Preparation method of anion exchange membrane and bromine extraction system and bromine extraction method of bromine-containing brine

Abstract

The invention discloses a preparation method of an anion exchange membrane as well as a bromine extraction system and a bromine extraction method of bromine-containing brine, and aims to solve the problem that a bromine extraction system in the prior art is easy to generate pole plate scaling. The preparation method of the anion-exchange membrane comprises the following steps: pretreating an anion-exchange base membrane and then putting the anion-exchange base membrane into plasma equipment for plasma treatment; putting the anion exchange membrane subjected to plasma treatment into a grafting monomer solution for grafting reaction; and performing interfacial polymerization treatment on the anion exchange membrane after the grafting reaction to obtain the anion exchange membrane for diaphragm electrolysis-gaseous membrane absorption coupled bromine extraction. The method is suitable for extracting bromine-containing brine, and can achieve the effects of improving the purity of a rear-end bromine product and avoiding the influence of organic matters and ions easy to scale on system operation and product purity.

Description

Technical Field

[0001] This invention relates to the field of bromine extraction technology, and in particular to a method for preparing anion exchange membrane and a bromine extraction system and method for bromine-containing brine, applicable to high-hardness bromine-containing brine. Background Technology

[0002] Bromine is mainly dispersed in the Earth's crust hydrosphere in the form of bromide ions. The aquatic environments in which it exists are often divided into seawater, salt lake brine, underground brine, and mine brine. Among them, seawater has the largest bromine reserves and the widest distribution. However, direct extraction of bromine from seawater faces difficulties such as large investment and high costs, and there has been little improvement in the technology to date. On the other hand, current research has found that salt lake brine and underground brine have high-quality bromine resources and the highest yields. As a result, bromine extraction from underground brine has received increasing attention.

[0003] As a basic chemical raw material, bromine and its compounds are increasingly widely used. Examples include bromine-containing flame retardants in the building and furniture industry, bromine-containing intermediates in organic synthesis, and inorganic bromides such as sodium bromide, calcium bromide, and zinc bromide in offshore oil drilling, as well as photosensitive agents in photography. With the booming development of China's downstream bromine industries, bromine has broad prospects for production and application.

[0004] Currently available bromine extraction methods mainly include air blowing, steam distillation, ion exchange adsorption, membrane separation, hypergravity gas technology, and solvent extraction. While each method has its own characteristics, they all have certain limitations. Air blowing, currently the most common bromine extraction method, still suffers from low bromine recovery rates and large equipment footprints. Steam distillation has high energy consumption, requiring a large amount of heat energy, increasing costs, and is suitable for brine with high bromine content. Ion exchange adsorption has certain selectivity issues and requires high-quality resins. Membrane separation requires consideration of membrane material selection, membrane fouling, and maintenance, and is also limited by membrane flux and lifespan. Hypergravity gas technology has complex equipment and high costs, limiting its large-scale application. Solvent extraction introduces organic solvents, and the difficulty in continuously using organic solvents and the degree of separation from bromine still need improvement.

[0005] Currently, most bromine extraction technologies involve an oxidation step of bromide ions. Common oxidation methods use oxidizing agents such as chlorine, hydrogen peroxide, and hypochlorous acid. Chlorine is a toxic and hazardous chemical; if the equipment is not properly sealed during oxidation, chlorine can escape into the air, polluting the operating environment. Oxidation with 30% hydrogen peroxide is too costly and poses certain risks during transportation and use. Compared to chlorine oxidation, while 10% sodium hypochlorite oxidation avoids the risk of chlorine leakage, it consumes twice as much acid, and sodium hypochlorite is several times more expensive than chlorine, leading to increased production costs.

[0006] In recent years, electro-oxidation has attracted much attention in the field of bromine extraction and recovery, mainly due to its environmental friendliness, ease of operation, and high bromine purity. This method efficiently converts bromide ions directly into bromine gas or bromides, achieving high recovery efficiency. By adjusting operating parameters, the bromine yield and purity can be flexibly controlled. Compared with traditional methods, electro-oxidation requires no additional chemical reagents, helping to reduce waste generation and thus being more environmentally friendly. Furthermore, its equipment is simple and inexpensive, making it particularly suitable for small- to medium-scale processes. For underground brine, since the chloride ion concentration is significantly higher than the bromide ion concentration, and considering the standard oxidation potentials of chloride and bromide ions are 1.161 V and 0.890 V respectively, the effect of oxidizing bromide ions while preventing chloride ions from being oxidized can be achieved by controlling the potential.

