Microbial Treatment of Lateritic Ni-ore for Iron Beneficiation and Their Characterization

This study aims at studying effect of anaerobic dissimilatory iron (III) reducing bacterial consortium on different phases of iron present in lateritic nickel ore. Such conversion in lateritic nickel ore are helpful in better recovery of sorbed metal values like Ni and Co by subsequent bioleaching or acid leaching. Here properties of thermally and microbially reduced lateritic nickel ore are compared vis-à-vis original ore. An anaerobic dissimilatory iron (III) reducing bacterial consortium capable of using glucose as carbon source and lateritic nickel ore as terminal electron acceptor was used for microbial reduction of ore under anaerobic condition. Microbial reduction changes the initial light brown colour of the lateritic nickel ore to dark brown. The change in colour is due to the conversion of goethite to magnetite, which is confirmed from the XRD pattern. The FTIR spectra and the UV-Visible spectra support the presence both goethite and hematite. The study shows that changes in phases brought about by microbial treatment are different than those by thermal treatment. The carrier mediated exchange interaction between Fe2+ and Fe3+ ions in lateritic nickel ore sample treated with IRB consortium is responsible for higher ferromagnetic ordering. The thermal reduction of the same sample showed lowering of ferromagnetic ordering due to the decreasing percentage of Fe2+ and Fe3+ ions.