Anoxic treatment for thiosulfate separation from formate containing dithionite industrial effluent and electrochemical sulfur recovery

The present work deals with utilization of formate present in the dithionite industrial effluent for thiosulfate separation and electrochemical sulfur recovery. In anoxic treatment, Pseudomonas aeruginosa and Proteus mirabilis were used for formate utilization and thiosulfate reduction. The organisms utilized sodium formate as a carbon source and thiosulfate as a terminal electron acceptor, it degraded the organic compounds fully present in the effluent. Thiosulfate got reduced to sulfide or hydrogen sulfide, where thiosulfate reduction was insignificant. Impact of iron surface on anoxic thiosulfate reduction was also investigated in the present study. An electrochemical two chambered membrane cell was used to recover sulfur from the biogenic sulfide electrolyte. Three different types of surface pattern (flattened, twisted and cylindrical) of Ti-TiO2/IrO2/RuO2 coated mesh anodes were used to comparing the sulfide to sulfur conversion process. Rotating cylindrical mesh electrode gave maximum sulfur recovery efficiency (96%) when compared to twisted (91%) and flattened (61%) electrodes. In this process, excess sodium hydroxide was also recovered at the catholyte during biogenic sulfide oxidation.