[0007] Chinese patent CN 118007150 A uses electro-oxidation coupled with a gaseous membrane for bromine extraction, realizing a bromine extraction process in which bromide ions are oxidized and then reduced. However, the process of oxidizing bromide ions to elemental bromine at the anode, absorbing elemental bromine with alkali to obtain bromide ions and bromate, and reducing bromate to bromide ions at the cathode requires strict potential control of the electrolysis device. At the same time, this process uses a cation exchange membrane. The patent mentions treating seawater or brine, but in reality, brine in many regions has problems with high hardness and high organic matter content. Divalent cations such as calcium and magnesium will continuously migrate to the cathode plate and form scale. Long-term operation can easily lead to problems such as scale formation on the electrode plate and organic matter affecting the purity of bromine products. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing anion exchange membranes and a bromine extraction system and method for bromine-containing brine, avoiding the impact of organic matter and easily scale-forming ions on system operation and product purity, and achieving the goal of economical, environmentally friendly, safe and convenient bromine resource utilization.

[0009] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing anion exchange membrane, comprising the following steps:

[0011] The anion exchange base membrane was pretreated and then subjected to plasma treatment.

[0012] The plasma-treated anion exchange membrane was placed in a grafting monomer solution for grafting reaction.

[0013] The grafted anion exchange base membrane was subjected to interfacial polymerization to obtain anion exchange membrane for bromine extraction via membrane electrolysis-gas membrane absorption coupling.

[0014] The anion exchange membrane prepared by the above-mentioned technical solution is applied to the diaphragm electrolysis-gas membrane absorption coupling bromine extraction in bromine-containing brine, realizing the extraction of bromine from the bromine-containing brine system. On the one hand, it avoids the scaling problem of calcium and magnesium ions at the cathode in high hardness systems; on the other hand, the modification by the above method can improve the antioxidant and antifouling ability of the anion membrane in bromine-containing systems, prevent impurities and pollutants from entering the cathode side, improve the purity of sodium hydroxide on the cathode side, and can be used as the absorbent for gas membranes.

[0015] Optionally, the pretreatment operation involves sanding the anion exchange membrane base membrane with sandpaper and soaking it in hydrochloric acid.

[0016] The above technical solution can increase the surface roughness of the anion exchange base membrane.

[0017] Furthermore, the interface aggregation process includes:

[0018] The grafted anion exchange membrane was placed in the interfacial polymerization reaction tank frame for fixation, and the grafted monomer solution on the surface of the grafted anion exchange membrane was dried.

[0019] The aqueous solution was poured into the interfacial polymerization reaction tank for aqueous phase treatment;

[0020] After aqueous phase treatment, the anion exchange base membrane is drained of water and then air-dried.

[0021] The dried anion exchange base membrane was placed in the interfacial polymerization reaction tank, and the oil phase solution was poured into the interfacial polymerization reaction tank for oil phase treatment.

[0022] The anion exchange substrate membrane after oil phase treatment is obtained by draining the oil phase solution and then vacuum drying.

[0023] The modified anion exchange membrane prepared by the above technical solution improves the antioxidant properties of the anion exchange membrane and avoids the degradation of its performance caused by bromine molecules in the solution.

[0024] Furthermore, the conditions for the aqueous phase treatment are as follows: the concentration of aqueous monomer in the aqueous solution is 1% to 3%, the concentration of co-solvent is 5% to 10%, and the standing time is 5 to 8 hours.

[0025] Optionally, the aqueous monomer includes one or a combination of m-phenylenediamine, p-phenylenediamine, piperazine, and diethylenetriamine.

[0026] Optionally, the co-solvent is ethanol.

[0027] Furthermore, the conditions for the oil phase treatment are as follows: the concentration of oil phase monomers in the oil phase solution is 0.2%~0.8%, and the standing time is 8~12h.

[0028] Optionally, the oil phase monomer includes one or a combination of several of pyromellitic methyl chloride, isophthaloyl chloride, and sebacate.

[0029] Optionally, the oil phase solvent is one or a combination of several of n-hexane, cyclohexane, and kerosene.

[0030] Optionally, the sun-drying conditions are: sun-drying temperature 20-40℃, sun-drying to constant weight.

[0031] Furthermore, the vacuum drying conditions are: vacuum drying temperature 50-80℃, vacuum degree -0.05MPa to -0.1MPa, and vacuum drying time 2-5 h.

[0032] Furthermore, the conditions for plasma treatment are: discharge current 2~8 A, discharge duration 120~600 s.

[0033] Furthermore, the grafting reaction conditions are as follows: grafting monomer solution concentration 2%~10%, grafting reaction time 30~120 min, and grafting reaction temperature 20~60℃.

