Reduction of copper smelting slag using waste cooking oil

Currently, waste cooking oil (WCO) as a renewable energy is not widely utilized. Copper slag cleaning in an electric furnace is a critical process for reducing the excessive magnetite (Fe3O4) present in the copper slag to decrease the slag viscosity, which can promote the sedimentation of matte/copper in the slag, thus reducing the copper content of slag. In this study, laboratory-scale experiments were performed for copper slag cleaning using WCO as a reductant instead of traditional fossil fuel-based reductants. The results showed that the Fe3O4 content of the copper slag significantly decreased from 17.8% to 4.2% with the addition of 2 mL of WCO at 1250 °C. To better understand the reduction process, the cracking characteristics of WCO over corundum and Fe3O4 were investigated at 600–1300 °C. The cracking of 1 mL of WCO over corundum and Fe3O4 at 1300 °C yielded 1450 and 1770 mL of gases (H2, CO, CO2, and methane (CH4)), respectively. Combined with thermodynamic analysis, it was found that all the cracking products participated in the reaction of copper slag cleaning. This work offers a novel approach for the clean utilization of WCO for copper slag cleaning.