Bioleaching of Indian Ocean nodules with in situ iron precipitation by anaerobic Mn reducing consortia

Abstract

In the present study selective iron-free extraction of Cu, Ni, Co and Mn from Indian Ocean manganese nodules by manganese reducing consortium is described. The consortium isolated from manganese ore mines of Joda, Odisha (India) and enriched with Indian Ocean manganese nodules was used for bioleaching under facultative anaerobic conditions in mineral salt media using organic carbon source. Bioleaching was carried out at 30°C without agitation. Recoveries of Mn, Ni and Co increased with time, while maximum Cu recovery occurred during the initial period followed by a decrease. A notable finding was that Fe dissolution remained extremely low, i.e. less than 42mgL−1 (3.0%), possibly due to in situ precipitation of iron. X-ray diffraction patterns of bioleach residues indicated formation of FePO4 and MnCO3 phases. Iron dissolution remained consistently low even with increasing pulp density and decreasing particle size. The Mn reducing consortia may thus help in selective leaching of Mn while preventing Fe from contaminating the leach liquor, which is desirable in downstream processing of metal production from Mn-nodule and ferromanganese ores.