[0034] Optionally, the grafting monomer is one or a combination of several of vinylbenzyltrimethylammonium chloride, methacryloyloxyethyltrimethylammonium chloride, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, and acryloyloxyethyltrimethylammonium chloride.

[0035] Optionally, the anion exchange base membrane is made of one or a combination of polyvinylidene fluoride (PVDF), polypropylene (PP), polytetrafluoroethylene (PTFE), and polysulfone (PSF).

[0036] In a second aspect, the present invention provides a bromine extraction system for bromine-containing brine, comprising a diaphragm electrolysis module and a gaseous membrane absorption module;

[0037] The diaphragm electrolysis module includes:

[0038] Used to remove Br from high-hardness bromine-containing brine to be treated - An anode plate used for electrolytic oxidation to generate Br2;

[0039] Cathode plate used for electrolyzing sodium chloride solution to produce sodium hydroxide;

[0040] The anion exchange membrane prepared by the method of any one of the first aspects is disposed between the anode plate and the cathode plate to isolate the anode chamber and the cathode chamber.

[0041] The gaseous membrane absorption module includes a hollow fiber gaseous membrane assembly for absorbing and extracting Br2 generated at the anode;

[0042] The hollow fiber gaseous membrane module is placed in the anode chamber.

[0043] In the above technical solution, the core of the diaphragm electrolysis module is the anode plate, the cathode plate, and the anion exchange membrane. During system operation, acidified high-hardness bromine-containing brine is transported to the anode chamber. The anode chamber parameters are set according to the preset electrolysis conditions. Bromine ions in the high-hardness bromine-containing brine are electrolyzed and oxidized on the anode plate, converting into bromine molecules Br2. Calcium ions in the high-hardness bromine-containing brine cannot pass through the anion exchange membrane and are retained on the anolyte side. The catholyte is transported to the cathode chamber. Under the preset electrolysis conditions, chloride ions in the catholyte migrate to the anode chamber through the anion exchange membrane. At the same time, a reduction reaction occurs in the cathode chamber to generate hydrogen gas. At this time, the catholyte changes from sodium chloride to sodium hydroxide. The catholyte after the reaction can be used as an absorbent in hollow fiber gaseous membrane modules.

[0044] The core of the gaseous membrane absorption module is a hollow fiber gaseous membrane assembly. During system operation, bromide ions in the high-hardness bromine-containing brine are electrolytically oxidized on the anode plate to form bromine molecules Br2 in the anode chamber. The bromine molecules Br2 diffuse through the hollow fiber gaseous membrane assembly to the tube side of the gaseous membrane element of the hollow fiber gaseous membrane assembly. The absorbent is then transported to the tube side of the gaseous membrane element, and the diffused bromine molecules Br2 react with the absorbent to achieve bromine enrichment in the absorbent.

[0045] Optionally, the top of the cathode chamber is provided with a sealed partition to prevent Br2 from escaping.

[0046] Optionally, the hollow fiber gaseous membrane module is disposed in the anode chamber on the side near the anode plate.

[0047] Optionally, the anode plate may be made of one of the following materials: graphite, boron-doped diamond, lead oxide, platinum, and titanium-coated noble metal electrodes.

[0048] Optionally, the material of the gaseous membrane of the hollow fiber gaseous membrane module includes one of polytetrafluoroethylene, polyvinylidene fluoride, and polypropylene.

[0049] Thirdly, the present invention provides a method for extracting bromine from bromine-containing brine, based on the bromine extraction system for bromine-containing brine described in the second aspect, comprising the following steps:

[0050] The acidity of the bromine-containing brine is adjusted to obtain acidified bromine-containing brine;

[0051] Acidified bromine-containing brine is passed into an anode chamber isolated by an anion exchange membrane for electrolytic oxidation to obtain Br2;

[0052] The catholy solution is passed into the cathode chamber for electrolysis to obtain the reacted catholy solution.

[0053] The catholy solution after the reaction is transported to the gaseous membrane absorption module as the absorbent.

[0054] Br2 is absorbed using a hollow fiber gaseous membrane module of the gaseous membrane absorption module to obtain bromine-extracted products.

[0055] In the above technical solution, the anion exchange membrane prepared by the preparation method of the first aspect is applied to the bromine extraction method of diaphragm electrolysis-gas membrane absorption coupling in bromine-containing brine, realizing the extraction of bromine element in bromine-containing brine system. On the one hand, it avoids the scaling problem of calcium and magnesium ions on the cathode in high hardness system; on the other hand, after modification, it can improve the antioxidant and anti-fouling ability of the anion membrane in bromine-containing system, prevent impurities and pollutants from entering the cathode side, improve the purity of sodium hydroxide on the cathode side, and can be used as the absorbent of gas membrane.

