A bipolar membrane and methods of making and using the same

Abstract

The application discloses a bipolar membrane and a preparation and use method thereof, wherein the bipolar membrane comprises a cation exchange membrane, a metal catalyst layer and an anion exchange layer; the cation exchange membrane comprises a substrate and a cation exchange layer arranged on at least one surface of the substrate, and the cation exchange layer is added with a sulfonic acid type ionic liquid; the metal catalyst layer is arranged on one surface of the substrate, so that the two surfaces of the substrate are respectively the cation exchange layer and the metal catalyst layer; the anion exchange layer is arranged on the surface of the metal catalyst layer, and comprises an imidazole derivative after quaternary ammonium and a quaternary ammonium type ionic liquid, wherein the quaternary ammonium type ionic liquid is more than 25% of the weight of the imidazole derivative. The application has the advantages of high concentration of generated acid and alkali, stable membrane structure, stable performance and the like, and is suitable for long-term and stable preparation of high-concentration acid and alkali.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of preparation of electrodialysis membrane, and particularly relates to a bipolar membrane and a preparation and use method thereof. BACKGROUND

[0002] The bipolar membrane is a special ion exchange membrane, which usually comprises a cation exchange layer and an anion exchange layer. The bipolar membrane has the characteristics that, under the action of a direct current electric field, H2O between the anion and cation membrane layers is dissociated into H+ and OH- and is transmitted through the anion and cation membranes, respectively, as H+ and OH- ion sources. That is, under the reverse voltage, water is decomposed at the interface layer of the bipolar membrane to generate H+ and OH- and is migrated to the solution through the anion and cation membranes. The bipolar membrane realizes the process of water dissociation to generate H + and OH - The process is simple, waste discharge is less, and has good prospects in the fields of electrolysis of water to produce hydrogen and reduction of carbon dioxide, and the like. Meanwhile, the bipolar membrane has been widely applied in the fields of inorganic preparation of acids and bases, such as sodium sulfate, sodium chloride, lithium sulfate, lithium chloride, sodium nitrate, and the like.

[0003] With the exploration in the fields of organic acids and organic bases, many application cases and scenes of the bipolar membrane have been developed at present, such as formic acid (Ferrer J, et al, 2006a), acetic acid (YUL, et al, 2003a), lactic acid (Lee E, et al, 1998; Li H, et al, 2004), citric acid (Novalic S. and Kulbe K, 1998a; Pinacci P. and Radaeli M, 2002), beta-amino propionic acid (CN 109851515 B), tetramethyl ammonium hydroxide, and the like. However, in the above-mentioned bipolar membrane conversion projects of inorganic salts or organic acids and bases which have been disclosed, considering the energy consumption and the acid and base production capacity and tolerance of the bipolar membrane itself, the concentration of the prepared acid and base is usually between 1-2N, which greatly limits the reuse of the acid and base and the development of the bipolar membrane application. Taking the scheme disclosed in Chinese patent application CN109851515A as an example, the scheme uses 3-aminopropionitrile and sodium hydroxide aqueous solution as raw materials, reacts to obtain 3-aminopropanesodium solution, and then directly converts the 3-aminopropanesodium into sodium hydroxide and product beta-amino propionic acid through bipolar membrane electrodialysis. Since the previous 3-aminopropionitrile needs to be mixed with the sodium hydroxide aqueous solution with a concentration of 32%, and the concentration of the alkali produced by the conventional bipolar membrane electrodialysis is 8%, the subsequent concentration needs to be carried out to meet the reuse conditions, which increases the processing procedure and cost of acid and base reuse. As for the bipolar membrane conversion process of inorganic acids and bases such as sulfuric acid and lithium carbonate to prepare high-purity lithium hydroxide, due to the limitation of the concentration of the prepared acid and base of the bipolar membrane itself, the cost and site requirement of the subsequent concentration process are also greatly increased. SUMMARY

[0004] Therefore, the technical problem to be solved by the present invention is the defect of low acid and alkali production concentration of the currently disclosed bipolar membrane, thereby providing a bipolar membrane that effectively increases the acid and alkali production concentration and a preparation and use method thereof.

[0005] A bipolar membrane comprising:

[0006] A cation exchange membrane comprises a substrate and a cation exchange layer disposed on at least one surface of the substrate, wherein the cation exchange layer comprises a sulfonated polymer monomer and a sulfonic acid ionic liquid, wherein the sulfonic acid ionic liquid accounts for more than 10% by weight of the sulfonated polymer monomer; preferably, the sulfonic acid ionic liquid accounts for 10% to 20% by weight of the sulfonated polymer monomer, for example, the sulfonic acid ionic liquid accounts for 10%, 12%, 14%, 16%, 18%, 20%, 20%, etc., of the weight of the sulfonated polymer monomer;

[0007] The metal catalyst layer is disposed on one surface of the substrate so that the two opposite surfaces of the substrate are respectively a cation exchange layer and a metal catalyst layer;

[0008] The anion exchange layer is arranged on the surface of the metal catalyst layer, which includes a quaternized imidazole derivative and a quaternary ammonium ionic liquid, wherein the quaternary ammonium ionic liquid is more than 25% by weight of the imidazole derivative; preferably, the quaternary ammonium ionic liquid is 25%-60% by weight of the imidazole derivative, for example: the quaternary ammonium ionic liquid is 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60% and the like by weight of the imidazole derivative.

[0009] The cation exchange layers are arranged on both surfaces of the substrate, and the metal catalyst layer is arranged on the surface of one of the cation exchange layers.

[0010] The cation exchange layer is made of a sulfonated polymer monomer cross-linked with a sulfonic acid ionic liquid, wherein the molar ratio of the sulfonic acid ionic liquid to the sulfonated polymer monomer is 1:(7-12), preferably 1:(9-10); for example, the molar ratio of the sulfonic acid ionic liquid to the sulfonated polymer monomer is 1:7, 1:8, 1:9, 1:10, 1:11 or 1:12.

