A selective electrodialysis device and its use

Abstract

The application belongs to the field of water treatment equipment and application technology, and particularly relates to a selective electrodialysis device and application thereof. The selective electrodialysis device comprises an electrodialysis cell, an anode and a cathode arranged on the two sides of the electrodialysis cell, and a cation exchange membrane and an anion exchange membrane arranged between the anode and the cathode in sequence. The cation exchange membrane is made of sulfonated polybenzimidazole as a base material, and the surface of the cation exchange membrane is coated with polystyrene sodium sulfonate containing porous micro-nano materials. A protective layer containing polydiphenylpiperidine is coated on the side of the cation exchange membrane facing the anode. The anion exchange membrane is made of quaternary amine polyfluorosulfone or polyether sulfone as a base material, and the surface of the anion exchange membrane is coated with polydimethyl diallyl ammonium chloride. The device can efficiently separate monovalent ions and polyvalent ions, the functionalization of the ion exchange membrane increases the membrane charge density, promotes the rapid migration of ions under the action of an electric field, and improves the ion transfer rate. The device is stable in operation, has a high separation rate and a high current efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to a selective electrodialysis device and its application, belonging to the field of water treatment equipment and application technology. BACKGROUND

[0002] Membrane separation has the advantages of high separation efficiency, simple process operation, low energy consumption, no secondary pollution, etc., among which selective electrodialysis can effectively separate monovalent ions and multivalent ions. For example, in the prior art, patent application No. CN115448429A discloses a monovalent selective bipolar membrane electrodialysis device and a method for treating high-salinity wastewater. It discloses that under the action of an electric field, ions in high-salinity wastewater undergo directional migration. Due to electrostatic repulsion, monovalent Cl - preferentially enters the cation exchange fiber network and penetrates through the monovalent selective anion exchange membrane into the acid chamber on the positive membrane side of the bipolar membrane, where H + is generated by the hydrolysis of the bipolar membrane, and finally flows out as a certain concentration of HCl solution; monovalent Na + ions preferentially enter the anion exchange fiber network and penetrate through the monovalent selective cation exchange membrane into the base chamber on the negative membrane side of the bipolar membrane, where OH - is generated by the hydrolysis of the bipolar membrane, and finally flows out as a certain concentration of NaOH solution; due to the electrostatic repulsion of the anion and cation exchange fiber network and the double interception effect of the monovalent selective ion exchange membrane, SO4 2- , CO3 2- , and a small amount of Ca 2+ , Mg 2+ high-valence cations remaining after softening are intercepted in the salt chamber, thereby greatly improving the purity of the HCl and NaOH solutions. However, it can only be used to separate high-salinity wastewater containing Ca 2+ , Mg 2+ , CO3 2- , Na + , SO4 2- , and Cl - , and obtain NaOH solution without Ca 2+ , Mg 2+ , and acid liquid water.

[0003] The prior art usually adopts extraction and adsorption to extract lithium, but the extraction process is long, secondary pollution exists, and the adsorption has the defects of competitive adsorption and limited adsorption capacity. There are also methods for separating lithium ions and magnesium ions during lithium extraction to solve the problem of extracting lithium from salt lake brine with high magnesium-lithium ratio. However, the current selective electrodialysis device still has problems such as low separation rate and low current efficiency. On the one hand, during operation, pollutants in the treatment solution often cause a sharp decrease in current efficiency, or the selective ion membrane is operated for a long time. When there are magnesium ions in the cathode liquid, Mg(OH)2gel-like precipitate is easily generated in the cathode chamber, adhering to the cathode side membrane surface or the cathode plate, causing pollution and scaling, reducing separation selectivity, and increasing operating power consumption. On the other hand, while the selective electrodialysis separates monovalent ions, it also concentrates and enriches ions, which causes serious reverse migration of concentrated ions, resulting in a decrease in current efficiency. SUMMARY

[0004] (1) Technical problems to be solved

[0005] In order to solve the above-mentioned problems of the prior art, the present application provides a selective electrodialysis device and application, which can efficiently separate monovalent ions and polyvalent ions, and the device is stable in operation, has high separation rate and high current efficiency.

[0006] (2) Technical solutions

[0007] In order to achieve the above-mentioned purposes, the main technical solutions adopted by the present application include:

[0008] A selective electrodialysis device, comprising an electrodialysis tank, an anode and a cathode are respectively arranged on both sides of the electrodialysis tank, and a cation exchange membrane and an anion exchange membrane are arranged in sequence between the anode and the cathode, wherein the cation exchange membrane takes sulfonated polybenzimidazole membrane as a base material, is coated with porous micro-nano material polystyrene sodium sulfonate, and the surface of the cation exchange membrane facing the anode is coated with a protective layer containing polydiphenylpiperidine; the anion exchange membrane takes quaternary amine poly sulfone or polyether sulfone membrane as a base material, and the surface of the anion exchange membrane is coated with polydimethyl diallyl ammonium chloride.

[0009] The selective electrodialysis device as described above, preferably, the preparation method of the porous micro-nano material is that metal hydrochloride and tetrakis(4-pyridyl biphenyl) ethylene are dispersed in N,N-dimethyl formamide at a mass ratio of 1-3:1, ultrasonic treatment is performed for 10-20 minutes, and then reaction is carried out at 120-150℃ for 60-90h, and the metal hydrochloride is zinc chloride, nickel chloride or copper chloride.

[0010] Further, the mixture of the metal hydrochloride and tetrakis(4-pyridyl biphenyl) ethylene is dispersed in N,N-dimethylformamide at a concentration of 5-10 mg / mL; when the amount of N,N-dimethylformamide is too small, the system has high viscosity, and the metal hydrochloride and tetrakis(4-pyridyl biphenyl) ethylene are difficult to uniformly disperse (even if ultrasonic treatment is performed), which may cause local high concentration of the reaction, uneven product; when the amount of N,N-dimethylformamide is too large, the concentration of the reactants is too low, which may reduce the reaction rate, and even may inhibit the coordination reaction (coordination of metal ions and pyridine groups) due to dilution effect, thereby reducing the yield; therefore, the mass concentration of the mixture of the metal hydrochloride and tetrakis(4-pyridyl biphenyl) ethylene in N,N-dimethylformamide is preferably 5-10 mg / mL.

[0011] The selective electrodialysis device as described above, preferably, the concentration of the sodium polystyrene sulfonate coated in the cation exchange membrane is 10-30 g / L; and the concentration of the polydimethyl diallyl ammonium chloride coated in the anion exchange membrane is 15-25 g / L.

[0012] In the present application, the sodium polystyrene sulfonate with a concentration of 10-30 g / L can effectively increase the charge density of the cation exchange membrane, promote the rapid migration of ions under the action of an electric field, and improve the ion transfer rate; the polydimethyl diallyl ammonium chloride with a concentration of 15-25 g / L in the anion exchange membrane can effectively increase the charge density, thereby improving the ion transfer rate.

[0013] The porous micro-nano material added in the present application can further adsorb or mineralize residual pollutants or small-molecule organic matters after degradation.