[0056] By controlling the oxidation-reduction potential range through electro-oxidation technology, bromide ions are electrolytically oxidized to bromine without the need for additional oxidants, avoiding the use of chlorine gas, improving system safety while reducing reagent costs, and offering simple and environmentally friendly operation. Using hollow fiber gaseous membrane modules for gaseous membrane bromine separation technology, compared to traditional air stripping bromine extraction technology, reduces the footprint and power costs, achieving a bromine extraction rate of over 80%, with low energy consumption and simple operation. Coupled with electro-oxidation, the entire process is simple to operate. This bromine extraction method achieves bromine resource recovery in an environmentally friendly and low-cost manner, realizing the resource recovery and efficiency of wastewater.

[0057] Optionally, the acidity is adjusted by setting the pH to below 3.

[0058] In the above technical solution, the oxidation of bromide ions to bromine requires low acidity conditions, with the pH adjusted to below 3, which is beneficial for the extraction of bromine-containing wastewater. Considering that hydroxide ions generated in the cathode chamber can easily migrate to the anode chamber through the anion exchange membrane, adjusting the pH to below 3 can also avoid the hydrolysis of elemental bromine and the precipitation of easily scale-forming ions such as calcium and magnesium.

[0059] Furthermore, the conditions for the electrolytic oxidation are as follows: the electrochemical oxidation potential is 0.9~1.4 V, the reaction pH in the anode chamber is 1.5~3, the temperature of the bromine-containing brine is 25℃~45℃, and the electrolytic oxidation residence time is 0.5-4h.

[0060] In the above technical solution, the electrochemical oxidation potential is 0.9~1.4 V to avoid the over-oxidation of bromine. The technical parameters obtained from the above experiment can convert bromide ions into Br2, thus avoiding their over-oxidation into BrO3.

[0061] Optionally, the Br2 absorption conditions are as follows: the bromine content of the absorbent in the hollow fiber gas membrane module is 3~3.5 mol / L.

[0062] In the above technical solution, the bromine content of the absorption liquid is controlled at 3~3.5 mol / L. Replacing the absorption liquid with a new one can prevent the absorption liquid from becoming oversaturated and reducing the treatment efficiency.

[0063] Optionally, the absorbent includes one or a combination of sodium hydroxide, potassium hydroxide, sodium sulfite, and potassium sulfite.

[0064] Optionally, the electrolysis conditions are as follows: the electrolyte concentration in the cathode chamber is 10%-30%.

[0065] In the above technical solution, an electrolyte concentration of 10%-30% can efficiently reduce bromine for bromine collection.

[0066] Optionally, the cathode liquid is sodium chloride.

[0067] Optionally, the acidity is adjusted using 31% hydrochloric acid as a pH adjuster.

[0068] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0069] The anion exchange membrane prepared by the method of the present invention is applied to the bromine extraction method of diaphragm electrolysis-gas membrane absorption coupling in bromine-containing brine. On the one hand, it avoids the scaling problem of calcium and magnesium ions at the cathode in high hardness systems; on the other hand, after modification, it can improve the antioxidant and antifouling ability of the anion exchange membrane in bromine-containing systems, prevent impurities and pollutants from entering the cathode side, improve the purity of sodium hydroxide on the cathode side, and can be used as the absorbent of the gas membrane.

[0070] By controlling the oxidation-reduction potential range through electro-oxidation technology, bromide ions are electrolytically oxidized to bromine without the need for added acid or additional oxidants, avoiding the use of chlorine gas, improving system safety while reducing reagent costs, and offering simple and environmentally friendly operation. Using hollow fiber gaseous membrane modules for gaseous membrane bromine separation technology, compared to traditional air stripping bromine extraction technology, reduces the footprint and power costs, achieving a bromine extraction rate of over 80%, with low energy consumption and simple operation. Coupled with electro-oxidation, the entire process is simple to operate. This bromine extraction method achieves bromine resource recovery in an environmentally friendly and low-cost manner, realizing the resource recovery and efficiency of wastewater. Attached Figure Description

[0071] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0072] Figure 1This is a schematic diagram of the bromine extraction system of diaphragm electrolysis-gas membrane absorption coupling for bromine-containing brine according to some embodiments of the present invention.

[0073] Explanation of reference numerals in the attached figures:

[0074] 1. Anode plate; 2. Cathode plate; 3. Hollow fiber gaseous membrane module; 4. Anion exchange membrane; 5. Anode chamber; 6. Cathode chamber; 7. Power supply; 8. Bromine-containing feed pump; 9. Absorbent pump; 10. Cathode liquid pump; 11. Raw material tank; 12. Absorbent storage tank; 13. Cathode liquid storage tank. Detailed Implementation

[0075] The above content is further illustrated below with specific embodiments, but it should not be construed as limiting the scope of the invention to the following embodiments. All technologies implemented based on the above content of this invention fall within the scope of this invention.