[0011] And / or, the degree of ammonium of the quaternized imidazole derivative is 40-85%, for example, the degree of ammonium of the quaternized imidazole derivative is 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, etc.;

[0012] And / or, the mesh number of the substrate is 120-260 mesh, for example, the mesh number of the substrate is 120 mesh, 140 mesh, 160 mesh, 180 mesh, 200 mesh, 220 mesh, 240 mesh, 260 mesh, etc.;

[0013] And / or, the loading amount of the metal catalyst layer on the substrate is 0.5-5 g / m 2 , preferably 1-1.5g / m 2 For example, the loading amount of the metal catalyst layer is 0.5 g / m 2 , 1g / m 2 , 1.5g / m 2 , 2.0g / m 2 , 2.5g / m 2 3.0g / m 2 3.5g / m 2 , 4.0g / m 2 4.5g / m 2 , 5g / m 2 wait;

[0014] And / or, the thickness of the anion exchange layer is 30-80 μm; for example, the thickness of the anion exchange layer is 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, or 80 μm.

[0015] The sulfonic acid ionic liquid is selected from one or more of 1-propylsulfonic acid-3-methylimidazolium chloride (CAS: 1034558-51-4) and 1-propylsulfonic acid-3-vinylimidazolium chloride (CAS: 1416152-27-6);

[0016] And / or, the sulfonated polymer monomer is a sulfonated polystyrene monomer;

[0017] And / or, the quaternary ammonium ionic liquid is selected from one or more of butyltrimethylammonium chloride, hexyltrimethylammonium chloride, propyltrimethylammonium bromide, tetrapropylammonium hydrogen sulfate, tetraoctylammonium bromide and butyltriethylammonium bromide (CAS: 13028-69-8);

[0018] And / or, the imidazole derivative includes 2-methyl-1-vinylimidazole or 1,2-dimethylimidazole; in the present invention, quaternary ammonium groups are used as exchange groups of the anion exchange membrane layer. Therefore, the degree of ammonium here refers to the ratio of the halogenated hydrocarbon on the polymer to the tertiary amine reacting to form a quaternary ammonium salt.

[0019] And / or, the substrate is selected from any one of nylon mesh, PET mesh, PP mesh, PVC mesh, and PE mesh;

[0020] And / or, the catalyst in the metal catalyst layer is a metal salt, preferably a water-soluble metal salt, more preferably a water-soluble metal chloride. The metal in the metal salt includes one or more of titanium (Ti), tin (Sn), chromium (Cr), cobalt (Co), nickel (Ni), platinum (Pt), silver (Ag), or ruthenium (Ru).

[0021] A method for preparing a bipolar membrane, comprising:

[0022] Preparation of the cation exchange membrane: Prepare the raw materials of the cation exchange layer into a membrane-building solution, and prepare the membrane-building solution on at least one side of the substrate. For example, the membrane-building solution can be prepared on one side of the substrate, or the membrane-building solution can be prepared on the entire surface of the substrate. Remove the solution, dry and polymerize it, and cool it to obtain the cation exchange membrane.

[0023] Preparation of the metal catalyst layer: preparing the raw materials for preparing the metal catalyst layer into a suspension, evenly applying the suspension to the other side of the cation exchange membrane opposite to the cation exchange layer, and drying to obtain the metal catalyst layer;

[0024] Preparation of anion exchange layer: The raw materials of the anion exchange layer are prepared into anion membrane materials, the anion membrane materials are attached to the metal catalyst layer, and a bipolar membrane is obtained through ultraviolet light initiation and / or hot pressing reaction.

[0025] In the preparation step of the cation exchange membrane, the raw materials of the cation exchange layer include a sulfonated polymer monomer, a solvent, a cross-linking agent and a sulfonic acid ionic liquid, and / or the membrane-building liquid is attached to the substrate by impregnation, and / or the dry polymerization process is: first volatilizing at 25-30°C and humidity ≤55% for more than 5 hours, and then drying, preferably, the drying conditions are 100-120°C and more than 24 hours;

[0026] In the steps of preparing the metal catalyst layer, the raw materials of the metal catalyst layer include a metal salt, a quaternary ammonium, and an acid solution; the preparation process of the suspension liquid is as follows: the metal salt is added with an acid solution to coordinate with the quaternary ammonium in a weakly acidic environment of pH 3-5, and the suspension liquid is obtained after ultrasonic treatment; and / or, the suspension liquid is applied to the cation exchange membrane by ultrasonic spraying; and / or, the drying conditions are 100-120° C. and 1.5-2 hours;

[0027] In the preparation step of the anion exchange layer, the raw materials of the anion exchange layer include imidazole derivatives, quaternary ammonium reagents, solvents and quaternary ammonium ionic liquids; the ultraviolet light initiation time is 1-10 minutes; the pressure of the hot pressing reaction is 0.1-0.4 MPaG and the temperature is 100-130°C.

