Crown ether derivatives for electrodialysis, electrodialysis membranes and treatment methods

Abstract

The application belongs to the technical field of electrodialysis membranes, and discloses a crown ether derivative for electrodialysis, an electrodialysis membrane and a treatment method. The crown ether derivative has good hydrophilicity, can not only enhance the transmission rate of monovalent cations, but also has the characteristics of specifically complexing and adsorbing divalent or higher valence cations. The crown ether derivative is used for modifying treatment of an electrodialysis cation exchange membrane, and the obtained modified cation exchange membrane has high performance and high selectivity, and can efficiently separate monovalent metal salts from divalent metal salts. When the modified cation exchange membrane is applied to concentrated brine treatment, efficient treatment of concentrated brine can be realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrodialysis membrane, in particular to a crown ether derivative for electrodialysis, an electrodialysis membrane and a treatment method. BACKGROUND

[0002] As a kind of electrodialysis membrane, bipolar membrane is composed of anode film, intermediate layer and cathode film, with anion and cation selectivity.Under the action of direct current electric field, H + And OH - Are dissociated from H + O through anode film; OH - Through cathode film.Therefore, bipolar membrane has important application prospect in the fields of acid-base production, resource recovery, hydrogen production by electrolysis of water and the like.The electrodialysis device chamber is composed of bipolar membrane, cation exchange membrane and anion exchange membrane, which can be used for the treatment of concentrated brine.Electrodialysis is a membrane separation technology that ions in concentrated brine solution migrate through ion exchange membrane under the action of potential difference, to realize dilution, concentration and separation and purification, and is widely used in the fields of seawater desalination, wastewater treatment and chemical production.With the development of industry, the application field of electrodialysis is gradually expanded, which puts forward higher requirements on the separation performance of electrodialysis.

[0003] In the prior art, the ion selectivity of cation exchange membrane in the electrodialysis device is low, and the separation of monovalent metal salt and divalent metal salt cannot be effectively realized.Therefore, it is urgent to develop an electrodialysis membrane that can efficiently separate monovalent salt and divalent salt. SUMMARY

[0004] To solve the above technical problems, the present application provides a crown ether derivative for electrodialysis, an electrodialysis membrane and a treatment method.The crown ether derivative has good hydrophilicity, can not only enhance the transmission rate of monovalent cations, but also has the characteristics of specific complexation and adsorption of divalent and higher valence cations.The crown ether derivative of the present application is used for the modification treatment of electrodialysis cation exchange membrane, and the obtained modified cation exchange membrane has high performance and high selectivity, can efficiently separate monovalent metal salt and divalent metal salt, and is applied to the treatment of concentrated brine, which is expected to realize efficient treatment of concentrated brine.

[0005] To solve the above technical problems, the present application adopts the following technical scheme:

[0006] In a first aspect, the present application provides a crown ether derivative for electrodialysis membrane, the structure of the crown ether derivative is shown as formula (I),

[0007]

[0008] The crown ether derivative of the present application is not only rich in hydrophilic group side chains, but also rich in oxygen atoms without shared electron pairs. Among them, the hydrophilic group side chains endow the crown ether derivative with good hydrophilicity, and the hydrophilic group side chains can form hydrogen bonds with water molecules, which can enhance the monovalent cation transport rate; the oxygen atoms endow the crown ether derivative with specific complex adsorption of divalent or more cations, and transport of monovalent cations. When the crown ether derivative of the present application is used to prepare a cation exchange membrane, the separation of monovalent cations (Na + , K + , etc.) and divalent or more cations (Mg 2+ , Ca 2 , Ba 2+ , Cu 2+ , Fe 3+ , etc.) can be realized, and a cation exchange membrane capable of efficiently separating monovalent metal salts and divalent metal salts is expected.

[0009] In a second aspect, the present application also provides a preparation method of the above-mentioned crown ether derivative, comprising: dissolving droxidopa, an organic ester compound and a catalyst in a solvent, heating to obtain the crown ether derivative.

