Aqueous alkaline processing of chromite mine overburden

Abstract

The Sukinda Chromite Mine Overburden (COB) waste contains mainly FeOOH in addition to minor amounts of Ni and Co associated respectively in FeOOH and MnO2 matrices. The other gangue minerals of COB are hematite, quartz, altered chromite, etc in the finely isolated dispersed forms. At present, COB is considered as a source for Ni and Co as there is no other specific Ni-source in India. The COB may also be considered as a very low grade iron ore which may be exploited in the future. Similar to Ni-laterites, the COB also attempted for beneficiation-metal extraction with some success, however, such processes also produce huge COB processed waste containing almost all the original iron values. The direct aqueous processing route appears to be attractive due to the fine size as well as low nickel and high water contents of COB, as such or as its wet concentrates. The Aqueous Alkaline Processing (AAP) of COB is explored here mainly for facilitating iron mineral phase changes similar to bauxite digestion under mild conditions. Under such redox conditions, the reactive iron minerals are likely to transform with minor Co-MnO2 changes. Many other elements, such as Al, Mg, Si, Cr, etc., also influence the process mineralogy. By the recent process mineralogical, intensification techniques and reaction dynamics synergies, the COB-AA pre-treatment and down-stream sequential and simultaneous tests need evaluation to facilitate process evolution. In sum, the AAP opens up options and possibilities for COB prospecting.