[0076] It should be understood that all experimental procedures not detailed in the experiment are routine experimental procedures well known to those skilled in the art.

[0077] Example 1

[0078] This embodiment provides a method for preparing (modifying) anion exchange membranes for bromine extraction via diaphragm electrolysis-gas membrane absorption coupling, comprising the following steps:

[0079] Pretreatment of polyvinylidene fluoride membrane: The polyvinylidene fluoride membrane was sanded with sandpaper and then soaked in 3mol / L hydrochloric acid for 2 hours.

[0080] The pretreated polyvinylidene fluoride (PVDF) membrane was placed in a plasma device for plasma treatment. The discharge current was set to 4 A and the discharge time to 360 s. The plasma-treated anion exchange membrane was then placed in vinylbenzyltrimethylammonium chloride for grafting reaction. The concentration of the grafting monomer solution was 6%, the grafting reaction time was 60 min, and the grafting reaction temperature was 30℃. After grafting, the PVDF membrane was dried with filter paper and fixed in an interfacial polymerization reaction chamber. A 2% aqueous solution of m-phenylenediamine was poured into the reaction chamber and allowed to stand for 5 h. Then, the water was drained and the membrane was dried in a fume hood. A 0.4% cyclohexane oil solution of isophthaloyl chloride was then poured in evenly. After 8 h, the reaction solution was drained immediately and the membrane was placed in a vacuum drying oven for 2 h to obtain an anion exchange membrane 4 for bromine extraction via membrane electrolysis-gas membrane absorption coupling.

[0081] Example 2

[0082] This embodiment provides a bromine extraction system for bromine-containing brine via diaphragm electrolysis and gaseous membrane absorption coupling, such as... Figure 1As shown, it includes a diaphragm electrolysis module and a gaseous membrane absorption module;

[0083] The diaphragm electrolysis module includes:

[0084] Used to remove Br from high-hardness bromine-containing brine to be treated - An anode plate 1 for electrolytic oxidation to generate Br2; a cathode plate 2 for electrolytic oxidation of sodium chloride solution to generate sodium hydroxide; an anion exchange membrane 4 prepared using the preparation method of Example 1, wherein the anion exchange membrane 4 is disposed between the anode plate 1 and the cathode plate 2 to isolate the anode chamber 5 and the cathode chamber 6; the gaseous membrane absorption module includes a hollow fiber gaseous membrane assembly 3 for absorbing and extracting the Br2 generated at the anode; the hollow fiber gaseous membrane assembly 3 is placed in the anode chamber 5.

[0085] Example 3

[0086] This embodiment provides a specific bromine extraction system for bromine-containing brine using a membrane electrolysis-gas membrane absorption coupling method, based on Embodiment 2. Figure 1 As shown, it includes a diaphragm electrolysis module and a gaseous membrane absorption module. The core of the diaphragm electrolysis module is an anode plate 1, a cathode plate 2, and an anion exchange membrane 4 prepared using the preparation method of Example 1. The core of the gaseous membrane absorption module is a hollow fiber gaseous membrane module 3.

[0087] The bromine extraction system specifically includes an anode plate 1, a cathode plate 2, a hollow fiber gaseous membrane module 3, an anion exchange membrane 4, an anode chamber 5, a cathode chamber 6, a power supply 7, a bromine-containing feed liquid transfer pump 8, an absorbent transfer pump 9, a cathode liquid transfer pump 10, a raw material tank 11, an absorbent storage tank 12, and a cathode liquid storage tank 13.

[0088] The positive terminal of the power supply 7 is connected to the anode plate 1, and the negative terminal of the power supply 7 is connected to the cathode plate 2. The anion exchange membrane 4 is disposed between the anode plate 1 and the cathode plate 2, isolating the anode chamber 5 and the cathode chamber 6. The outlet of the raw material tank 11 is connected to the inlet of the bromine-containing liquid transfer pump 8, and the outlet of the bromine-containing liquid transfer pump 8 is connected to the anode chamber 5. The outlet of the cathode liquid storage tank 13 is connected to the inlet of the cathode liquid transfer pump 10, and the outlet of the cathode liquid transfer pump 10 is connected to the cathode chamber 6. The outlet of the absorbent liquid storage tank 12 is connected to the inlet of the absorbent liquid transfer pump 9, the outlet of the absorbent liquid transfer pump 9 is connected to the inlet of the hollow fiber gaseous membrane module 3, and the outlet of the hollow fiber gaseous membrane module 3 is connected to the circulation inlet of the absorbent liquid storage tank 12.

