Electromicrobial Hybrid System for High-Purity Sulfur Recovery from High-Salinity Wastewater

High-salinity wastewater contains a high concentration of sulfate (SO42–), posing environmental risks while offering potential for resource recovery. This study developed an electromicrobial hybrid system to achieve simultaneous SO42– removal and elemental sulfur (S0) recovery by integrating electrolytic hydrogen-mediated microbial sulfate reduction, H2S stripping, and off-field electrochemical oxidation. Sulfate reduction occurred in the cathode of the electrolytic-hydrogen-fed reactor, where the generated sulfide was stripped as H2S into an off-field oxidation unit using a FeCN63–/FeCN64– redox mediator. FeCN63– oxidized H2S to S0, while FeCN64– was regenerated to FeCN63– at the anode. The reactor performance was enhanced by introducing PU@RGO@MnO2 carriers, with the optimal SO42– removal current identified as 300 mA (6.7 A m–2). SO42– removal and S0 recovery performance was tested under this condition. H2S stripping coupled with sulfate reduction and off-field sulfide oxidation eliminated the inhibition of high concentration sulfide on sulfate-reducing bacteria, achieving 100% H2S-to-S0 conversion. Therefore, the system achieved an efficient SO42– removal rate of 464.3 ± 7.1 mg of SO42–-S L–1 d–1 and a S0 production rate of 450.6 ± 8.6 mg of S0-S L–1 d–1 (SO42– removal efficiency = 92.6 ± 1.3%; S0 recovery efficiency = 89.8 ± 1.6%), with a remarkable electrical energy efficiency of 62.5 ± 1.9% and an energy consumption of 20 kWh kg S0–1. The recovered S0 exhibited high purity (99.15%) and could be efficiently separated via gravity settling. The recovered S0 exhibited an electrochemical performance comparable to that of commercial S0 in the lithium–sulfur battery. This study provides a sustainable approach for wastewater treatment and sulfur recovery, bridging environmental remediation with energy storage application.