Self-flotation of galena in a complex sulphide ore from a copper mine in Namibia

The copper mine in Namibia, which processes a complex sulphide ore, faces a process challenge of high lead content in the copper concentrate. This study investigated the effectiveness of the self-flotation of galena in lowering the lead content in the copper concentrate by producing separate lead and copper concentrates. Differential flotation experiments were conducted with the first stage tailored for the self-flotation of galena (i.e., no lead collector was added). The effect of residence time during the self-flotation stage on Pb and Cu recoveries was investigated. The results showed an inverse relationship between lead recovery and residence time. Self-flotation of residence time of 20 seconds (lowest residence time tested) produced the best results. Incorporating a self-flotation stage made it possible to produce two quality concentrates of lead and copper. The concentrate had a copper recovery of only 2% and a lead recovery of 92%, while the copper concentrate had a copper recovery of 97% and a lead recovery of 5%. There is scope to optimise other operating parameters such as pH as well as the dosage conditioning time of the frother during self-flotation.