Electricity-Driven Synergistic Sulfur Recovery and Sulfate Elimination in Seawater

High sulfate (SO42-) concentration inhibits seawater utilization but provides a potential source for elemental sulfur (S0) production. The aim of this study was to investigate the feasibility of SO42- removal with the enhancement of S0 recovery simultaneously using a biotic-abiotic hybrid electrochemical (BAHE) process. Long-term operation (i.e., ∼ 240 d) of the biotic electrochemical unit (i.e., single-chamber bioelectrochemical system) obtained a low S0 recovery of 0.78 ± 0.08 % with high SO42- removal exceeding 95 %. The non-conductive S0 precipitated on the anodic surface inhibited continuous electrochemical oxidation of S2-, resulting in the S2- accumulation in the effluent of the bioelectrochemical process and low S0 recovery. In contrast, efficient S2- oxidation took place on the anode surface of the abiotic electrochemical process with electricity generation. The final S2- concentration in the BAHE process was much lower than that in the individual bioelectrochemical process (3 ± 1 vs. 539 ± 60 mg/L). Efficient S0 recovery (i.e., 71.73 ± 7.17 %) and SO42- reduction (92 ± 5 %) were realized in the BAHE process, mainly attributed to the synergistic effect between the single-chamber bioelectrochemical and abiotic electrochemical cells. Our results may provide a promising way for both seawater utilization and elemental sulfur production.