[0010] Preferably, the specific preparation method of the crown ether derivative comprises:

[0011] Under an inert gas atmosphere, droxidopa and a catalyst sodium hydroxide are added to dimethyl sulfoxide, and refluxed at 100-120℃ for 30-40min to obtain a first reaction liquid;

[0012] The organic ester compound is added to dimethyl sulfoxide and stirred uniformly to obtain a second reaction liquid;

[0013] Half of the second reaction liquid is added dropwise to the first reaction liquid at a rate of 1-5d / min, and after refluxing at 50-70℃ for 1-2h, the remaining amount of the second reaction liquid is continuously added dropwise at a rate of 1-5d / min, and continues to reflux at 50-70℃ for 12-16h to obtain a crude product;

[0014] Concentrated hydrochloric acid is further added to the crude product, and dimethyl sulfoxide is removed by water vapor distillation, and the filter cake is washed with water and acetone, and dried to obtain a crystal, which is the crown ether derivative.

[0015] The present application uses droxidopa containing hydrophilic group side chains and an organic ester compound in a dimethyl sulfoxide solution of a sodium hydroxide catalyst under a nitrogen atmosphere, and heats and refluxes to obtain a crude product, which is separated and purified to obtain a crown ether derivative containing rich hydrophilic group side chains. It not only contains a crown ether structure, but also contains rich hydrophilic groups such as hydroxyl (-OH), carboxyl (-COOH) and amino (-NH2). Among them, the oxygen atoms rich in the crown ether structure in the crown ether derivative can specifically adsorb metal cations such as alkali metal ions, alkaline earth metal ions and transition metal ions (Be2+ Mg 2+ Ca 2 + Ba 2+ Cu 2+ Fe 2+ Fe 3+ Zn 2+ Al 3+ and the like) to form a complex. The crown ether derivative is used to prepare a cation exchange membrane, which is expected to realize the separation of multivalent metal ions from monovalent metal ions in a solution containing metal ions.

[0016] Preferably, the inert gas atmosphere is N2 or helium;

[0017] The molar ratio of the carbidopa to the organic ester compound is (1-2):1;

[0018] The organic ester compound is diethylene glycol bis-p-toluene sulfonate (CAS No.: 7460-82-4); the carbidopa is (2S,3R)-2-amino-3-(3,4-dihydroxyphenyl)-3-hydroxypropionic acid, molecular formula C9H 11 NO5 (CAS No.: 23651-95-8);

[0019] The amount of carbidopa in the first reaction solution is 0.1-0.2 mol / 100 ml of dimethyl sulfoxide solvent;

[0020] The amount of sodium hydroxide in the first reaction solution is 0.2-0.3 mol / 100 ml of dimethyl sulfoxide solvent;

[0021] The amount of organic ester compound in the second reaction solution is 0.05-0.15 mol / 30 ml of dimethyl sulfoxide solvent.

[0022] In a third aspect, the present application further provides a treatment method of an electrodialysis membrane, comprising the following steps:

[0023] S1. Adding the crown ether derivative, the silicone solution, and the two-dimensional MXene material in a mass ratio of (2-3):(1-1.5):(0.2-0.5) to a good solvent, stirring uniformly to obtain a modified solution;

[0024] S2. Mixing the modified solution with a film-forming agent uniformly, coating on the surface of a cation exchange membrane, and heat treating under an inert atmosphere, and cooling to room temperature to obtain a modified cation exchange membrane.

[0025] The modified solution prepared from the crown ether derivative, the organic silicon solution and the two-dimensional MXene material in the above ratio is dissolved in a film forming agent, coated on the surface of a cation exchange membrane to prepare a modified cation exchange membrane; wherein the hydrophilic group side chain of the crown ether derivative forms a hydrogen bond with water molecules to enhance the monovalent cation transmission rate, and the oxygen atom of the crown ether derivative specifically complexes and adsorbs divalent or more cations, and transmits monovalent cations, so as to give the modified cation exchange membrane to realize the separation of monovalent cations (Na + , K + , etc.) and divalent or more cations (Mg 2+ , Ca 2 +, Ba 2+ , Cu 2+ , Fe 3+ , etc.) in wastewater; the organic silicon solution gives the modified cation exchange membrane high mechanical strength, high temperature resistance, oxidation resistance stability, corrosion resistance and the like; the two-dimensional MXene material can provide an ion transmission channel for monovalent ions (Na + , K + , etc.), intercepts divalent cations, does not intercept beneficial monovalent cations, has anti-pollution property, and prolongs the service life of the cation exchange membrane.

