A bipolar membrane, a preparation method, an activation method and an application thereof

Abstract

The application relates to the technical field of bipolar membrane electrodialysis, and provides a bipolar membrane, a preparation method, an activation method and application thereof. The bipolar membrane provided by the application has obviously improved service life and is not prone to bubble and delamination phenomena during long-time operation. The preparation method comprises the following steps: forming an adhesive layer between the cation exchange layer and the catalyst layer, and / or forming an adhesive layer between the anion exchange layer and the catalyst layer. Preferably, the cation exchange layer is provided with sulfonic acid groups, and the anion exchange layer is provided with quaternary ammonium groups.

Description

Technical Field

[0001] This invention relates to the field of bipolar membrane electrodialysis technology, specifically to a bipolar membrane and its preparation, activation, and applications. Background Technology

[0002] A bipolar membrane is a type of ion exchange membrane with special functions. It is typically composed of three parts: a cation exchange layer, an intermediate catalyst layer, and an anion exchange membrane layer. Under the influence of an electric field, the catalyst layer in the middle of the bipolar membrane can dissociate water molecules into hydrogen ions and hydroxide ions, which are then continuously transported to both ends of the membrane. No gas is produced in this process. Therefore, a bipolar membrane electrodialysis stack system, formed by alternating bipolar membranes with anion and cation exchange membranes, can convert salts into acids and bases. Thus, bipolar membrane electrodialysis plays an increasingly important role in fields such as lithium extraction from salt lakes, waste salt treatment, and the recovery of organic acids and bases.

[0003] The biggest problem with bipolar membranes used in high electric fields and strong acid / alkali environments is their lifespan. Currently, the average lifespan of bipolar membranes is generally no more than one year, and sometimes as short as 3-6 months. In existing technologies, most bipolar membranes are bonded together by electrostatic attraction or thermo-pressing to form two layers of anion and cation exchange membranes with opposite charges. However, during application, especially when the bipolar membrane is placed under the influence of strong electrolytes or strong electric fields, bubbling can easily occur between the anion and cation exchange membrane layers, leading to peeling and detachment, which significantly reduces the membrane's durability and lifespan.

[0004] The scientific journal *Electrochimica Acta*, Volume 31, pp. 1175-1176, reported that bipolar membranes with a three-layer composite structure prepared using common inorganic metal catalysts such as ruthenium trichloride are prone to ion leakage and anode / cation layer delamination, leading to a significant reduction in the lifespan of the bipolar membrane. Chinese Patent Publication No. CN104593819A discloses a method for preparing a three-layer composite bipolar membrane using polyethylene glycol and transition metals as catalysts, which can suppress catalyst leakage to some extent through coordination. Summary of the Invention

[0005] This invention provides a bipolar membrane, its preparation method, activation method, and application. The bipolar membrane provided by this invention has a significantly improved service life and is less prone to bubbles and delamination during long-term operation.

[0006] To achieve its objective, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing a bipolar membrane, the bipolar membrane comprising a cation exchange layer, an anion exchange layer, and a catalyst layer located between the cation exchange layer and the anion exchange layer, characterized in that the preparation method comprises the following steps: forming an adhesive layer between the cation exchange layer and the catalyst layer, and / or forming an adhesive layer between the anion exchange layer and the catalyst layer; preferably, the adhesive layer is formed at least between the anion exchange layer and the catalyst layer;

[0008] Preferably, the cation exchange layer has sulfonic acid groups, and the anion exchange layer has quaternary ammonium groups.

[0009] Another aspect of the present invention provides a bipolar membrane, the bipolar membrane comprising a cation exchange layer, an anion exchange layer, and a catalyst layer located between the cation exchange layer and the anion exchange layer;

[0010] An adhesive layer is provided between the cation exchange layer and the catalyst layer, and / or an adhesive layer is provided between the anion exchange layer and the catalyst layer;

[0011] Preferably, the cation exchange layer has sulfonic acid groups, and the anion exchange layer has quaternary ammonium groups.

[0012] In another aspect, the present invention also provides a bipolar membrane prepared by the preparation method described above or an activation method for the bipolar membrane described above, wherein the bipolar membrane is activated under the action of an electric field and then washed with water;

[0013] Preferably, the current density during the activation is 400-1000 A / m. 2 The activation time is preferably 1-3 hours; the electric field is, for example, a direct current electric field;

[0014] Preferably, during the activation process, the bipolar membrane is placed in an aqueous acetate solution, the concentration of which is preferably 1-10 wt%, and the acetate is preferably sodium acetate and / or potassium acetate.

[0015] In another aspect, the present invention also provides an application in which the bipolar membrane prepared by the above-described preparation method or the bipolar membrane described above is used in a bipolar membrane electrodialysis device, or in the fields of lithium extraction from salt lakes, waste salt treatment or organic acid and alkali recovery.

[0016] Preferably, the bipolar membrane is activated using the activation method described above before application.

[0017] The technical solution provided by this invention has the following beneficial effects:

[0018] The bipolar membrane preparation method provided by this invention is simple, and the resulting bipolar membrane has a longer service life and is less prone to bubble formation and delamination during long-term operation. Furthermore, the bipolar membrane is activated under an electric field before application, which further improves its performance, achieving a better balance between voltage drop across the membrane, resistance to degradation, and service life. Attached Figure Description

[0019] Figure 1 The diagram shown is a schematic diagram of the structure of a bipolar membrane in one embodiment. Detailed Implementation

[0020] To facilitate understanding of the present invention, the following description, in conjunction with embodiments, will further illustrate the invention. It should be understood that the following embodiments are merely for a better understanding of the invention and do not imply that the invention is limited to these embodiments.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The term "and / or" may be used herein to include any and all combinations of one or more of the associated listed items.

[0022] Where specific experimental steps or conditions are not specified in the examples, the corresponding conventional experimental steps or conditions in this technical field can be followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0023] In this specification, the terms “first”, “second”, etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0024] This invention provides a method for preparing a bipolar membrane, the bipolar membrane comprising a cation exchange layer, an anion exchange layer, and a catalyst layer located between the cation exchange layer and the anion exchange layer. The preparation method includes the following steps: forming an adhesive layer between the cation exchange layer and the catalyst layer, and / or forming an adhesive layer between the anion exchange layer and the catalyst layer. Preferably, the cation exchange layer has sulfonic acid groups, and the anion exchange layer has quaternary ammonium groups.

[0025] The present invention provides a bipolar membrane with significantly improved service life compared with a bipolar membrane without an adhesive layer by forming an adhesive layer between the cation exchange layer and the catalyst layer, and / or between the anion exchange layer and the catalyst layer. The membrane is less prone to peeling and bubbles are less likely to form in the bipolar membrane interlayer, which can significantly improve the performance degradation of the bipolar membrane during long-term operation.

[0026] More preferably, an adhesive layer is formed at least between the anion exchange layer and the catalyst layer to facilitate obtaining better bipolar membrane performance.