[0014] The selective electrodialysis device as described above, preferably, the cation protection layer is coated on the side of the cation exchange membrane facing the anode, and the cation protection layer is polydiphenylpiperidine containing organic framework catalytic material A.

[0015] Further, the concentration of the polydiphenylpiperidine in the cation protection layer is 0.5-2 mol / L dichloromethane solution, and the amount of the organic framework catalytic material A is 5-15% of the polydiphenylpiperidine.

[0016] Further, the preparation method of the organic framework catalytic material A is as follows: a mixture of 2,4-diformylphloroglucinol and diaminobenzenesulfonic acid with a molar ratio of 1:1.2-1.6 is added to a mixed solution of N,N-dimethylformamide and mesitylene, then TiO2 nanoparticles deposited with noble metal are dispersed in the mixed solution, and after ultrasonic treatment for 15-40 min, reaction is carried out at 110-140 ℃ for 40-60 h to obtain the organic framework catalytic material A, and the noble metal is Pt, Au, Rh, etc.

[0017] The mixture of N,N-dimethylformamide and mesitylene is mixed in a volume ratio of 1:4; the concentration of 2,4-diformylphloroglucinol and diaminobenzene sulfonic acid in the mixture is 0.1 mol / L and 0.12-0.16 mol / L, respectively; the mass fraction of the TiO2 nanoparticles with noble metal deposited thereon in the mixture is 2-5%; and the mass fraction of the noble metal in the TiO2 nanoparticles is 0.5-10%.

[0018] The method as described above, preferably, a side of the anion exchange membrane facing the anode is coated with a polystyrene protective layer containing the organic framework catalytic material B.

[0019] The preparation method of the organic framework catalytic material B is as follows: a mixture of 2,4-diformylphloroglucinol and p-phenylenediamine in a molar ratio of 1:1.2-1.6 is added to a mixture of N,N-dimethylformamide and mesitylene, then TiO2 nanoparticles with noble metal deposited thereon are dispersed in the mixture, ultrasonic treatment is performed for 15-45 min, and then reaction is performed at 120-150℃ for 40-60 h.

[0020] The selective electrodialysis device as described above, preferably, a side of the cation exchange membrane and the anion exchange membrane facing the cathode is provided with a barrier layer, the barrier layer is a petroleum ether solution containing N-methyl-4-piperidone and 4-trifluoromethyl biphenyl in a molar ratio of 1:1-1.4, which is coated and then dried, and the concentration of N-methyl-4-piperidone is 0.5-3 mol / L.

[0021] The selective electrodialysis device as described above, preferably, a group of cation exchange membranes, anion exchange membranes, cation exchange membranes, and anion exchange membranes arranged in the order of anode to cathode are referred to as an electrodialysis unit, and ≥1 electrodialysis unit is arranged between the anode plate and the cathode plate.

[0022] The selective electrodialysis device as described above, preferably, an electrode membrane is arranged between the cation exchange membrane and the anode, an electrode membrane is arranged between the anion exchange membrane and the cathode, and a baffle or a screen is arranged between any adjacent cation exchange membrane and anion exchange membrane.

[0023] Further, the electrode membrane is a quaternary aminized polyphenyl ether membrane, and the use of quaternary aminized polyphenyl ether can prevent cations from entering the electrode chamber to cause electrode water scaling and affect the electrode efficiency.

[0024] The selective electrodialysis device as described above, preferably, an anode chamber is formed between the anode and the electrode membrane close to the anode, and a chlorine gas absorber is further arranged in the anode chamber.

[0025] In a preferred embodiment, the selective electrodialysis device further comprises a pre-filter, which is arranged at the front end of the electrodialysis device, i.e. the pre-filter is arranged to treat the solution before the solution enters the electrodialysis device, and the filter membrane of the pre-filter is a polyolefin membrane containing adsorbent material.

[0026] Further, the adsorbent material is prepared by reacting tetra-(4-aminophenyl)ethylene (6-10 mol / L) and 2,6-divinyl naphthalene in a molar ratio of 4:1 in a toluene and ethyl acetate (volume ratio of 3:1) solution for 48-72 h, and then rinsing and drying.

[0027] The selective electrodialysis device as described above, preferably, the cation exchange membrane, the separator or the screen, the anion exchange membrane and the separator or the screen are provided in multiple groups, and the multiple groups are arranged in the above order in sequence.

[0028] The selective electrodialysis device as described above is used in the separation of lithium and magnesium ions, and specifically, the solution containing lithium and magnesium ions is treated by the selective electrodialysis device, and lithium ions are enriched in the concentrated solution chamber formed by the separator or the screen opposite to the side of the cation exchange membrane and / or the anion exchange membrane with the protective layer; magnesium ions are blocked in the dilute solution chamber formed by the separator or the screen opposite to the side of the cation exchange membrane and / or the anion exchange membrane with the blocking layer, so as to separate the magnesium ions from the lithium ions.

[0029] Specifically, the space between the cation exchange membrane and the anion exchange membrane is alternately formed into a concentrated solution chamber and a dilute solution chamber by the separator or the screen, and after the salt lake brine is treated by the selective electrodialysis device, lithium ions are enriched in the concentrated solution chamber, and magnesium ions are blocked in the dilute solution chamber, so as to realize the separation and concentration of lithium ions.

[0030] (Three) beneficial effects

[0031] The beneficial effects of the present application are:

[0032] The selective electrodialysis device provided by the present application increases the charge density of the ion exchange membrane by functionalizing the ion exchange membrane, promotes the rapid migration of ions under the action of an electric field, and improves the ion transfer rate. At the same time, the porous micro-nano material is provided to adsorb and mineralize small molecular organic pollutants, so as to inhibit the migration of the small molecular organic pollutants into the membrane and cause pollution. In addition, the polydiphenylpiperidine in the protective layer of the cation exchange membrane has a strong repulsion to multivalent cations such as magnesium, which weakens the interaction between the multivalent cations and monovalent cations such as lithium, so as to effectively intercept the multivalent cations without reducing the transmission rate of the monovalent cations.

[0033] The selective electrodialysis device provided by the application is characterized in that a protective layer is arranged on the cation exchange membrane and the anion exchange membrane, and an organic framework catalytic material in the protective layer is used to adsorb and catalytically degrade organic pollutants, thereby effectively solving the problems of separation efficiency reduction and operation power consumption increase caused by organic pollution during device operation; in addition, the barrier layer of the cation exchange membrane and the anion exchange membrane effectively inhibits ion reverse migration when the solution concentration in the concentrated solution chamber is high, thereby improving the current efficiency and the single / multiple ion separation rate of the selective electrodialysis device.

[0034] The selective electrodialysis device provided by the application can be used for efficiently separating monovalent ions such as lithium ions and sodium ions and multivalent ions such as magnesium ions, manganese ions, ferrous ions and iron ions, and the device has stable operation and the current efficiency is improved by about 30%. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 It is a structural schematic diagram of a preferred selective electrodialysis device of the application.

[0036] Figure 2 It is a structural schematic diagram of a preferred selective electrodialysis device in Example 1 of the application.

