Electro-adsorption material for electrochemical extraction of bromine and preparation method and application thereof

Abstract

The application provides an electrosorption material for electrochemically extracting bromine and a preparation method and application thereof. The electrosorption material comprises bismuth oxybromide nanosheets and polyethylenedioxythiophene loaded on the surface of the bismuth oxybromide nanosheets, and the mass ratio of the bismuth oxybromide nanosheets to the polyethylenedioxythiophene is 1-10:0.1-5. The electrosorption material provided by the application has a large adsorption capacity, good cycle stability and excellent selective adsorption. The electrosorption material still has adsorption capacity for a solution with a bromide ion content of less than 100 mg / L, and is suitable for extracting bromine in oilfield brine.

Description

Technical Field

[0001] This invention belongs to the field of bromine extraction technology, specifically relating to an electroadsorption material for electrochemical extraction of bromine, its preparation method, and its application. Background Technology

[0002] Bromine is an important chemical raw material, mainly used in fine chemicals, high-end manufacturing, environmental protection, petrochemicals, pharmaceuticals, and energy storage. It has over a hundred related high-value-added products and is an essential resource for a complete industrial system. The demand for bromine and bromine-based chemicals is increasing year by year, making it a scarce resource in my country. Bromine resources mainly include groundwater from oil and gas fields, brine from salt lakes, bittern from sea salt fields, and brine from salt mines. Among these, underground brine from oil and gas fields and brine from salt lakes have the highest relative bromine concentration and the best quality. Therefore, bromine extraction from brine has attracted increasing attention.

[0003] my country's bromine resources are low in grade and limited in quantity, mainly originating from underground brine in Shandong Province. Due to continuous extraction year after year, the bromine content of this brine has rapidly declined, leading to increased extraction costs and difficulties. Therefore, the development of bromine extraction technologies suitable for low-grade resources is receiving increasing attention. Furthermore, due to technological issues, the utilization rate of underground brine is low, resulting in significant resource waste and a bromine resource crisis, necessitating the development and utilization of more bromine-containing resources. However, extracting bromine from brine faces many challenges, such as the low bromine content and the interference of chlorine present in the brine with extraction processes.

[0004] To selectively extract bromine from brine, various bromine extraction technologies have emerged, including common methods such as adsorption, solvent extraction, and precipitation. Considering environmental factors, ion exchange, membrane separation, and electrically switched ion exchange (ESIX) have also been proposed. Compared to ESIX, other technologies suffer from drawbacks such as long production cycles, high costs, environmental unfriendliness, and complex processes. Therefore, the more efficient, energy-saving, and environmentally friendly ESIX technology has attracted significant attention. This technology selectively extracts target ions (such as Li₂O₃) by adjusting the redox state of electroactive ion exchange materials (EXIMs) coated on a thin-film electrode. + ,Br - Cl - I - Cs + Rapid adsorption and desorption of ions (such as...). With continuous improvement and optimization of electroactive ion exchange materials, the adsorption capacity for target ions and the cycling stability of the materials themselves have been significantly improved.

[0005] ESIX technology operates under mild conditions, using electricity as the driving force. Besides the chemical or physical adsorption of the membrane material itself, the application of potential increases its adsorption and desorption of cations and anions, making it suitable for separating ions at low concentrations in solution. The separation process requires no chemical regeneration, avoiding secondary pollution from chemical regenerators. Applying this technology to the separation of bromine from oilfield brine hinges on developing a functional membrane material that is both electroactive and selectively adsorbs bromine ions. Electroactive materials can conduct both electrons and ions; by altering the redox state of the electroactive material, the insertion and removal of target ions can be achieved. However, currently used electrode active materials for bromine extraction from oilfield brine have low adsorption capacity and poor cycling performance, failing to effectively meet the practical application requirements of bromine extraction from oilfield brine. Summary of the Invention

[0006] To solve all or part of the above-mentioned technical problems, the present invention provides the following technical solutions:

[0007] One of the objectives of this invention is to provide an electroadsorption material for the electrochemical extraction of bromine, the electroadsorption material comprising bismuth oxybromine nanosheets and polyethylene dioxythiophene (PEDOT) coated on the surface of the bismuth oxybromine nanosheets, wherein the mass ratio of the bismuth oxybromine nanosheets to the polyethylene dioxythiophene is 1~10:0.1~5.