[0028] In the preparation step of the cation exchange membrane, the crosslinking agent is selected from one or more polyvinylbenzenes, preferably one or more of divinylbenzene, trivinylbenzene, divinyltoluene, and divinylethylbenzene; the total amount of the crosslinking agent is 5-15 wt% of the mass of the sulfonated polymer monomer; the amount of the solvent is 1-3 times the total mass of the sulfonic acid ionic liquid and the crosslinking agent; and the immersion time is 2-8 min;

[0029] In the step of preparing the metal catalyst layer, the acid solution is an inorganic acid, the quaternary ammonium salt is selected to be as close as possible to the quaternary ammonium type in the anion film layer after quaternization, for example, trimethylpropylammonium bromide (CAS: 2650-50-2), etc., the ultrasonic spraying is performed using a fan-shaped ultrasonic atomizing nozzle or a vortex-type ultrasonic atomizing nozzle, the input air source pressure of the ultrasonic spraying is 0.5-0.8 MPa, and the operating speed is less than 900 mm / s;

[0030] In the step of preparing the anion exchange layer, the content of the mixture of the imidazole derivative and the quaternary ammonium agent is 15-50% of the solvent content, preferably 15-35%, for example, the content of the mixture of the imidazole derivative and the quaternary ammonium agent is 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc. of the solvent content; the quaternary ammonium agent includes any one of bromopropane, chloropropane, iodomethane, and 1,4-dichlorobutane; and / or the molar ratio of the quaternary ammonium ionic liquid to the imidazole derivative is 1:(5-12), for example, the molar ratio of the quaternary ammonium ionic liquid to the imidazole derivative is 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, etc.;

[0031] The solvent is selected from one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC) and N-methylpyrrolidone (NMP), preferably N,N-dimethylformamide (DMF).

[0032] Methods for using bipolar membranes include:

[0033] The bipolar membrane is combined with mature commercial anion exchange membrane and cation exchange membrane to be installed in a three-compartment bipolar membrane electrodialysis membrane device or a two-compartment electrodialysis device for application in the fields of lithium extraction from salt lakes, waste salt resource utilization, material purification or recovery of organic acids and alkalis.

[0034] Three-compartment bipolar membrane electrodialysis device or two-compartment electrodialysis device is suitable for the preparation and recovery of high-concentration acids and bases. The current density during use is 400-1000A / m 2 , preferably 600-1000A / m 2 The concentration of the salt chamber is maintained between 2.5-1.1N (equivalent concentration N is 2.5-1.1), the conductivity of the organic acid / organic base chamber in the two-compartment bipolar membrane system is sufficient to maintain the full current state under the operating current density, and the water inlet conditions meet the water inlet requirements of conventional bipolar membrane electrodialysis;

[0035] and / or, the operating pressure is less than 0.1 MPa, and / or, the operating temperature is 25-45° C., and / or, the membrane surface flow rate during operation is 3-9 cm / s, preferably 5-9 cm / s.

[0036] The operating temperature is 30-40℃.

[0037] The technical solution of the present invention has the following advantages:

[0038] 1. The bipolar membrane provided by the present invention can maximize the cation exchange membrane and anion exchange layer for H by adding ionic liquid. + and OH - The selective permeability of the bipolar membrane anion and cation exchange membrane is increased, thereby increasing the ion exchange capacity of the bipolar membrane anion and cation exchange membrane, thereby improving the acid and base concentration and yield obtained in the application; at the same time, monomers with strong tolerance under acidic and alkaline conditions are further selected to enhance the acid and base tolerance effect, and then the bonding effect of the anion and cation exchange membrane is enhanced by ultraviolet light initiation and / or hot pressing, thereby ensuring the life and stability of the bipolar membrane. In addition, the main structure support of the substrate has the advantages of stable membrane structure, high acid and base concentration, stable performance, etc., and is suitable for long-term and stable preparation of high-concentration acids and bases. The implementation mechanism of the present invention is as follows:

[0039] The study found that the main reason for the limitation of acid and base concentration is that the H + and OH - There is a certain limit to the transmission rate through the cation exchange membrane and anion exchange layer of the corresponding bipolar membrane. Therefore, under a fixed current, the generated H + and OH - , the amount of water passing through the cation exchange membrane and anion exchange layer corresponding to the bipolar membrane is small, resulting in low efficiency; therefore, when the water dissociation voltage of the bipolar membrane is fixed, the amount of acid / base produced per unit energy consumption is small, and the concentration is low. The Vehicle mechanism believes that: protons combine with carriers, and under the action of electroosmosis, concentration difference, and pressure difference, they diffuse and transfer in the form of hydrated hydrogen ions; this diffusion process is called proton transfer. In solution, protons usually combine with water molecules to form hydrated hydrogen ions, which can be free between water molecules and negatively charged carriers. When the charge carrier combines with the hydrated hydrogen ion to form a proton-charge carrier complex, the charge carrier can transfer protons through its transfer. Hydrogen ions and hydroxide ions realize charge transfer by vibrating between water molecules through hydrogen bonds, not as a whole, so the faster the migration, the greater the mobility, H + The mobility is 32.5×10 -4 cm·sec -1 , OH - The mobility is 17.8×10 -4 cm·sec -1 . The mobility of other ions is less than 6×10 -4 cm·sec -1 In comparison, H + With OH -Ions have a great ion migration rate. The higher the fixed ion concentration in the membrane, the higher the selective permeability of the membrane to the counter ions, which helps H + With OH - Rapid migration increases the corresponding acid and base concentration and yield. Therefore, by adding a specific type of ionic liquid to the bipolar membrane, the present invention can effectively increase the fixed ion concentration in the membrane, thereby improving the acid and base concentration and yield obtained in the application;

[0040] In addition, bipolar membranes are used in high electric field and strong acid and alkali environments, and they also need to have stability and lifespan suitable for relatively high concentrations of acid and alkali. Studies have found that in alkaline environments, the side chain cations of the polymer skeleton are easily affected by OH - Attack, nucleophilic substitution, Hofmann degradation and Ylide reaction occur. Therefore, the present invention effectively blocks OH by adding ionic liquid. - The attack on the side chain cations effectively improves the stability of high concentration acids and bases and the binding capacity of anion and cation exchange membranes, thereby ensuring the stability of bipolar membrane applications.

