Dissolution of uranium from silicate-apatite ore by Acidithiobacillus ferrooxidans

Bioleaching of a low-grade Indian silicate-apatite uranium ore containing 0.024% U3O8 and 10.6% iron with minor amounts of base metals has been reported. The studies involved extraction of uranium using enriched culture containing Acidithiobacillus ferrooxidans (A. ferrooxidans) derived from the source mine water employing bio-chemically generated ferric ion as an oxidant. Parameters such as particle size of the ore, pulp density, and pH of lixiviant media were optimised. Maximum uranium bio-dissolution of 98% was achieved using ore of mixed particles of < 76 μm size. Uranium bio-recovery was found to be 96% at the pulp density (PD) of 10% (w/v) and 20% (w/v) with the particles of < 76 μm size in 40 days at 2.0 pH and 35 °C temperature. At 1.7 pH and 20% (w/v) PD, 98% uranium bio-recovery was achieved with a rise in redox potential from 595 mV to 715 mV in 40 days. Uranium bio-dissolution may be correlated with the generation of ferric ions through the bio-chemical action on the ore. The work illustrated the efficacy of leaching of uranium by the involvement of bacteria by indirect mechanism.