Synchronous electrooxidation-reduction bromine extraction method
By simultaneously generating bromine molecules at the anode and carrying out chemical disproportionation and electroreduction reactions at the cathode, the problem of hydrogen byproduct at the cathode in electrochemical oxidation methods has been solved, achieving efficient enrichment and green extraction of bromine and reducing production costs.
Patent Information
- Application Number
- CN202511303345.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-12
- Publication Date
- 2025-11-18
AI Technical Summary
Existing electrochemical oxidation bromine extraction technology suffers from problems such as large amounts of hydrogen produced as cathode byproducts, high risk, and high cost, leading to increased production costs and low bromine extraction rates, which limits its industrial application.
A simultaneous electro-oxidation-reduction method is used to generate bromine molecules in the anodic electrolytic cell and blow them into the cathodic electrolytic cell for chemical disproportionation and electro-reduction reactions. By controlling the potential and using a membrane for separation, efficient enrichment of bromine ions is achieved, reducing hydrogen generation.
It significantly improved the bromine extraction rate and power utilization efficiency, reduced hydrogen byproducts, and achieved a green and efficient bromine resource extraction process.
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Figure CN120967364A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a simultaneous electro-oxidation-reduction method for bromine extraction, belonging to the field of green electrochemical technology. Background Technology
[0002] Bromine is a reactive nonmetallic element, and bromine and its compounds are important chemical raw materials, widely used in flame retardants, pharmaceuticals, pesticides, dyes, and other fields. Currently, the mainstream industrial bromine extraction technology is the "air blowing-sulfur dioxide absorption method." While this method is mature, it has significant drawbacks: First, it uses large amounts of highly toxic chlorine gas as an oxidant, posing significant safety and environmental risks; second, using sulfur dioxide as an absorbent generates large amounts of waste acid during the production process, resulting in high subsequent treatment costs and environmentally unfriendly practices.
[0003] Electrochemical oxidation method directly uses electrical energy to oxidize Br - Oxidation to Br2 avoids the use of hazardous chemicals and is considered a green and environmentally friendly method for bromine extraction. However, current electrochemical technologies generally suffer from a significant, often overlooked, flaw: current electro-oxidation methods primarily focus on selectively oxidizing bromide ions by controlling the anodic oxidation potential, with minimal attention paid to cathode reduction. According to the principle of electroneutrality, for every 1 mol of Br2 produced at the anode, 1 mol of H2 is inevitably produced at the cathode. For bromine extraction companies, the byproduct hydrogen production is relatively small compared to bromine production (mass ratio approximately 1:80), but it is extremely dangerous, easily exploding upon contact with static electricity or open flames. It requires expensive purification, compression, storage, or combustion treatment facilities, resulting in high investment, low returns, wasted hydrogen, and indirectly wasted electricity, increasing production costs. This significantly offsets the environmental and cost advantages of electrochemical methods, becoming a key bottleneck restricting its industrial application. Currently, electrochemical oxidation methods for bromine extraction still suffer from high costs and low extraction rates.
[0004] Therefore, there is an urgent need in this field for a novel electrochemical bromine extraction method that can solve the problem of hydrogen production as a byproduct at the cathode and at the same time efficiently enrich bromine resources. Summary of the Invention
[0005] To address the aforementioned deficiencies in existing technologies, this invention provides a green, safe, and efficient method for simultaneous electro-oxidation-reduction bromine extraction.