[0041] 2. In the method for using a bipolar membrane provided by the present invention, the bipolar membrane can be used for conventional two-compartment and three-compartment bipolar membrane electrodialysis. With sufficient electrolyte, the acid-base concentration generated at a certain current density can be greater than 4N, and it has the advantages of low energy consumption, long-term stable performance and long life. DETAILED DESCRIPTION

[0042] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0043] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0044] Source of raw materials: sulfonated polystyrene, manufacturer Qiyue Biological; 1-propylsulfonic acid-3-methylimidazolium chloride, 1-propylsulfonic acid-3-vinylimidazolium chloride, hydroxypropyltrimethylammonium chloride, tetraoctylammonium bromide ionic liquid, all manufacturers are Orlike New Material Technology Co., Ltd.

[0045] Example 1

[0046] A method for preparing a bipolar membrane, comprising:

[0047] S1. Preparation of cation exchange membrane

[0048] In the reaction kettle, 700 g of N, N-dimethylformamide (DMF) was added, 250 g of sulfonated polystyrene (SPS, about 1.3 mol) and 25.5 g of divinylbenzene were added under stirring, 32 g of 1-propyl sulfonic acid-3-methyl imidazole chloride ionic liquid (about 0.13 mol) was slowly introduced, and the mixture was fully mixed to form a building film solution, the molar ratio of the sulfonic acid type ionic liquid to the sulfonated polymer monomer was about 1:10, a 200 mesh PVC mesh cloth was used for immersion for 2 min, the solvent was volatilized at room temperature with humidity ≤55%, and the sample was dried in an oven at 100°C for 24 h. After cooling to room temperature, a cation exchange membrane with a cation exchange layer was prepared.

[0049] S2, preparation of a metal catalytic layer

[0050] 4 g of hydroxypropyltrimethylammonium chloride and 10 g of tin dichloride were adjusted to pH = 3 with hydrochloric acid to form a suspension, a fan-shaped ultrasonic atomizing nozzle was used to spray the suspension on one surface of the cation exchange membrane prepared in S1, the input air source pressure was set to 0.65 MPa, and the running speed was 500 mm / s. The spraying amount was 1.1 g / m 2 of the metal catalytic layer, and then the sample was dried in an oven at 120°C for 2 h to obtain a metal catalytic layer on the basis of the cation exchange membrane.

[0051] S3, preparation of an anion exchange layer

[0052] A balance was used to weigh 200 g of 2-methyl-1-vinylimidazole and 100 g of bromopropane after drying, which were dissolved in 800 g of N, N-dimethylformamide (DMF) at 55°C. Tetraoctylammonium bromide ionic liquid 120 g was slowly introduced into the mixture, which was stirred uniformly for quaternary ammonium, and the degree of ammoniation was controlled at 80%. An anion membrane material was obtained. The anion membrane material was evenly scraped on one side of the cation exchange membrane containing the metal catalytic layer, with a scraping thickness of 50 μm. After being irradiated by 275 nm ultraviolet light for 5 min, the sample was taken out and placed in a hot press at a temperature of 100°C and a pressure of 0.2 MPaG. After 2 h of hot pressing reaction, a bipolar membrane suitable for high concentration acid and alkali was obtained.

[0053] Activation of the bipolar membrane: the bipolar membrane was placed in a commercial anion-cation membrane group to form a membrane stack (the bipolar membrane and the commercial anion-cation membrane were collectively used to form a membrane stack), and a direct current field with a current density of 800 A / m 2 was maintained for 1 h. Each compartment was washed with deionized water.

[0054] The activated bipolar membrane group of the present invention can be used to recycle high concentration acid and alkali. During use, the operating pressure is 0.05 MPa, the operating temperature is 35 ° C, the operating membrane surface flow rate is 6 cm / s, and the operating current density is 800 A / m 2 .

[0055] Example 2

[0056] A method for preparing a bipolar membrane, comprising:

[0057] Preparation of S1 cation exchange membrane

[0058] 750 g of N,N-dimethylformamide (DMF) was added to a reactor, and 250 g of sulfonated polystyrene (SPS, about 1.3 mol) and 30 g of divinylethylbenzene were added under stirring. 25 g of 1-propylsulfonic acid-3-methylimidazolium chloride ionic liquid (about 0.10 mol) and 5 g of 1-propylsulfonic acid-3-vinylimidazolium chloride (about 0.02 mol) were slowly introduced and fully mixed to form a membrane-building solution. The molar ratio of the sulfonic acid ionic liquid to the sulfonated polymer monomer was about 1:10.8. A 210-mesh PE mesh was used for impregnation for 3 minutes, the solvent was evaporated at room temperature for 6 hours, and the mixture was placed in a 100° C. oven for drying and polymerization for 24 hours. After cooling to room temperature, a cation exchange layer was obtained.

[0059] Preparation of S2 metal catalytic layer

[0060] Take 4g of hydroxypropyltrimethylammonium chloride and 15g of ruthenium dichloride and adjust the pH to 3 with hydrochloric acid to form a suspension. Use a fan-shaped ultrasonic atomizing nozzle to set the input air source pressure to 0.8 MPa and the operating speed to spray at 700 mm / s. Spray the suspension onto the cation exchange membrane described in S1 in the above-mentioned manner. The spraying amount is 3g / m based on the weight of the metal catalyst layer finally formed. 2 , and then placed it in an oven at 120°C for 2 hours to obtain a metal catalyst layer on the basis of the cation exchange membrane;

[0061] Preparation of S3 anion exchange layer

[0062] Weigh 215g of dried 2-methyl-1-vinyl imidazole and 87g of bromopropane on a balance, dissolve in 730g of N,N-dimethylformamide (DMF) and polymerize at 55°C. Slowly introduce 55g of butyltrimethylammonium chloride ionic liquid into the mixture and stir evenly for quaternization. Control the degree of ammonium at 70% to obtain a negative membrane material. The negative membrane material is evenly scraped onto one side of a cation exchange membrane containing a metal catalyst layer to a thickness of 45μm. After initiation with 275nm ultraviolet light for 5min, the material is removed and placed in a hot press at a temperature of 105°C and a pressure of 0.3MPaG. After hot pressing for 2h, the material is removed to obtain a bipolar membrane suitable for high-concentration acid and alkali. Activation of the bipolar membrane:

[0063] The bipolar membrane is placed in a commercial cathode-anode membrane group to form a membrane stack (the bipolar membrane is placed in the membrane stack together with the commercial cathode-anode membrane), 15% sodium sulfate aqueous solution is used, a direct current field with a current density of 1000 A / m 2 is applied for 1 h, and each compartment is washed with deionized water.

