Optimization study of the leaching of roasted zinc sulphide concentrate with sulphuric acid solutions

The Taguchi method was used to determine the optimum conditions for the dissolution of roasted zinc sulphide concentrate in H2SO4 solutions. The experimental parameters and their ranges were between 13 and 55 °C for the reaction temperature, 0.1–0.3 g cm−3 for solid-to-liquid ratio, 24.02–48.77% for acid concentration (by mass), 10–50 min for reaction time, and 300–800 rpm for stirring speed. The optimum conditions were found to be 55 °C, 0.1 g cm−3, 37.26% (by mass) H2SO4, 50 min and 300 rpm, respectively. Under these conditions, the dissolution of Zn+Cu in H2SO4 solutions was approximately 99%. In addition, some experiments were performed for alternative parameter levels, to minimise Fe dissolution while keeping the dissolution of Zn+Cu around maximum.