[0027] Furthermore, the adhesive layer is formed by applying an adhesive solution to the location where the adhesive layer needs to be formed and then drying it. Specifically, for example, when an adhesive layer needs to be formed between the cation exchange layer and the catalyst layer, the adhesive solution is applied to the bonding region between the cation exchange layer and the catalyst layer during the preparation of the bipolar membrane, thereby forming the adhesive layer; the formation of the adhesive layer at other locations is similar and will not be described in detail. Preferably, the concentration of the adhesive solution is 0.5wt%-20wt%, for example, 0.5wt%, 1wt%, 3wt%, 10wt%, 15wt%, 20wt%, etc. Specifically, for example, the adhesive is pre-prepared with water into an emulsion within this concentration range.

[0028] Preferably, the adhesive is an aqueous adhesive, preferably selected from one or more of polyurethane adhesives, isocyanate adhesives, acrylate adhesives, and styrene-butadiene latex. The inventors have found that using the preferred adhesive can form strong hydrogen bonds with the sulfonic acid groups of the cation exchange layer and / or the quaternary ammonium groups of the anion exchange layer, enabling a tighter and more secure bond between the anion and cation exchange layers. This can largely prevent interpenetration between the anion and cation exchange layers in the bipolar membrane, further improving water dissociation efficiency. It also helps to more effectively reduce the probability of anion and cation exchange layer peeling under long-term harsh operating conditions, thus more effectively extending the service life of the bipolar membrane and reducing performance degradation. More preferably, the adhesive is a polyurethane adhesive. The inventors have found that using a polyurethane adhesive is beneficial for obtaining a bipolar membrane with better performance, further improving the voltage drop across the membrane and performance degradation during long-term operation.

[0029] More preferably, the water-based adhesive is selected from Wanhua. One or more combinations of a series of water-based adhesives, more preferably 1630B and / or 1336 can yield bipolar films with better performance.

[0030] In some embodiments, the thickness of the adhesive layer is 50-1000 nm, such as 50 nm, 80 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 700 nm, 900 nm, 1000 nm, etc., preferably 100-500 nm. The inventors have found that controlling the thickness of the adhesive layer within the preferred range is beneficial to achieving both good interfacial bonding strength and bipolar film application performance, and is also beneficial to further improve the voltage drop across the bipolar film.

[0031] Furthermore, the catalyst layer is obtained by applying a catalyst solution to the location where the catalyst layer needs to be formed and then drying it; the catalyst in the catalyst solution is a transition metal salt, which is preferably a water-soluble compound, more preferably a water-soluble transition metal chloride; preferably, the transition metal salt forms a complex with dopamine.

[0032] The inventors have discovered that in the adhesive-based bipolar membrane system of this invention, transition metal salts, particularly water-soluble transition metal chlorides, react with dopamine to form complexes. On one hand, this allows the holes in the transition metal to form chelate coordination with the lone pairs of electrons on the amino and hydroxyl groups of dopamine, which helps to firmly anchor the transition metal in the dopamine structure and reduce the loss of catalyst, especially water-soluble catalyst. On the other hand, the cation exchange layer can generate electrostatic interactions with the amino and hydroxyl groups on the dopamine of the catalyst layer stacked thereon. Dopamine carries a positive charge, while the sulfonic acid groups abundant in the cation exchange layer carry a strong negative charge. Thus, through strong electrostatic interactions, the cation exchange layer and the catalyst layer are firmly bonded together. Furthermore, the amino and hydroxyl groups abundant in dopamine can also generate strong hydrogen bonds with the polar groups on the adhesive layer stacked thereon, firmly bonding the adhesive layer and the catalyst layer to the cation exchange layer / anion exchange layer. Through the combined action of dopamine, adhesives, and cation exchange layers, the bonding strength between the layers in the bipolar membrane can be further enhanced, thereby improving the service life and performance of the bipolar membrane.

[0033] Preferably, the preparation of the catalyst solution includes: reacting the catalyst with dopamine in an environment with a pH of 3-5 (e.g., pH = 3, 3.5, 4, 4.5, 5, etc.) and dispersing it uniformly to obtain a suspension; preferably, the reaction is carried out in the presence of ammonium persulfate. Specifically, the catalyst solution can be uniformly coated onto the surface where the catalyst layer is to be formed by ultrasonic spraying, and then dried (e.g., dried in an oven at 50-150°C for 0.5-2 hours) to obtain the catalyst layer. The inventors have discovered that under the above-mentioned weakly acidic conditions, especially in the presence of ammonium persulfate, transition metal salts, especially water-soluble transition metal chlorides, can react with dopamine to form complexes, and can form a tight and robust composite membrane system between the catalyst layer, adhesive layer, cation exchange layer, and other structures. Specifically, the required weakly acidic environment can be provided by adding pH adjusting agents such as hydrochloric acid. The inventors discovered that a pH higher than 5 is unfavorable for the polymerization of dopamine catalyzed by ammonium persulfate, while a pH lower than 3 results in low stability of the complexes formed between dopamine and transition metals, hindering the immobilization of the transition metals. Conducting the above reaction in a weakly acidic environment (pH 3-5) in the presence of ammonium persulfate promotes the polymerization of dopamine, further enabling the anchoring of metal ions within dopamine.

[0034] Preferably, the molar ratio of the transition metal element in the catalyst to the dopamine is 1:1 to 1:100, more preferably 1:2 to 1:100, such as 1:2, 1:10, 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, 1:90, 1:100, etc. Using this preferred molar ratio helps to balance better catalyst layer adhesion strength and catalytic effect, and further improves the long-term performance of the bipolar membrane. It also helps to obtain a bipolar membrane with better resistance to degradation during long-term operation. More preferably, the molar ratio is 1:2 to 1:20, which helps to obtain a bipolar membrane with even better performance.

[0035] Preferably, the ammonium persulfate is added to the reaction system as an aqueous solution of ammonium persulfate with a concentration of 4-6 wt%, and the dopamine is added to the reaction system as an aqueous solution of dopamine with a concentration of 0.5-2 wt%. The volume ratio of the aqueous solution of ammonium persulfate to the aqueous solution of dopamine is preferably 1-3:20.

[0036] Preferably, there is no particular limitation on the specific type of transition metal salt, and those skilled in the art can determine the specific type of transition metal salt as a catalyst according to the application requirements; the transition metal element in the transition metal salt is, for example, but not limited to, one or more of Fe, Sn, Cu, Cr, Co, Ni, Pd, Pt, Ag, Au or Ru, preferably Sn or Rh.

[0037] Further, the cation exchange layer is prepared using a first film-forming solution, wherein the first film-forming material contained in the first film-forming solution is preferably one or more of sulfonated polyether ether ketone, sulfonated polyphenylene ether, sulfonated polysulfone, and sulfonated polyether sulfone; the first film-forming solution can be prepared using concentrations conventionally used in the art for preparing cation exchange membranes, preferably 4-40 wt%, such as 4%, 10%, 20%, 30%, 40%, etc.; the solvent in the first film-forming solution is preferably one or more of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone, more preferably N,N-dimethylformamide. The degree of sulfonation of the first film-forming material is, for example, 40%-100%, where the degree of sulfonation refers to the molar percentage of sulfonic acid groups in the first film-forming material.

