Investigation into Regularities of Leaching Sulfated Cinders of Roasting Copper–Zinc Middlings

Abstract—Results of an analysis of thermodynamic characteristic and the investigation into kinetic regularities of leaching a new type of sulfated copper–zinc middlings formed with the removal of sulfide materials that cannot be effectively selected by flotation are presented. When analyzing the kinetic curves, it is established that the reaction rate abruptly differs between the initial time period (30 min) and the subsequent period at any acid concentration in a range of 0–20 g/dm³. In the initial instant, the rate is controlled only by the external diffusion, while after 30 min of the process, the kinetic obstacles start to manifest themselves. Reaction orders of cinder leaching are determined to be as follows: 1.0 ± 0.1 for copper, 0.87 ± 0.1 for zinc, and 0.56 ± 0.1 for iron. A calculation of the apparent rate constant of the leaching reaction showed its weak temperature dependence, which correlates well with the thermodynamic analysis data.