[0006] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A simultaneous electro-oxidation-reduction method for bromine extraction, wherein the method is carried out in an electrolysis device consisting of an anodic electrolytic cell and a cathodic electrolytic cell, the anodic electrolytic cell and the cathodic electrolytic cell being separated by a diaphragm; the method includes the following steps: S1. A bromine-containing raw material solution is introduced into the anodic electrolytic cell, and a working electrode and a reference electrode are set in the anodic electrolytic cell; S2. Add electrolyte to the cathode electrolytic cell and set a counter electrode in the cathode electrolytic cell; S3. Apply an oxidation potential to the working electrode to cause the bromide ions in the anodic electrolytic cell to undergo an electrochemical oxidation reaction to generate bromine molecules; S4. Gas is introduced into the anodic electrolytic cell through a gas blowing device to blow out the generated bromine molecules and carry them to the cathode electrolytic cell; S5. In the cathode electrolytic cell, the bromine molecules that are carried in first undergo a disproportionation reaction with hydroxide ions in the electrolyte to generate bromide ions and hypobromate ions; subsequently, the hypobromate ions undergo an electrochemical reduction reaction on the counter electrode to regenerate bromide ions and hydroxide ions. S6. Continuously replenish the bromine-containing raw material solution to the anode electrolytic cell and continue the reaction in steps S3 to S5 to continuously enrich bromide ions in the cathode electrolyte. S7. The reaction ends, and a concentrated bromine salt solution is obtained from the cathode electrolytic cell.
[0007] This invention fully utilizes two electrochemical processes: electro-oxidation at the anode and electro-reduction at the cathode. It achieves the electro-oxidation of bromide ions at the anode to generate bromine molecules, which are then blown out and chemically captured and electro-reduced at the cathode. Its specific working principle is as follows: In an H-type electrolytic cell, by controlling the working potential of the anode, bromide ions in the brine solution undergo a selective electro-oxidation reaction at the anode to generate bromine molecules. Simultaneously, in the initial stage of the reaction, an electro-reduction reaction occurs at the cathode, releasing hydrogen gas and generating hydroxide ions. Cations (such as sodium and potassium ions) in the anode electrolytic cell migrate to the cathode electrolytic cell via a proton exchange membrane positioned between the two electrolytic cells to maintain ion balance in the cathode electrolyte. The electro-oxidation and electro-reduction reactions are shown below:
[0008] When the concentration of bromine molecules in the anolyte reaches a certain value (at which point the molar amount of hydroxide ions in the catholyte is twice that of bromine molecules), bromine molecules are blown out of the anolyte using a gas blowing device and introduced into the catholyte with the gas flow. In the catholyte, bromine molecules undergo the following disproportionation reaction with hydroxide ions:
[0009] Bromine molecules are captured by hydroxide ions, undergoing a disproportionation reaction to generate bromide ions and hypobromate ions, while water is produced. The subsequent cathode reaction then shifts to a predominantly hypobromate reduction, thus inhibiting hydrogen evolution. Because the reduction potential of hypobromate ions is lower than that of hydrogen ions, they are more readily electroreduced at the cathode. Therefore, hypobromate ions and hydrogen ions compete for reduction, as detailed in the following electroreduction reactions:
[0010] Hypobromate ions are reduced to bromide ions at the cathode, while hydroxide ions are regenerated. As shown in reaction equations (1) and (2), the entire process of converting bromine molecules to bromide ions does not consume hydroxide ions; hydroxide ions play a catalytic cycling role in the chemical capture and electroreduction of bromine molecules. The competitive reduction reaction between hypobromate ions and hydrogen ions inhibits the evolution of hydrogen gas at the cathode, thereby reducing the formation of hydrogen byproducts.
[0011] As bromine molecules continuously transfer from the anodic electrolytic cell to the cathodic electrolytic cell, a dynamic equilibrium is established between the aforementioned electro-oxidation reaction, chemical disproportionation reaction, and electro-reduction reaction, achieving continuous and efficient conversion and enrichment of bromine molecules into bromide ions.
[0012] Based on the above technical solution, the present invention can also be improved as follows: Furthermore, in step S1, the bromine-containing raw material liquid is selected from any one of concentrated seawater, salt lake brine, underground brine, or industrial waste liquid containing bromide ions.
[0013] Furthermore, in step S1, the working electrode is a carbon material electrode, preferably a carbon felt electrode or a carbon cloth electrode.
[0014] Furthermore, in step S1, the reference electrode is any one of an Ag / AgCl electrode, a saturated calomel electrode, or a mercurous sulfate electrode.
[0015] Furthermore, in step S3, the oxidation potential is 1.24V to 1.54V relative to the standard hydrogen electrode.
[0016] Furthermore, in step S2, the electrolyte is a sodium bromide solution or a sodium hydroxide solution with a concentration of 5 g / L to 10 g / L.
