Iron Recovery from Waste Copper Slag by Using Coal and Secondary Aluminum Dross as Co-Reductants

In this work, a new and carbon-free reductant, i.e., secondary aluminum dross, is used to replace coal to recycle valuable metals from copper slag by smelting reduction. The influence of substitution ratio on slag properties and metal recovery was investigated. The results show that the metal recovery is mainly determined by the settlement of the generated metals after reduction because of the rapid increase of slag viscosity. Although the viscosity of the final slag was 0.3–0.4 Pa·s when using coal as the primary reductant at 1550°C, only 95.4% Fe was recovered because of the slag foaming effect. The viscosity was still kept at an acceptable level at the substitution ratio of 50% but the foaming phenomenon disappeared, leading to an almost complete recovery of iron (98.2%). However, the final slags became extremely viscous with a further increase of aluminum dross content, greatly impeding the separation of metal droplets.