[0037] REFERENCE SIGNS

[0038] 1: electrodialysis cell;

[0039] 11: feed liquid; 12: acceptable liquid; 13: concentrated liquid; 14: dilute liquid;

[0040] 2: anode;

[0041] 3: cathode;

[0042] 4: cation exchange membrane;

[0043] 5: anion exchange membrane;

[0044] 6: partition plate or partition net;

[0045] 7: polar membrane. DETAILED DESCRIPTION

[0046] The selective electrodialysis device provided by the application is characterized in that a protective layer is arranged on the cation exchange membrane and the anion exchange membrane, and an organic framework catalytic material in the protective layer is used to adsorb and catalytically degrade organic pollutants, thereby effectively solving the problems of separation efficiency reduction and operation power consumption increase caused by organic pollution during device operation; in addition, the barrier layer of the cation exchange membrane and the anion exchange membrane effectively inhibits ion reverse migration when the solution concentration in the concentrated solution chamber is high, thereby improving the current efficiency and the single / multiple ion separation rate of the selective electrodialysis device.

[0047] The cation exchange membrane is obtained by coating 10-30 g / L of a polystyrene sodium sulfonate casting solution on a substrate of sulfonated polybenzimidazole, drying the substrate, and further containing porous micro-nano materials in the casting solution, wherein the amount of the porous micro-nano materials accounts for 3-10% of the polystyrene sodium sulfonate. The porous micro-nano materials are prepared by dispersing metal (zinc, nickel, copper, etc.) hydrochloride and tetrakis(4-pyridylphenyl)ethylene in N,N-dimethylformamide at a mass ratio of 1-3:1, ultrasonicating for 15-30 minutes, and then reacting at 120-150°C for 60-90 hours, preferably, the mass concentration of the mixture of the metal hydrochloride and tetrakis(4-pyridylphenyl)ethylene in N,N-dimethylformamide is 5-10 mg / mL.

[0048] It is found through a large number of experimental studies that the coating of polystyrene sodium sulfonate can increase the charge density of the cation exchange membrane, promote the rapid migration of ions under the action of an electric field, and improve the ion transfer rate. Too high a concentration will affect the coating effect, and too low a charge density will not significantly increase the charge density, therefore, the concentration of the polystyrene sodium sulfonate is preferably 10-30 g / L, and the amount of the porous micro-nano materials accounts for 3-10% of the polystyrene sodium sulfonate.

[0049] The cation exchange membrane further has a protective layer on the surface of the dilute liquid chamber side, i.e., the side facing the anode is coated with a cation protective layer, and the cation protective layer is polydiphenylpiperidine containing organic framework catalytic material A. The preparation method of the organic framework catalytic material A is as follows: 2,4-diformylphloroglucinol and diaminobenzenesulfonic acid (molar ratio 1:1.2-1.6) are added to a mixed solution of N,N-dimethylformamide and mesitylene at a volume ratio of 1:4, then TiO2 nanoparticles deposited with noble metals such as Pt, Au, and Rh are dispersed in the mixed solution, ultrasonicated for 15-40 minutes, and then reacted at 110-140°C for 40-60 hours to obtain the organic framework catalytic material A. The TiO2 nanoparticles deposited with noble metals are obtained by adding TiO2 nanoparticles to a noble metal salt solution, stirring for several hours, drying, and then calcining at 300-400°C for 4-6 hours under an inert gas, wherein the mass ratio of the TiO2 nanoparticles deposited with noble metals in the mixed solution is 2-5%, and the mass ratio of the noble metals to TiO2 is 0.5-10%.

[0050] The amount of the organic framework catalytic material A is preferably 5-15% of the polydiphenylpiperidine, and the concentration of the polydiphenylpiperidine is 0.5-2 mol / L dissolved in dichloromethane solution.

[0051] The polydiphenylpiperidine adopted in the application has strong repulsion to multivalent cations such as magnesium and weakens the interaction with monovalent cations such as lithium, so that the multivalent cations are effectively intercepted without reducing the transmission rate of monovalent cations; meanwhile, the organic framework catalytic material A in the application can adsorb and catalytically degrade organic pollutants, effectively solving the problems of reduced separation efficiency and increased operating power consumption caused by organic pollution during the operation of the device, and the sulfonic acid groups of the organic framework catalytic material A have stronger electrostatic interaction with multivalent cations, so that the multivalent cations are adsorbed in advance to limit the transmission before selective separation.

[0052] The anion exchange membrane adopts a quaternary amine poly sulfone or poly ether sulfone film as a substrate, and the surface is coated with 15-25 g / L polydimethyl diallyl ammonium chloride, which can effectively increase the charge density and thus improve the ion transmission rate.

[0053] The side of the anion exchange membrane facing the anode, i.e. the side surface close to the dilute liquid chamber, is also coated with a protective layer containing polystyrene of the organic framework catalytic material B. The preparation method of the organic framework catalytic material B is as follows: a mixture of 2,4-diformylphloroglucinol and p-phenylenediamine with a molar ratio of 1:1.2-1.6 is added to a mixed solution of N,N-dimethylformamide and mesitylene with a volume ratio of 1:4, then TiO2 nanoparticles (2-5 wt%) deposited with noble metals such as Pt, Au and Rh (noble metals account for 0.5-10% of the mass of TiO2) are dispersed in the mixed solution, and after ultrasonic treatment for 0.5 h, the reaction is carried out at 110-140℃ for 60 h to obtain the product.

[0054] The addition of the organic framework catalytic material B can adsorb and catalytically degrade organic pollutants, preventing the anion exchange membrane from being polluted by organic matter during operation.

[0055] The side of the cation exchange membrane facing the cathode and the side of the anion exchange membrane facing the anode, i.e. the side surface close to the concentrated liquid chamber, is coated with a barrier layer, which is obtained by coating a petroleum ether solution of a mixture of N-methyl-4-piperidone and 4-trifluoromethyl biphenyl with a molar ratio of 1:1-1.4 and then drying, and the barrier layer effectively inhibits ion back migration when the solution concentration in the concentrated liquid chamber is high. The concentration of N-methyl-4-piperidone is 0.5-3 mol / L.

[0056] Most preferably, the petroleum ether solution of N-methyl-4-piperidone and 4-trifluoromethyl biphenyl with a molar ratio of 1:1.2, wherein the concentration of N-methyl-4-piperidone is 1.5 mol / L. A chlorine gas absorber is arranged in the anode chamber. The chlorine gas absorber can control the escape of chlorine gas, achieving safe handling and resource recycling.

[0057] The selective electrodialysis device is provided with a pre-filter, and a polyolefin membrane doped with an adsorbent material is used in the pre-filter, and the adsorbent material is prepared by reacting a mixture of tetra-(4-aminophenyl)ethylene (6-10 mol / L) and 2,6-divinyl naphthalene in a molar ratio of 4:1 in a toluene and ethyl acetate solution in a volume ratio of 3:1 for 48-72 h, and then rinsing and drying.