[0038] Further, the anion exchange layer is prepared using a second membrane-forming solution, wherein the second membrane-forming material contained in the second membrane-forming solution is preferably one or more of quaternized brominated polyphenylene ether, quaternized polysulfone, and quaternized polyethersulfone. Preferably, the degree of quaternization of the second membrane-forming material is 40-70%, which is beneficial for maintaining high ion conductivity while avoiding excessive membrane swelling. The second membrane-forming solution can use concentrations conventionally used in the preparation of cation exchange membranes, preferably 4-40 wt%, such as 4%, 10%, 20%, 30%, 40%, etc.; the solvent in the second membrane-forming solution is preferably one or more of N,N-dimethylformamide, N,N-dimethylacetamide, chlorobenzene, and N-methylpyrrolidone, more preferably N,N-dimethylformamide. The quaternization reagent is, for example, trimethylamine, vinylimidazole, N,N-dimethylformamide, etc., and the quaternization reagent can be dissolved in a solvent, such as chlorobenzene. The degree of bromination of brominated polyphenylene ether is, for example, 30-70%. The degree of bromination refers to the molar percentage of bromine on the methyl group in the brominated polyphenylene ether.

[0039] The first and second film-forming materials mentioned above can be commercially available products or prepared using methods known in the art.

[0040] Furthermore, the preparation method can be specifically carried out using Scheme 1, Scheme 2, or Scheme 3 as follows;

[0041] Scheme 1 includes the following steps S1a-S4a:

[0042] S1a provides a cation exchange layer;

[0043] S2a, a catalyst solution is applied to the surface of the cation exchange layer and dried to form the catalyst layer;

[0044] S3a, apply adhesive liquid to the surface of the catalyst layer and dry to form an adhesive layer;

[0045] S4a, the anion exchange layer is stacked on the surface of the adhesive layer.

[0046] Figure 1 The diagram shown is a schematic diagram of the bipolar membrane obtained using Scheme 1 in one embodiment.

[0047] The second scheme includes the following steps S1b-S4b:

[0048] S1b provides the cation exchange layer;

[0049] S2b, an adhesive liquid is applied to the surface of the cation exchange layer and dried to form an adhesive layer;

[0050] S3b, a catalyst liquid is applied to the surface of the adhesive layer in step S2b and dried to form the catalyst layer;

[0051] S4b, an adhesive liquid is applied to the surface of the catalyst layer and dried to form an adhesive layer;

[0052] S5b, the anion exchange layer is stacked on the surface of the adhesive layer in step S4b.

[0053] Scheme 3 includes the following steps S1c-S4c:

[0054] S1c provides a cation exchange layer;

[0055] S2c, an adhesive liquid is applied to the surface of the cation exchange layer and dried to form an adhesive layer;

[0056] S3c, Apply a catalyst solution to the surface of the adhesive layer and dry to form the catalyst layer;

[0057] S4c, the anion exchange layer is stacked on the surface of the catalyst layer.

[0058] In Schemes 1, 2, and 3 above, the specific operations for providing the cation exchange layer and the stacked anion exchange layer can be performed using conventional methods in the art, and there are no particular limitations. Specifically, the cation exchange layer can be formed, for example, by dissolving the film-forming material in a solvent to prepare a first film-forming solution of the required concentration, then casting it on an ultra-flat glass plate while the solvent evaporates, followed by drying (e.g., drying at 100°C for 24 hours), and then cooling it to room temperature to obtain the cation exchange layer. The anion exchange layer can be formed, for example, by dissolving the film-forming material in a solvent to prepare a second film-forming solution of the required concentration, and using a casting method, applying the second film-forming solution to the surface of the adhesive layer (e.g., the adhesive layer formed in step S3a of Scheme 1 and the adhesive layer formed in step S4b of Scheme 2) or the surface of the catalyst layer (e.g., the catalyst layer formed in step S3c of Scheme 3) already formed in the previous steps on an ultra-flat glass plate to obtain a composite multilayer bipolar film structure. The relevant content regarding the first and second film-forming solutions can be referred to the above description and will not be repeated here. Preferably, the bipolar membrane is prepared using the above-mentioned Scheme 2.

[0059] A second aspect of the present invention provides a bipolar membrane, the bipolar membrane comprising a cation exchange layer, an anion exchange layer, and a catalyst layer located between the cation exchange layer and the anion exchange layer;

[0060] An adhesive layer is provided between the cation exchange layer and the catalyst layer, and / or an adhesive layer is provided between the anion exchange layer and the catalyst layer;

[0061] Preferably, the cation exchange layer has sulfonic acid groups, and the anion exchange layer has quaternary ammonium groups.

[0062] In some embodiments, the thickness of the adhesive layer is 50-1000nm, such as 50nm, 80nm, 100nm, 200nm, 300nm, 400nm, 500nm, 700nm, 900nm, 1000nm, etc., preferably 100-500nm;

[0063] Preferably, the adhesive layer is formed by an aqueous adhesive, preferably selected from one or more of polyurethane adhesives, isocyanate adhesives, acrylate adhesives, and styrene-butadiene latex, more preferably polyurethane adhesives; even more preferably, the aqueous adhesive is selected from Wanhua adhesives. One or more combinations of a series of water-based adhesives, more preferably 1630B and / or 1336.

[0064] In some embodiments, the catalyst in the catalyst layer is a catalyst containing a transition metal element, preferably a transition metal salt, and the transition metal salt forms a complex with dopamine. The specific type of transition metal salt is not particularly limited; those skilled in the art can determine the specific type of transition metal salt as a catalyst according to application requirements. Specifically, the transition metal element in the transition metal salt is, for example, but not limited to, one or more of Fe, Sn, Cu, Cr, Co, Ni, Pd, Pt, Ag, Au, or Ru. The transition metal salt is preferably a water-soluble compound, more preferably a water-soluble transition metal chloride.

[0065] Preferably, the first film-forming material used in the cation exchange layer is one or more of sulfonated polyether ether ketone, sulfonated polyphenylene ether, sulfonated polysulfone, and sulfonated polyether sulfone;

[0066] Preferably, the second film-forming material used in the anion exchange layer is one or more of quaternized brominated polyphenylene ether, quaternized polysulfone, and quaternized polyethersulfone, and preferably the degree of quaternization of the second film-forming material is 40-70%.

[0067] Preferably, the bipolar membrane is prepared using the method described above. Unless otherwise specified, all other aspects of the bipolar membrane can be found in the preceding description of its preparation method.