[0026] In summary, under the synergistic effect of the crown ether derivative, the organic silicon solution and the two-dimensional MXene material, the modified cation exchange membrane with high performance and high ion selectivity is obtained. The modified cation exchange membrane can be used for concentrated brine treatment, efficiently separates monovalent cations and divalent cations, realizes the separation of monovalent salt and divalent salt, and thus realizes zero discharge of concentrated brine.

[0027] Preferably, in step S1, the mass ratio of the crown ether derivative, the organic silicon solution and the two-dimensional MXene material is (2-3):(1-1.5):(0.2-0.5); the modified cation exchange membrane prepared from the crown ether derivative, the organic silicon solution and the two-dimensional MXene material in the mass ratio has high mechanical strength, corrosion resistance, high performance and good ion selectivity, and can realize efficient separation of monovalent cations and divalent cations.

[0028] Preferably, the two-dimensional MXene material is a 5mg / ml-10mg / ml single-layer Ti3C2Tx dispersion liquid. The MXene material is obtained by removing A atoms from a MAX phase ceramic through liquid phase etching or the like to obtain a transition metal carbon or carbide with a two-dimensional structure, which has good electrical conductivity and rich surface chemical properties.

[0029] The organic silicon solution is tetramethylsilane or epoxy-modified silicone oil.

[0030] The good solvent includes any one of N-methylpyrrolidone, N,N-dimethylformamide and N,N-dimethylacetamide. The crown ether derivative, the organic silicon solution and the two-dimensional MXene material account for 5%-10% of the mass of the good solvent.

[0031] The good solvent of the application can dissolve the crown ether derivative, the organic silicon solution and the two-dimensional MXene material into a modified solution with uniform components.

[0032] Preferably, in step S2, the modified solution accounts for 10%-25% of the mass of the film-forming agent.

[0033] The film-forming agent includes 1,3,5-benzene triformyl chloride or polyvinylpyrrolidone, both in liquid form. Under the action of the film-forming agent of the application, the modified solution is uniformly coated and solidified on the surface of the cation exchange membrane to form a modified cation exchange membrane. The hydrogen bond sites in the pore size channels on the modified cation exchange membrane can form specific interactions with water molecules, which can force water molecules to pass through the proton channels for transmission and conduction, thereby significantly enhancing the conduction efficiency of water molecules. The thickness of the modified cation exchange membrane layer is 20-50 μm.

[0034] The heat treatment in an inert atmosphere is heat treatment at 80-150℃ for 15-36h in an N2 or helium atmosphere.

[0035] The cation exchange membrane includes a standard membrane (commercial CSE membrane) or a blended cross-linked proton exchange membrane (commercial CMB membrane), both of which are commercially available. The CSE membrane and the CMB membrane are both strong acid Na, and the material is perfluorosulfonic acid.

[0036] Preferably, the modified cation exchange membrane is treated with a mixed gas for low-temperature plasma treatment to introduce a hydrophilic group. The mixed gas is 50% O2 and 50% NH. The power of the plasma is 80-100W, and the plasma treatment time is 90-120s. The low temperature is 10-15℃. The hydrophilic group is -OH, -COOH and -NH2. When the mixed gas containing O2 and NH is used for treatment in the application, the active particles in the plasma can react with the surface of the modified cation exchange membrane to introduce oxygen-containing (-OH, -COOH), nitrogen-containing (-NH2) and other functional groups. These functional groups can enhance the hydrophilicity and ionic conductivity of the membrane.

[0037] In a fourth aspect, the application also provides an electrodialysis membrane prepared by the treatment method of the electrodialysis membrane.

[0038] In a fifth aspect, the electro-dialysis device comprises: an anode, a cathode, an electro-dialysis membrane assembly, a sensor and a current controller; wherein the anode is a titanium electrode, a rare metal layer with a thickness of 10-20 nm is arranged on the surface of the titanium electrode, the rare metal is at least one of cerium, platinum, dysprosium and ruthenium, so as to improve the conductivity, corrosion resistance and other effects of the electrode; the cathode is a stainless steel electrode.

