Investigating the selective extraction of metals from nickel sulfide tailings using salt roasting and acid leaching

The recovery of nickel and copper from nickel sulfide flotation tailings was studied by magnesium carbonate salt roasting followed by sulfuric acid leaching. Leaching was performed under atmospheric conditions using a gyratory water bath. The tailings material was roasted with and without magnesium carbonate at varying mass ratio (0.15 to 0.75), temperature (300 – 700 °C), and time (1 – 5 h). Subsequent leaching tests were performed using sulfuric acid at different concentrations (1 – 5 M). The influence of leaching time and temperature was investigated as well. The results after inductively coupled plasma optical emission spectroscopy analysis demonstrated that, under the optimum roasting and leaching conditions, about 98 % nickel was leached into solution while only approximately 38 % iron was present. Relatively high concentrations of other valuable metals such as copper, manganese and cobalt were also extracted into the leach solution. The salt roasting-acid leaching process consequently presents a feasible approach for selective recovery of valuable minerals from the sulfide tailings, thereby reducing downstream and purification costs.