Method for enriching bromide ions through trigger type electroreduction

Abstract

The invention belongs to the technical field of green electrochemical synthesis, and particularly relates to a method for enriching bromide ions through trigger type electroreduction, which specifically comprises the following steps: S1, adding an electrolyte A into an anode electrolytic bath, and installing a counter electrode; s2, an electrolyte B is added into a cathode electrolytic cell, a working electrode and a reference electrode are installed, and the working electrode is made of a carbon fiber material; s3, setting the reduction potential of the working electrode; s4, continuously introducing bromine-containing air into the electrolyte B of the cathode electrolytic bath at a set flow rate, and returning the air to the air blowing system for recycling after the air is discharged from the cathode electrolytic bath; and S5, stopping introducing the bromine-containing air, and terminating the electroreduction reaction. The method does not generate toxic and harmful byproducts, has excellent process safety and lower energy consumption level, fundamentally solves the problems of high energy consumption, serious pollution and more byproducts in the traditional bromide ion enrichment process, and has the characteristics of greenness, environmental protection and high safety.

Description

Technical Field

[0001] This invention relates to a method for trigger-based electroreduction enrichment of bromide ions, belonging to the field of green electrochemical synthesis technology. Background Technology

[0002] Bromine, a chemically reactive nonmetallic element, can react with a variety of substances, and its bromides have wide applications in many fields such as pharmaceuticals, flame retardants, pesticides, photosensitive materials, and petroleum products. Currently, the main methods for producing bromine include steam distillation, air blowing, solvent extraction, ion exchange resin methods, membrane separation, and precipitation. Among these, the air blowing method is the most mature and widely used, and it is also the mainstream process widely adopted in my country's bromine production industry. This process uses intermediate brine produced during underground brine or seawater salt production as raw material. After acidification, chlorine oxidation, and other steps, bromine is enriched through acid or alkaline absorption—essentially reducing bromine molecules to bromide ions to increase the bromide ion concentration, thereby obtaining a completed absorption liquid. This completed liquid undergoes a second chlorination oxidation before entering a distillation tower, where it undergoes steam distillation, condensation, and purification processes to finally obtain the bromine product.

[0003] However, the extraction of bromine requires the use of large quantities of hazardous raw materials such as acids, chlorine, and sulfur dioxide, resulting in a process characterized by high energy consumption, high pollution, and high risk. In recent years, various new environmentally friendly bromine extraction technologies have been researched and reported to address these issues. Among them, electro-oxidation, as a promising method, primarily improves the oxidation of bromide ions by controlling the oxidation potential to achieve electrochemical oxidation of bromide ions in seawater (brine), replacing the traditional chlorine oxidation process. Nevertheless, in the reduction and enrichment stages of bromine molecules, traditional alkaline or acidic absorption processes are still commonly used, or more expensive absorbents such as urea and sodium formate are relied upon to convert bromine molecules into bromide ions for bromine enrichment. Regardless of whether alkaline, acidic, or other absorption methods are used, large quantities of acidic and alkaline chemicals are required. These substances not only severely corrode production equipment but also significantly increase energy consumption, placing considerable environmental and operational pressure on enterprises. Therefore, developing green, environmentally friendly, and clean new processes for bromine molecule reduction and bromide ion enrichment is of significant practical importance for promoting the sustainable development of bromine production technology. Summary of the Invention

[0004] To address the aforementioned technical problems in the prior art, this invention provides a method for trigger-based electroreduction enrichment of bromide ions.

[0005] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A method for trigger-type electroreduction enrichment of bromide ions, specifically including the following steps: S1. Add electrolyte A to the anodic electrolytic cell and install the counter electrode; S2. Add electrolyte B to the cathode electrolytic cell and install the working electrode and reference electrode. The working electrode is made of carbon fiber material. S3. Set the reduction potential of the working electrode; S4. The bromine-containing air is continuously introduced into the electrolyte B of the cathode electrolytic cell at a set flow rate, so that the bromine molecules trigger an electroreduction reaction to be converted into bromide ions. The air is discharged from the cathode electrolytic cell and returned to the gas blowing system for recycling. S5. Stop the flow of bromine-containing air; the electroreduction reaction will terminate.