[0058] After being treated by the pre-filter, the suspended solids, solid impurities and macromolecular organic matters in the water are effectively blocked, so that the selective electrodialysis device can be normally operated.

[0059] In one embodiment of the present application, a selective electrodialysis device is provided, which comprises an electrodialysis cell, and an anode and a cathode are arranged on two sides of the electrodialysis cell, respectively, and the anode and the cathode are used for connecting a positive electrode and a negative electrode of a power supply, respectively. A cation exchange membrane, a baffle or a screen, an anion exchange membrane, a baffle or a screen, a cation exchange membrane, a baffle or a screen, an anion exchange membrane, a baffle or a screen, and the like are arranged alternately between the anode and the cathode, wherein the baffle or the screen can be made of polypropylene or polypropylene-polyethylene composite material, and the baffle or the screen can form a space, i.e., a compartment, on both sides of the membrane, and can also improve the flow state, the number of pairs of the cation exchange membrane and the anion exchange membrane is greater than or equal to 1, and the interval region between the cation exchange membrane and the anion exchange membrane is alternately formed into a concentrated liquid chamber and a dilute liquid chamber, and a polar membrane is arranged on the side of the anode and the cathode, respectively, and the electrode (the anode and the cathode) and the polar membrane form a polar chamber. All the concentrated liquid chambers can be connected by a pipeline for liquid inlet or liquid outlet, and all the dilute liquid chambers can be connected by a pipeline for liquid inlet or liquid outlet. As shown in FIG. Figure 1 In the working process of the device, feed liquid 11 and acceptable liquid 12 are added into the dilute liquid chamber and the concentrated liquid chamber of the device through the feed pipe, and after working, the concentrated liquid 13 formed in the concentrated liquid chamber flows out through the pipeline, and the dilute liquid 14 formed in the dilute liquid chamber flows out through the pipeline. The polar membrane material is quaternary amine polyphenyl ether, the material of the anode can be titanium coated with ruthenium, titanium coated with lead dioxide or graphite, and the material of the cathode can be titanium coated with ruthenium, graphite or stainless steel.

[0060] The present application also provides an application of the selective electrodialysis device in lithium-magnesium ion separation, and specifically, the interval region between the cation exchange membrane and the anion exchange membrane is formed into a concentrated liquid chamber and a dilute liquid chamber, and after the salt lake brine is treated by the selective electrodialysis device, lithium ions are enriched in the concentrated liquid chamber, and magnesium ions are blocked in the dilute liquid chamber, so that the separation and concentration of lithium ions are realized.

[0061] To better explain and facilitate understanding of the present invention, a detailed description of the invention is provided below with reference to the accompanying drawings and specific embodiments. While exemplary embodiments of the invention are shown below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a clearer and more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art. Unless otherwise specified, all reagents used in the embodiments are of analytical grade or higher and may be commercially available products.

[0062] Example 1

[0063] A selective electrodialysis apparatus, comprising an electrodialysis cell, such as Figure 2 As shown, an anode 2 and a cathode 3 are respectively provided on both sides of the electrodialysis cell 1. The anode 2 is connected to the positive terminal of the power supply, and the cathode 3 is connected to the negative terminal of the power supply. The materials of the anode 2 and the cathode 3 are titanium-coated lead dioxide. Starting from the anode 2 side, a cation exchange membrane 4 is first set, followed by a partition or mesh 6, then an anion exchange membrane 5, then another partition or mesh 6, and so on, forming an alternating arrangement of cation exchange membrane-partition or mesh-anion exchange membrane-partition or mesh-cation exchange membrane until the cathode side. The first and last membranes are both cation exchange membranes 4. In other words, between anode 2 and cathode 3, cation exchange membrane 4, separator or mesh 6, anion exchange membrane 5, separator or mesh 6, cation exchange membrane 4, etc. are alternately arranged in sequence. The interval between cation exchange membrane 4 and anion exchange membrane 5 and cation exchange membrane 4 alternately forms a concentrate chamber, a dilute chamber, and another concentrate chamber. That is, from the anode to the cathode, the sequence is cation exchange membrane, concentrate chamber (with separator or mesh inside), anion exchange membrane, dilute chamber (with separator or mesh inside), cation exchange membrane, concentrate chamber, etc. The separator or mesh is set as a mesh, mainly to provide a cavity, i.e., a compartment, between the anode and cathode membranes. An electrode membrane 7 is set on one side of the anode and cathode. A separator or mesh 6 is also set between the electrode membrane 7 and anode 2 and cathode 3. An electrode compartment is formed between the electrode (anode, cathode) and the electrode membrane. The anode compartment is formed between anode 2 and electrode membrane 7, and the cathode compartment is formed between cathode 3 and electrode membrane 7. The material of electrode membrane 7 is quaternary ammonium polyphenylene ether.

[0064] The cation exchange membrane used is obtained by coating a sulfonated polybenzimidazole with a casting solution containing porous micro-nano materials and 10 g / L of polystyrene sulfonic acid sodium, and then drying, wherein the casting solution also contains porous micro-nano materials, and the porous micro-nano materials are prepared by dispersing zinc chloride and tetra(4-pyridyl biphenyl) ethylene in N,N-dimethylformamide at a mass ratio of 2:1, ultrasonicating for 20 minutes, and then reacting at 120°C for 90 hours. The preparation method specifically comprises the following steps:

[0065] (1) First, immerse the sulfonated polybenzimidazole membrane as the base film in deionized water for 2 hours to remove surface impurities, and then dry or absorb the surface moisture with filter paper.

[0066] (2) Preparation of the casting solution: disperse zinc chloride and tetra(4-pyridyl biphenyl) ethylene in N,N-dimethylformamide at a mass ratio of 2:1, wherein the mass concentration of zinc chloride and tetra(4-pyridyl biphenyl) ethylene in the N,N-dimethylformamide solvent is 5-10 mg / mL, ultrasonicate at an ultrasonic power of 300-500 W for 20 minutes, and then react the ultrasonicated dispersion at 120°C for 90 hours. After the reaction is completed, cool to room temperature, filter the product, wash with N,N-dimethylformamide (DMF) and deionized water alternately for 3-5 times (to remove unreacted raw materials and impurities), and then vacuum dry at 60-80°C for 12 hours to obtain white or light yellow porous micro-nano material powder.

[0067] Weigh 10 g of polystyrene sulfonic acid sodium, add 1 L of deionized water, stir until completely dissolved, form a transparent PSS solution, then add 0.5 g of the prepared porous micro-nano material powder, stir uniformly, and then ultrasonicate again for 10-15 minutes to ensure uniform dispersion of the material in the casting solution, forming a stable suspension state casting solution.

[0068] Slowly immerse the base film in the casting solution, stand for 10-30 seconds to allow the casting solution to evenly adhere to the surface of the base film, then slowly take it out and hang it vertically to drain the excess liquid.

[0069] (3) Place the coated membrane in an oven and dry at 60-80°C for 2-4 hours (low-temperature slow drying to avoid cracking of the membrane surface due to rapid solvent evaporation), until the membrane is completely dry, forming a uniform composite membrane layer.

