Bioleaching of uranium from low grade black schists by <Emphasis Type="Italic">Acidithiobacillus ferrooxidans</Emphasis>

Summary The feasibility of bacterial recovery of uranium from the low grade black schists occurring in the Okcheon district, South Korea, was investigated. Following the introduction of Acidithiobacillus ferrooxidans, 80% of the uranium could be extracted from the schists, which contain 0.01% U₃O₈ by weight, within 60 h at a pulp density of 100 g-ore/l. Only 18% of the uranium was extracted without microbial activity. The uranium-leaching efficiency was not greatly affected by the addition of Fe²⁺ in the range of 5–9 g/l, and the leaching efficiency of uranium from the schists by A. ferrooxidanscould be efficiently maintained at high pulp densities (up to 500 g-ore/l).