[0068] In the bipolar membrane provided by this invention, the specific thicknesses of the anion exchange layer, cation exchange layer, and catalyst layer can be reasonably determined by those skilled in the art based on the application requirements of the specific product, and there are no particular limitations. For reference, for example, the thickness of the anion exchange layer can be 20-150 μm, the thickness of the catalyst layer can be 0.1-1000 nm, and the thickness of the cation exchange layer can be 50-150 μm. One of the key features of the bipolar membrane provided by this invention is that an adhesive layer is provided between the catalyst layer and the anion exchange layer and / or between the catalyst layer and the cation exchange layer, and preferably, the preferred method mentioned above in this invention is used to prepare the bipolar membrane during the preparation process.

[0069] In another aspect, this invention also provides a bipolar membrane prepared by the preparation method described above, or an activation method for the bipolar membrane described above. The activation method includes: activating the bipolar membrane under an electric field, followed by washing with water, for example, rinsing it clean. The inventors have found that activating the bipolar membrane under an electric field before application improves its performance, achieving a better balance between voltage drop across the membrane, attenuation resistance, and service life.

[0070] The electric field is, for example, a direct current electric field. Preferably, during the activation, the current density is 400-1000 A / m. 2 For example, 400A / m 2 500A / m 2 600A / m 2 700A / m 2 800A / m 2 900A / m 2 1000A / m 2 The activation time is preferably 1-3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, etc.; preferably, during the activation, the bipolar membrane is placed in an acetate aqueous solution, the concentration of which is preferably 1-10 wt%. Preferably, the acetate is sodium acetate and / or potassium acetate, more preferably sodium acetate. The inventors have discovered that after the bipolar membrane is activated under an electric field, especially after activation under the above-mentioned preferred acetate solution and / or current conditions, the performance of the bipolar membrane can be further improved. This allows the channels inside the adhesive layer to undergo a certain degree of ionization under the action of the electric field, which is beneficial for improving the ion permeability of the adhesive layer, keeping the membrane voltage of the bipolar membrane within a more ideal range, and further improving the resistance to degradation during long-term use.

[0071] Another aspect of the present invention provides an application in which the bipolar membrane prepared by the method described above, or the bipolar membrane described above, is used in a bipolar membrane electrodialysis device, or in the fields of lithium extraction from salt lakes, waste salt treatment, or recovery of organic acids and alkalis. Preferably, the bipolar membrane is activated using the activation method described above before application.

[0072] The technical solution of the present invention will be further described below through the following embodiments, but it is not intended that the present invention is limited to the following embodiments. The following embodiments are preparation methods of bipolar films using Scheme 1. For the preparation processes of bipolar films in Scheme 2 and Scheme 3, the corresponding steps of Scheme 1 can be referred to.

[0073] The structural schematic diagram of the bipolar film prepared in the following examples is shown in the figure. Figure 1 From top to bottom, the layers are sequentially stacked: a cation exchange layer (i.e., cation membrane layer) 1, a catalyst layer 2, an adhesive layer 3, and an anion exchange layer (i.e., anion membrane layer) 4. The catalyst layer 2 and the adhesive layer 3 form the intermediate interface between the cation exchange layer 1 and the anion exchange layer 4.

[0074] The present invention will be described in more detail below through examples.

[0075] Raw material description:

[0076] Sulfonated polyether ether ketone: prepared according to the reference (Journal of Membrane Science 229(2004)95-106), with a sulfonation degree of approximately 95%;

[0077] N,N-Dimethylformamide: Purchased from Aladdin, 99% purity.

[0078] N-Methylpyrrolidone: Purchased from Aladdin, 98% purity.

[0079] Dopamine: Purchased from Aladdin, 98% purity.

[0080] Brominated polyphenylene ether: prepared according to the reference (Energy & Environmental Science, 2012, 5(7): 7888-7892), with a bromination degree of about 55%;

[0081] Vinylimidazole: Purchased from Aladdin, purity 99%;

[0082] 1630B Waterborne Adhesive: Polyurethane Adhesive, Wanhua Chemical; 1336 Water-based Adhesive: Polyurethane adhesive, Wanhua Chemical; 161 Water-based Adhesives: Isocyanate-based adhesives, Wanhua Chemical;

[0083] Bipolar membrane hydrolysis voltage test: The test was conducted in an electrolytic cell. The cation exchange layer of the bipolar membrane was positioned opposite the positive electrode side of the electrolytic cell, and the anion exchange layer was positioned opposite the negative electrode side. The electrolyte was a 0.5 mol / L NaCl aqueous solution, and the current density was 1000 A / m. 2 .

[0084] Long-cycle life verification: 11 bipolar membranes, 10 cation membranes (ASTOM CMX cation membranes), and 10 anion membranes (ASTOM AMX anion membranes) were assembled into a bipolar membrane stack and treated with a 15wt% sodium sulfate aqueous solution to investigate the long-cycle performance of the bipolar membranes.

[0085] Membrane stack performance degradation: Calculated using the initial performance of the membrane stack (specifically, current efficiency) as a benchmark. The specific formula is: (Initial membrane stack performance - Performance of the membrane stack at a certain moment) / Initial membrane stack performance * 100%

[0086] Example 1

[0087] 1) Preparation of cation exchange layer:

[0088] The dried sulfonated polyether ether ketone was weighed using a balance, then dissolved in N,N-dimethylformamide to prepare a first film-forming solution with a mass fraction of 10 wt%. The solution was then cast onto an ultra-flat glass plate (with solvent evaporation), and then dried in a 100°C forced-air oven for 24 hours. After being removed and cooled to room temperature, a cation exchange layer with a thickness of 150 μm was obtained.

[0089] 2) Preparation of the catalyst layer:

[0090] A certain amount of dopamine was weighed and prepared into a 0.5 wt% dopamine aqueous solution. The pH was adjusted to 4 using 0.5 mol / L hydrochloric acid solution. A 5 wt% ammonium persulfate aqueous solution (volume ratio of ammonium persulfate to dopamine aqueous solution was 1:20) was added. SnCl2 was added to the dopamine aqueous solution according to a transition metal element to dopamine molar ratio of 1:2. After ultrasonic dispersion, the catalyst solution was obtained. The prepared catalyst solution was uniformly sprayed onto the upper surface of the cation exchange layer using ultrasonic spraying. The layer was then dried in a 50℃ oven for 2 hours, resulting in a uniformly adhered catalyst layer with a thickness of 100 nm.

[0091] 3) Preparation of adhesive layer:

[0092] Will 1630B water-based adhesive is prepared into a pre-coated emulsion (i.e., adhesive solution) with a concentration of 0.5wt% using water. The adhesive solution is then evenly applied to the upper surface of the catalyst layer formed in step 2) by brushing. The entire membrane is then placed in a 50°C oven and dried for 0.5 hours to obtain a three-layer structure composed of a cation exchange layer / catalyst layer / adhesive layer, wherein the thickness of the adhesive layer is 100nm.

