Kinetics analysis of copper extraction from copper smelting slag by sulfuric acid oxidation leaching

Copper smelting slag (CSS) is generally produced from the pyrometallurgy of copper sulfide concentrate, the current storage disposal methods of CSS not only occupy precious land and pollute the environment, but also waste resources. To recover copper from the CSS and explore the atmospheric pressure oxidative leaching kinetics of copper extraction from CSS with sulfuric acid was investigated intensively. In this study, the effect of particle size, sulfuric acid concentration, temperature, liquid-to-solid ratio, and hydrogen peroxide added amount were investigated comprehensively. The results indicated that the decrease of particle size and increase of other parameters can significantly promote the leaching of copper. Under the optimum conditions, 90.7 % of the copper in the CSS was effectively leached, other copper in the leaching slag mainly existed in the form of fine-grained embedded copper sulfide. The dominant phase of the leaching slag is magnetite, which could be further recovered by conventional magnetic separation. Moreover, the kinetics of copper atmospheric pressure oxidative leaching in CSS were further expounded. The results indicated that the copper leaching kinetic conforms to the shrinking core model, and the overall leaching reaction was controlled by the internal diffusion control with an activation energy of 11.22 KJ/mol. The apparent reaction order of sulfuric acid and particle size are determined to be 0.965 and 0.478 respectively. Finally, the kinetics model equation is established for copper at normal pressure as:$1-\frac{2}{3}\eta -{\left(1-\eta \right)}^{2/3}=0.032·C_{H_{2}S{O}_4}^{0.965}·r_0^{-0.956}·t$. This research could provide an alternative solution for the efficient utilization of CSS.