[0039] The electro-dialysis membrane assembly is made of the treatment method of the electro-dialysis membrane or the modified cation exchange membrane.

[0040] The cathode of the electro-dialysis membrane assembly is connected to the negative pole of a direct current power supply through a wire, and the anode is connected to the positive pole of the direct current power supply through a wire; the sensor and the current controller are connected on the wire between the whole direct current power supply and the anode of the electro-dialysis membrane assembly of the electro-dialysis membrane assembly; the current sensor is a Hall current sensor for detecting the current of the electro-dialysis device; the current controller can monitor and record the current data in real time, accurately control and adjust the current size through the membrane assembly, prevent the current from being too large to cause damage to the membrane assembly and the electrode, improve the efficiency of the electro-dialysis, ensure the safety of the electro-dialysis device, and prolong the service life. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 It is a structural schematic diagram of the electro-dialysis device of the present application.

[0042] Figure 2 It is an infrared spectrum diagram of the crown ether derivative of the present application. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described in detail below in combination with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application. The specific embodiments described herein are only used to explain the present application and do not limit the present application. The "up", "down", "left" and "right" defined in the present application are limited to the view shown in the drawings of the present application specification. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0044] The preparation method of the Ti3C2Tx dispersion liquid of the two-dimensional MXene material is as follows: Ti3AlC2 and TiC powders with a molar ratio of 1:1 are calcined at 1350°C under an argon atmosphere to obtain a Ti3AlC2 precursor, then the Ti3AlC2 precursor is soaked in 70% hydrofluoric acid for 3h to obtain a crude product Ti3C2Tx, and the crude product is washed with deionized water and centrifuged at 4000r / min for 15min to remove residual hydrofluoric acid. Repeat this operation until the pH value of the supernatant is about 7, discard the supernatant, and then filter and dry to obtain the MXene material Ti3C2Tx, dissolve the Ti3C2Tx in deionized water, ultrasonic for 2h under an argon atmosphere, and centrifuge at 4000r / min for 1h to obtain a 5mg / ml-10mg / ml single-layer Ti3C2Tx dispersion liquid.

[0045] The reaction mechanism of the crown ether derivative is as follows: under the action of the base catalyst, two oxygen anions are generated from carbidopa, and only the carbon cation connected by the glycol dimethylbenzenesulfonate is ring-closed to form the crown ether derivative. The reaction mechanism is shown in formula (II).

[0046]

[0047] Formula (II).

[0048] The specific preparation method of the crown ether derivative is as follows:

[0049] In a 250ml three-necked flask equipped with a reflux device, 0.15mol carbidopa, 100ml dimethyl sulfoxide and 0.30mol sodium hydroxide are sequentially added under N2 atmosphere, and refluxed at 115°C for 30min to ensure that the sodium hydroxide is completely dissolved to obtain a first reaction liquid;

[0050] 0.075mol glycol dimethylbenzenesulfonate is diluted with 30ml dimethyl sulfoxide to prepare a glycol dimethylbenzenesulfonate / dimethyl sulfoxide solution as a second reaction liquid;

[0051] The 15ml of the above obtained diethylene glycol dipara-toluenesulfonate / dimethyl sulfoxide solution was added dropwise into the above first reaction liquid at a rate of 5d / min, then refluxed at 60℃ for 1h, and then the remaining 15ml of the diethylene glycol dipara-toluenesulfonate / dimethyl sulfoxide solution was continuously added dropwise at a rate of 5d / min, and then refluxed at 60℃ for 16h (color reaction with FeCl3 solution was used for tracking, and if no purple color appeared, it indicated that the reaction was complete). 1.5ml of concentrated hydrochloric acid was added, and dimethyl sulfoxide solvent was removed by steam distillation, and then filtered, and the filter cake was washed with water, and dried, and then the obtained solid was dispersed into 100ml of acetone for recrystallization, and then stirred for 30min, and then filtered, and then washed with acetone, and then dried, and then the crystal yield could reach 75%. It was a crown ether derivative containing hydrophilic -OH, -COOH, and -NH2 in the side chain. Compared with the commonly used solvent n-butanol for preparing crown ether, dimethyl sulfoxide could better dissolve droxidopa, sodium hydroxide, and diethylene glycol dipara-toluenesulfonate, and improve the product yield.