[0093] 4) Preparation of anion exchange layer:

[0094] Weigh the dried brominated polyphenylene ether using a balance, dissolve it in N,N-dimethylformamide solution to prepare a 20wt% brominated polyphenylene ether solution, mix trimethylamine and chlorobenzene in a mass ratio of 1:10 to obtain a mixed solution, slowly add the mixed solution to the above brominated polyphenylene ether solution (the volume ratio of the mixed solution to the brominated polyphenylene ether solution is 1:2) to obtain a quaternized polyphenylene ether solution with a quaternization degree of about 55% (i.e., the second film-forming solution), apply the second film-forming solution to the upper surface of the adhesive layer in the three-layer structure obtained in step 3) on an ultra-flat glass plate using a casting method, and dry it in a 50°C oven for 2 hours to form an anion exchange layer (100μm thick) on the adhesive layer, thus obtaining a composite four-layer bipolar film structure.

[0095] 5) Activation of the bipolar membrane:

[0096] The bipolar membrane is placed in an electrolytic cell, with the cation exchange layer of the bipolar membrane aligned with the positive electrode side and the anion exchange layer aligned with the negative electrode side. A 3 wt% sodium acetate aqueous solution is added, and then a current density of 1000 A / m is passed through it. 2 The DC power supply was maintained for 1 hour, and then the bipolar membrane was removed and rinsed with deionized water.

[0097] Comparative Example 1

[0098] The bipolar membrane was prepared according to Example 1, except that step 2) was not performed, that is, no catalyst layer was formed between the cation exchange layer and the adhesive layer, and the cation exchange layer and the adhesive layer were directly contacted and stacked.

[0099] Comparative Example 2

[0100] The bipolar membrane was prepared according to Example 1, except that step 3) was not performed, that is, no adhesive layer was formed between the catalyst layer and the anion exchange layer, and the catalyst layer and the anion exchange layer were directly contacted and stacked.

[0101] The bipolar membranes of Example 1, Comparative Example 1, and Comparative Example 2 were tested according to the aforementioned bipolar membrane hydrolysis voltage test method. Test results: The voltage drop across the bipolar membrane of Example 1 was 1.15V, while the voltage drop across the bipolar membrane of Comparative Example 1 was 5.0V, and the voltage drop across the bipolar membrane of Comparative Example 2 was 1.10V.

[0102] The bipolar membranes of Example 1, Comparative Example 1, and Comparative Example 2 were tested according to the aforementioned long-cycle life verification method. The results showed that: the bipolar membrane prepared in Example 1 did not show any bubbles or delamination after one year of operation, and its performance decreased by 15% compared to the initial membrane stack; the bipolar membrane of Comparative Example 1 also did not show any delamination after one year of operation, and its performance decreased by 30% compared to the initial membrane stack; while the bipolar membrane in Comparative Example 2 showed bubbles in the middle layer after three months of operation, and after six months of operation, the anion and cation membrane layers showed obvious delamination, and the membrane stack performance decreased by 60% compared to the initial membrane stack performance.

[0103] Example 2

[0104] 1) Preparation of cation exchange layer:

[0105] The dried sulfonated polyether ether ketone was weighed using a balance, then dissolved in N-methylpyrrolidone to prepare a first film-forming solution with a mass fraction of 10 wt%. The solution was then cast onto an ultra-flat glass plate (with solvent evaporation), and then dried in a 100°C forced-air oven for 24 hours. After being removed and cooled to room temperature, a cation exchange layer with a thickness of 150 μm was obtained.

[0106] 2) Preparation of the catalyst layer:

[0107] A certain amount of dopamine was weighed and prepared into a 2wt% dopamine aqueous solution. The pH was adjusted to 4 using 0.5mol / L hydrochloric acid solution. A 5wt% ammonium persulfate aqueous solution was added (the volume ratio of ammonium persulfate to dopamine aqueous solution was 3:20). RhCl3 was added to the dopamine aqueous solution according to a transition metal element to dopamine molar ratio of 1:50. After ultrasonic dispersion, the catalyst solution was obtained. The prepared catalyst solution was uniformly sprayed onto the upper surface of the cation exchange layer using an ultrasonic spraying method. The layer was then dried in a 100℃ oven for 1 hour, resulting in a uniformly adhered catalyst layer with a thickness of 250nm.

[0108] 3) Preparation of adhesive layer:

[0109] Will 1336 water-based adhesive is prepared into a pre-coated emulsion (i.e., adhesive liquid) with a concentration of 10wt% using water. The adhesive liquid is then evenly applied to the upper surface of the catalyst layer formed in step 2) by brushing. The entire membrane is then placed in an oven at 100℃ and dried for 0.5h to obtain a three-layer structure composed of a cation exchange layer / catalyst layer / adhesive layer, wherein the thickness of the adhesive layer is 500nm.

[0110] 4) Preparation of anion exchange layer:

[0111] Weigh the dried brominated polyphenylene ether using a balance, dissolve it in N-methylpyrrolidone solution to prepare a 20wt% brominated polyphenylene ether solution, mix vinylimidazole and chlorobenzene in a mass ratio of 1:15 to obtain a mixed solution, slowly add the mixed solution to the above brominated polyphenylene ether solution (the volume ratio of the mixed solution to the brominated polyphenylene ether solution is 1:2) to obtain a quaternized polyphenylene ether solution with a quaternization degree of about 55% (i.e., the second film-forming solution), apply the second film-forming solution to the upper surface of the adhesive layer in the three-layer structure obtained in step 3) on an ultra-flat glass plate using a casting method, and dry it in a 50℃ oven for 2 hours to form an anion exchange layer (thickness of 120μm) on the adhesive layer, thus obtaining a composite four-layer bipolar film structure.

[0112] 5) Activation of the bipolar membrane:

[0113] The activation method and process of the bipolar membrane are the same as those in Example 1.

[0114] The bipolar membrane of Example 2 was tested according to the aforementioned bipolar membrane hydrolysis voltage test method and long-cycle life verification method.

[0115] Test results: The voltage drop across the bipolar membrane prepared in Example 2 was 1.20V. Long-term lifetime verification of the bipolar membrane prepared in Example 2 showed that no bubbles appeared and no delamination occurred after one year of operation, with a performance degradation of 20% compared to the initial membrane stack.

[0116] Example 3

[0117] 1) Preparation of cation exchange layer:

[0118] The cation exchange layer was prepared according to step 1) of Example 1.

[0119] 2) Preparation of the catalyst layer:

[0120] A certain amount of dopamine was weighed and prepared into a 0.5 wt% dopamine aqueous solution. The pH was adjusted to 4 using 0.5 mol / L hydrochloric acid solution. A 5 wt% ammonium persulfate aqueous solution (the volume ratio of ammonium persulfate to dopamine aqueous solution was 1:20) was added. SnCl2 was added to the dopamine aqueous solution according to a transition metal element to dopamine molar ratio of 1:80. After ultrasonic dispersion, a catalyst solution was obtained. The prepared catalyst solution was uniformly sprayed onto the upper surface of the cation exchange layer using an ultrasonic spraying method. The layer was then dried in a 100℃ oven for 2 hours, resulting in a uniformly adhered catalyst layer with a thickness of 400 nm.