[0008] The PEDOT in the electroadsorption material forms a conjugated molecular chain with freely moving π electrons. When an electric field is applied, the π electrons move in a directional manner to form a current. Combining it with bismuth oxybromine nanosheets can improve the conductivity and adsorption performance of the composite material. The electroadsorption material has a large adsorption capacity, fast adsorption rate and excellent selective adsorption for bromine, and is not affected by other anions in the sample during adsorption. Furthermore, the composite material also exhibits good cycling stability and low solubility.

[0009] In some embodiments, according to BET testing, the specific surface area of ​​the electroadsorption material is 5 to 10 times that of pure bismuth oxybromine nanosheets. Pure bismuth oxybromine nanosheets have a relatively smooth surface, resulting in poor conductivity and low adsorption efficiency when used directly as a bromine adsorption material. This invention discovers that the surface roughness of bismuth oxybromine nanosheets coated with PEDOT increases. This rough surface increases the specific surface area of ​​the material, making it 5 to 10 times larger than that of uncomposite bismuth oxybromine nanosheets, thus providing more abundant active sites for bromine capture and release.

[0010] In some embodiments, the bismuth oxybromine nanosheets have a diameter of 50-1000 nm and a thickness of 50-500 nm, and the poly(ethylene dioxythiophene) coating thickness on the surface of the bismuth oxybromine nanosheets is 10-1000 nm.

[0011] Thermogravimetric analysis (TG test) showed that the initial weight loss temperature of the electroadsorption material was 350℃, indicating that it has good high temperature resistance and can adapt to most brine temperature environments.

[0012] The second objective of this invention is to provide a method for preparing the aforementioned electroadsorption material, comprising:

[0013] Bismuth oxybromide nanosheets were synthesized using a hydrothermal method.

[0014] A mixed reaction system containing the bismuth oxybromine nanosheets, 3,4-ethylenedioxythiophene (EDOT), ammonium persulfate and / or ferric chloride is reacted at 0°C to 5°C to polymerize the 3,4-ethylenedioxythiophene into polyethylenedioxythiophene, which is then coated onto the surface of the bismuth oxybromine nanosheets, thereby obtaining an electroadsorption material composed of bismuth oxybromine nanosheets and polyethylenedioxythiophene.

[0015] In the presence of ammonium persulfate and / or ferric chloride, EDOT undergoes a polymerization reaction to generate PEDOT, which is then coated onto the surface of bismuth oxybromide nanosheets. The resulting electroadsorption material exhibits significantly improved surface roughness and an appropriate coating thickness, enabling bromide ions to pass through the PEDOT shell into the BiOBr interlayer.

[0016] In some embodiments, the concentration of bismuth oxybromide nanosheets in the mixed reaction system is 23~200 g / L.

[0017] In some embodiments, the mass ratio of bismuth oxybromide nanosheets to 3,4-ethylenedioxythiophene in the mixed reaction system is 1~10:0.1~5.

[0018] In some embodiments, the concentration of ammonium persulfate and / or ferric chloride in the mixed reaction system is 0.1~5 mol / L.

[0019] In some embodiments, the reaction time is 8 to 16 hours.

[0020] In some embodiments, the hydrothermal method includes: reacting a reaction system containing a bismuth source, a bromine source, a strong base, and a solvent at a temperature of 150-180°C, wherein the pH of the reaction system is 5-8, to obtain bismuth oxybromine nanosheets.

[0021] In some embodiments, the concentration of the bismuth source in the reaction system is 0.1~1 mol / L, and the concentration of the bromine source is 0.1~1 mol / L.

[0022] In some embodiments, the bismuth source includes Bi(NO3)3∙5H2O, and the bromine source includes KBr.

[0023] In some embodiments, the concentration of the strong base in the reaction system is 0.1 mol / L. The strong base includes, for example, one or a combination of NaOH and KOH.

