Impact of ferro-silicon and gypsum on the recovery of copper from copper slag

High demand in metals coupled with the depletion of metal reserves, slag has become a second source. The demand in copper remaining high while Copper mines are being lesser are lesser, any treatable copper source are targeted. The current investigation focuses on the impact of ferro-silicon and gypsum collected from hydrometallurgical plants both to favour the formation of matte and. Carbon monoxide was blown in at 0.04 l/min for reduction. The head samples and products were characterized using XRF, XRD and SEM. The copper slag, ferrosilicon and gypsum were crushed and milled together for 15 min to obtain a homogeneous head sample. An alumina tube furnace set at 1400 °C was used for the experiment. Based on previous work, the basicity was kept at 0.7 through gypsum addition. The sample was kept for two hours in the furnace at the set temperature and the furnace was switched-off to cool down slowly. A graphite crucible was used. The little matte observed in the head sample entrapped from previous matte production. However, the final produced slag showed more matted formed collecting more copper with high iron content, thus low copper grade due to ferrosilicon addition. Although the distinction between the new matte and new slag was a challenge due to the matte layer very thin, the recovery of copper from the slag was successful. The correlation between the amount of ferrosilicon and the matte grade was found to be inverse proportional due to the amount of iron added through ferrosilicon. Also, the role played by gypsum both on the formation of copper matte and as a flux was very effective in copper coupled with good slag-matte immiscibility. The characterized raw Cu slag showed trace of Ge in the SEM-EDS results and a fayalitic slag containing some little matte.