[0070] (4) Soak the dried membrane in deionized water for 12 hours to remove unreacted PSS and residual solvents, thereby obtaining a cation exchange membrane coated with porous micro-nano material-containing polystyrene sulfonic acid sodium (sulfonic acid groups dissociate in water, imparting selective permeability to the membrane for cations).

[0071] The cation exchange membrane is further covered with a polydiphenylene piperidine protective layer containing organic framework catalytic material A on the surface of the side close to the dilute liquid chamber, wherein the organic framework catalytic material A is prepared by adding a mixture of 2,4-diformylphloroglucinol and diamino benzene sulfonic acid in a molar ratio of 1:1.4 to a mixed solution of N,N-dimethylformamide and mesitylene in a volume ratio of 1:4, wherein the concentration of 2,4-diformylphloroglucinol in the mixed solution is 0.1 mol / L, the concentration of diamino benzene sulfonic acid in the mixed solution is 0.14 mol / L, then TiO2 nanoparticles with Pt deposited thereon are dispersed in the mixed solution at a mass concentration of 2%, and ultrasonic treatment is performed for 0.5 h, followed by constant temperature reaction at 120℃ for 60 h to obtain the organic framework catalytic material A. The TiO2 nanoparticles with Pt deposited thereon can be prepared by chemical deposition or impregnation reduction, and the specific preparation method is as follows: TiO2 nanoparticles are added to a noble metal salt solution and stirred for several hours, then dried, and calcined at 300-400℃ under inert gas for 4-6 h. The mass fraction of the TiO2 nanoparticles with noble metal deposited thereon in the mixed solution is 2wt%, and the mass fraction of the noble metal Pt in TiO2 is 5wt%.

[0072] A polydiphenylene piperidine protective layer containing organic framework catalytic material A is sprayed on one side of the cation exchange membrane prepared above, wherein the polydiphenylene piperidine content is 0.5-2 mol / L dichloromethane solution, and the amount of the organic framework catalytic material A contained therein is 5-15% of the polydiphenylene piperidine.

[0073] A barrier layer is sprayed on the other side of the cation exchange membrane, wherein the barrier layer is specifically a solution of N-methyl-4-piperidone and 4-trifluoromethyl biphenyl petroleum ether in a molar ratio of 1:1-1.4, wherein the concentration of N-methyl-4-piperidone is 1.5 mol / L, and the mixed solution is coated on the cation exchange membrane and dried at 60℃ for 12 h.

[0074] The anion exchange membrane uses quaternary aminized polysulfone as a substrate, and the surface is coated with 25 g / L polydimethyl diallyl ammonium chloride. The surface of the side close to the dilute liquid chamber of the anion exchange membrane is further covered with a polystyrene protective layer containing organic framework catalytic material B, wherein the organic framework catalytic material B is prepared by adding 2,4-diformylphloroglucinol and p-phenylenediamine (2,4-diformylphloroglucinol 0.1 mol / L and diamino benzene sulfonic acid 0.14 mol / L) in a molar ratio of 1:1.4 to a mixed solution of N,N-dimethylformamide and mesitylene in a volume ratio of 1:4, then dispersing TiO2 nanoparticles with Au deposited thereon in the mixed solution at a mass concentration of 2-5%, and ultrasonic treatment is performed for 0.5 h, followed by constant temperature reaction at 110℃ for 60 h to obtain the organic framework catalytic material B. The above-prepared organic framework catalytic material B is added to polystyrene, and the amount is 5-10% of the mass of the polystyrene.

[0075] The other surface of the anion exchange membrane is coated with a barrier layer, which is specifically a N-methyl-4-piperidone and 4-trifluoromethyl biphenyl petroleum ether solution with a molar ratio of 1:1.2, wherein the concentration of N-methyl-4-piperidone is 1.5 mol / L, and the mixed solution is coated on the anion exchange membrane and dried at 60°C for 12h.

[0076] The cation exchange membrane and the anion exchange membrane coated with the barrier layer are arranged on the side of the concentrated solution chamber.

[0077] A chlorine gas absorber is arranged in the anode chamber. The selective electrodialysis device is provided with a pre-filter, and a polyolefin membrane containing an adsorbent material is used in the pre-filter, and the adsorbent material is prepared by reacting tetra-(4-aminophenyl) ethylene and 2,6-divinyl naphthalene in a toluene and ethyl acetate solution for 48h, and then rinsing and drying.

[0078] Specifically, the preparation method of the pre-filter is that a mixture of tetra-(4-aminophenyl) ethylene (8 mol / L) and 2,6-divinyl naphthalene (2 mol / L) is reacted in a toluene and ethyl acetate solution with a volume ratio of 3:1 for 48h, and then rinsed with ethanol and dried at 80°C.

[0079] The pre-filter is arranged in front of the electrodialysis device, which is a pre-filter, and the produced water after being treated by the pre-filter enters the electrodialysis device for single and multi-valent ion separation.

[0080] In the application of the device, a liquid containing lithium ions of 400mg / L and magnesium ions of 12000mg / L is added to the dilute solution chamber and the concentrated solution chamber of the electrolytic cell of the selective electrodialysis device, 2% sodium sulfate solution is added to the two electrode chambers, the power supply is connected, and the current density is set to 300A / m 2 After 60min, detection is performed. Ion chromatography is used to measure ion concentration, and the permeation amount is calculated according to the concentration difference.

[0081] The separation rate of lithium ions and magnesium ions by the selective electrodialysis device is tested. The initial water sample contains lithium ions of 400mg / L and magnesium ions of 12000mg / L, the current density is 300A / m 2 , the membrane surface flow rate is 4cm / s, the lithium-magnesium separation rate is calculated according to the ratio of the permeation amount of lithium ions migrating from the dilute solution chamber to the concentrated solution chamber to the permeation amount of magnesium ions migrating from the dilute solution chamber to the concentrated solution chamber, and the current efficiency = ion permeation molar number x Faraday constant / electric quantity x 100%. The test results are as follows: lithium-magnesium separation rate 46.9, current efficiency 88.3%.

[0082] Example 2

[0083] In the embodiment, the selective electrodialysis device is provided, which comprises an electrodialysis tank, an anode and a cathode are respectively arranged on two sides of the electrodialysis tank, the anode and the cathode are made of graphite, a cation exchange membrane, a separator or a screen, an anion exchange membrane, a separator or a screen, and a cation exchange membrane are sequentially and alternately arranged between the anode and the cathode, an electrode membrane is arranged on a side of the anode electrode and the cathode electrode close to the separator or the screen, an anode chamber is formed between the anode electrode and the electrode membrane, and a cathode chamber is formed between the cathode electrode and the electrode membrane. The material of the electrode membrane is quaternary amine polyphenyl ether.

[0084] The cation exchange membrane used is obtained by coating 20 g / L of a polystyrene sulfonic acid sodium casting solution on a sulfonated polybenzimidazole and drying, wherein the casting solution further contains porous micro-nano materials, and is prepared by dispersing nickel chloride and tetrakis(4-pyridyl biphenyl) ethylene in N,N-dimethylformamide at a mass ratio of 3:1, ultrasonicating for 20 minutes, and reacting at 150 DEG C for 75 hours.