[0121] 3) Preparation of adhesive layer:

[0122] Will 161. Aqueous adhesive is prepared into a pre-coated emulsion (i.e., adhesive solution) with a concentration of 20wt% using water. The adhesive solution is then evenly applied to the upper surface of the catalyst layer formed in step 2) by brushing. The entire membrane is then placed in an oven at 100℃ and dried for 0.5h to obtain a three-layer structure composed of a cation exchange layer / catalyst layer / adhesive layer, wherein the thickness of the adhesive layer is 1000nm.

[0123] 4) Preparation of anion exchange layer:

[0124] The anion exchange layer was prepared according to step 4) of Example 1.

[0125] 5) Activation of the bipolar membrane:

[0126] The activation method and process of the bipolar membrane are the same as those in Example 1.

[0127] The bipolar membrane in Example 3 was tested according to the aforementioned bipolar membrane hydrolysis voltage test method and long-cycle life verification method.

[0128] Test results: The voltage drop across the bipolar membrane prepared in Example 3 was 1.70V. Long-term lifetime verification of the bipolar membrane prepared in Example 3 showed that no bubbles appeared or delamination occurred after one year of operation, and the performance of the bipolar membrane stack decreased by 20% compared to the initial membrane stack.

[0129] Example 4

[0130] 1) Preparation of cation exchange layer:

[0131] The cation exchange layer was prepared according to step 1) in Example 1.

[0132] 2) Preparation of the catalyst layer:

[0133] A certain amount of dopamine was weighed and prepared into a 2wt% dopamine aqueous solution. The pH was adjusted to 5 using 0.5mol / L hydrochloric acid solution. A 5wt% ammonium persulfate aqueous solution was added (the volume ratio of ammonium persulfate to dopamine aqueous solution was 1:20). RhCl3 was added to the dopamine aqueous solution according to a transition metal element to dopamine molar ratio of 1:100. After ultrasonic dispersion, the catalyst solution was obtained. The prepared catalyst solution was uniformly sprayed onto the upper surface of the cation exchange layer using an ultrasonic spraying method. The layer was then dried in a 100℃ oven for 1 hour, resulting in a uniformly adhered catalyst layer with a thickness of 350nm.

[0134] 3) Preparation of adhesive layer:

[0135] Will 1630B water-based adhesive was prepared into a pre-coated emulsion (i.e., adhesive solution) with a concentration of 20wt% using water. The adhesive solution was then evenly applied to the upper surface of the catalyst layer formed in step 2) by brushing. The entire membrane was then placed in a 50°C oven and dried for 0.5 hours to obtain a three-layer structure composed of a cation exchange layer / catalyst layer / adhesive layer, wherein the thickness of the adhesive layer was 1000 nm.

[0136] 4) Preparation of anion exchange layer:

[0137] The anion exchange layer was prepared according to step 4) of Example 1.

[0138] 5) Activation of the bipolar membrane:

[0139] The activation method and process of the bipolar membrane are the same as those in Example 1.

[0140] The bipolar membrane in Example 4 was tested according to the aforementioned bipolar membrane hydrolysis voltage test method and long-cycle life verification method.

[0141] Test results: The voltage drop across the bipolar membrane prepared in Example 4 was 1.50V. The bipolar membrane prepared in Example 4 was subjected to long-cycle life verification. The results showed that the bipolar membrane prepared in Example 4 did not produce bubbles or delamination after one year of operation, and its performance decreased by 13% compared with the initial membrane stack.

[0142] Example 5

[0143] This embodiment refers to the preparation of bipolar membrane in Example 1, except that step 5) is not performed, that is, the bipolar membrane is not activated.

[0144] The bipolar membrane of Example 5 was tested according to the aforementioned bipolar membrane hydrolysis voltage test method and long-cycle life verification method.

[0145] Test results: The voltage drop across the bipolar membrane prepared in Example 5 was 8.0V. The bipolar membrane prepared in Example 5 was subjected to long-cycle life verification. The results showed that no bubbles appeared or delamination occurred after one year of operation. The performance of the bipolar membrane prepared in Example 5 was reduced by 35% compared with the initial membrane stack.

[0146] Example 6

[0147] The bipolar film was prepared according to Example 1, except that in step 3) when preparing the adhesive layer, the adhesive layer from Example 1 was used instead of the one described in Example 1. 1630B water-based adhesive replaced with 161 Water-based adhesive.

[0148] The bipolar membrane of Example 6 was tested according to the aforementioned bipolar membrane hydrolysis voltage test method and long-cycle life verification method.

[0149] Test results: The voltage drop across the bipolar membrane prepared in Example 6 was 1.50V. The bipolar membrane prepared in Example 6 was subjected to long-cycle lifetime verification. The results showed that the bipolar membrane prepared in Example 6 did not produce bubbles or delamination after one year of operation, and its performance decreased by 18% compared with the initial membrane stack.

[0150] Comparing the experimental results of Examples 1 and 6, under basically the same conditions, the bipolar membrane obtained by the present invention using polyurethane adhesive to form the adhesive layer has better performance, and can obtain better voltage drop across the membrane and better long-cycle operation performance.

[0151] Example 7

[0152] 1) Preparation of cation exchange layer:

[0153] The cation exchange layer was prepared according to step 1) in Example 1.

[0154] 2) Preparation of the catalyst layer:

[0155] A certain amount of dopamine was weighed and prepared into a 0.5 wt% dopamine aqueous solution. The pH was adjusted to 4 using 0.5 mol / L hydrochloric acid solution. A 5 wt% ammonium persulfate aqueous solution (volume ratio of ammonium persulfate to dopamine aqueous solution was 1:20) was added. SnCl2 was added to the dopamine aqueous solution according to a 1:1 molar ratio of transition metal element to dopamine. After ultrasonic dispersion, a catalyst solution was obtained. The prepared catalyst solution was uniformly sprayed onto the upper surface of the cation exchange layer using an ultrasonic spraying method. The layer was then dried in a 50℃ oven for 2 hours, resulting in a uniformly adhered catalyst layer with a thickness of 100 nm.

[0156] 3) Preparation of adhesive layer:

[0157] The adhesive layer is prepared according to step 3) of Example 1.

[0158] 4) Preparation of anion exchange layer:

[0159] The cation exchange layer was prepared according to step 4) of Example 1.

[0160] 5) Activation of the bipolar membrane:

[0161] The activation method and process of the bipolar membrane are the same as those in Example 1.

[0162] The bipolar membrane of Example 7 was tested according to the aforementioned bipolar membrane hydrolysis voltage test method and long-cycle life verification method.

