Distinct Roles of Acidophiles in Complete Oxidation of High-Sulfur Ferric Leach Product of Zinc Sulfide Concentrate

Abstract

A two-step process, which involved ferric leaching with biologically generated solution and subsequent biooxidation with the microbial community, has been previously proposed for the processing of low-grade zinc sulfide concentrates. In this study, we carried out the process of complete biological oxidation of the product of ferric leaching of the zinc concentrate, which contained 9% of sphalerite, 5% of chalcopyrite, and 29.7% of elemental sulfur. After 21 days of biooxidation at 40°C, sphalerite and chalcopyrite oxidation reached 99 and 69%, respectively, while the level of elemental sulfur oxidation was 97%. The biooxidation residue could be considered a waste product that is inert under aerobic conditions. The results of this study showed that zinc sulfide concentrate processing using a two-step treatment is efficient and promising. The microbial community, which developed during biooxidation, was dominated by <i>Acidithiobacillus caldus</i>, <i>Leptospirillum ferriphilum, Ferroplasma acidiphilum, Sulfobacillus thermotolerans, S. thermosulfidooxidans,</i> and <i>Cuniculiplasma</i> sp. At the same time, <i>F. acidiphilum</i> and <i>A. caldus</i> played crucial roles in the oxidation of sulfide minerals and elemental sulfur, respectively. The addition of <i>L. ferriphilum</i> to <i>A. caldus</i> during biooxidation of the ferric leach product proved to inhibit elemental sulfur oxidation.