[0064] The activated bipolar membrane group can be used for recovery of high-concentration acid and alkali, and during use, the operating pressure is 0.05 MPa, the operating temperature is 35 DEG C, the operating membrane surface flow rate is 6 cm / s, and the operating current density is 800 A / m 2 .

[0065] Example 3

[0066] The preparation method of the bipolar membrane comprises the following steps:

[0067] Preparation of S1 cation exchange membrane

[0068] 700 g of N,N-dimethylformamide (DMF) is added to a reaction kettle, 220 g of sulfonated polystyrene (SPS, about 1.19 mol) and 27.5 g of tri-vinyl ethylbenzene are added under stirring, 22 g of 1-propyl sulfonic acid-3-methyl imidazole chloride ionic liquid (about 0.09 mol) and 7.5 g of 1-propyl sulfonic acid-3-vinyl imidazole chloride (about 0.04 mol) are slowly introduced and fully mixed to form a membrane building solution, the molar ratio of the sulfonic acid type ionic liquid to the sulfonated polymer monomer is about 1:9.15, 210-mesh PVC mesh cloth is used for impregnation for 3 min, solvent volatilization is carried out at room temperature for 8 h, and the polymerization is carried out at 100 DEG C for 24 h, then the cation exchange layer is obtained after the reaction kettle is taken out, cooled to room temperature and cooled to room temperature.

[0069] Preparation of S2 metal catalytic layer

[0070] 4 g of hydroxypropyl trimethyl ammonium chloride and 15.5 g of titanium trichloride are adjusted to pH = 4 with hydrochloric acid to form a suspension, a fan-shaped ultrasonic atomizing nozzle is used for spraying, the input air source pressure is set to 0.6 MPa, and the running speed is 700 mm / s, the suspension is sprayed on the cation exchange membrane in S1 according to the above setting, the spraying amount is 3 g / m 2 , and then the cation exchange membrane is placed in a 120 DEG C oven for drying for 2 h, and the metal catalytic layer is obtained on the basis of the cation exchange membrane.

[0071] Preparation of S3 anion exchange layer

[0072] 200 g of dried 2-methyl-1-vinylimidazole was weighed on a balance and mixed with 95 g of chloropropane, dissolved in 750 g of N,N-dimethylformamide (DMF) and polymerized at 55° C. 100 g of tetraoctylammonium bromide ionic liquid was slowly introduced into the mixture and stirred evenly for quaternization, with the degree of ammonium controlled at 75% to obtain a negative membrane material; the negative membrane material was evenly scraped onto one side of a cation exchange membrane containing a metal catalyst layer to a thickness of 45 μm, and subjected to ultraviolet light initiation at 275 nm for 6 minutes. After removal, the membrane was placed in a hot press and reacted at a temperature of 100° C. and a pressure of 0.35 MPaG for 2 hours. After removal, a bipolar membrane suitable for high-concentration acids and bases was obtained.

[0073] Activation of bipolar membrane: The bipolar membrane is placed in a commercial cation membrane to form a two-compartment membrane stack. In a 12% sodium chloride aqueous solution, the current density is 800A / m 2 The DC electric field was maintained for 1 h, and each compartment was rinsed clean with deionized water.

[0074] The activated bipolar membrane group of the present invention can be used to recycle high concentration acid and alkali. During use, the operating pressure is 0.055 MPa, the operating temperature is 32 ° C, the operating membrane surface flow rate is 8 cm / s, and the operating current density is 750 A / m 2 .

[0075] Example 4

[0076] The method is the same as that of Example 1, except that the amount of tin dichloride added in step S2 is 0.5 g, and other operations and conditions remain unchanged to prepare a bipolar membrane.

[0077] Example 5

[0078] The method is the same as that in Example 1, except that: referring to the method in Example 1, the only difference is that in S3, 2-methyl-1-vinylimidazole and bromopropane are replaced with 1,2-dimethylimidazole and 1,4-dichlorobutane when preparing the negative film layer, and other operations and conditions remain unchanged.

[0079] Example 6

[0080] The method is the same as that of Example 1, except that nickel chloride (NiCl2) is used instead of ruthenium dichloride in step S2.

[0081] Example 7

[0082] The method is the same as that of Example 1, except that the current density is 400A / m 2 , membrane surface flow rate 5cm / s.

