Carbothermic reduction of Zambian sulphide concentrates in presence of lime

Abstract

The investigation focuses on an alternative route to metallic phase extraction from complex Zambian copper–cobalt sulphide mineral concentrates, derived from the Copperbelt region. In the context of developing a novel process route for metal extraction without sulphur dioxide emission and slag waste generation, we have studied the reduction of copper–cobalt sulphide concentrates via carbothermic reduction in the presence of lime by following the equilibrium: MS+CaO+C = M+CaS+CO(g), where M represents the metallic copper, cobalt and iron. The effects of stoichiometric ratios of MS/CaO and MS/C were analysed over a range of temperature between 1073 and 1273 K. The reaction mechanism was analysed by identifying the phases formed, which were characterised by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) techniques. The metallic phase analysis confirmed the presence of 85–97 wt-% alloy, which formed as a result of carbothermic reduction. The extent of metallization was analysed by plotting percentage reduction (%R) for each reaction against time (t), from which three different regions of overall reaction were determined. Based on this approach, the overall reaction mechanism is discussed.