Bioreactor leaching of uranium from a low grade Indian silicate ore

Bio-leaching studies were carried out in a 2 L bioreactor- BIOSTAT-B® equipped with a PLC based controller at 20–40% (w/v) pulp density using enriched culture of A.ferrooxidans for Turamdih uranium ore (Jharkhand, India). With the enriched culture of A.ferrooxidans adapted on Fe(II) at pH 2.0, 35 °C and 20% (w/v) pulp density, a 98.3% uranium recovery was recorded in 14 days. The leaching of uranium in the bioreactor improved the dissolution rate by reducing the time from 40 days in shake flask as per our earlier studies to 14 days. While investigating the importance of biogenic Fe(III) in the bio-leaching process a maximum recovery of 84.7% U3O8 was observed at pH 2.0 and 20% (w/v) pulp density in 10 h as compared to the uranium leaching of 38.3% in the control experiments. On raising the pulp density to 30%, uranium bio-recovery increased to 87.6% in 10 h at pH 2.0 with <76 μm size material. This showed a distinct advantage because of better mixing of slurry in the bioreactor with auto-controlled conditions that improved the kinetics.

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► This study for bioreactor leaching of uranium from silicate ore is the first attempt with such low tenor material.
► With bacterial species, 98.3% uranium is recovered in 14 days against 40 days in shake-flask.
► With bacteria and biogenic Fe(III), 87.6% uranium leaching is observed in 10 h at same conditions.
► Studies prove the worth of bioreactors in better mixing of slurry that improves the kinetics.