[0024] In some embodiments, the reaction time is 8 to 12 hours.

[0025] A third objective of this invention is to provide a bromine-active electrode, wherein the bromine-active electrode comprises the aforementioned electroadsorption material.

[0026] In some embodiments, the bromine active electrode includes a conductive substrate and a composite film layer formed on the conductive substrate, the composite film layer including the electroadsorption material, the conductive material, and the binder.

[0027] In some embodiments, the mass ratio of the electroadsorption material, conductive material, and binder is 4~8:0.1~1:0.5~1.5. For example, the electroadsorption material, conductive material, and binder are uniformly mixed according to the above mass ratio, and an appropriate amount of solvent is added to form a slurry. The slurry is then coated onto a conductive substrate and cured to form the composite film layer. The slurry made from the electroadsorption material has good ductility, allowing for large-area and long-term use with small-batch preparation; the electroadsorption material is low in cost and has good economic advantages, thus possessing promising prospects for industrialization and commercialization.

[0028] In some embodiments, the conductive material includes one or more of carbon black, graphene, and acetylene black, but is not limited thereto.

[0029] In some embodiments, the adhesive includes one or more of polyvinylidene fluoride, polyacrylic acid, polymethacrylic acid, and polyvinyl alcohol, but is not limited thereto.

[0030] In some embodiments, the conductive substrate is made of one or more of carbon, titanium, and nickel, but is not limited thereto. For example, the conductive substrate may be carbon paper, carbon sheet, titanium sheet, nickel foam, etc.

[0031] The fourth objective of this invention is to provide a system for extracting bromine, comprising: a working electrode, a counter electrode, and a reference electrode, wherein the working electrode is the aforementioned bromine active electrode.

[0032] The fifth objective of this invention is to provide the application of the electroadsorption material, the bromine active electrode, or the bromine extraction system in the extraction of bromine from brine.

[0033] In some embodiments, the brine is oilfield brine. This invention reveals that the electroadsorption material composed of bismuth oxybromine nanosheets and the aforementioned polyethylene dioxythiophene exhibits strong stability, and its bromide ion extraction is controlled by the applied redox potential, making it less susceptible to interference from other impurities in the sample. This makes it particularly suitable for bromide ion extraction from oilfield brine or other more extreme environments.

[0034] The sixth objective of this invention is to provide a method for extracting bromine from oilfield brine, using the aforementioned bromine extraction system, comprising:

[0035] The bromine active electrode in the system is pretreated by placing the bromine active electrode in water and applying a voltage of -0.8 to -1.2V to desorb at least some of the bromine in the bromine active electrode.

[0036] The pretreated bromine-active electrode is placed in oilfield brine, and a voltage of 0.6-1.2V is applied to cause the bromine-active electrode to adsorb bromide ions in the oilfield brine to achieve bromine extraction.

[0037] The method for extracting bromine from oilfield brine does not require acid or alkali washing to remove bromide ions. The adsorption and desorption of bromine can be achieved by applying voltage. The entire electro-adsorption process is simple, efficient, low-cost, and environmentally friendly.

[0038] Compared with the prior art, the present invention has at least the following beneficial effects: the electro-adsorption material for bromine extraction prepared by the present invention has a large adsorption capacity, good cycle stability and excellent selective adsorption; the electro-adsorption material still has a certain adsorption capacity for solutions with bromide ion content below 100 mg / L. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of this application 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 recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is an electron microscope image of BiOBr nanosheets prepared in one embodiment of the present invention;

[0041] Figure 2 This is an electron microscope image of the BiOBr@PEDOT composite material prepared in one embodiment of the present invention;

[0042] Figure 3 This is a schematic diagram of the extraction of bromide ions using a three-electrode system constructed in one embodiment of the present invention.

[0043] Figure 4 This is a comparison chart of the adsorption performance of the bromine active electrode prepared in one embodiment of the present invention under voltage conditions of 0.6V, 0.8V, 1.0V, and 1.2V.

