Application of Biogenic Thiosulfate Produced by Methylophaga sulfidovorans for Sustainable Gold Extraction

Thiosulfate is an alternative lixiviant that eliminates many environmental and social drawbacks of cyanide leaching used by most gold operations. Biogenic thiosulfate (Bio-TS) was produced by the bacterium Methylophaga sulfidovorans with sodium sulfide as a substrate and used to leach gold powder and gold from an oxide ore. Growth curve studies were used to determine the growth conditions of the bacteria in batch flask conditions regarding pH and inoculum load. The effect of sulfide dosage and addition time on Bio-TS concentration was studied. The optimal conditions for the growth and generation of Bio-TS were determined to be pH 7-8, 30 degrees C, and in the environment of a sealed flask rotating in a high salinity medium. Production of Bio-TS from sodium sulfide was confirmed by iodometric titration and IC/UV-vis methods. Gold was leached with a maximum extraction efficiency of 61.9% from ore after 24 hata 10% pulp density, 0.1 L/min air, and 50 degrees C. Sustainable indicators and green metrics were combined for multicriteria analysis to quantify the sustainability of this novel proposed method relative to cyanidation and thiosulfate gold leaching processes.

Automated summary

Thiosulfate, an alternative lixiviant to cyanide, was produced using Methylophaga sulfidovorans bacteria and used to leach gold from ore. Optimal conditions for the growth of bacteria and generation of thiosulfate were determined. The proposed method showed higher sustainability compared to cyanidation and thiosulfate gold leaching processes.