Chemical benefication of nickel overburden of Sukinda mining corporation

Abstract

Utilisation of mine waste, generated during mining of different ores is of utmost importance due to disposal problems. Sukinda region of Orissa is one of the main source of chromite ore in India. The estimated reserves are around 17 million tonnes. In the process of mining chrome ore an overburden of 10 tonnes for each tonne of ore is generated and is dumped as waste. The overburden. contains 0.04 - 0.9% Ni, 0.02 - 0.06% Co and major amounts of iron and silica. So far it has not been commercially exploited due to presence of large quantity of silica. The objective of the present invention is to selectively remove silica by alkali pressure leaching. In the present investigation alkali pressure leaching was carried out in different concentrations of sodium hydroxide. Various parameters such as oxygen pressure, temperature, leaching period and sodium hydroxide concentration were studied. It was observed that maximum upgrading of 1.65% Ni and 0.09% Co could be achieved with 48% yield of concentrate at 7.5 N NaOH concentration, oxygen pressure 40 atmospheres, leaching temperature 200degreesC and 4 hours of leaching period. The pH of the leach liquor was 11.0. Chromium could not be leached out completely (only 40% removed) which indicated the complex form of chromium with iron. Aluminium could be completely removed. The beneficiated overburden can be utilised for recovery of nickel and cabalt by hydrometallurgical or pyrometallurgical processes.