Effect of ferric ions on the anaerobic bio-dissolution of jarosites by Acidithiobacillus ferrooxidans.

Large amounts of jarosites are produced during zinc hydrometallurgy and bioleaching, as well as in acid sulfate soils and acid mine drainage environments. As such, understanding the behavior of jarosite dissolution is important for analyzing the iron cycle process and promoting the control and treatment of jarosites. In general, soluble ferric ions and jarosites coexist in acid environments; however, the relationship between soluble ferric ions and jarosites under anaerobic reductive conditions is still not well understood. In this study, the effect of adding Fe3+ on the promotion of the bio-dissolution of jarosites using Acidithiobacillus ferrooxidans is investigated. With the addition of 12 mM Fe3+, the efficiency and maximum rate of jarosite bio-dissolution were found to reach 84.1% and 2.66 mmol/(L·d), respectively. The addition of Fe3+ at concentrations higher than 12 mM did not further improve the jarosite bio-dissolution. These results indicate that the mechanisms underlying these improvements include: (i) the reduction of the zeta potential due to the compression of the diffusion layer of the electric double layer by Fe3+; (ii) bacteria growth enhancement and the stabilization of the pH of cultures via the reduction of soluble Fe3+. Based on these observations, this study serves to promote the development of jarosite bio-dissolution using Acidithiobacillus ferrooxidans and challenges the idea that soluble Fe3+ suppresses the bio-dissolution reaction of solid Fe3+ substances such as jarosite when soluble ferric ions and jarosite coexist.