Behaviour of Co and Ni during aqueous sulphur dioxide leaching of nickel smelter slag

The behaviour of Co and Ni during aqueous sulphur dioxide leaching of nickel smelter slag from INCO was studied. The study is part of a major research project aimed at developing an effective means for extracting valuable metals from slag using aqueous sulphur dioxide. Leaching experiments were carried out under different conditions in a batch reactor. Maximum extractions of Co and Ni after 3 h were 77% and 35%, respectively. The rate of extraction of both metals was independent of stirring speed between 450 and 700 rpm. The shrinking core model was used to explain the behaviour of Co and Ni. Co extraction was limited by both ash layer diffusion and surface chemical reaction, whereas Ni extraction was limited only by ash layer diffusion. Scanning electron microscopy-energy dispersive spectroscopy analysis showed that die slag becomes porous after leaching and follows the shrinking core-form of dissolution. (C) 2000 Elsevier Science B.V. All rights reserved.