Effects of O2 on aqueous SO2 leaching of Co, Cu and Ni from discard smelter slag

Abstract

AbstractIn the leaching of non‐ferrous smelter slag with a dissolved gas mixture of SO2 and O2, the behaviour of Co, Cu, Ni, Zn and Fe was studied in a 1‐L batch reactor. The parameters investigated include PSO2, PO2, temperature, particle size and pH. Co, Zn and Fe behaved similarly while Ni and Cu displayed distinguishable characters. The addition of O2 prevented the precipitation of Cu after dissolution, and increased acidity of the leaching solution. The increase in acid strength resulted in an increase in the extraction of Co, Zn and Fe. The effect of acidity on Cu and Ni extraction was however much weaker. The combination of SO2 and O2 was found to be a more effective oxidant of Fe(II) to Fe(III) than O2 alone. Simultaneous extraction of valuable metals and removal of Fe could be achieved by leaching at pH of 3 to 4. Maximum selectivities obtained for Co, Ni and Cu over Fe were 300, 2000 and 4000, respectively.