Geomicrobiological study of experimental leaching of uranium. Geomicrobiology of a bench-scale reactor for the (bio)leaching of uranium

The impact of a native microbial consortium in relation to varied iron (FeII/FeIII) geochemistry on the (bio)leaching of a non-sulfidic weathered uranium ore is examined in this work. Results from column studies show that a mine-derived native microbial population was capable of oxidising a continuous supply of leachant, containing 4.1 mM Fe(II), within 10 days of operation. In doing so, the natural consortium is able to restore redox conditions amenable to enhanced uranium extraction. Due to the weathered nature of the ore, the majority of uranium was extracted in the initial stages of leaching. As such, any elevated Fe(II) which is originally present irreversibly hampers the maximal uranium recovery when compared to Fe(III)-rich leaching counterparts. The iron-oxidising activity critical to enhanced uranium extraction, was attributed to bacteria from two families within the phylum Firmicutes: Alicyclobacillaceae and Sulfobacillaceae. The microbial community active during leaching showed changes from the source mine-derived material dominated by Actinobacteria (Mycobacterium) with Firmicutes predominately attached to the solid-phase (ripios) and a Proteobacteria-rich leachate. The presence of eukaryotes, mostly fungi, was mainly limited to the ripios on the top of the columns. Published as: Vázquez-Campos X, Kinsela AS, Collins RN, Neilan BA, Waite TD. (2017). Uranium extraction from a low-grade, stockpiled, non-sulfidic ore: Impact of added iron and the native microbial consortia. Hydrometallurgy 167: 81–91. 10.1016/j.hydromet.2016.11.002