Role of ferric ions in bioleaching of uranium from low tenor Indian ore

The role of biogenic ferric ions in leaching of uranium by Acidithiobacillus ferrooxidans from a low
grade ore of Turamdih mines, India, has been investigated. Using the enriched culture of bacterial
isolate containing mainly A. ferrooxidans from the source mine water, biorecovery of 98% uranium
at 20% (w/v) pulp density, pH 1.7 and 35oC temperature using ,76 mm particles in 40 days was
obtained. The effect of temperature on bioleaching of uranium showed higher recovery at 35oC.
The uranium dissolution was facilitated by iron(III) available in the leach liquor because of
bacterial oxidation of pyrite and chemical dissolution of magnetite present in the ore under acidic
conditions. The biogenically generated Fe(III) ions enhanced uranium dissolution from the
uraninite ore. The bioleaching of uranium appeared to follow a chemical control kinetic model with
the reaction of lixiviant, Fe(III) and acid on the surface of the solid in the temperature range 25–
35oC. Phase identification by XRD and the study of surface morphology of the ore and the residue
by SEM study corroborated the above mechanism of uranium leaching