[0017] Furthermore, in step S2, the counter electrode is a carbon material electrode, preferably a carbon felt electrode or a carbon cloth electrode.
[0018] Furthermore, the membrane is a cation-selective permeable membrane.
[0019] Furthermore, the membrane is a proton exchange membrane or a cation exchange membrane.
[0020] Furthermore, in step S4, the gas introduced by the gas blowing device is air or an inert gas, such as nitrogen.
[0021] The beneficial effects of this invention are as follows: The simultaneous electro-oxidation-reduction bromine extraction method designed in this invention achieves efficient oxidation of bromide ions to bromine molecules in the anodic region by coupling anodic electro-oxidation and cathodic electro-reduction processes. After gas stripping separation, the bromine molecules are then captured in situ and electrochemically reduced and enriched in the cathodic region. This process fully utilizes the electrochemical oxidation and reduction reactions, significantly improving energy efficiency and greatly suppressing side reactions, especially reducing or even eliminating hydrogen evolution, thus achieving a green and efficient bromine extraction process. Attached Figure Description
[0022] Figure 1 This is a process flow diagram of the simultaneous electro-oxidation-reduction bromine extraction equipment of the present invention. Detailed Implementation
[0023] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.
[0024] Example 1 Concentrated seawater after desalination, with a bromide ion concentration of 130 mg / L, was added to the anolyte, which has an inlet and an outlet. A carbon felt electrode (W) was installed as the working electrode, and an Ag / AgCl electrode as the reference electrode (R). 200 mL of a 5 g / L sodium bromide aqueous solution was added to the catholyte as the electrolyte, and a carbon felt electrode was installed as the counter electrode (C). A Nafion 115 proton exchange membrane was used as the separator between the anolyte and catholyte. During the electrochemical oxidation-reduction reaction, the oxidation potential of the working electrode W was set to 1.34 V (vs. Ag / AgCl), i.e., 1.54 V vs. SHE, to convert bromide ions in the anolyte into bromine molecules. The generated bromine was blown out of the anolyte using an aeration device and carried into the catholyte for reduction, thus increasing the bromide ion concentration. Concentrated seawater was continuously replenished through the inlet and outlet of the anolyte, treating a total of 20 L of concentrated seawater. After running for 30 hours, the electro-oxidation-reduction reaction was stopped, and 201 mL of concentrated bromide solution was obtained in the cathode electrolytic cell. The bromide ion concentration was 14.4 g / L, and the electro-oxidation-reduction extraction rate of bromine was 81%.
[0025] The formula for calculating the extraction rate is: Extraction rate = (Mass of bromide ions in the cathodic electrolytic cell solution after the reaction - Mass of bromide ions in the cathodic electrolytic cell solution before the reaction) / Total mass of bromine in concentrated seawater × 100%.
[0026] Example 2 Salt lake brine with a bromide ion concentration of 550 mg / L was added to the anolyte, which has an inlet and an outlet. A carbon felt electrode was installed as the working electrode (W), and a saturated calomel electrode was installed as the reference electrode (R). 200 mL of a 6 g / L sodium hydroxide aqueous solution was added to the catholyte as the electrolyte, and a carbon cloth electrode was installed as the counter electrode (C). A CMI7000S cation exchange membrane was used as the separator between the anolyte and catholyte. During the electrochemical oxidation-reduction reaction, the oxidation potential of the working electrode W was set to 1.20 V (vs. SCE), i.e., 1.44 V vs. SHE, to convert bromide ions in the anolyte into bromine molecules. The generated bromine was blown out of the anolyte using an aeration device and carried into the catholyte for reduction, thus increasing the bromide ion concentration. Salt lake brine was continuously replenished through the inlet and outlet of the anolyte, and a total of 20 L of brine was treated. After running for 25 hours, the electro-oxidation-reduction reaction was stopped, and 205 mL of concentrated bromide solution was obtained in the cathode electrolytic cell. The bromide ion concentration was 49.5 g / L, and the electro-oxidation-reduction extraction rate of bromine was 92%.
