THE INFLUENCE OF FERRO-SILICON ADDITION ON THE REDUCTION AND SULFURIZATION OF Co, Cu AND Ge-BEARING SMELTER SLAG WITH CARBON AND CALCIUM SULFATE

The current appetite for base metals, primary metals resources are being depleted; theneed to recycling waste of primary metallurgy such as slag is on the rise. This study investigates the recovery of Ge, Cu and Co with ferrosilicon addition from Ge-copper bearing slag from STL/Gecamines in the Democratic Republic of Congo during carbothermic reduction and sulfurization. Characterization was conducted using XRF, XRD and SEM-EDS while a bench scale alumina tube furnace was used for the experiments. Coke was used as reductant while calcium sulfate (CaSO₄-high purity) was added for sulfurization. Graphite crucibles were used for the experiments and the furnace set for 1400 °C using Eurotherm temperature controller. To limit the interaction between the graphite crucible and the slag, CO was blown in at 0.01 l/min. Products were characterized using XRD coupled with Origin 8.5 software and SEM-EDS. Results have revealed that Cu, Co and Ge were displaced to a matte phase. However, the displacement of Ge from the silicates matrix to the metallic phase was observed. The formation of CuGeFe, CoFe, CuS, FeS and some Cu were present in the metallic phase when FeSi increased in presence of CaSO₄ whereas more amorphous slag was produced due to high silica content.