Breaking the Fe3O4-Wrapping-Copper Microstructure for Enhancing the Copper-Slag separation

Precipitation of Fe3O4 particles and the accompanied formation of the Fe3O4-wrapping-copper structure are the main obstacle for copper recovery from the molten slag during the pyrometallurgical smelting of copper concentrates. Herein, by replacing the commercial powdery pyrite or anthracite with the pyrite-anthracite pellets as the reductants, more Fe3O4 particles in the molten slag can be removed, resulting in the deep fracture of the Fe3O4-wraping-copper microstructure and fully exposure of the copper matte cores. Resultantly, using 1 wt.% composite pellet as the reductant, the copper matte droplets are enlarged greatly from 25 μm to the size being observed by naked eyes, with the copper content being enriched remarkably from 1.2 wt.% to 4.5 wt.%. The DFT calculation results imply that the formation of the Fe3O4-wrapping-copper structure is due to the preferential adhesion of Cu2S on the Fe3O4 particles. The XPS and FTIR as well as Raman spectroscopy results all reveal that the high-efficiency conversion of Fe3O4 to FeO can decrease the volume fraction of solid phase and promote the depolymerization of silicate network structure, which promotes the settling of copper matte droplets due to lowered slag viscosity, contributing to the high-efficiency copper-slag separation for copper recovery. The results can provide new insights for enhanced in-situ enrichment of copper from the molten slag.