Kinetics of copper extraction from copper smelting slag by pressure oxidative leaching with sulfuric acid

The accumulation of copper smelting slag not only pollutes the environment but also wastes resources, using oxygen pressure acid leaching process to treat copper slag has incomparable advantages over other processes, but there are few researches reported at home and abroad. In this paper, copper slag was treated by this process. Under the premise of fully studying the influence of various factors on copper dissolution, the selective leaching behavior and kinetics of copper oxy-pressure acid system in copper slag were expounded. The experimental results showed that the dissolution kinetics analysis of the experimental data based on the shrinking core model for various conditions indicated that the reaction rate of leaching was mainly controlled by the chemical reaction during its early stages, then switched to be controlled by mixed chemical-reaction and product-layer diffusion which could be ignored because of its short lifetime, and finally was controlled solely by diffusion through a surface product layer in the later stage. The activation energy was calculated to be 47.03 kJ.mol/L in the early surface chemical reaction controlling stage and 11.35 kJ.mol/L in the later diffusion controlling stage, respectively. The leaching rate of copper is mainly determined by the chemical reaction control stage, in which the reaction orders of sulfuric acid concentration, oxygen partial pressure and particle size are 0.83, 0.92 and -1, respectively.