[0006] This invention provides a method for trigger-based electroreduction enrichment of bromide ions. By employing carbon fiber as the working electrode and utilizing its unique adsorption and capture capabilities for bromine molecules, the electrochemical reduction conversion of bromine molecules to bromide ions is efficiently achieved, thereby enriching bromide ions. Based on the significant difference in reduction potential between bromine molecules and hydrogen ions in water, this invention ensures that only bromine molecules (Br2) undergo the electroreduction reaction (Br2 + 2e-) by setting the reduction potential of the working electrode. - → 2Br - ), while hydrogen ions in water (H) + This method avoids the hydrogen evolution reaction during reduction, thus achieving high selectivity for the target reaction. Using bromine molecules as the "trigger source" for the electroreduction process, a control mechanism is implemented where the reaction is immediately triggered and continues in the presence of bromine molecules, and automatically stops when bromine molecules are absent. The specific process is as follows: After bromine-containing air is introduced into the cathode electrolyzer, bromine molecules contact the working electrode and trigger the reduction reaction, gaining electrons to generate bromide ions; simultaneously, an oxidation reaction of water occurs in the anolyte, releasing oxygen and generating hydrogen ions. The generated hydrogen ions migrate through the ion-exchange membrane to the cathode chamber, maintaining the system's charge balance and reaction continuity, thereby forming a complete electrochemical redox cycle. The specific electroredox reactions are as follows: .

[0007] Based on the above technical solution, the present invention can also be improved as follows: Furthermore, the electrolyte A is one of sulfuric acid, phosphoric acid, or perchloric acid aqueous solutions with a mass concentration of 2% to 10%.

[0008] Furthermore, the counter electrode is one of a carbon rod electrode, a platinum electrode, or a titanium electrode.

[0009] Furthermore, the electrolyte B is one of the aqueous solutions of hydrogen bromide, sodium bromide, or potassium bromide with a concentration of 5-10 g / L.

[0010] Furthermore, the working electrode is one of a carbon paper electrode, a carbon cloth electrode, or a carbon felt electrode, preferably a carbon felt electrode.

[0011] Furthermore, the reference electrode is one of an Ag / AgCl electrode, a saturated calomel electrode (SCE), or a mercurous sulfate electrode.

[0012] Furthermore, the reduction potential is set to -1.4V to 0.0V relative to the saturated calomel electrode, preferably -1.0V to 0.0V.

[0013] Furthermore, in step S4, the concentration of bromine in the bromine-containing air is 0.5–6.0 mg / L.

[0014] Furthermore, in step S4, the bromine-containing air is introduced into the cathode electrolytic cell at a flow rate of 500–2000 mL / min.

[0015] Furthermore, a proton exchange membrane or a cation exchange membrane is provided between the anode electrolytic cell and the cathode electrolytic cell.

[0016] Furthermore, the anode electrolytic cell and the cathode electrolytic cell are each equipped with a stirring device.

[0017] The beneficial effects of this invention are as follows: the entire process of this invention does not produce toxic or harmful byproducts, has excellent process safety and low energy consumption, and can be used as a novel bromide ion enrichment technology in the process of extracting bromine from seawater or brine; it fundamentally solves the problems of high energy consumption, high pollution and many byproducts in the traditional bromide ion enrichment process, and has the characteristics of being green, environmentally friendly and safe. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of an embodiment of the present invention. Detailed Implementation

[0019] 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.