[0044] Figure 5 This describes the change in adsorption capacity of a bromine active electrode prepared according to an embodiment of the present invention for a solution with an initial bromine concentration of 150 mg / L, without replacing the bromine active electrode (green mark) and with each replacement of the bromine active electrode (orange mark). Detailed Implementation

[0045] The technical solutions of the present invention will be described in detail below with reference to specific embodiments, so that those skilled in the art can better understand and implement the technical solutions of the present invention. Specific functional details disclosed herein should not be construed as limiting, but are merely intended to form the basis of the claims and to teach those skilled in the art. Unless otherwise stated,

[0046] The raw materials and reagents used in the following specific embodiments are all commercially available, and the detection and characterization methods used are conventional methods in the field.

[0047] Example 1

[0048] 3.88g 0.952 g of KBr was dispersed in 120 mL of ultrapure water and stirred continuously. Then, 1 M NaOH was added to the mixture to adjust the pH to 6. After magnetic stirring for 0.5 h, the mixture was poured into a 150 mL polytetrafluoroethylene-lined stainless steel autoclave and heated in a constant temperature drying oven at 160°C for 24 h to obtain BiOBr. After the reaction was completed, the mixture was cooled to room temperature. The prepared BiOBr was then repeatedly washed with ultrapure water and ethanol to remove residual ions, and the washed BiOBr was dried in a vacuum oven at 60°C for 12 h.

[0049] 4.58 g of 3,4-ethylenedioxythiophene was added dropwise to 100 ml of deionized water and stirred until homogeneous to form solution A. 3.05 g of the prepared bismuth oxybromine nanosheets were then added to solution A and stirred for 1 h to form solution B. 3.43 g of ammonium persulfate was dissolved in 30 ml of deionized water to form an ammonium persulfate solution. This ammonium persulfate solution was added to the stirring solution B to obtain solution C. Solution C was then stirred at 0 °C for 12 h to obtain the BiOBr@PEDOT composite material. The composite material was rinsed three times with 100 ml of 0.001 mol / L HCl solution and deionized water to remove residual polymer and other ions. The washed composite material was then dried in a vacuum drying oven at 50 °C for 12 h.

[0050] Figure 1These are electron microscope images of the BiOBr prepared in this embodiment. Figure 1 It can be seen that BiOBr exhibits a stacked nanosheet structure with a sheet diameter of approximately 787 nm and a sheet thickness of approximately 81 nm. Figure 2 This is an electron microscope image of the BiOBr@PEDOT composite material prepared in this embodiment, for comparison. Figure 1 , 2 It can be seen that BiOBr in the composite material still retains its original nanosheet structure, indicating that the modification of PEDOT did not change the structure of BiOBr. Furthermore, PEDOT is well coated on the surface of BiOBr nanosheets, transforming the original smooth surface of BiOBr nanosheets into a rougher surface. This increases the specific surface area of ​​the composite material by 6 times compared to pure BiOBr nanosheets, providing more active sites for Br capture and release.

[0051] Based on TG characterization, the mass ratio of BiOBr to PEDOT in the BiOBr@PEDOT composite material was found to be approximately 1:1.5.

[0052] According to thermogravimetric analysis, the initial weight loss temperature of the BiOBr@PEDOT composite material is 350℃, indicating that it has good high-temperature resistance.

[0053] A bromine-active electrode was prepared using the BiOBr@PEDOT composite material described above: Dry BiOBr@PEDOT composite material powder, polyvinylidene fluoride, and carbon black were mixed in a mass ratio of 8:1:1, and N-methylpyrrolidone (N-methylpyrrolidone) was added in a volume twice that of the solid powder. The mixture was then ground for 2 hours to form a uniform slurry. The slurry was then coated onto a 3 cm thick surface using a scraper. 2 A 0.5 mm thick coating is applied to carbon paper and dried at 80 °C for 5 h to form a composite film layer on the carbon paper, thus obtaining a bromine active electrode.

