pyrrolidone solution and stirred evenly to obtain a membrane solution with a sulfonated polyphenylene sulfone mass fraction of 7.5%.

[0078] (2) 5 mL of the membrane solution prepared in step (1) was dropped onto a 5 cm × 10 cm glass plate, and the membrane was formed by the casting method and dried at 60°C for 9 hours to obtain a pure sulfonated polyphenylene sulfone membrane.

[0079] In this comparative example, the same method as in Example 1 was used to test the ion flux and selectivity of the obtained sulfonated polyphenylene sulfone membrane during electrodialysis separation of magnesium hydrogen. The results are shown in Table 1.

[0080] Comparative Example 2 (Sulfonated Polyphenylene Sulfone / Ti3C2T x Nanosheet membrane)

[0081] The cation exchange membrane of Comparative Example 2 is added with Ti3C2T x Nanosheets, but no sulfonated polyphenylene sulfone / Ti3C2T2 nanosheets were sprayed on the membrane surface. x The nanosheet film is the base film in Example 1.

[0082] This comparative example uses the same method as in Example 1 to test the sulfonated polyphenylene sulfone / Ti3C2T x The ion flux and selectivity of the nanosheet membrane in the electrodialysis separation of hydrogen and magnesium are shown in Table 1.

[0083] Comparative Example 3 (Commercial Membrane CIMS)

[0084] Comparative Example 3 uses the CIMS membrane produced by Japan's Astom Corporation.

[0085] In this comparative example 3, the ion flux and selectivity in the electrodialysis separation of magnesium hydrogen were tested using the same method as in Example 1. The results are shown in Table 1.

[0086] Table 1 shows the ion flux and selectivity of the membranes obtained in the embodiments of the present invention and the comparative examples during the electrodialysis separation of magnesium hydrogen.

[0087]

[0088] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a highly selective monovalent cation exchange membrane, characterized in that: The following steps are involved: Step 1: Prepare quaternized polyphenylene ether solution: The brominated polyphenylene ether is dissolved in an organic solvent A and stirred to obtain a brominated polyphenylene ether solution, a tertiary amine is added, and a quaternization reaction occurs between the tertiary amine and the brominated polyphenylene ether to obtain a reaction product; the reaction product is dropped into an organic solvent B to obtain a precipitate, and the precipitate is dried to obtain a solid, namely the quaternized polyphenylene ether; the quaternized polyphenylene ether is dissolved in the organic solvent A to obtain a quaternized polyphenylene ether solution; Step 2: Preparation of sulfonated polyphenylene sulfone / Ti3C2T x Membrane solution: Dissolve sulfonated polyphenylene sulfone in organic solvent C, then add Ti3C2T x Nanosheets are stirred evenly to prepare sulfonated polyphenylsulfone / Ti3C2T x membrane solution; Step 3: Prepare basement membrane: Sulfonated polyphenylene sulfone / Ti3C2T x The membrane liquid is coated on a glass plate to form a film and then dried by heat treatment to obtain a base membrane; Step 4: Preparation of highly selective monovalent cation exchange membrane: The quaternized polyphenylene ether solution of step 1 is sprayed on the base membrane of step 3 and then heat-treated and dried to obtain a highly selective monovalent cation exchange membrane.

2. The preparation method according to claim 1, wherein: The organic solvent A and the organic solvent C are independently selected from 1-methyl-2-pyrrolidone, dimethylformamide or dimethyl sulfoxide; the organic solvent B is petroleum ether or ethyl acetate.

3. The preparation method according to claim 1, wherein: In step 1, the degree of bromination of the brominated polyphenylene ether is 17.5-40.0%, the mass fraction of the brominated polyphenylene ether solution is 15-20%, the tertiary amine is trimethylamine, N,N-dimethyloctylamine or N,N-dimethylhexadecylamine, the mass ratio of the tertiary amine to the brominated polyphenylene ether is 0.4-1.2:1, the quaternization reaction time is 24-96 hours, and the reaction temperature is 25-60°C.

4. The preparation method according to claim 1, wherein: In step 1, the mass fraction of the quaternized polyphenylene ether solution is 1-2%.

5. The preparation method according to claim 1, wherein: In step 2, the sulfonation degree of the sulfonated polyphenylene sulfone is 20-30%, and the sulfonated polyphenylene sulfone is in the form of sulfonated polyphenylene sulfone / Ti3C2T x The mass fraction of Ti3C2T in the membrane solution is 7.0-16.0%. x The mass ratio of the nanosheets to the sulfonated polyphenylene sulfone is 0-0.01:

1.

6. The preparation method according to claim 1, wherein: In step 3, the heat treatment temperature is 60 to 90° C., and the drying time is 6 to 10 hours.

7. The preparation method according to claim 1, wherein: In step 4, the quaternized polyphenylene ether solution is mixed with the sulfonated polyphenylene sulfone / Ti3C2T x The volume ratio of membrane liquid is 1:5~20.

8. The preparation method according to claim 1, wherein: In step 4, the heat treatment temperature is 60-90° C., and the drying time is 1-2 hours.

9. A highly selective monovalent cation exchange membrane prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the highly selective monovalent cation exchange membrane according to claim 9 in electrodialysis separation of hydrogen and magnesium.

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