[0027] Example 3 Underground brine with a bromide ion concentration of 220 mg / L was added to the anolyte, which had an inlet and an outlet. A carbon cloth electrode was installed as the working electrode (W), and a mercurous sulfate electrode was installed as the reference electrode (R). 200 mL of a 7 g / L sodium bromide aqueous solution was added to the catholyte as the electrolyte, and a carbon felt electrode was installed as the counter electrode (C). A Nafion 115 proton exchange membrane was used as the separator between the anolyte and catholyte. During the electrochemical oxidation-reduction reaction, the oxidation potential of the working electrode W was set to 0.64 V (vs. Hg / Hg₂SO₄), i.e., 1.3 V vs. SHE, to convert bromide ions in the anolyte into bromine molecules. The generated bromine was blown out of the anolyte using an aeration device and carried into the catholyte for reduction, thus increasing the bromide ion concentration. The underground brine was continuously replenished through the inlet and outlet of the anolyte, and a total of 20 L of underground brine was treated. After running for 30 hours, the electro-oxidation-reduction reaction was stopped, and 202 mL of concentrated bromide solution was obtained in the cathode electrolytic cell. The bromide ion concentration was 23.9 g / L, and the electro-oxidation-reduction extraction rate of bromine was 85%.
[0028] Example 4 Produced water from the oil and gas field, with a bromide ion concentration of 256 mg / L, was added to the anolyte, which has an inlet and an outlet. A carbon felt electrode (W) was installed as the working electrode, and a saturated calomel electrode (R) as the reference electrode. 200 mL of an 8 g / L sodium bromide aqueous solution was added to the catholyte as the electrolyte, and a carbon cloth electrode (C) was installed as the counter electrode. A CMI7000S cation exchange membrane was used as the separator between the anolyte and catholyte. During the electrochemical oxidation-reduction reaction, the oxidation potential of the working electrode W was set to 1.10 V (vs. SCE), i.e., 1.34 V vs. SHE, to convert bromide ions in the anolyte into bromine molecules. The generated bromine was blown out of the anolyte using an aeration device and carried into the catholyte for reduction, thus increasing the bromide ion concentration. Produced water from the oil and gas field was continuously replenished through the inlet and outlet of the anolyte, and a total of 20 L of produced water was treated. After running for 30 hours, the electro-oxidation-reduction reaction was stopped, and 203 mL of concentrated bromide solution was obtained in the cathode electrolytic cell. The bromide ion concentration was 28.1 g / L, and the electro-oxidation-reduction extraction rate of bromine was 87%.
[0029] Example 5 A bromide-containing wastewater with a bromide ion concentration of 1500 mg / L was added to the anolyte, which has an inlet and an outlet. A carbon cloth electrode was installed as the working electrode W, and an Ag / AgCl electrode was installed as the reference electrode R. 400 mL of a 10 g / L sodium hydroxide solution was added to the catholyte as the electrolyte, and a carbon cloth electrode was installed as the counter electrode C. A Nafion 117 proton exchange membrane was used as the separator between the anolyte and catholyte. During the electrochemical oxidation-reduction reaction, the oxidation potential of the working electrode W was set to 1.19 V (vs. Ag / AgCl), i.e., 1.39 V vs. SHE, to convert bromide ions in the anolyte into bromine molecules. The generated bromine was blown out of the anolyte using a blower and entered the catholyte along with the air for reduction, thus increasing the bromide ion concentration. The bromide-containing wastewater was continuously replenished through the inlet and outlet of the anolyte, and a total of 15 L of bromide-containing wastewater was treated. After running for 21 hours, the electro-oxidation-reduction reaction was stopped, and 406 mL of concentrated bromide solution was obtained in the cathode electrolytic cell, with a bromide ion concentration of 52.8 g / L and an electro-oxidation-reduction extraction rate of 95% for bromine.