[0083] Example 8

[0084] A method for preparing a bipolar membrane, comprising:

[0085] Preparation of S1 cation exchange membrane

[0086] In a reaction kettle, 270 g of N,N-dimethylformamide (DMF) was added, 220 g of sulfonated polystyrene (SPS, 1.19 mol) and 13.5 g of tri-vinyl ethylbenzene were added under stirring, 22 g of 1-propyl sulfonic acid-3-methyl imidazole chloride ionic liquid (0.09 mol) and 14.85 g of 1-propyl sulfonic acid-3-vinyl imidazole chloride (0.069 mol) were slowly introduced and mixed thoroughly to form a membrane forming solution, the molar ratio of the sulfonic acid type ionic liquid to the sulfonated polymer monomer was about 1:7.5, a 125 mesh PVC mesh cloth was used for immersion for 8 min, the solvent was volatilized at room temperature for 8 h, and the polymerization was dried in an oven at 100°C for 24 h, after cooling to room temperature, the cation exchange layer was obtained;

[0087] Preparation of S2 metal catalytic layer

[0088] 4 g of hydroxypropyl trimethyl ammonium chloride and 15.5 g of titanium trichloride were adjusted to pH = 4 with hydrochloric acid to form a suspension, a fan-shaped ultrasonic atomizing nozzle was used, the input air source pressure was set to 0.6 Mpa, and the running speed was 700 mm / s for spraying, the suspension was sprayed on the cation exchange membrane described in S1 according to the above setting, and the spraying amount was 3 g / m 2 of the metal catalytic layer formed finally, and then it was placed in a 120°C oven for drying for 2 h, and a metal catalytic layer was obtained on the basis of the cation exchange membrane;

[0089] Preparation of S3 anion exchange layer

[0090] After drying, 200 g of 2-methyl-1-vinyl imidazole and 95 g of chloropropane were weighed on a balance and mixed, dissolved in 1970 g of N,N-dimethylformamide (DMF), and polymerized at 55°C, 100 g of tetraoctyl ammonium bromide ionic liquid was slowly introduced into the mixture, stirred uniformly for quaternary ammonium, and the ammonium degree was controlled at 40%, to obtain a negative membrane material; the negative membrane material was evenly scraped on one side of the cation exchange membrane containing the metal catalytic layer, the scraping thickness was 79 μm, it was initiated by 275 nm, 6 min ultraviolet light, taken out and placed in a hot press, and after hot pressing reaction at a temperature of 130°C, a pressure of 0.35 MPaG, and for 2 h, a bipolar membrane suitable for high concentration acid and alkali was obtained.

[0091] Activation of the bipolar membrane: the bipolar membrane was placed in a commercial anion membrane to form a two-compartment membrane stack, a direct current electric field with a current density of 400 A / m 2 was maintained for 1 h, and each compartment was washed clean with deionized water.

[0092] The activated bipolar membrane group of the present invention can be used to recycle high concentration acid and alkali. During use, the operating pressure is 0.055 MPa, the operating temperature is 32 ° C, the operating membrane surface flow rate is 8 cm / s, and the operating current density is 750 A / m 2 .

[0093] Example 9

[0094] A method for preparing a bipolar membrane, comprising:

[0095] S1. Preparation of cation exchange membrane

[0096] 690 g of N,N-dimethylformamide (DMF) was added to a reactor, 200 g of sulfonated polystyrene (SPS, about 1.085 mol) and 30 g of divinylbenzene were added under stirring, and 22.9 g of 1-propylsulfonic acid-3-methylimidazolium chloride ionic liquid (about 0.095 mol) was slowly introduced and fully mixed to form a membrane-building solution, wherein the molar ratio of the sulfonic acid ionic liquid to the sulfonated polymer monomer was about 1:11.4, and a 260-mesh PVC mesh was used for impregnation for 2 minutes. The solvent was evaporated for 6 hours at room temperature with a humidity of ≤55%, and then dried in a 100° C. oven for 24 hours. After being taken out and cooled to room temperature, a cation exchange membrane having a cation exchange layer was prepared;

[0097] S2. Preparation of Metal Catalytic Layer

[0098] Take 4g of hydroxypropyltrimethylammonium chloride and 10g of tin dichloride and adjust the pH to 3 with hydrochloric acid to form a suspension. Use a fan-shaped ultrasonic atomizing nozzle to set the input air source pressure to 0.65 MPa and the operating speed to spray at 500 mm / s. Spray the suspension onto one surface of the cation exchange membrane described in S1 in the above-mentioned manner. The spraying amount is 1.1g / m based on the weight of the metal catalyst layer finally formed. 2 , and then placed it in an oven at 120°C for 2 hours to obtain a metal catalyst layer on the basis of the cation exchange membrane;

[0099] Preparation of S3 anion exchange layer

[0100] 200 g of dried 2-methyl-1-vinylimidazole was weighed on a balance and mixed with 100 g of bromopropane, dissolved in 600 g of N,N-dimethylformamide (DMF) and polymerized at 55° C. 120 g of tetraoctylammonium bromide ionic liquid was slowly introduced into the mixture and stirred evenly for quaternization, with the degree of ammonium controlled at 85% to obtain a negative membrane material; the negative membrane material was evenly scraped onto one side of a cation exchange membrane containing a metal catalyst layer to a thickness of 50 μm, and then initiated with ultraviolet light at 275 nm for 5 minutes. After being removed from the mixture, the mixture was placed in a hot press at a temperature of 100° C. and a pressure of 0.2 MPaG. After hot pressing for 2 hours, the mixture was removed from the hot press to obtain a bipolar membrane suitable for high-concentration acids and bases.

[0101] Activation of bipolar membrane: Place the bipolar membrane in a commercial cation / cation membrane group to form a membrane stack (the bipolar membrane and the commercial cation / cation membrane together form a membrane stack device), in a 15% sodium sulfate aqueous solution, the current density is 1000A / m 2 The DC electric field was maintained for 1 h, and each compartment was rinsed clean with deionized water.

[0102] The activated bipolar membrane group of the present invention can be used to recycle high concentration acid and alkali. During use, the operating pressure is 0.05 MPa, the operating temperature is 35 ° C, the operating membrane surface flow rate is 9 cm / s, and the operating current density is 800 A / m 2 .

[0103] Comparative Example 1

[0104] The method was the same as that in Example 1, except that 1-propylsulfonic acid-3-methylimidazolium chloride ionic liquid was not added when preparing the S1 cation exchange membrane, and tetraoctylammonium bromide ionic liquid was not added when preparing the anion exchange layer in S3. Other operations and conditions remained unchanged to prepare a bipolar membrane.

