Recovery of Zinc and Copper from Lead Slag by the Combined Process of Beneficiation and Roasting

The valuable metals copper and zinc were successfully recovered from a water-quenched lead smelting slag containing zinc in Gansu Province. This study focuses on the application of the direct reduction roasting-flotation process for extracting these metals from the slag phase. To comprehend the recovery principle of copper and zinc minerals in the slag phase, various techniques including thermodynamic analysis, scanning electron microscopy, energy dispersive spectrometry, and mineral liberation analyzer were employed. The findings demonstrate that zinc minerals can be easily recovered through reduction roasting processes. Following roasting, chalcopyrite within the slag phase recrystallizes into larger particles which become exposed on the surface of vitreous gangue material. By optimizing parameters such as roasting time (90 min), coke dosage (12.5%), and roasting temperature (1250°C), a remarkable volatilization rate of 99.27% for zinc in the slag phase was achieved while successfully recovering high-purity zinc oxide dust. Copper ores undergo a transition from being difficult to dissociate into monomers to becoming easier to dissociate, thereby enhancing their flotation recovery potential. Through one rough flotation followed by three cleaning flotation during process, a concentrate with an impressive copper grade of 18.24% and copper recovery rate of 56.22% was obtained.