[0089] During operation of the above-mentioned bromine-containing brine diaphragm electrolysis-gas membrane absorption coupled bromine extraction system, the operating status of the diaphragm electrolysis module is as follows:

[0090] The acidified high-hardness bromine-containing brine is transported from the raw material tank 11 to the anode chamber 5 by the bromine-containing liquid transfer pump 8. The power supply 7 is turned on, and the electrochemical potential, electrolysis oxidation time, pH and temperature of the anode chamber are adjusted according to the preset electrolysis oxidation conditions, so that the bromide ions in the high-hardness bromine-containing brine are electrolyzed and oxidized on the anode plate 1 and converted into bromine molecules Br2. The calcium ions in the high-hardness bromine-containing brine cannot pass through the anion exchange membrane 4 and are trapped in the anode chamber 5.

[0091] The cathode liquid transfer pump 10 is turned on to transport the cathode liquid from the cathode liquid storage tank 13 to the cathode chamber 6. Under the preset electrolytic oxidation conditions, the chloride ions in the cathode liquid migrate to the anode chamber 5 through the anion exchange membrane 4. At the same time, a reduction reaction occurs in the cathode chamber 6 to generate hydrogen gas. At this time, the cathode liquid is changed from sodium chloride to sodium hydroxide. The catholy liquid after the reaction can be transported to the absorbent storage tank 12 for use as an absorbent.

[0092] The operating status of the gaseous membrane absorption module is as follows:

[0093] The bromide ions in the high-hardness bromine-containing brine are electrolytically oxidized on the anode plate 1 to form bromine molecules Br2 in the anode chamber 5. The bromine molecules Br2 diffuse through the hollow fiber gaseous membrane module 3 to the tube side of the gaseous membrane element of the hollow fiber gaseous membrane module 3. The absorbent transfer pump 9 is turned on to transport the absorbent from the absorbent storage tank 12 to the tube side of the gaseous membrane element. The diffused bromine molecules Br2 react with the absorbent to achieve the enrichment of bromine in the absorbent.

[0094] Among them, the membrane material of hollow fiber gaseous membrane module 3 is polytetrafluoroethylene (PTFE).

[0095] Sodium chloride is used as the catholyte, and part of the absorbent is sodium hydroxide obtained by electrolysis in cathode chamber 6. Solid sodium hydroxide is added to adjust the concentration of sodium hydroxide in the absorbent to 3 mol / L. The diffused bromine molecules Br2 react with the sodium hydroxide absorbent to obtain sodium bromide and sodium bromate solutions. The sodium bromide and sodium bromate solutions obtained by absorption and enrichment are separated and purified by operations such as evaporation and crystallization.

[0096] The cathode chamber 6 is equipped with a sealed partition at the top to prevent Br2 from escaping; the hollow fiber gaseous membrane assembly is located in the anode chamber 5 on the side near the anode plate 1; the anode plate 1 is made of boron-doped BDD electrode (diamond electrode).

[0097] Among them, the hollow fiber gaseous membrane module is composed of multiple U-shaped hollow fiber membrane filaments. The lower part of the multiple U-shaped membrane filaments is fixed to the anode chamber 5 by a component to prevent the membrane filaments from floating. The peristaltic pump for conveying the absorbent is connected inside the membrane filaments of the hollow fiber gaseous membrane module so that the absorbent can be circulated and conveyed.

[0098] Example 4

[0099] This embodiment provides a bromine extraction method based on the bromine-containing brine diaphragm electrolysis-gas membrane absorption coupled bromine extraction system of Embodiment 3, including the following steps:

[0100] The pH of the high-hardness bromine-containing brine was adjusted to 2.5 using 31% hydrochloric acid to obtain acidified bromine-containing brine.

[0101] Acidified bromine-containing brine was pumped into the anode chamber 5 of the bromine extraction system in Example 3. The electrolysis voltage was set to 1.2 V, the solution temperature in the anode chamber 5 was set to 26 °C, the running time was set to 2 h, and the reaction pH in the anode chamber 5 was set to 2.5 for electrolytic oxidation to obtain Br2. By detecting the brine ion concentration at the outlet of the anode chamber 5 at different residence times, the pumping rate of the subsequently acidified raw brine and the discharge rate of the brine after bromine extraction were determined to maintain the dynamic balance of the initial concentration of brine ions in the electrolysis.