[0163] Test results: The voltage drop across the bipolar membrane prepared in Example 7 was 1.17V. The bipolar membrane prepared in Example 7 was subjected to long-cycle lifetime verification. The results showed that the bipolar membrane prepared in Example 7 did not produce bubbles or delamination after one year of operation, and its performance decreased by 19% compared with the initial membrane stack.

[0164] Example 8

[0165] 1) Preparation of cation exchange layer:

[0166] The cation exchange layer was prepared according to step 1) in Example 1.

[0167] 2) Preparation of the catalyst layer:

[0168] The catalyst layer was prepared according to step 2) in Example 1.

[0169] 3) Preparation of adhesive layer:

[0170] Will 1630B water-based adhesive was prepared into a pre-coated emulsion (i.e., adhesive solution) with a concentration of 20wt% using water. The adhesive solution was then evenly applied to the upper surface of the catalyst layer formed in step 2) by brushing. The entire membrane was then placed in a 50°C oven and dried for 0.5 hours to obtain a three-layer structure composed of a cation exchange layer / catalyst layer / adhesive layer, wherein the thickness of the adhesive layer was 1000 nm.

[0171] 4) Preparation of anion exchange layer:

[0172] The anion exchange layer was prepared according to step 4) of Example 1.

[0173] 5) Activation of the bipolar membrane:

[0174] The activation method and process of the bipolar membrane are the same as those in Example 1.

[0175] The bipolar membrane of Example 8 was tested according to the aforementioned bipolar membrane hydrolysis voltage test method and long-cycle life verification method.

[0176] Test results: The voltage drop across the bipolar membrane prepared in Example 8 was 1.38V. Long-cycle life verification of the bipolar membrane prepared in Example 8 showed that no bubbles or delamination occurred after one year of operation, and the performance of the bipolar membrane stack decreased by 15% compared with the initial membrane stack.

[0177] Comparing Examples 1 and 8, under essentially the same conditions, Example 1, with the adhesive layer thickness controlled within 100-500 nm, exhibits better bipolar film performance.

[0178] Example 9

[0179] 1) Preparation of cation exchange layer:

[0180] The cation exchange layer was prepared according to step 1) in Example 1.

[0181] 2) Preparation of the catalyst layer:

[0182] The catalyst layer was prepared according to step 2) in Example 1.

[0183] 3) Preparation of adhesive layer:

[0184] The adhesive layer was prepared according to step 3) in Example 1.

[0185] 4) Preparation of anion exchange layer:

[0186] The anion exchange layer was prepared according to step 4) of Example 1.

[0187] 5) Activation of the bipolar membrane:

[0188] The procedure is carried out according to step 5 of Example 1, except that the sodium acetate aqueous solution in Example 1 is replaced with a 3wt% potassium acetate aqueous solution.

[0189] The bipolar membrane of Example 9 was tested according to the aforementioned bipolar membrane hydrolysis voltage test method and long-cycle life verification method.

[0190] Test results: The voltage drop across the bipolar membrane prepared in Example 9 was 1.20V. The bipolar membrane prepared in Example 9 was subjected to long-cycle lifetime verification. The results showed that no bubbles appeared or delamination occurred after one year of operation. The performance of the bipolar membrane prepared in Example 9 was reduced by 15% compared with the initial membrane stack.

[0191] A comparison of Examples 1 and 9 shows that the bipolar membrane in this invention is more effective when activated in an aqueous sodium acetate solution.

[0192] Table 1 Summary of Experimental Results

[0193]

[0194]

[0195] Note: If the data in Table 1 is inconsistent with the textual descriptions in the preceding embodiments / comparative examples, the preceding textual descriptions shall prevail.

[0196] As can be seen from the above experimental results, in this embodiment, adding an adhesive layer between the catalyst layer and the cation exchange layer and / or anion exchange layer of the bipolar membrane can significantly improve the long-term operation performance of the bipolar membrane, extend its service life, reduce the performance degradation during long-term operation, and prevent bubbles and stratification from occurring during long-term operation, compared to Comparative Example 2 without an adhesive layer.

[0197] From the experimental comparison of Example 1, Comparative Example 1 and Comparative Example 2, it can be seen that by introducing dopamine into the catalyst layer in this invention, the catalyst layer and the adhesive layer can produce a synergistic effect, which can more significantly improve the performance degradation of the bipolar membrane during long-term operation, while taking into account the relatively low voltage drop across the membrane.

[0198] A comparison of Examples 1 and 5 shows that by activating the bipolar membrane of the present invention under an electric field, the performance of the bipolar membrane of the present invention can be significantly improved, achieving a better balance between voltage drop across the membrane and performance degradation during long-term operation.

[0199] It is readily understood that the above embodiments are merely illustrative examples for clear explanation and do not imply that the invention is limited thereto. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a bipolar membrane, the bipolar membrane comprising a cation exchange layer, an anion exchange layer, and a catalyst layer located between the cation exchange layer and the anion exchange layer, characterized in that, The preparation method includes the following steps: forming an adhesive layer between the cation exchange layer and the catalyst layer, and / or forming an adhesive layer between the anion exchange layer and the catalyst layer; The cation exchange layer contains sulfonic acid groups, and the anion exchange layer contains quaternary ammonium groups; The adhesive in the adhesive layer is a water-based adhesive, selected from one or more of polyurethane adhesives, isocyanate adhesives, acrylate adhesives, and styrene-butadiene latex; The catalyst layer is obtained by applying a catalyst solution to the location where the catalyst layer needs to be formed and then drying it; the catalyst in the catalyst solution is a transition metal salt, and the transition metal salt forms a complex with dopamine. The cation exchange layer was prepared using a first membrane-building solution.

2. The preparation method according to claim 1, characterized in that, The adhesive layer is formed at least between the anion exchange layer and the catalyst layer.

3. The preparation method according to claim 1, characterized in that, The adhesive layer is formed by applying adhesive liquid to the location where the adhesive layer needs to be formed and then drying it.

4. The preparation method according to claim 3, characterized in that, The concentration of the adhesive liquid is 0.5 wt%-20 wt%.

5. The preparation method according to claim 3, characterized in that, The water-based adhesive is selected from Wanhua Adwel. Aquolin Vesmody One or more combinations of a series of water-based adhesives.

6. The preparation method according to claim 5, characterized in that, The water-based adhesive is selected from Adwel. 1630B and / or Adwel 1336.

7. The preparation method according to any one of claims 1-6, characterized in that, The thickness of the adhesive layer is 50-1000 nm.

8. The preparation method according to claim 7, characterized in that, The thickness of the adhesive layer is 100-500 nm.

9. The preparation method according to any one of claims 1-6, characterized in that, The catalyst layer is obtained by applying a catalyst solution to the location where the catalyst layer needs to be formed and then drying it.

10. The preparation method according to claim 9, characterized in that, The transition metal salt is a water-soluble compound.

11. The preparation method according to claim 10, characterized in that, The transition metal salt is a water-soluble transition metal chloride.