[0052] Figure 2 The infrared spectrum of the crown ether derivative of the present application is shown in Figure 1. Figure 2 It can be seen that there are relatively strong absorption peaks near 3610cm -1 , 3406cm -1 , 3390cm -1 , 2910cm -1 , 2894cm -1 , 1703cm -1 , 1590cm -1 , 1413cm -1 , 1370cm -1 , 1250cm -1 , 1080cm -1 , 906cm -1 , 815cm -1 , 730cm -1 , etc. 3610cm-1 is the stretching vibration of -OH; 3406cm -1 , 3390cm -1 nearby appear two absorption peaks, which are the stretching vibration absorption peaks of -NH2; 2910cm -1 , 2894cm -1 are C-H stretching vibration peaks; 1703cm -1 nearby is the characteristic vibration peak of -COOH; 1590cm -1 , 1413cm -1 , 1370cm -1 nearby are the skeleton vibrations of benzene ring; 906cm -1 , 815cm -1 , 730cm -1fingerprint region of benzene ring; 1250 cm -1 , 1080 cm -1 nearby is the stretching vibration peak of ether bond (C-O-C); wherein, 1250 cm -1 is the characteristic vibration of aromatic ether bond; the above results show that the molecular structure of the crown ether derivative contains groups such as -CH, -NH2, -COOH, C-O-C, benzene ring, etc., which are consistent with the above molecular structure.

[0053] The application will be further described in detail below with specific examples.

[0054] Example 1

[0055] I. The crown ether derivative, the organic silicon solution (tetramethylsilane, CAS: 75-76-3) and the single-layer Ti3C2Tx dispersion of the two-dimensional MXene material were added to N,N-dimethylformamide in a mass ratio of 2:1.5:0.5, stirred uniformly to obtain a modified solution, wherein the crown ether derivative, the organic silicon solution and the single-layer Ti3C2Tx dispersion of the two-dimensional MXene material accounted for 5% of the mass of N,N-dimethylformamide;

[0056] II. After the modified solution was uniformly mixed with the polyvinylpyrrolidone film former (the modified solution accounted for 10% of the mass of the polyvinylpyrrolidone), it was coated on the surface of the cation exchange membrane: commercial CSE membrane, and then heat-treated at 80-150°C for 15-36h under N2 atmosphere, and cooled to room temperature to obtain the modified cation exchange membrane.

[0057] Example 2

[0058] I. The crown ether derivative, the organic silicon solution (epoxy-modified silicone oil, model: BSM-204) and the single-layer Ti3C2Tx dispersion of the two-dimensional MXene material were added to N,N-dimethylacetamide in a mass ratio of 3:1:0.2, stirred uniformly to obtain a modified solution, wherein the crown ether derivative, the organic silicon solution and the single-layer Ti3C2Tx dispersion of the two-dimensional MXene material accounted for 7% of the mass of N,N-dimethylformamide;

[0059] II. After the modified solution was uniformly mixed with the 1,3,5-benzene triformyl chloride film former (the modified solution accounted for 20% of the mass of the 1,3,5-benzene triformyl chloride), it was coated on the surface of the cation exchange membrane: commercial CMB membrane, and then heat-treated at 80-150°C for 15-36h under N2 atmosphere, and cooled to room temperature to obtain the modified cation exchange membrane.

[0060] Example 3

[0061] One, the crown ether derivative, the organic silicon solution (epoxy modified silicone oil, model: BSM-204) and the two-dimensional MXene material monolayer Ti3C2Tx dispersion with a mass ratio of 2.5:1:0.3 are added into N,N-dimethylformamide, stirred uniformly to obtain a modified solution, wherein the crown ether derivative, the organic silicon solution and the two-dimensional MXene material monolayer Ti3C2Tx account for 10% of the mass of N,N-dimethylformamide;

[0062] Two, after the modified solution is uniformly mixed with the polyvinylpyrrolidone film former (the modified solution accounts for 10% of the mass of the polyvinylpyrrolidone), it is coated on the surface of the cation exchange membrane: commercial CSE membrane, and is heat treated at 80-150℃ for 15-36h under N2 atmosphere, and is cooled to room temperature to obtain the modified cation exchange membrane.