[0085] The cation exchange membrane used further has a polydiphenylpiperidine protective layer containing organic framework catalytic material A on a surface of a side close to the dilute liquid chamber, and a barrier layer is coated on another surface.

[0086] Specifically, the cation exchange membrane is prepared according to the method in Embodiment 1, except that in the preparation method of the organic framework catalytic material A, a mixture of 2,4-diformylphloroglucinol and diaminobenzenesulfonic acid at a molar ratio of 1:1.2 is added to a mixed solution of N,N-dimethylformamide and mesitylene at a volume ratio of 1:4, and then TiO2 nanoparticles with Au deposited thereon are dispersed in the mixed solution, ultrasonicated for 0.5 h, and reacted at 110 DEG C for 60 h to obtain the organic framework catalytic material A; wherein the mass ratio of the TiO2 nanoparticles with the noble metal deposited thereon in the mixed solution is 5 wt%, and the mass ratio of the noble metal Au in the TiO2 is 0.5 wt%.

[0087] The other surface of the cation exchange membrane is sprayed with a barrier layer, wherein the barrier layer is specifically prepared by dissolving N-methyl-4-piperidone and 4-trifluoromethyl biphenyl at a molar ratio of 1:1.2 in petroleum ether, wherein the concentration of N-methyl-4-piperidone is 1.5 mol / L, and the mixed solution is coated on the cation exchange membrane and dried at 60 DEG C for 12 h.

[0088] The anion exchange membrane is made of quaternary aminated polyether sulfone, and the surface is coated with 20 g / L polydimethyl diallyl ammonium chloride. The anion exchange membrane is further coated with a polystyrene protective layer containing organic framework catalytic material B on the surface of the side of the dilute liquid chamber. The organic framework catalytic material B is prepared by adding 2,4-diformylphloroglucinol and p-phenylenediamine (molar ratio 1:1.6) into a mixed solution of N,N-dimethylformamide and mesitylene, then dispersing TiO2 nanoparticles deposited with Pt in the mixed solution, and then ultrasonicating for 0.5 h and reacting at 130°C for 60 h. In the process, the mass fraction of the TiO2 nanoparticles deposited with noble metal in the mixed solution is 5 wt%, and the mass fraction of the noble metal Pt in the TiO2 is 0.5 wt%.

[0089] The anion exchange membrane is made of quaternary aminated polyether sulfone, and the surface is coated with 20 g / L polydimethyl diallyl ammonium chloride.

[0090] The cation exchange membrane and the anion exchange membrane are coated with a barrier layer on the surface of the side of the concentrated liquid chamber. The barrier layer is obtained by coating a petroleum ether solution of N-methyl-4-piperidone and 4-trifluoromethyl biphenyl (molar ratio 1:1.2) and then drying.

[0091] A chlorine gas absorber is arranged in the anode chamber. The selective electrodialysis device is provided with a pre-filter, and a polyolefin membrane containing an adsorbent material is used in the pre-filter. The adsorbent material is prepared by reacting a mixture of tetra-(4-aminophenyl) ethylene (8 mol / L) and 2,6-divinyl naphthalene (2 mol / L) in a toluene and ethyl acetate solution for 60 h, and then washing with ethanol and drying at 80°C.

[0092] The selective electrodialysis device is tested for its effect on separating a liquid containing lithium ions and magnesium ions according to the operation in Example 1.

[0093] The selective electrodialysis device is tested for its separation rate of lithium ions and magnesium ions. The initial water sample contains 400 mg / L of lithium ions and 12,000 mg / L of magnesium ions, the current density is 300 A / m2, and the membrane surface flow rate is 4 cm / s. The test results are as follows: the lithium-magnesium separation rate is 48.3, and the current efficiency is 87.6%. 2

[0094] Example 3

[0095] In this example, the selective electrodialysis device includes an electrodialysis cell, which has the same structure as that in Example 1. An anode and a cathode are arranged on the two sides of the electrodialysis cell, respectively. Cation exchange membranes, separators or screens, anion exchange membranes, separators or screens, and cation exchange membranes are arranged alternately between the anode and the cathode. The spaces between the cation exchange membranes and the anion exchange membranes alternately form concentrated liquid chambers and dilute liquid chambers. An electrode membrane is arranged on one side of the anode and the cathode. The electrode (anode or cathode) and the electrode membrane form an electrode chamber. The material of the electrode membrane is quaternary aminated polyphenyl ether.​

[0096] The preparation method of the cation exchange membrane is the same as that in Example 1, except that the cation exchange membrane is prepared by coating 30 g / L of a polystyrene sulfonic acid sodium casting solution on the sulfonated polybenzimidazole, drying, and then adding porous micro-nano materials, and then dispersing a mixture of copper chloride and tetrakis(4-pyridyl biphenyl) ethylene in a mass ratio of 1:1 in N,N-dimethylformamide for ultrasonic treatment for 20 minutes, and then reacting at 130°C for 60 hours.

[0097] The cation exchange membrane further has a polydiphenylene piperidine protective layer containing organic framework catalytic material A on the surface of the side close to the dilute liquid chamber, and a barrier layer on the other surface. Specifically, the preparation of the cation exchange membrane is the same as that in Example 1, except that the mixture of 2,4-diformylphloroglucinol and diaminobenzene sulfonic acid in a molar ratio of 1:1.6 is added to a mixed solution of N,N-dimethylformamide and mesitylene in a volume ratio of 1:4, and then TiO2 nanoparticles (3%) with Rh (10%) deposited thereon are dispersed in the mixed solution, ultrasonic treatment is performed for 0.5 hours, and then reaction is performed at 140°C for 60 hours to obtain the organic framework catalytic material A, wherein the mass ratio of the TiO2 nanoparticles with the noble metal deposited thereon in the mixed solution is 3wt%, and the mass ratio of the noble metal Rh in the TiO2 is 10wt%.

[0098] The anion exchange membrane is made of quaternary aminated polysulfone, and the surface is coated with 15 g / L of polydimethyl diallyl ammonium chloride. The anion exchange membrane further has a polystyrene protective layer containing organic framework catalytic material B on the surface of the side close to the dilute liquid chamber. The preparation method of the organic framework catalytic material B is as follows: a mixture of 2,4-diformylphloroglucinol (0.1 mol / L) and p-phenylenediamine in a molar ratio of 1:1.5 is added to a mixed solution of N,N-dimethylformamide and mesitylene in a volume ratio of 1:4, and then TiO2 nanoparticles (3%) with Rh (10%) deposited thereon are dispersed in the mixed solution, ultrasonic treatment is performed for 0.5 hours, and then reaction is performed at 140°C for 60 hours to obtain the organic framework catalytic material B, wherein the mass ratio of the TiO2 nanoparticles with the noble metal deposited thereon in the mixed solution is 3wt%, and the mass ratio of the noble metal Rh in the TiO2 is 10wt%.