[0105] Comparative Example 2

[0106] The method is the same as that of Example 1, except that 5 g of 1-propylsulfonic acid-3-methylimidazolium chloride ionic liquid is added in S1 during the preparation of the cation exchange membrane, and other operations and conditions remain unchanged.

[0107] Experimental Example 1- Initial Performance Test of Bipolar Membrane Stack

[0108] The bipolar membranes prepared in the above examples and comparative examples were subjected to performance tests. The performance test parameters and corresponding test methods are as follows:

[0109] Unit processing capacity:

[0110] Where:

[0111] PC—unit processing capacity, Kg acid / base (h·m 2 );

[0112] A—Effective area of ​​membrane stack, m 2 ;

[0113] n—number of membrane pairs in the membrane stack;

[0114] M—molar mass of acid or base, g / mol;

[0115] V t —Acid-base endpoint volume, L;

[0116] C t—Acid and base endpoint concentration, mol / L;

[0117] t—running time, s;

[0118] Unit processing energy consumption:

[0119] Where:

[0120] W—unit processing capacity, Kwh / t acid / alkali;

[0121] —Average value of two adjacent voltages,

[0122] —The average value of the voltage recorded twice adjacently,

[0123] M—molar mass of acid or base, g / mol;

[0124] V t —Acid / base endpoint volume, L;

[0125] C t —Acid and base endpoint concentration, mol / L;

[0126] Δt—time interval between two adjacent times, s;

[0127] Current efficiency:

[0128] Where:

[0129] η—current efficiency, %;

[0130] F—Faraday constant 96485, C / mol;

[0131] —The average value of the voltage recorded twice adjacently,

[0132] n—number of pairs of membrane stacks;

[0133] V t —Acid-base endpoint volume, L;

[0134] C t —Acid and base endpoint concentration, mol / L;

[0135] Δt—time interval between two adjacent times, s;

[0136] Water dissociation voltage of bipolar membrane: 1000A / m 2 Direct current, the cation exchange layer of the bipolar membrane is 1 mol / L OH - , one side of the cation exchange layer is 1 mol / LH+ The voltage across the bipolar membrane.

[0137] The initial performance of the operation under the sodium sulfate system is shown in Table 1 below.

[0138] Table 1

[0139]

[0140] By comparing the above examples 1-9 with the comparative examples 1-2, it can be seen that the addition of specific ionic liquids in the cation exchange layer and the anion exchange layer can maximize the increase in the cation exchange membrane and the anion exchange layer for H + and OH - The selective permeability of the bipolar membrane anion and cation exchange membrane is increased, thereby increasing the ion exchange capacity, thereby increasing the upper limit of the prepared acid and base concentration. The prepared acid and base do not need to be subsequently concentrated to meet the conditions for reuse, and the effect is significant.

[0141] Experimental Example 2-Life and Stability Performance Test

[0142] The results of long-term operation of the above embodiments and comparative examples are shown in Table 2.

[0143] Table 2

[0144]

[0145]

[0146] The data in Tables 1-2 above demonstrate that the present invention not only improves the acid and base concentrations and yields achieved in applications, but also, through further optimization of the raw materials and process conditions of the anion exchange layer, ensures the stability of high-concentration acids and bases and the binding capacity of the anion and cation exchange membrane, thereby ensuring the stability of bipolar membrane applications. Furthermore, the present invention also validates the effects of other metal elements in the metal catalyst layer, demonstrating that replacing only the metal element in the metal catalyst layer produces essentially equivalent results.

[0147] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A bipolar membrane, characterized in that include: A cation exchange membrane comprising a substrate and a cation exchange layer disposed on at least one surface of the substrate, wherein the cation exchange layer comprises a sulfonated polymer monomer and a sulfonic acid type ionic liquid, wherein the sulfonic acid type ionic liquid accounts for more than 10% by weight of the sulfonated polymer monomer; The metal catalyst layer is disposed on one surface of the substrate so that the two opposite surfaces of the substrate are respectively a cation exchange layer and a metal catalyst layer; The anion exchange layer is arranged on the surface of the metal catalyst layer, and comprises quaternized imidazole derivatives and quaternary ammonium ionic liquids, wherein the quaternary ammonium ionic liquid accounts for more than 25% of the weight of the imidazole derivatives.

2. The bipolar membrane according to claim 1, characterized in that The cation exchange layers are arranged on both surfaces of the substrate, and the metal catalyst layer is arranged on the surface of one of the cation exchange layers.

3. The bipolar membrane according to claim 1 or 2, characterized in that The cation exchange layer is made of a sulfonated polymer monomer cross-linked with a sulfonic acid ionic liquid, and the molar ratio of the sulfonic acid ionic liquid to the sulfonated polymer monomer is 1: (7-12); and / or, the degree of ammonium of the quaternized imidazole derivative is 40-85%; And / or, the mesh size of the substrate is 120-260 mesh; And / or, the loading amount of the metal catalyst layer on the substrate is 0.5-5 g / m 2 ; And / or, the thickness of the anion exchange layer is 30-80 μm.

4. The bipolar membrane according to claim 3, characterized in that The molar ratio of the sulfonic acid ionic liquid to the sulfonated polymer monomer is 1:(9-10); And / or, the loading amount of the metal catalyst layer on the substrate is 1-1.5 g / m 2 .

5. The bipolar membrane according to claim 1 or 2, characterized in that The sulfonic acid ionic liquid is selected from one or more of 1-propylsulfonic acid-3-methylimidazolium chloride and 1-propylsulfonic acid-3-vinylimidazolium chloride; and / or, the sulfonated polymer monomer is a sulfonated polystyrene monomer; And / or, the quaternary ammonium ionic liquid is selected from one or more of butyltrimethylammonium chloride, hexyltrimethylammonium chloride, propyltrimethylammonium bromide, tetrapropylammonium hydrogen sulfate, tetraoctylammonium bromide and butyltriethylammonium bromide; and / or, the imidazole derivatives include 2-methyl-1-vinylimidazole or 1,2-dimethylimidazole; And / or, the substrate is selected from any one of nylon mesh, PET mesh, PP mesh, PVC mesh, and PE mesh; And / or, the catalyst in the metal catalyst layer is a metal salt.