[0020] Example 1 according to Figure 1 The diagram shows the construction of an H-type dual-chamber electrolytic cell system. The carbon felt electrode is the working electrode W, the carbon rod electrode is the counter electrode C, and the Ag / AgCl electrode is the reference electrode R. The diaphragm between the anolyte and catholyte is a Nafion 115 proton exchange membrane. 500 mL of a 6% (w / w) sulfuric acid aqueous solution is added to the anolyte, and 500 mL of a 5 g / L sodium bromide aqueous solution is added to the catholyte. The potential of the working electrode W is set to -0.5 V (vs. SCE). Stirring is started (see...). Figure 1Both the anode and cathode electrolytic cells are equipped with magnetic stirrs (which, through stirring, ensure solution homogenization and facilitate redox reactions on the electrode surfaces). Air carrying bromine is continuously bubbled into the sodium bromide electrolyte in the cathode electrolytic cell at a flow rate of 2000 mL / min, triggering an electroreduction reaction in the sodium bromide electrolyte to convert bromine molecules into bromide ions. The average bromine concentration in the air carrying bromine is 0.5 mg / L. The bubbled air exits from above the cathode electrolytic cell and returns to the original bubbling system, continuing to carry bromine molecules into the cathode electrolytic cell; the air is recycled. After 60 hours of operation, the bromide ion concentration in the cathode electrolytic cell is measured to be 10.5 g / L. Bubbling of bromine-carrying air is then stopped, and the electroreduction reaction automatically terminates. The solution volume in the cathode electrolytic cell is approximately 501 mL. Calculations show that the bromine electroreduction enrichment yield is 92%.

[0021] The formula for calculating the electroreduction enrichment yield is: Enrichment yield = (Mass of bromide ions in the cathode electrolytic cell solution after the reaction - Mass of bromide ions in the cathode electrolytic cell solution before the reaction) / Total mass of bromine carried by air × 100%.

[0022] Example 2 according to Figure 1 The diagram shows the construction of an H-type dual-chamber electrolytic cell system. A carbon paper electrode serves as the working electrode (W), a platinum electrode as the counter electrode (C), and a saturated calomel electrode as the reference electrode (R). A Nafion 115 proton exchange membrane is used as the diaphragm between the anolyte and catholyte. 500 mL of a 2% (w / w) phosphoric acid aqueous solution is added to the anolyte, and 500 mL of a 10 g / L potassium bromide aqueous solution is added to the catholyte. The potential of the working electrode W is set to -1.4 V (vs. SCE). Stirring is started, and air carrying bromine is continuously bubbled into the electrolyte solution in the catholyte at a flow rate of 1500 mL / min. This triggers an electroreduction reaction in the catholyte, converting bromine molecules into bromide ions. The average bromine concentration in the air carrying bromine is 0.8 mg / L. The air is then blew out from above the catholyte and returned to the original bleed system to continue carrying bromine molecules back into the catholyte, thus recycling the air. After 60 hours of operation, the bromide ion concentration in the cathode electrolyzer was measured to be 14.9 g / L. The introduction of bromine-carrying air was then stopped, and the electroreduction reaction automatically terminated. The solution volume in the cathode electrolyzer was approximately 501 mL, and the bromine electroreduction enrichment yield was 95%.

[0023] Example 3 according to Figure 1The diagram shows the construction of an H-type dual-chamber electrolytic cell system. A carbon felt electrode serves as the working electrode (W), a carbon rod electrode as the counter electrode (C), and a mercurous sulfate electrode as the reference electrode (R). A CMI7000S cation exchange membrane is used as the diaphragm between the anolyte and catholyte. 500 mL of a 10% (w / w) perchloric acid aqueous solution is added to the anolyte, and 500 mL of a 6 g / L hydrogen bromide aqueous solution is added to the catholyte. The potential of the working electrode W is set to 0.0 V (vs. SCE). Stirring is started, and air carrying bromine is continuously bubbled into the hydrobromic acid electrolyte in the catholyte at a flow rate of 800 mL / min. This triggers an electroreduction reaction in the catholyte, converting bromine molecules into bromide ions. The average bromine concentration in the air carrying bromine is 1.7 mg / L. The air is then blew out from above the catholyte and returned to the original bleed system to continue carrying bromine molecules back into the catholyte, thus recycling the air. After 60 hours of operation, the bromide ion concentration in the cathode electrolyzer was measured to be 15.2 g / L. The introduction of bromine-carrying air was then stopped, and the electroreduction reaction automatically terminated. The solution volume in the cathode electrolyzer was approximately 502 mL, and the bromine electroreduction enrichment yield was 95%.

