The leaching behavior of copper and iron recovery from reduction roasting pyrite cinder

Pyrite cinder (PyC) is an iron-enriched solid waste material, which is an important iron resource for steel industry. However, the separation or extraction of iron minerals and heavy metals from PyC was ineffective, because of the fine disseminated granularity and the intergrowth between iron minerals and toxic heavy metals during high temperature roasting. In this paper, a novel method to extract copper and iron from the PyC by reduction roasting-leaching-magnetic separation was proposed. The effect of various parameters on the copper leaching behavior were studied, and the corresponding kinetics model was established. Under the optimized leaching conditions, the maximum copper leaching recovery of 82.18% was reached. A high-quality iron concentrate with Fe content of 65.58% and copper content of 0.17% was obtained subsequently from the leaching residuals through magnetic separation. It showed that the leaching process was controlled by mixed diffusion and chemical reaction, with a corresponding activation energy of 27.97 kJ/mol. The free copper oxide, combined copper oxide and secondary copper sulfide were extracted completely in H₂SO₄ solution. However, chalcopyrite as a form of primary copper sulfide dissolved partly. The leaching mechanism was confirmed by chemical phase and XPS analysis.