6. The bipolar membrane according to claim 5, characterized in that The catalyst in the metal catalyst layer is a water-soluble metal salt; The metal elements in the metal catalyst layer include one or more of titanium, tin, chromium, cobalt, nickel, platinum, silver, or ruthenium.

7. The bipolar membrane according to claim 6, characterized in that The water-soluble metal salt is a water-soluble metal chloride.

8. The method for preparing a bipolar membrane according to any one of claims 1 to 7, characterized in that: include: Preparation of cation exchange membrane: preparing the raw materials of the cation exchange layer into a membrane-building liquid, preparing the membrane-building liquid on at least one side of the substrate, taking it out, drying and polymerizing it, and cooling it to obtain the cation exchange membrane; Preparation of the metal catalyst layer: preparing the raw materials for preparing the metal catalyst layer into a suspension, evenly applying the suspension to the other side of the cation exchange membrane opposite to the cation exchange layer, and drying to obtain the metal catalyst layer; Preparation of anion exchange layer: The raw materials of the anion exchange layer are prepared into anion membrane materials, the anion membrane materials are attached to the metal catalyst layer, and a bipolar membrane is obtained through ultraviolet light initiation and / or hot pressing reaction.

9. The method according to claim 8, characterized in that In the preparation steps of the cation exchange membrane, the raw materials of the cation exchange layer include a sulfonated polymer monomer, a solvent, a cross-linking agent, and a sulfonic acid ionic liquid; and / or, the membrane-building liquid is attached to the substrate by impregnation; and / or, the dry polymerization process includes: first volatilizing at 25-30°C and humidity ≤55% for more than 5 hours, and then drying; In the steps of preparing the metal catalyst layer, the raw materials of the metal catalyst layer include a metal salt, a quaternary ammonium, and an acid solution; the preparation process of the suspension liquid is as follows: the metal salt is added with an acid solution to coordinate with the quaternary ammonium in a weakly acidic environment of pH 3-5, and the suspension liquid is obtained after ultrasonic treatment; and / or, the suspension liquid is applied to the cation exchange membrane by ultrasonic spraying; and / or, the drying conditions are 100-120° C. and 1.5-2 hours; In the preparation step of the anion exchange layer, the raw materials of the anion exchange layer include imidazole derivatives, quaternary ammonium reagents, solvents and quaternary ammonium ionic liquids; the ultraviolet light initiation time is 1-10 minutes; the pressure of the hot pressing reaction is 0.1-0.4 MPaG and the temperature is 100-130°C.

10. The method according to claim 9, characterized in that The drying conditions are 100-120° C. and more than 24 hours.

11. The method according to claim 9, characterized in that In the preparation step of the cation exchange membrane, the crosslinking agent is selected from one or more polyvinylbenzenes; the total amount of the crosslinking agent is 5-15wt% of the mass of the sulfonated polymer monomer; the amount of the solvent is 1-3 times the total mass of the sulfonic acid ionic liquid and the crosslinking agent; and the immersion time is 2-8 minutes; In the step of preparing the metal catalyst layer, the acid solution is an inorganic acid, the quaternary ammonium comprises trimethylpropylammonium bromide, the ultrasonic spraying is performed using a fan-shaped ultrasonic atomizing nozzle or a vortex-type ultrasonic atomizing nozzle, the input gas source pressure of the ultrasonic spraying is 0.5-0.8 MPa, and the operating speed is less than 900 mm / s; In the step of preparing the anion exchange layer, the content of the mixture of the imidazole derivative and the quaternary ammonium agent is 15-50% of the solvent content; the quaternary ammonium agent includes any one of bromopropane, chloropropane, iodomethane, and 1,4-dichlorobutane; and / or the molar ratio of the quaternary ammonium ionic liquid to the imidazole derivative is 1:(5-12); The solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone.

12. The method according to claim 11, characterized in that In the preparation step of the cation exchange membrane, the cross-linking agent is selected from one or more of divinylbenzene, trivinylbenzene, divinyltoluene, and divinylethylbenzene; In the step of preparing the anion exchange layer, the content of the mixture of the imidazole derivative and the quaternary ammonium agent is 15-35% of the solvent content; The solvent is N,N-dimethylacetamide.

13. The method for using the bipolar membrane according to any one of claims 1 to 7, characterized in that: include: The bipolar membrane is installed in a three-compartment bipolar membrane electrodialysis membrane device or a two-compartment electrodialysis device together with an anion exchange membrane and a cation exchange membrane for application in the fields of lithium extraction from salt lakes, waste salt resource recovery, material purification or recovery of organic acids and alkalis.

14. The method of use according to claim 13, wherein: In a three-compartment bipolar membrane electrodialysis device or a two-compartment electrodialysis device, the current density during use is 400-1000 A / m 2 , and / or, the concentration of the salt chamber is maintained between 2.5-1.1N, and / or, the operating pressure is <0.1MPa, and / or, the operating temperature is 25-45°C, and / or, the membrane surface flow rate during operation is 3-9cm / s.

15. The method of use according to claim 14, characterized in that: The operating temperature is 30-40℃.

16. The method of use according to claim 14, characterized in that: Before operation, the bipolar membrane is activated under the action of an electric field and then washed with water.

17. The method of use according to claim 16, characterized in that: During the activation, the current density is 400-1000 A / m 2 , activation time is 0.5-5h.

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