[0054] Adsorption-desorption operations were performed using an electrochemical workstation in a three-electrode system. The bromine active electrode prepared above was used as the working electrode, a platinum wire as the counter electrode, and an Ag / AgCl electrode as the reference electrode. Before adsorption, the working electrode was pretreated by placing it in pure water and applying a potential of -1V to desorb bromide ions from the working electrode. The pretreated working electrode was then placed in a bromine-containing solution with a concentration of 100 mg / L, and adsorption tests were performed at voltages of 0.6V, 0.8V, 1.0V, and 1.2V. Figure 3 This is a schematic diagram of the constructed three-electrode system for extracting bromide ions.

[0055] Figure 4 This describes the adsorption performance of the bromine active electrode under different voltage conditions in this embodiment. Figure 4It is evident that the bromine active electrode exhibits adsorption capacity for bromide ions within a voltage range of 0.6–1.2 V, with superior adsorption performance at 1.0 V, reaching an adsorption capacity of 16.41 mg / g. This bromine active electrode demonstrates a high adsorption rate (the adsorption data shown in Table 1 refer to the time required to reach maximum adsorption capacity), achieving maximum adsorption capacity in 30 minutes. Compared to conventional adsorbents, which require approximately two hours to reach adsorption equilibrium, the adsorption rate is significantly improved.

[0056] Table 1. Bromine adsorption performance of the bromine active electrode in Example 1 under different voltage conditions.

[0057] ;

[0058] The bromine-active electrode prepared in Example 1 was used to test its adsorption performance under low bromide ion content in solution at a voltage of 1.0 V. Figure 5 The adsorption capacity of the bromine active electrode prepared in Example 1 for a solution with an initial bromine concentration of 150 mg / L is shown, with the bromine active electrode (marked in green) being used without replacement and with each replacement (marked in orange). It can be seen that the adsorption capacity is higher in the first three adsorption cycles after replacing the bromine active electrode, because the bromine concentration in the solution is above 100 mg / L at this point. After three adsorption cycles, the bromine concentration in the solution decreases to below 100 mg / L, but the adsorption capacity remains stable for the next five cycles, and the adsorption capacity for each of the last five cycles remains above 10 mg / g. Even with repeated use of the same electrode and a continuously decreasing solution concentration without replacing the membrane electrode, the bromine active electrode prepared in this invention still exhibits a certain adsorption capacity in subsequent uses.

[0059] Example 2

[0060] 3.88g 0.952 g of KBr was dispersed in 120 mL of ultrapure water and stirred continuously. Then, 1 M NaOH was added to the mixture to adjust the pH to 6. After magnetic stirring for 0.5 h, the mixture was poured into a 150 mL polytetrafluoroethylene-lined stainless steel autoclave and heated in a constant temperature drying oven at 160°C for 24 h to obtain BiOBr. After the reaction was completed, the mixture was cooled to room temperature. The prepared BiOBr was then repeatedly washed with ultrapure water and ethanol to remove residual ions, and the washed BiOBr was dried in a vacuum oven at 60°C for 12 h.

[0061] 15.25g of 3,4-ethylenedioxythiophene was added dropwise to 100ml of deionized water and stirred until homogeneous to form solution A. 3.05g of the prepared bismuth oxybromine nanosheets were then added to solution A and stirred for 1 hour to form solution B. 8.1g of ferric chloride was dissolved in 30ml of deionized water to form a ferric chloride solution. This ferric chloride solution was added to the stirring solution B to obtain solution C. Solution C was then stirred at 5℃ for 16 hours to obtain the BiOBr@PEDOT composite material. The composite material was rinsed three times with 100ml of 0.001mol / L HCl solution and deionized water to remove residual polymer and other ions. The washed composite material was then dried in a vacuum drying oven at 50℃ for 12 hours.

[0062] The bromine active electrode prepared in Example 2 was tested using the same method as in Example 1. The adsorption capacity, adsorption rate and cycle stability of the bromine active electrode prepared in this example were comparable to those in Example 1.

