Innovative methodology for comprehensive and harmless utilization of waste copper slag via selective reduction-magnetic separation process

It is very difficult to extract valuable metals from copper slag and nickel laterite through traditional separation processes due to their complex mineral structure. In this work, a selective co-reduction and magnetic separation process was developed to economically and eco-friendly clean copper slag and synchronously upgrade nickel laterite. Through the innovative process, not only the valuable metals, such as Fe, Ni and Cu, can be recovered, but also the hazardous elements can be removed from copper slag, including As, Pb and Zn. Under optimum conditions, a crud Fe-Ni-Cu alloy assaying 2.51% Ni,1.07%Cu and 87.94% Fe can be manufactured as feed for producing weathering steel, and the corresponding recoveries of Ni, Cu and Fe were 87.15%, 79.68% and 68.96%, respectively. The final tailings containing less toxic elements can be used as raw materials for cement. The mechanism of co-reduction of copper slag and nickel laterite was revealed by XRD, SEM-EDS and EPMA techniques. The results show that a suitable proportion of copper slag and nickel laterite was essential to acquire appropriate amount of liquid phase, thereby improve metallic alloy particles migration and growth, which will significantly increase metal recovery in magnetic separation. The leaching toxicity was used to characterize the environmental impact of tailings obtained by co-reduction and magnetic separation process. (C) 2018 Elsevier Ltd. All rights reserved.