[0063] Three, the modified cation exchange membrane is treated by low-temperature plasma with a mixed gas of O and NH in a volume ratio of 50%:50% at 12℃, power 100W, 1Pa for 100s, and the gas flow rate is 3L / min. When the plasma surface treatment is introduced, O2 and argon Ar can produce a chemical reaction on the surface of the modified cation exchange membrane, so as to introduce new hydrophilic groups -OH, -COOH and -NH2. The plasma surface etching can also roughen the surface of the modified layer of the modified cation exchange membrane, and will not penetrate the modified layer, so as to increase the contact area between the membrane layers without damaging the crown ether derivative, thereby improving the performance of the bipolar membrane.

[0064] Comparative Example 1

[0065] The commercially available cation exchange membrane has a product model: commercial CSE membrane, and is made of perfluorosulfonic acid.

[0066] Comparative Example 2

[0067] Compared with Example 2, the modified solution of this embodiment only contains the crown ether derivative.

[0068] Specifically, after the modified solution is uniformly mixed with the 1,3,5-benzene tricarbonyl chloride film former (the modified solution accounts for 20% of the mass of the 1,3,5-benzene tricarbonyl chloride), it is coated on the surface of the cation exchange membrane: commercial CSE membrane, and is heat treated at 80-150℃ for 15-36h under N2 atmosphere, and is cooled to room temperature to obtain the modified cation exchange membrane.

[0069] Comparative Example 3

[0070] Compared with Example 2, the modified solution of this embodiment only contains the organic silicon solution and the two-dimensional MXene material monolayer Ti3C2Tx dispersion with a mass ratio of 1:0.2.

[0071] Specifically,

[0072] Adding a silicone solution and a two-dimensional MXene material monolayer Ti3C2Tx dispersion in a mass ratio of 1:0.2 to N,N-dimethylacetamide and stirring evenly to obtain a modified solution, wherein the silicone solution and the two-dimensional MXene material monolayer Ti3C2Tx dispersion account for 5% of the mass of N,N-dimethylacetamide;

[0073] After the modified solution and 1,3,5-benzenetricarboxylic acid chloride film-forming agent are evenly mixed (the modified solution accounts for 20% of the mass of 1,3,5-benzenetricarboxylic acid chloride), it is coated on the surface of a cation exchange membrane: a commercial CSE membrane, and heat-treated at 80-150°C for 15-36h under a N2 atmosphere, and cooled to room temperature to obtain a modified cation exchange membrane.

[0074] Application Example 1

[0075] The present invention provides an electrodialysis device, such as Figure 1 shown. Figure 1 Schematic diagram of the structure of the electrodialysis device of the present invention.

[0076] Figure 1 The electrodialysis device includes an anode, a cathode, an electrodialysis membrane assembly, a sensor, and a current controller. The anode is a titanium electrode with a 20nm thick cerium metal layer on its surface to improve its conductivity and corrosion resistance. The cathode is a stainless steel electrode. The cathode is connected to the negative pole of a DC power supply via a wire, while the anode is connected to the positive pole of a DC power supply via a wire. A Hall effect current sensor and a current controller are connected to the wire between the positive pole of the DC power supply and the anode of the electrodialysis membrane assembly. The Hall effect current sensor is used to detect the current in the electrodialysis device. The current controller can monitor and record current data in real time and accurately control and adjust the current through the electrodialysis membrane assembly to prevent excessive current from damaging the membrane assembly and electrodes, thereby ensuring the safety of the electrodialysis device and extending its service life.

[0077] Figure 1 The structure of the electrodialysis membrane assembly is: -│anion exchange membrane│bipolar membrane│cation exchange membrane│anion exchange membrane│bipolar membrane│cation exchange membrane│anion exchange membrane│+, Figure 1 A is an anion exchange membrane, C is a cation exchange membrane, and BP is a bipolar membrane. The left side of the bipolar membrane is the acid chamber, the right side is the base chamber, and the brine chamber is between the cation exchange membrane and the anion exchange membrane. All anion exchange membranes in the electrodialysis membrane assembly are commercial AMX, and the bipolar membrane is commercial HP-BP-02.