[0102] Fresh sodium hydroxide absorbent is pumped into the membrane fibers of the central control fiber gas membrane module 3 to absorb Br2, resulting in sodium bromide and sodium bromate solutions. The absorption is circulated until the bromine content of the absorbent is above 3 mol / L, at which point the fresh absorbent is replaced.

[0103] Sodium hydroxide obtained by electrolysis in cathode chamber 6 is used as the absorbent in part of the centrally controlled fiber gaseous membrane module 3. The sodium bromide and sodium bromate solutions obtained by absorption and enrichment are separated and purified by operations such as evaporation and crystallization.

[0104] Testing revealed that the organic matter permeability of cathode chamber 6 was 5.1%, and the purity of the final separated sodium bromide product was 98.5%, while the purity of the sodium bromate product was 95%.

[0105] Comparative Example 1

[0106] This comparative example provides a treatment method for a bromine-containing brine diaphragm electrolysis-gas membrane absorption coupled bromine extraction system. All other steps are the same as in Example 4, except that the discharge current of the plasma treatment in the preparation method of the anion exchange membrane 4 is 2 A.

[0107] Testing revealed that the organic matter permeability of cathode chamber 6 was 8.3%, and the purity of the final separated sodium bromide product was 97.9%, while the purity of the sodium bromate product was 93.3%.

[0108] Comparative Example 2

[0109] This comparative example provides a treatment method for a bromine-containing brine diaphragm electrolysis-gas membrane absorption coupled bromine extraction system. All other steps are the same as in Example 4, except that the plasma treatment discharge time in the preparation method of the anion exchange membrane 4 is 600 s.

[0110] Testing revealed that the organic matter permeability of cathode chamber 6 was 9.6%, and the purity of the final separated sodium bromide product was 96.1%, while the purity of the sodium bromate product was 92.1%.

[0111] Comparative Example 3

[0112] This comparative example provides a method for treating bromine-containing brine using a membrane electrolysis-gas membrane absorption coupled bromine extraction system. All other steps are the same as in Example 4, except that the concentration of the grafted monomer solution in the preparation method of the anion exchange membrane 4 is 9%.

[0113] Testing revealed that the organic matter permeability of cathode chamber 6 was 10.2%, and the purity of the final separated sodium bromide product was 94.8%, while the purity of the sodium bromate product was 92.7%.

[0114] Comparative Example 4

[0115] This comparative example provides a treatment method for a bromine-containing brine diaphragm electrolysis-gas membrane absorption coupled bromine extraction system. All other steps are the same as in Example 4, except that the grafting reaction time in the preparation method of the anion exchange membrane 4 is 30 min.

[0116] Testing revealed that the organic matter permeability of cathode chamber 6 was 10.6%, and the purity of the final separated sodium bromide product was 95.2%, while the purity of the sodium bromate product was 93.1%.

[0117] Comparative Example 5

[0118] This comparative example provides a method for treating bromine-containing brine using a membrane electrolysis-gas membrane absorption coupled bromine extraction system. All other steps are the same as in Example 4, except that the grafting reaction temperature in the preparation method of the anion exchange membrane 4 is 20°C.

[0119] Testing revealed that the organic matter permeability of cathode chamber 6 was 7.4%, and the purity of the final separated sodium bromide product was 97.5%, while the purity of the sodium bromate product was 94.2%.

[0120] Comparative Example 6

[0121] This comparative example provides a method for treating bromine-containing brine using a membrane electrolysis-gas membrane absorption coupled bromine extraction system. All other steps are the same as in Example 4, except that the concentration of the oil phase monomer in the preparation method of the anion exchange membrane 4 is 0.2%.

[0122] Testing revealed that the organic matter permeability of cathode chamber 6 was 9.8%, and the purity of the final separated sodium bromide product was 96.5%, while the purity of the sodium bromate product was 92.8%.

[0123] Comparative Example 7

[0124] This comparative example provides a treatment method for a bromine-containing brine diaphragm electrolysis-gas membrane absorption coupled bromine extraction system. All other steps are the same as in Example 4, except that the concentration of aqueous monomer in the preparation method of anion exchange membrane 4 is 1.5%.

[0125] Testing revealed that the organic matter permeability of cathode chamber 6 was 10.1%, and the purity of the final separated sodium bromide product was 96.9%, while the purity of the sodium bromate product was 93.8%.

[0126] The experimental results above show that the bromine extraction system and method for bromine-containing brine using diaphragm electrolysis-gas membrane absorption coupling can selectively oxidize bromide ions to elemental bromine without adding any oxidizing agents. Sodium hydroxide obtained from the electrolysis of sodium chloride in the cathode chamber is used as the absorbent to absorb and enrich elemental bromine, converting it into industrial products such as sodium bromide and sodium bromate. By setting up and modifying anion exchange membranes, the purity of the downstream bromine products is improved, avoiding the impact of organic matter and easily scale-forming ions on system operation and product purity. This achieves the goal of economical, environmentally friendly, safe, and convenient bromine resource utilization.