[0063] Example 3

[0064] 3.88g 0.952 g of KBr was dispersed in 120 mL of ultrapure water and stirred continuously. Then, 1 M NaOH was added to the mixture to adjust the pH to 6. After magnetic stirring for 0.5 h, the mixture was poured into a 150 mL polytetrafluoroethylene-lined stainless steel autoclave and heated in a constant temperature drying oven at 160°C for 24 h to obtain BiOBr. After the reaction was completed, the mixture was cooled to room temperature. The prepared BiOBr was then repeatedly washed with ultrapure water and ethanol to remove residual ions, and the washed BiOBr was dried in a vacuum oven at 60°C for 12 h.

[0065] 0.305 g of 3,4-ethylenedioxythiophene was added dropwise to 100 ml of deionized water and stirred until homogeneous to form solution A. 3.05 g of the prepared bismuth oxybromine nanosheets were then added to solution A and stirred for 1 hour to form solution B. 6.85 g of ammonium persulfate was dissolved in 30 ml of deionized water to form an ammonium persulfate solution. Ferric chloride solution was added to the stirring solution B to obtain solution C. Solution C was stirred at 3°C ​​for 8 hours to obtain the BiOBr@PEDOT composite material. The composite material was rinsed three times with 100 ml of 0.001 mol / L HCl solution and deionized water to remove residual polymer and other ions. The washed composite material was then dried in a vacuum drying oven at 50°C for 12 hours.

[0066] The bromine active electrode prepared in Example 3 was tested using the same method as in Example 1. The adsorption capacity, adsorption rate and cycle stability of the bromine active electrode prepared in this embodiment were comparable to those in Example 1.

[0067] Comparative Example 1

[0068] Comparative Example 1 uses pure BiOBr nanosheets to construct a bromine active electrode. The BiOBr nanosheets are the same as those prepared in Example 1. The rest of the process is the same as in Example 1.

[0069] By comparing Example 1 and Comparative Example 1, it was found that compared with the bromine active electrode constructed from BiOBr nanosheets alone, the bromine active electrode based on BiOBr@PEDOT composite material exhibited better conductivity and adsorption capacity. Under the same adsorption conditions, when the desorption solution was deionized water, the bromine active electrode of Example 1 had a 10-fold increase in adsorption capacity and a 50% increase in adsorption rate compared with Comparative Example 1.

[0070] Comparative Example 2

[0071] The only difference between Comparative Example 2 and Example 1 is that Comparative Example 2 uses a simple PEDOT material mixed with polyvinylidene fluoride and carbon black in a mass ratio of 8:1:1 to prepare the electrode.

[0072] This invention uses the bromine-active electrodes from Examples 1, 1, and 2 above to test real oilfield brine samples (Br). - Bromine extraction was tested at a concentration of approximately 200 mg / L. Under the same conditions and with a potential of 1.0 V applied, the adsorption capacity of pure BiOBr in Comparative Example 1 was 4.7 mg / g, the adsorption capacity of pure PEDOT material in Comparative Example 2 was 6.8 mg / g, while the adsorption capacity of the bromine active electrode in Example 1 was 35 mg / g. This indicates that the combination of BiOBr and PEDOT produces a certain synergistic effect. The adsorption capacity of pure BiOBr is much smaller than that of the BiOBr@PEDOT composite material. This is because the conductivity of the pure BiOBr electrode is poor, while the doping of PEDOT can improve the conductivity of the bromine active electrode and also increase the surface roughness of the BiOBr nanosheets, providing abundant active sites.

[0073] All aspects, embodiments, features, and examples of this invention are to be regarded as illustrative in all respects and are not intended to limit the invention, the scope of which is defined only by the claims. Other embodiments, modifications, and uses will become apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0074] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0075] Although the invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of the invention, and that elements of the embodiments can be substituted with substantially equivalents. Furthermore, many modifications can be made without departing from the scope of the invention to adapt particular situations or materials to the teachings of the invention. Therefore, this invention is not intended to be limited to the specific embodiments disclosed for carrying out the invention, but rather is intended to encompass all embodiments falling within the scope of the appended claims. Moreover, unless specifically stated otherwise, any use of the terms first, second, etc., does not indicate any order or importance, but is used to distinguish one element from another.