[0078] The membranes obtained in Examples 1-3 and Comparative Examples 1-3 were used to replace the cation exchange membranes in the above electrodialysis membrane modules to prepare electrodialysis membrane modules, and were used to treat concentrated brine.

[0079] The structure of the electrodialysis membrane assembly of Examples 1-3 and Comparative Examples 2-3 is: - | anion exchange membrane | bipolar membrane | modified cation exchange membrane | anion exchange membrane | bipolar membrane | modified cation exchange membrane | anion exchange membrane | +.

[0080] The structure of the electrodialysis membrane assembly of Comparative Example 1 is: - | anion exchange membrane | bipolar membrane | cation exchange membrane | anion exchange membrane | bipolar membrane | cation exchange membrane | anion exchange membrane | +.

[0081] The specific test process of the electrodialysis device for treating concentrated brine is as follows: first, immerse the membrane to be tested in a 0.1 mol / L NaCl / MgCl2 solution for 24 h for equilibration, then install the membrane to be tested in the electrodialysis device, add 100 ml of 0.1 mol / L NaCl / MgCl2 solution to the concentrated brine chamber of the electrodialysis device through a pipeline, add 100 ml of 0.3 mol / L NaCl solution to the electrode chamber, add HCl to the acid chamber, and add NaOH to the alkali chamber. The initial acid concentration of the acid chamber and the initial alkali concentration of the alkali chamber are both 0.01 mol / L. In the experiment, all the solutions are circulated by a peristaltic pump. The current density of the electrodialysis device is 25-30 mAcm-2, and after 1 h of operation, samples are taken from the acid chamber, the alkali chamber, and the concentrated brine chamber, and the ion concentrations in each chamber are tested by inductively coupled plasma spectroscopy. The results are shown in Table 1. -1 -2

[0082] Table 1

[0083]

[0084]

[0085] As can be seen from Table 1, the concentration of HCl in the acid chamber of Examples 1-3 is above 0.987 mol / L, and the concentration of NaOH in the alkali chamber is above 0.979 mol / L, both of which are superior to those of Comparative Examples 1-3; the ion concentrations of MgCl2 and NaCl in the concentrated brine chamber of Examples 1-3 are lower than those in the concentrated brine chamber of Comparative Examples 1-3. This indicates that only in the electrodialysis device composed of the membranes obtained by the modification method of Examples 1-3 can the efficient separation of Mg2+ and Na+ in concentrated brine be achieved, and the membranes obtained by Comparative Examples 1-3 are inferior to those of Examples 1-3. 2+ +

[0086] In summary, the modified cation exchange membrane obtained by the treatment method of the electrodialysis membrane of the present application has high performance and high selectivity, and can efficiently separate monovalent salt and divalent salt. When it is used for concentrated brine treatment, it can efficiently separate monovalent cations and divalent cations, realize the separation of monovalent salt and divalent salt, and thus realize the zero discharge of concentrated brine.

[0087] ​​​​The above merely provides the preferred embodiment of the present application, and is not used to limit the present application, and any modification, equivalent replacement or improvement made in the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing a crown ether derivative for electrodialysis membrane, characterized in that: The structure of the crown ether derivative is shown in formula (I), Formula (I); The preparation steps of the crown ether derivative include: The crown ether derivative is prepared by dissolving droxidopa, an organic ester compound and a sodium hydroxide catalyst in a solvent and heating the mixture. Wherein, the molar ratio of droxidopa to the organic ester compound is (1-2):1; The organic ester compound is diethylene glycol di-p-toluenesulfonate, and droxidopa is (2S, 3R)-2-amino-3-(3, 4-dihydroxyphenyl)-3-hydroxypropionic acid.

