Final Project Report on "Microbial Leaching of uranium from Narwapahar ore"

Uranium ore from Narwapahar Mines, UCIL contains 0.047% U 3 O 8 with some refractory minerals and high apatite (5%) results in a maximum 78% recovery through conventional processing at UCIL, with a fairly high consumption of sulfuric acid and pyrolusite, and loss of uranium as uranium
phosphate. To avoid usage of non-eco-friendly oxidants, obviate the influence of phosphate, and improve the overall process output of uranium, an alternate extraction technology using microbial isolate(s) was
proposed under this project.

A.ferrooxidans isolated from Narwapahar mine water was found amenable to uranium bioleaching.
Optimum uranium bio-recovery is achieved at 10% PD (w/v) of 96% pH 1.7 and 35 o C in 40 days with the fine particles of <45µm size. Under the optimum condition at pH 1.7, rise in redox potential is recorded to be 538-708 in 40days. Bioleaching of uranium seems to follow the indirect mechanism of leaching with the involvement of Fe (III) biogenically generated by A.ferrooxidans. Uranium recovery was also examined using another isolate of L.ferrooxidans which showed 98% uranium leaching at 40 o C, which shows the possibility of improving the kinetics of the process thus, requiring further studies by applying thermophiles.

In case of 2.0kg laboratory column leaching, 57% bio-recovery in 40 days at pH 1.7 was observed. The
dissolution of uranium in column under chemical leaching conditions (control experiment) recorded a
lower value of 39%. To test the efficacy of L. ferrooxidans, column was operated under similar conditions
resulting in uranium biorecovery of 66%. The acid consumption using A.ferrooxidans and L.ferrooxidans
was estimated to be 3.2 and 2.8kg/T ore; as against 5.4kg/T in control experiments.