[0099] The cation exchange membrane and the anion exchange membrane are coated with a barrier layer on the surface of the side close to the concentrated liquid chamber, and a petroleum ether solution of N-methyl-4-piperidone and 4-trifluoromethyl biphenyl (molar ratio 1:1.2) is coated and dried to obtain the barrier layer, wherein the concentration of N-methyl-4-piperidone is 1.5 mol / L. A chlorine gas absorber is arranged in the anode chamber. The selective electrodialysis device is provided with a pre-filter, and a polyolefin membrane containing adsorbent material is used in the pre-filter. The adsorbent material is prepared by reacting tetrakis-(4-aminophenyl) ethylene (8 mol / L) and 2,6-divinyl naphthalene (2 mol / L) in a toluene and ethyl acetate solution in a volume ratio of 3:1 for 72 hours, and then washing with ethanol and drying at 80°C.

[0100] The selective electrodialysis device was tested for separating lithium ions and magnesium ions from a liquid according to the procedure of Example 1. The selective electrodialysis device of this example was tested for lithium ion and magnesium ion separation rate, with an initial water sample containing 400 mg / L lithium ions and 12000 mg / L magnesium ions, and a current density of 300 A / m 2 The membrane surface flow rate was 4 cm / s, and the test results were as follows: lithium-magnesium separation rate 47.5, current efficiency 89.1%.

[0101] Example 4

[0102] In this example, the selective electrodialysis device comprises an electrodialysis cell, and an anode and a cathode are arranged on both sides of the electrodialysis cell. The anode is connected to the positive electrode of a power supply, and the cathode is connected to the negative electrode of the power supply. The anode and the cathode are made of titanium coated with lead dioxide. Cation exchange membranes, separators or screens, anion exchange membranes, separators or screens, and cation exchange membranes are arranged alternately between the anode and the cathode. There are 10 cation exchange membranes and 10 anion exchange membranes. The spacing between the cation exchange membranes and the anion exchange membranes alternately forms a concentrated liquid chamber and a dilute liquid chamber. An electrode membrane is arranged on one side of the anode and the cathode. The electrode (anode or cathode) and the electrode membrane form an electrode chamber. The material of the electrode membrane is quaternary amine polyphenyl ether.

[0103] The cation exchange membrane and the anion exchange membrane are prepared according to the method of Example 1, except that the cation exchange membrane is obtained by coating a 25 g / L polystyrene sulfonic acid sodium casting solution on a sulfonated polybenzimidazole, and then drying. The casting solution further contains a porous micro-nano material. The porous micro-nano material is prepared by dispersing zinc chloride 6 g / L and tetra(4-pyridyl biphenyl) ethylene in N,N-dimethylformamide at a mass ratio of 1.5:1, ultrasonicating for 20 minutes, and then reacting at 140°C for 60 hours.

[0104] The cation exchange membrane further has a polydiphenylpiperidine protective layer containing organic framework catalytic material A on the surface of the dilute liquid chamber side. The organic framework catalytic material A is prepared by adding a mixture of 2,4-diformylphloroglucinol and diamino benzene sulfonic acid at a molar ratio of 1:1.3 to a mixture of N,N-dimethylformamide and mesitylene at a volume ratio of 1:4, wherein the concentration of 2,4-diformylphloroglucinol in the mixture is 0.1 mol / L. Then, TiO2 nanoparticles (3 wt%) with Pt (5 wt%) deposited thereon are dispersed in the mixture, ultrasonicated for 0.5 h, and then reacted at 120°C for 60 h to obtain the organic framework catalytic material A.

[0105] The anion exchange membrane is made of quaternary aminated polysulfone, and the surface is coated with 20 g / L polydimethyl diallyl ammonium chloride. The anion exchange membrane is further coated with a polystyrene protective layer containing organic framework catalytic material B on the surface of the dilute liquid chamber side. The preparation method of the organic framework catalytic material B is as follows: a mixture of 2,4-diformylphloroglucinol (0.1 mol / L) and p-phenylenediamine in a molar ratio of 1:1.2 is added to a mixture of N,N-dimethylformamide and mesitylene in a volume ratio of 1:4, and then TiO2 nanoparticles (3 wt%) deposited with Pt (5 wt%) are dispersed in the mixture. After ultrasonic treatment for 0.5 h, the mixture is reacted at 120°C for 60 h to obtain the organic framework catalytic material B.

[0106] The cation exchange membrane and the anion exchange membrane are coated with a barrier layer on the surface of the concentrated liquid chamber side. The barrier layer is obtained by coating a petroleum ether solution of N-methyl-4-piperidone and 4-trifluoromethyl biphenyl (molar ratio 1:1.2) and then drying.

[0107] A chlorine gas absorber is arranged in the anode chamber. The selective electrodialysis device is provided with a pre-filter, and a polyolefin membrane containing an adsorbent material is used in the pre-filter. The adsorbent material is prepared by reacting tetra-(4-aminophenyl)ethylene (8 mol / L) and 2,6-divinyl naphthalene (2 mol / L) in a toluene and ethyl acetate solution in a volume ratio of 3:1 for 65 h, and then rinsing and drying.

[0108] The selective electrodialysis device is tested for separating lithium ions and magnesium ions from a liquid according to the operation in Example 1. The separation rate of lithium ions and magnesium ions is tested for the selective electrodialysis device in this example. The initial water sample contains 400 mg / L of lithium ions and 12000 mg / L of magnesium ions, the current density is 300 A / m2, and the membrane surface flow rate is 4 cm / s. The test results are as follows: the lithium-magnesium separation rate is 47.2, and the current efficiency is 88.7%. 2

[0109] Comparative Example 1

[0110] The selective electrodialysis device in this comparative example is the same as that in Example 1, except that the polystyrene sulfonate coated on the cation exchange membrane does not contain porous micro-nano materials.

[0111] The preparation method of the polystyrene sulfonate coated on the cation exchange membrane and not containing porous micro-nano materials includes the following steps: (1) first, the sulfonated polybenzimidazole membrane is immersed in deionized water for 2 hours to remove surface impurities, and then air-dried or the surface water is absorbed with filter paper.

[0112] (2) 10 g of polystyrene sulfonate is added to 1 L of deionized water, stirred until completely dissolved, and a transparent PSS solution is formed as a casting solution. The base film is slowly immersed in the casting solution, and then slowly taken out and hung vertically to drain the excess liquid.​

[0113] (3) The coated membrane was placed in an oven and dried at 70°C for 3 hours until the membrane was completely dry and a uniform composite membrane layer was formed.

[0114] (4) The dried membrane was soaked in deionized water for 12 hours to remove unreacted PSS and residual solvent, thereby obtaining a cation exchange membrane coated with sodium polystyrene sulfonate. The selectivity electrodialysis device in this example was tested for lithium ion and magnesium ion separation rate, with an initial water sample containing 400 mg / L of lithium ions and 12000 mg / L of magnesium ions, a current density of 300 A / m 2 , and a membrane surface flow rate of 4 cm / s. The test results were as follows: lithium-magnesium separation rate 29.2, current efficiency 67.6%.