[0024] Example 4 according to Figure 1 The diagram shows the construction of an H-type dual-chamber electrolytic cell system. A carbon felt electrode serves as the working electrode (W), a titanium electrode as the counter electrode (C), and an Ag / AgCl electrode as the reference electrode (R). A CMI7000S cation exchange membrane is used as the diaphragm between the anolyte and catholyte. 500 mL of a 4% (w / w) sulfuric acid aqueous solution is added to the anolyte, and 500 mL of an 8 g / L hydrogen bromide aqueous solution is added to the catholyte. The potential of the working electrode W is set to -1.0 V (vs. SCE). Stirring is started, and air carrying bromine is continuously bubbled into the hydrobromic acid electrolyte in the catholyte at a flow rate of 600 mL / min. This triggers an electroreduction reaction in the catholyte, converting bromine molecules into bromide ions. The average bromine concentration in the air carrying bromine is 6.0 mg / L. The air is then blew out from above the catholyte and returned to the original bleed system to continue carrying bromine molecules back into the catholyte, thus recycling the air. After 60 hours of operation, the bromide ion concentration in the cathode electrolyzer was measured to be 32.8 g / L. The introduction of bromine-carrying air was then stopped, and the electroreduction reaction automatically terminated. The solution volume in the cathode electrolyzer was approximately 504 mL, and the bromine electroreduction enrichment yield was 97%.

[0025] Example 5 according to Figure 1The diagram shows the construction of an H-type dual-chamber electrolytic cell system. A carbon cloth electrode serves as the working electrode (W), a titanium electrode as the counter electrode (C), and a saturated calomel electrode as the reference electrode (R). A Nafion 117 proton exchange membrane is used as the diaphragm between the anolyte and catholyte. 500 mL of an 8% (w / w) phosphoric acid aqueous solution is added to the anolyte, and 500 mL of a 7 g / L sodium bromide aqueous solution is added to the catholyte. The potential of the working electrode W is set to -0.7 V (vs. SCE). Stirring is started, and air carrying bromine is continuously bubbled into the sodium bromide electrolyte in the catholyte at a flow rate of 1000 mL / min. This triggers an electroreduction reaction in the catholyte, converting bromine molecules into bromide ions. The average bromine concentration in the air carrying bromine is 5.1 mg / L. The air is then blew out from above the catholyte and returned to the original bleed system to continue carrying bromine molecules back into the catholyte, thus recycling the air. After 60 hours of operation, the bromide ion concentration in the cathode electrolyzer was measured to be 40.3 g / L. The introduction of bromine-carrying air was then stopped, and the electroreduction reaction automatically terminated. The solution volume in the cathode electrolyzer was approximately 506 mL, and the electroreduction enrichment yield of bromine was 96%.

[0026] Example 6 according to Figure 1 The diagram shows the construction of an H-type dual-chamber electrolytic cell system. A carbon felt electrode serves as the working electrode (W), a platinum electrode as the counter electrode (C), and mercurous sulfate as the reference electrode (R). A Nafion 117 proton exchange membrane is used as the diaphragm between the anolyte and catholyte. 500 mL of a 5% (w / w) perchloric acid aqueous solution is added to the anolyte, and 500 mL of a 9 g / L potassium bromide aqueous solution is added to the catholyte. The potential of the working electrode W is set to -0.3 V (vs. SCE). Stirring is started, and air carrying bromine is continuously bubbled into the potassium bromide electrolyte in the catholyte at a flow rate of 1500 mL / min. This triggers an electroreduction reaction in the catholyte, converting bromine molecules into bromide ions. The average bromine concentration in the air carrying bromine is 3.9 mg / L. The air is then blew out from above the catholyte and returned to the original bleed system to continue carrying bromine molecules back into the catholyte, thus recycling the air. After 60 hours of operation, the bromide ion concentration in the cathode electrolyzer was measured to be 46.5 g / L. The introduction of bromine-carrying air was then stopped, and the electroreduction reaction automatically terminated. The solution volume in the cathode electrolyzer was approximately 506 mL, and the bromine electroreduction enrichment yield was 97%.