Claims

1. A method for producing an anion exchange membrane, characterized by, The method comprises the following steps: The anion exchange base film is pretreated and then subjected to plasma treatment; The anion exchange base film subjected to plasma treatment is placed in a grafting monomer solution to perform grafting reaction; The anion exchange base film after grafting reaction is subjected to interfacial polymerization treatment to obtain an anion exchange membrane (4) for electrolysis-gaseous membrane absorption coupling bromine extraction.

2. The method for producing an anion exchange membrane according to claim 1, characterized by, The interfacial polymerization treatment comprises: The anion exchange base film after grafting reaction is fixed in an interfacial polymerization reaction pool frame, and the grafting monomer solution on the surface of the anion exchange base film after grafting reaction is absorbed; A water phase solution is poured into the interfacial polymerization reaction pool to perform water phase treatment; The anion exchange base film after water phase treatment is drained of water and then is air-dried; The anion exchange base film after air-drying is placed in the interfacial polymerization reaction pool, and an oil phase solution is poured into the interfacial polymerization reaction pool to perform oil phase treatment; The anion exchange base film after oil phase treatment is drained of the oil phase solution and then is vacuum-dried.

3. The method for producing an anion exchange membrane according to claim 2, characterized by, The water phase treatment is performed under the following conditions: the water phase monomer concentration in the water phase solution is 1% to 3%, the cosolvent concentration is 5% to 10%, and the standing time is 5 to 8 h.

4. The method for producing an anion exchange membrane according to claim 2, characterized by, The oil phase treatment is performed under the following conditions: the oil phase monomer concentration in the oil phase solution is 0.2% to 0.8%, and the standing time is 8 to 12 h.

5. The method for producing an anion exchange membrane according to claim 2, characterized by, The vacuum drying is performed under the following conditions: the vacuum drying temperature is 50 to 80℃, the vacuum degree is -0.05 MPa to -0.1 MPa, and the vacuum drying time is 2 to 5 h.

6. The method for producing an anion exchange membrane according to claim 1, characterized by, The plasma treatment is performed under the following conditions: the discharge current is 2 to 8 A, and the discharge time is 120 to 600 s.

7. The method for producing an anion exchange membrane according to claim 1, characterized by, The grafting reaction is performed under the following conditions: the grafting monomer solution concentration is 2% to 10%, the grafting reaction time is 30 to 120 min, and the grafting reaction temperature is 20 to 60℃.

8. A system for bromine extraction from a bromine-containing brine, characterized in that, The method comprises a diaphragm electrolysis module and a gaseous membrane absorption module. The diaphragm electrolysis module comprises: Process for the removal of Br from high-hard bromine-containing brines - Anode plate (1) for the electrolytic oxidation to Br2 a cathode plate (2) for electrolyzing sodium chloride solution to generate sodium hydroxide; The anion exchange membrane (4) prepared by the method of any one of claims 1 to 7 is arranged between the anode plate (1) and the cathode plate (2) to separate an anode chamber (5) and a cathode chamber (6). The gaseous membrane absorption module comprises a hollow fiber type gaseous membrane module (3) for absorbing Br2 generated by the anode. The hollow fiber type gaseous membrane module (3) is arranged in the anode chamber (5).

9. A method for bromine extraction from a bromine-containing brine, based on the system for bromine extraction from a bromine-containing brine according to claim 8, characterized in that, The method comprises the following steps: The acidity of the bromine-containing brine is adjusted to obtain acidified bromine-containing brine; The acidified bromine-containing brine is introduced into the anode chamber (5) separated by the anion exchange membrane (4) to perform electrolytic oxidation to obtain Br2; The cathode liquid is introduced into the cathode chamber (6) to perform electrolysis to obtain reacted cathode liquid; The reacted cathode liquid is transported to the gaseous membrane absorption module as absorption liquid; The hollow fiber type gaseous membrane module (3) of the gaseous membrane absorption module absorbs Br2 to obtain a bromine extraction product.

10. The method of claim 9, wherein the bromine-containing brine is characterized by, The electrolytic oxidation is performed under the following conditions: the electrochemical oxidation potential is 0.9 to 1.4 V, the reaction pH of the anode chamber (5) is 1.5 to 3, the temperature of the bromine-containing brine is 25℃ to 45℃, and the electrolytic oxidation residence time is 0.5 to 4 h.

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