Using acidophilic bacteria to catalyze the reductive dissolution of oxidized minerals is an innovative process that facilitates the extraction of valuable base metals (principally cobalt and nickel) from limonites, which are otherwise often regarded as waste products of laterite mining. The most appropriate conditions required to optimize reductive mineral dissolution are unresolved, and the current work has reassessed the roles of Acidithiobacillus spp. in this process and identified novel facets. Aerobic bio-oxidation of zero-valent sulfur (ZVS) can generate sufficient acidity to counterbalance that consumed by the dissolution of oxidized iron and manganese minerals but precludes the development of low redox potentials that accelerate the reductive process, and although anaerobic oxidation of sulfur by iron-reducing species can achieve this, less acid is generated. Limited reduction of soluble iron (III) occurs in pure cultures of Acidithiobacillus spp. (Acidithiobacillus thiooxidans and Acidithiobacillus caldus) that do not grow by iron respiration. This phenomenon (“latent iron reduction”) was observed in aerated cultures and bioreactors and was independent of electron donor used (ZVS or hydrogen). Sufficient ferrous iron was generated in the presence of sterilized hydrophilic sulfur (bio-ZVS) to promote the effective reductive dissolution of Mn (IV) minerals in limonite and the solubilization of cobalt in the absence of viable acidophiles.
|Journal||Frontiers in Microbiology|
|Publication status||Published - 26 Jul 2021|
Bibliographical noteFunding Information:
We are indebted to colleagues at the Natural History Museum (London, United Kingdom) for providing mineralogical and chemical data and supplying the Shevchenko limonite, and at the Bureau de Recherches G?ologiques et Mini?res (Orleans, France) for the Penamax limonite. Funding. This work was supported by the European Union Framework Program for Research and Innovation Horizon 2020 (?CROCODILE?; grant reference 776473) and the Natural Environment Research Council (United Kingdom) under its Security of Minerals Supply Program (grant reference NE/M010899/1).
This work was supported by the European Union Framework Program for Research and Innovation Horizon 2020 (“CROCODILE”; grant reference 776473) and the Natural Environment Research Council (United Kingdom) under its Security of Minerals Supply Program (grant reference NE/M010899/1).
© Copyright © 2021 Johnson, Smith and Santos.
- acid dissolution
- base metals
ASJC Scopus subject areas
- Microbiology (medical)