Claims

1. An electroadsorption material for the electrochemical extraction of bromine, characterized in that, include: The bismuth oxybromine nanosheets and polyethylene dioxythiophene coated on the surface of the bismuth oxybromine nanosheets, wherein the mass ratio of the bismuth oxybromine nanosheets to the polyethylene dioxythiophene is 1~10:0.1~5; The preparation method of the electroadsorption material includes: Bismuth oxybromide nanosheets were synthesized using a hydrothermal method. A mixed reaction system containing the bismuth oxybromine nanosheets, 3,4-ethylenedioxythiophene, ammonium persulfate and / or ferric chloride is reacted at 0~5°C to polymerize the 3,4-ethylenedioxythiophene to form polyethylenedioxythiophene, which is then coated onto the surface of the bismuth oxybromine nanosheets, thereby obtaining an electroadsorption material composed of bismuth oxybromine nanosheets and polyethylenedioxythiophene.

2. The electroadsorption material according to claim 1, characterized in that: According to BET testing, the specific surface area of ​​the electroadsorption material is 5 to 10 times that of the bismuth oxybromine nanosheets. And / or, the bismuth oxybromine nanosheets have a diameter of 50~1000 nm and a thickness of 50~500 nm, and the poly(ethylene dioxythiophene) coating thickness on the surface of the bismuth oxybromine nanosheets is 10~1000 nm. And / or, according to thermogravimetric analysis, the initial weight loss temperature of the electroadsorption material is 350°C.

3. The electroadsorption material according to claim 1, characterized in that: The concentration of bismuth oxybromide nanosheets in the mixed reaction system is 23~200 g / L.

4. The electroadsorption material according to claim 1, characterized in that: In the mixed reaction system, the mass ratio of bismuth oxybromide nanosheets to 3,4-ethylenedioxythiophene is 1~10:0.1~5.

5. The electroadsorption material according to claim 1, characterized in that: The concentration of ammonium persulfate and / or ferric chloride in the mixed reaction system is 0.1~5 mol / L.

6. The electroadsorption material according to claim 1, characterized in that: The reaction time is 8-16 h.

7. A bromine-active electrode, characterized in that, Includes the electroadsorption material as described in claim 1 or 2.

8. The bromine-active electrode according to claim 7, characterized in that: The bromine active electrode includes a conductive substrate and a composite film layer formed on the conductive substrate, wherein the composite film layer includes the electroadsorption material, conductive material and binder as described in claim 1 or 2.

9. The bromine-active electrode according to claim 8, characterized in that: The mass ratio of the electroadsorption material, the conductive material, and the binder is 4~8:0.1~1:0.5~1.

5.

10. The bromine-active electrode according to claim 8, characterized in that: The conductive material includes one or a combination of carbon black, graphene, and acetylene black.

11. The bromine-active electrode according to claim 8, characterized in that: The adhesive includes one or a combination of polyvinylidene fluoride, polyacrylic acid, polymethacrylic acid, and polyvinyl alcohol.

12. The bromine-active electrode according to claim 8, characterized in that: The conductive substrate is made of one or a combination of carbon, titanium, and nickel.

13. A system for extracting bromine, characterized in that, include: The electrode comprises a working electrode, a counter electrode, and a reference electrode, wherein the working electrode is the bromine active electrode according to any one of claims 7-12.

14. The use of the electroadsorption material of claim 1 or 2, the bromine active electrode of any one of claims 7-12, or the bromine extraction system of claim 13 in the extraction of bromine from brine.

15. The application according to claim 14, characterized in that: The brine is oilfield brine.

16. A method for extracting bromine from oilfield brine, characterized in that, The bromine extraction system according to claim 13 comprises: The bromine active electrode in the system is pretreated by placing the bromine active electrode in water and applying a voltage of -0.8 to -1.2V to desorb at least some of the bromine in the bromine active electrode. The pretreated bromine-active electrode is placed in oilfield brine, and a voltage of 0.6-1.2V is applied to cause the bromine-active electrode to adsorb bromide ions in the oilfield brine to achieve bromine extraction.

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