[0115] Comparative Example 2

[0116] In the selectivity electrodialysis device in this comparative example, neither the cation exchange membrane nor the anion exchange membrane had a protective layer on the side surface facing the dilute liquid chamber, and the rest were the same as in Example 1.

[0117] The selectivity electrodialysis device was tested for lithium ion and magnesium ion separation rate, with an initial water sample containing 400 mg / L of lithium ions and 12000 mg / L of magnesium ions, a current density of 300 A / m 2 , and a membrane surface flow rate of 4 cm / s. The test results were as follows: lithium-magnesium separation rate 23.4, current efficiency 62.1%.

[0118] Comparative Example 3

[0119] In the selectivity electrodialysis device in this comparative example, neither the cation exchange membrane nor the anion exchange membrane had a barrier layer on the side surface facing the concentrated liquid chamber, and the rest were the same as in Example 1.

[0120] The selectivity electrodialysis device was tested for lithium ion and magnesium ion separation rate, with an initial water sample containing 400 mg / L of lithium ions and 12000 mg / L of magnesium ions, a current density of 300 A / m 2 , and a membrane surface flow rate of 4 cm / s. The test results were as follows: lithium-magnesium separation rate 32.1, current efficiency 60.2%.

[0121] Comparative Example 4

[0122] In the selectivity electrodialysis device in this comparative example, the pre-filter used a polyolefin membrane that did not contain adsorbent material, and the rest were the same as in Example 1.

[0123] The selectivity electrodialysis device was tested for lithium ion and magnesium ion separation rate, with an initial water sample containing 400 mg / L of lithium ions and 12000 mg / L of magnesium ions, a current density of 300 A / m 2, the membrane surface flow rate is 5 cm / s, the test results are: lithium-magnesium separation rate 35.5, current efficiency 66.7%.

[0124] As can be seen from the above, coating the cation exchange membrane with the porous micro-nano material added can effectively improve the lithium-magnesium separation rate by 19.7 and the current efficiency by 20%; when the cation exchange membrane and the anion exchange membrane are both provided with a protective layer, the lithium-magnesium separation rate can be improved by 23.5 and the current efficiency can be improved by 26.2%; when the cation exchange membrane and the anion exchange membrane are both provided with a barrier layer, the lithium-magnesium separation rate can be improved by 14.8 and the current efficiency can be improved by 28.1%; the current filter using the polyolefin membrane containing the adsorption material can improve the lithium-magnesium separation rate by 11.4 and the current efficiency by 21.6% compared with the polyolefin membrane without the adsorption material; and the effect is significant.

[0125] The above is only a preferred embodiment of the present application, and does not limit the present application in other forms. Any person skilled in the art can modify or change the above disclosed technical content into equivalent embodiments. However, any simple modification, equivalent change and modification made according to the technical essence of the present application to the above embodiments still belong to the protection scope of the present application technical solution.

Claims

1. A selective electrodialysis unit, characterized in that, It includes an electrodialysis cell, an anode and a cathode are respectively arranged on both sides of the electrodialysis cell, a cation exchange membrane and an anion exchange membrane are sequentially arranged between the anode and the cathode, wherein the cation exchange membrane takes sulfonated polybenzimidazole as a base material, and the surface of the cation exchange membrane is coated with sodium polystyrene sulfonate containing porous micro-nano materials; and the side of the cation exchange membrane facing the anode is coated with a protective layer containing polydiphenylpiperidine; The anion exchange membrane takes quaternary aminated polysulfone or polyether sulfone as a base material, and the surface of the anion exchange membrane is coated with polydimethyl diallyl ammonium chloride.

2. The selective electrodialysis unit of claim 1, wherein, The preparation method of the porous micro-nano material is that metal hydrochloride and tetrakis(4-pyridine biphenyl) ethylene are dispersed in N,N-dimethyl formamide at a mass ratio of 1-3:1, ultrasonic treatment is performed for 10-20 minutes, and then reaction is performed at 120-150 DEG C for 60-90 hours to obtain the porous micro-nano material, wherein the metal hydrochloride is zinc chloride, nickel chloride or copper chloride.

3. The selective electrodialysis unit of claim 1, wherein, The concentration of the sodium polystyrene sulfonate coated in the cation exchange membrane is 10-30 g / L; and the concentration of the polydimethyl diallyl ammonium chloride coated in the anion exchange membrane is 15-25 g / L.

4. The selective electrodialysis unit of claim 1, wherein, The side of the cation exchange membrane facing the anode is coated with a cation protective layer, and the cation protective layer is polydiphenylpiperidine containing organic framework catalytic material A; the preparation method of the organic framework catalytic material A is that a mixture of 2,4-diformylphloroglucinol and diaminobenzenesulfonic acid at a molar ratio of 1:1.2-1.6 is added into a mixed solution of N,N-dimethyl formamide and mesitylene, then TiO2 nanoparticles deposited with noble metal are dispersed in the mixed solution, ultrasonic treatment is performed for 15-40 minutes, and then reaction is performed at 110-140 DEG C for 40-60 hours to obtain the organic framework catalytic material A, wherein the noble metal is Pt, Au or Rh.

5. The selective electrodialysis unit of claim 1, wherein, The side of the anion exchange membrane facing the anode is coated with a polyphenyl sulfone protective layer containing organic framework catalytic material B; the preparation method of the organic framework catalytic material B is that a mixture of 2,4-diformylphloroglucinol and p-phenylenediamine at a molar ratio of 1:1.2-1.6 is added into a mixed solution of N,N-dimethyl formamide and mesitylene, then TiO2 nanoparticles deposited with noble metal are dispersed in the mixed solution, ultrasonic treatment is performed for 15-45 minutes, and then reaction is performed at 120-150 DEG C for 40-60 hours to obtain the organic framework catalytic material B.

6. The selective electrodialysis unit of claim 1, wherein, The side of the cation exchange membrane and the side of the anion exchange membrane facing the cathode are provided with a barrier layer, and the barrier layer is obtained by coating a petroleum ether solution containing N-methyl-4-piperidone and 4-trifluoromethyl biphenyl at a molar ratio of 1:1-1.4 and then drying.

7. The selective electrodialysis unit of claim 1, wherein, A group of cation exchange membranes, anion exchange membranes, cation exchange membranes and anion exchange membranes arranged in the order of anode to cathode are referred to as an electrodialysis unit, and ≥1 electrodialysis unit is arranged between the anode and the cathode.

8. The selective electrodialysis unit of claim 7, wherein, A polar membrane is arranged between the cation exchange membrane and the anode, and a polar membrane is arranged between the anion exchange membrane and the cathode; and a baffle or a screen is arranged between any adjacent cation exchange membrane and anion exchange membrane.

9. The selective electrodialysis unit of claim 8, wherein, The polar membrane is a quaternary aminated polyphenyl ether membrane; The anode and the polar membrane close to the anode form an anode chamber, and a chlorine gas absorber is further arranged in the anode chamber.

10. Use of a selective electrodialysis device according to any one of claims 1-9 for lithium-magnesium ion separation.

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