Bio-Hydrometallurgical Processing of Non-Ferrous Metals from Copper Smelting Slag

Abstract

Stirred tank reactor (STR) leaching of non-ferrous metals from copper smelting slag was conducted using biogenic Fe 3+ solution containing H 2 SO 4 . The solution was initially obtained through biooxidation of FeS 2 +S° by using a moderately thermophilic microbial culture such as Sulfobacillus thermosulfidooxidans at 45°C and was applied as lixiviant in STR leaching experiments. The effect of pH, pulp density, temperature and initial Fe 3+ concentration on leaching behavior of Cu, Fe, Zn and Ni from the slag were investigated. The presence of high concentration of Fe 3+ ions was found to promote the leaching of copper and nickel while inhibiting the leaching of zinc and iron. Process pH was considered as the most significant parameter and the optimum leaching results were obtained at pH 1.8 with low fayalite dissolution and jarosite precipitation. During the leaching at this pH (1.8), 25% (w/v) pulp density and 65°C temperature in presence of 20 g/L initial Fe 3+ concentration, maximum extraction of Cu (90%) and Ni (85%) was observed in 4 hours whereas Fe extraction was minimum (19%). A schematic flowsheet of multistage leaching process was proposed. The result obtained from multistage batch leaching experiments will be step forward for continuous stirred tank reactor leaching for industrial scale implementation.