[0027] Example 7 according to Figure 1The diagram shows the construction of an H-type dual-chamber electrolytic cell system. A carbon felt electrode serves as the working electrode (W), a carbon rod electrode as the counter electrode (C), and mercurous sulfate as the reference electrode (R). A Nafion 117 proton exchange membrane is used as the diaphragm between the anolyte and catholyte. 500 mL of a 5% (w / w) phosphoric acid aqueous solution is added to the anolyte, and 500 mL of a 6 g / L sodium bromide aqueous solution is added to the catholyte. The potential of the working electrode W is set to -1.1 V (vs. SCE). Stirring is started, and air carrying bromine is continuously bubbled into the potassium bromide electrolyte in the catholyte at a flow rate of 1200 mL / min. This triggers an electroreduction reaction in the catholyte, converting bromine molecules into bromide ions. The average bromine concentration in the air carrying bromine is 2.5 mg / L. The air is then blew out from above the catholyte and returned to the original bleed system to continue carrying bromine molecules back into the catholyte, thus recycling the air. After 60 hours of operation, the bromide ion concentration in the cathode electrolyzer was measured to be 25.7 g / L. The introduction of bromine-carrying air was then stopped, and the electroreduction reaction automatically terminated. The solution volume in the cathode electrolyzer was approximately 503 mL, and the bromine electroreduction enrichment yield was 98%.

[0028] 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 trigger-based electroreduction enrichment of bromide ions, characterized in that, Specifically, the following steps are included: S1. Add electrolyte A to the anodic electrolytic cell and install the counter electrode; S2. Add electrolyte B to the cathode electrolytic cell and install the working electrode and reference electrode. The working electrode is made of carbon fiber material. S3. Set the reduction potential of the working electrode; S4. Bromine-containing air is continuously introduced into the electrolyte B of the cathode electrolytic cell, causing bromine molecules to trigger an electroreduction reaction and be converted into bromide ions. The air is then discharged from the cathode electrolytic cell and returned to the gas blowing system for recycling. S5. Stop the flow of bromine-containing air; the electroreduction reaction will terminate.

2. The method for trigger-based electroreduction enrichment of bromide ions according to claim 1, characterized in that, The electrolyte A is one of sulfuric acid, phosphoric acid, or perchloric acid aqueous solutions with a mass concentration of 2% to 10%.

3. The method for trigger-based electroreduction enrichment of bromide ions according to claim 1, characterized in that, The counter electrode is one of a carbon rod electrode, a platinum electrode, or a titanium electrode.

4. The method for trigger-based electroreduction enrichment of bromide ions according to claim 1, characterized in that, The electrolyte B is one of the following: an aqueous solution of hydrogen bromide, sodium bromide, or potassium bromide with a concentration of 5–10 g / L.

5. The method for trigger-based electroreduction enrichment of bromide ions according to claim 1, characterized in that, The working electrode is one of a carbon paper electrode, a carbon cloth electrode, or a carbon felt electrode.

6. The method for trigger-based electroreduction enrichment of bromide ions according to claim 1, characterized in that, The reference electrode is one of an Ag / AgCl electrode, a saturated calomel electrode, or a mercurous sulfate electrode.

7. The method for trigger-based electroreduction enrichment of bromide ions according to claim 1, characterized in that, The reduction potential is set to -1.4V to 0.0V relative to the saturated calomel electrode.

8. The method for trigger-based electroreduction enrichment of bromide ions according to claim 1, characterized in that, In step S4, the concentration of bromine in the bromine-containing air is 0.5–6.0 mg / L.

9. The method for trigger-based electroreduction enrichment of bromide ions according to claim 1, characterized in that, In step S4, the bromine-containing air is introduced into the cathode electrolytic cell at a flow rate of 500-2000 mL / min.

10. The method for trigger-based electroreduction enrichment of bromide ions according to claim 1, characterized in that, A proton exchange membrane or a cation exchange membrane is provided between the anode electrolytic cell and the cathode electrolytic cell.

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