Copper smelter slag treatment by ammonia solution: Leaching process optimization

Abstract

The feasibility of copper smelter slag processing by ammonia solution treatment was investigated. The central composite rotatable design (CCRD) and approximation method were used to determine the optimum conditions of zinc and copper recovery to a solution. The experimental design was done at five levels of the four operating parameters which were the initial concentration of NH₃, the initial Cl^– ions concentration, leaching time and solid/liquid ratio. Two mathematical models describing dependence of metal recovery on the operating parameters were obtained. The models are successful in predicting the responses. It was found that optimal parameters for zinc and copper recovery are as follows (values for copper are given in brackets): initial ${\text{C}_{\text{N}{\text{H}_3}}}$ 17.1% (19.9%), initial ${C_{\text{C}{\text{l}^ - }}}$ 160 g/L (160 g/L), leaching process duration 4.56 h (4.13 h), solid/liquid ratio 0.39 (0.53). The maximum Zn and Cu recoveries to solution, obtained experimentally under the conditions, are 81.16% and 56.48%, respectively.