2. The method for preparing the crown ether derivative according to claim 1, wherein Under an inert gas atmosphere, adding the droxidopa and sodium hydroxide catalyst to a solvent of dimethyl sulfoxide, and reflux at 100-120° C. for 30-40 minutes to obtain a first reaction solution; adding the organic ester compound into dimethyl sulfoxide solvent and stirring evenly to obtain a second reaction solution; Add half of the second reaction solution dropwise to the first reaction solution at a rate of 1-5 d / min, reflux at 50-70°C for 1-2 h, then continue to add the remaining amount of the second reaction solution dropwise at a rate of 1-5 d / min, and continue to reflux at 50-70°C for 12-16 h to obtain a crude product; Concentrated hydrochloric acid is then added to the crude product, and dimethyl sulfoxide is removed by steam distillation. After solid-liquid separation, the filter cake is washed with water and acetone, and dried to obtain crystals, which are crown ether derivatives.

3. The method for preparing the crown ether derivative according to claim 2, wherein: The inert gas atmosphere is N2 or helium; and / or The amount of droxidopa in the first reaction solution accounts for 0.1-0.2 mol / 100 ml of the volume of the solvent dimethyl sulfoxide; and / or The sodium hydroxide in the first reaction solution accounts for 0.2-0.3 mol / 100 ml of the volume of the solvent dimethyl sulfoxide; and / or The organic ester compound in the second reaction solution accounts for 0.05-0.15 mol / 30 ml of the volume of the solvent dimethyl sulfoxide.

4. A method for treating an electrodialysis membrane, characterized in that: The following steps are involved: S1. A method for treating an electrodialysis membrane using a crown ether derivative prepared by the method for preparing a crown ether derivative according to any one of claims 1 to 3, comprising adding the crown ether derivative, an organosilicon solution, and a two-dimensional MXene material in a mass ratio of (2-3):(1-1.5):(0.2-0.5) to a good solvent, stirring the mixture uniformly, and obtaining a modified solution. S2. After uniformly mixing the modified solution and the film-forming agent, the mixture is coated on the surface of the cation exchange membrane, and heat-treated under an inert atmosphere and cooled to room temperature to obtain a modified cation exchange membrane.

5. The method for treating an electroosmotic membrane according to claim 4, wherein: In step S1, The two-dimensional MXene material is a single-layer Ti3C2Tx dispersion of 5 mg / ml-10 mg / ml; and / or The organosilicon solution is tetramethylsilane or epoxy-modified silicone oil; and / or The good solvent includes any one of N-methylpyrrolidone, N,N-dimethylformamide and N,N-dimethylacetamide; and / or The crown ether derivative, organosilicon solution and two-dimensional MXene material account for 5%-10% of the mass of the good solvent.

6. The method for treating an electrodialysis membrane according to claim 5, characterized in that In step S2, the modified solution accounts for 10% to 25% of the mass of the film-forming agent; and / or The film-forming agent includes: 1,3,5-benzenetricarboxylic acid chloride or polyvinyl pyrrolidone; and / or The heat treatment under an inert atmosphere is: heat treatment at 80-150° C. for 15-36 hours under an N 2 or helium atmosphere; The cation exchange membrane includes: a standard membrane or a blended cross-linked proton exchange membrane.

7. The method for treating an electrodialysis membrane according to any one of claims 4 to 6, characterized in that: include: The modified cation exchange membrane obtained in S2 is subjected to low-temperature plasma treatment using a mixed gas to introduce hydrophilic groups; wherein the mixed gas is 50% O2 and 50% NH3 by volume; the plasma power is 80-100W, and the plasma treatment is performed for 90-120s at 0.1-10 Pa; the low temperature is 10-15°C; and / or The hydrophilic groups are -OH, -COOH, and -NH2.

8. An electrodialysis membrane, characterized in that The electrodialysis membrane is prepared by the treatment method of any one of claims 4 to 6.

9. An electrodialysis device, characterized in that include: Anode, cathode, electrodialysis membrane assembly, sensor and current controller; wherein, The electrodialysis membrane assembly is made by using the electrodialysis membrane treatment method according to any one of claims 4 to 6 or the modified cationic salt ion exchange membrane obtained according to claim 8; The anode is a titanium electrode, a rare metal layer is provided on the surface of the titanium electrode, and the rare metal is at least one of cerium, platinum, dysprosium, and ruthenium; The cathode is a stainless steel electrode; The structure of the electrodialysis membrane assembly is: -│anion exchange membrane│bipolar membrane│modified cation exchange membrane│anion exchange membrane│bipolar membrane│modified cation exchange membrane│anion exchange membrane│+.

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