Synergistic Enhancement of Electrochemical-Oxidative Chlorine-Free Bromine Extraction from Oil and Gas Field Water by Zero-Gap Electrolyzer and Carbon Cloth Electrode: A Study on Efficient, Selective Extraction and Resistance to Other Ions

Bromine, as a strategic fundamental chemical raw material, is crucial for modern industry, but the traditional chlorine displacement method poses safety risks in oilfield brine development and faces challenges like resource depletion and inefficient utilization. Addressing the need for high-concentration bromine brine development in underground oilfields, this study developed an electrochemical oxidation-based chlorine-free bromine extraction technology. Leveraging the standard redox potential difference between Br^- and Cl^- (0.271 V), the effective potential window for selective Br^- oxidation was determined as 1.0-1.52 V (vs. SHE) via linear sweep voltammetry (LSV). Within this window, efficient and preferential oxidation of Br^- over Cl^- and OH^- was achieved. In simulated brine with high chloride and low bromide concentrations, a Br^- conversion rate of 92.3% was attained with no Cl₂ generation. The self-designed zero-gap electrolyzer with carbon cloth as the anode reduced the reaction time by over 75% compared to a traditional H-type cell, oxidizing over 90% of Br^- within 12 min. Kinetic studies revealed that the reaction follows first-order kinetics, with current intensity positively correlated with Br^- concentration. Investigation of coexisting ions revealed that low concentrations of Cl^- promote the reaction, while high concentrations exert inhibitory effects. CO₃^2- exhibits a weak promoting effect, and Ca²⁺/Mg²⁺ show negligible impact. Notably, organic matter (e.g., ethylene glycol) concentrations exceeding 80 mg/L substantially compromise bromine recovery efficiency. This technology provides a feasible solution for the safe and green development of high-concentration bromine resources and holds significant importance for the upgrading of the bromine chemical industry.