[0030] Example 6 A bromide-containing wastewater with a bromide ion concentration of 3562 mg / L was added to the anolyte, which has an inlet and an outlet. A carbon felt electrode was installed as the working electrode (W), and a mercurous sulfate electrode was installed as the reference electrode (R). 400 mL of a 5 g / L sodium hydroxide aqueous solution was added to the catholyte as the electrolyte, and a carbon felt electrode was installed as the counter electrode (C). A CMI7000S cation exchange membrane was used as the separator between the anolyte and catholyte. During the electrochemical oxidation-reduction reaction, the oxidation potential of the working electrode W was set to 0.59 V (vs. Hg / Hg₂SO₄), i.e., 1.25 V vs. SHE, to convert bromide ions in the anolyte into bromine molecules. The generated bromine was blown out of the anolyte using a blower and carried into the catholyte for reduction, thus increasing the bromide ion concentration. The bromide-containing wastewater was continuously replenished through the inlet and outlet of the anolyte, and a total of 10 L of bromide-containing wastewater was treated. After running for 20 hours, the electro-oxidation-reduction reaction was stopped, and 410 mL of concentrated bromide solution was obtained in the cathode electrolytic cell. The bromide ion concentration was 85.2 g / L, and the electro-oxidation-reduction extraction rate of bromine was 98%.
[0031] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for simultaneous electro-oxidation-reduction bromine extraction, characterized in that, The method is carried out in an electrolysis apparatus consisting of an anodic electrolytic cell and a cathodic electrolytic cell, which are separated by a diaphragm; the method includes the following steps: S1. A bromine-containing raw material solution is introduced into the anodic electrolytic cell, and a working electrode and a reference electrode are set in the anodic electrolytic cell; S2. Add electrolyte to the cathode electrolytic cell and set a counter electrode in the cathode electrolytic cell; S3. Apply an oxidation potential to the working electrode to cause the bromide ions in the anodic electrolytic cell to undergo an electrochemical oxidation reaction to generate bromine molecules; S4. Gas is introduced into the anodic electrolytic cell through a gas blowing device to blow out the generated bromine molecules and carry them to the cathode electrolytic cell; S5. In the cathode electrolytic cell, the bromine molecules that are carried in first undergo a disproportionation reaction with hydroxide ions in the electrolyte to generate bromide ions and hypobromate ions; subsequently, the hypobromate ions undergo an electrochemical reduction reaction on the counter electrode to regenerate bromide ions and hydroxide ions. S6. Continuously replenish the bromine-containing raw material solution to the anode electrolytic cell and continue the reaction in steps S3 to S5 to continuously enrich bromide ions in the cathode electrolyte. S7. The reaction ends, and a concentrated bromine salt solution is obtained from the cathode electrolytic cell.
2. The simultaneous electro-oxidation-reduction bromine extraction method according to claim 1, characterized in that, In step S1, the bromine-containing raw material liquid is selected from any one of concentrated seawater, salt lake brine, underground brine, or industrial waste liquid containing bromide ions.
3. The simultaneous electro-oxidation-reduction bromine extraction method according to claim 1, characterized in that, In step S1, the working electrode is a carbon material electrode.
4. The simultaneous electro-oxidation-reduction bromine extraction method according to claim 1, characterized in that, In step S1, the reference electrode is any one of an Ag / AgCl electrode, a saturated calomel electrode, or a mercurous sulfate electrode.
5. The simultaneous electro-oxidation-reduction bromine extraction method according to claim 1, characterized in that, In step S3, the oxidation potential is 1.24V to 1.54V relative to the standard hydrogen electrode.
6. The simultaneous electro-oxidation-reduction bromine extraction method according to claim 1, characterized in that, In step S2, the electrolyte is a sodium bromide solution or a sodium hydroxide solution with a concentration of 5 g / L to 10 g / L.
7. The simultaneous electro-oxidation-reduction bromine extraction method according to claim 1, characterized in that, In step S2, the counter electrode is a carbon material electrode.
8. The simultaneous electro-oxidation-reduction bromine extraction method according to claim 1, characterized in that, The membrane is a cation-selective permeable membrane.
9. The simultaneous electro-oxidation-reduction bromine extraction method according to claim 8, characterized in that, The diaphragm is a proton exchange membrane or a cation exchange membrane.
10. The simultaneous electro-oxidation-reduction bromine extraction method according to claim 1, characterized in that, In step S4, the gas introduced by the air blowing device is air or an inert gas.