Development and evaluation of an early removal process for the beneficiation of arsenic-bearing copper ores

In conventional flotation flowsheets for treating copper sulphide ores containing small but significant amounts of arsenic, the arsenic is generally concentrated with the copper in final concentrate. Often, a penalty can be imposed by the smelter processing the concentrate, based on the arsenic content. In some cases the arsenic level is such that the smelter will not treat or accept the concentrate.A new approach to address this issue is reported in this paper, which is becoming more significant as the quality of the copper ore bodies currently being mined diminishes. A new flowsheet, based on the early removal of arsenic at the concentrator, has been developed and tested at bench-scale.The proposed flowsheet comprises three key steps: firstly, separation of arsenic and copper minerals using controlled-potential flotation to produce a low-arsenic high-copper concentrate and a high-arsenic low-copper concentrate. The low-arsenic concentrate can be sold without incurring any penalty for arsenic content. In the second stage, the high-arsenic concentrate is subjected to a low temperature roasting, where the arsenic is selectively fumed off into a low-volume stream product. The calcine from the roaster is high in copper and sulphur and can still be smelted directly. In the final stage of the flowsheet, the arsenic in the fume product is immobilised in a low temperature ceramic such that safe disposal back into the ground is possible.The new early removal flowsheet has been sequentially tested in the laboratory at small scale. The technical and economic merits of the flowsheet compared with that of the conventional copper flotation flowsheet show that there is a net benefit.