12. The preparation method according to claim 9, characterized in that, The preparation of the catalyst feed solution includes: reacting the catalyst with dopamine in an environment with a pH of 3-5, and dispersing it evenly to obtain a suspension.

13. The preparation method according to claim 12, characterized in that, The reaction was carried out in the presence of ammonium persulfate.

14. The preparation method according to claim 12, characterized in that, The molar ratio of the transition metal element to the dopamine in the catalyst is 1:1 to 1:

100.

15. The preparation method according to claim 14, characterized in that, The molar ratio of the transition metal element to the dopamine in the catalyst is 1:2 to 1:

100.

16. The preparation method according to claim 15, characterized in that, The molar ratio of the transition metal element to the dopamine in the catalyst is 1:2 to 1:

20.

17. The preparation method according to claim 13, characterized in that, The ammonium persulfate is added to the reaction system in an aqueous solution with a concentration of 4-6 wt%, and the dopamine is added to the reaction system in an aqueous solution with a concentration of 0.5-2 wt%. The volume ratio of the aqueous solution of ammonium persulfate to the aqueous solution of dopamine is 1-3:

20.

18. The preparation method according to claim 9, characterized in that, The transition metal element in the transition metal salt is one or more of Fe, Sn, Cu, Cr, Co, Ni, Pd, Pt, Ag, Au, or Ru.

19. The preparation method according to any one of claims 1-6, characterized in that, The first film-forming material contained in the first film-forming solution is one or more of sulfonated polyether ether ketone, sulfonated polyphenylene ether, sulfonated polysulfone, and sulfonated polyether sulfone; And / or, the anion exchange layer is prepared using a second film-forming solution, wherein the second film-forming material contained in the second film-forming solution is one or more of quaternized brominated polyphenylene ether, quaternized polysulfone, and quaternized polyethersulfone.

20. The preparation method according to claim 19, characterized in that, The degree of sulfonation of the first film-forming material is 40-100%; And / or, the degree of quaternization of the second film-forming material is 40-70%.

21. The preparation method according to claim 19, characterized in that, The concentration of the first film-forming solution is 4-40 wt%, and the solvent in the first film-forming solution is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone. And / or, the concentration of the second film-forming solution is 4-40 wt%; the solvent in the second film-forming solution is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, chlorobenzene and N-methylpyrrolidone.

22. The preparation method according to any one of claims 1-6, characterized in that, The preparation method is carried out according to Scheme 1, Scheme 2 or Scheme 3 as follows: Scheme 1 includes the following steps S1a-S4a: S1a provides a cation exchange layer; S2a, a catalyst solution is applied to the surface of the cation exchange layer and dried to form the catalyst layer; S3a, apply adhesive liquid to the surface of the catalyst layer and dry to form an adhesive layer; S4a, the anion exchange layer is stacked on the surface of the adhesive layer; The second scheme includes the following steps S1b-S4b: S1b provides the cation exchange layer; S2b, an adhesive liquid is applied to the surface of the cation exchange layer and dried to form an adhesive layer; S3b, a catalyst liquid is applied to the surface of the adhesive layer in step S2b and dried to form the catalyst layer; S4b, an adhesive liquid is applied to the surface of the catalyst layer and dried to form an adhesive layer; S5b, the anion exchange layer is stacked on the surface of the adhesive layer in step S4b; Scheme 3 includes the following steps S1c-S4c: S1c provides a cation exchange layer; S2c, an adhesive liquid is applied to the surface of the cation exchange layer and dried to form an adhesive layer; S3c, Apply a catalyst solution to the surface of the adhesive layer and dry to form the catalyst layer; S4c, the anion exchange layer is stacked on the surface of the catalyst layer.

23. A bipolar membrane, characterized in that, The bipolar membrane includes a cation exchange layer, an anion exchange layer, and a catalyst layer located between the cation exchange layer and the anion exchange layer; An adhesive layer is provided between the cation exchange layer and the catalyst layer, and / or an adhesive layer is provided between the anion exchange layer and the catalyst layer; The cation exchange layer contains sulfonic acid groups, and the anion exchange layer contains quaternary ammonium groups; The adhesive layer is formed by an aqueous adhesive, which is selected from one or more of polyurethane adhesives, isocyanate adhesives, acrylate adhesives, and styrene-butadiene latex. The catalyst in the catalyst layer is a catalyst containing a transition metal element, the catalyst is a transition metal salt, and the transition metal salt forms a complex with dopamine.

24. The bipolar film according to claim 23, characterized in that, The thickness of the adhesive layer is 50-1000 nm; And / or, the water-based adhesive is selected from Wanhua Adwel. Aquolin Vesmody One or more combinations of a series of water-based adhesives; And / or, the catalyst in the catalyst layer is a catalyst containing a transition metal element, wherein; The transition metal salt is a water-soluble compound; And / or, the first film-forming material used in the cation exchange layer is one or more of sulfonated polyether ether ketone, sulfonated polyphenylene ether, sulfonated polysulfone, and sulfonated polyether sulfone; And / or, the second film-forming material used in the anion exchange layer is one or more of quaternized brominated polyphenylene ether, quaternized polysulfone, and quaternized polyethersulfone.

25. The bipolar film according to claim 24, characterized in that, The thickness of the adhesive layer is 100-500 nm; And / or, the water-based adhesive is selected from Adwel. 1630B and / or Adwel 1336; And / or, the transition metal element is one or more of Fe, Sn, Cu, Cr, Co, Ni, Pd, Pt, Ag, Au, or Ru; the transition metal salt is a water-soluble transition metal chloride; And / or, the degree of quaternization of the second film-forming material is 40-70%.

26. The bipolar film according to claim 24, characterized in that, The bipolar film is prepared by the preparation method according to any one of claims 1-7.

27. The bipolar membrane prepared by the preparation method according to any one of claims 1-22 or the activation method of the bipolar membrane according to any one of claims 23-26, characterized in that, The bipolar film was activated under the action of an electric field and then washed with water.

28. The activation method according to claim 27, characterized in that, During the activation process, the current density is 400-1000 A / m. 2 The electric field is a direct current electric field.

29. The activation method according to claim 28, characterized in that, The activation time is 1-3 hours.

30. The activation method according to claim 27, characterized in that, During the activation process, the bipolar membrane is placed in an aqueous acetate solution.

31. The activation method according to claim 30, characterized in that, The concentration of the acetate aqueous solution is 1-10 wt%.

32. The activation method according to claim 30, characterized in that, The acetate is sodium acetate and / or potassium acetate.

33. An application characterized in that, The bipolar membrane prepared by the method according to any one of claims 1-22 or the bipolar membrane according to any one of claims 23-26 is used in a bipolar membrane electrodialysis device, or in the fields of lithium extraction from salt lakes, waste salt treatment or recovery of organic acids and alkalis.

34. The application according to claim 33, characterized in that, The bipolar membrane is activated using the activation method described in any one of claims 27-31 before application.

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