Process development for the separation of tetrahedrite from chalcopyrite in the Neves-Corvo ore of Somincor SA, Portugal

In the Somincor Neves Corvo ore, antimony occurs in the tetrahedrite-tennantite series of minerals while copper occurs in chalcopyrite and in other minerals present in minor quantities including the tetrahedrite-tennantite series. Current processing strategies do not directly address the control of antimony contamination of the final copper concentrate. The focus of this paper is to report initial findings of a major investigation undertaken on both a plant and laboratory scale. It was found that both collector type and concentration significantly affected copper/antimony selectivity. In particular, staged addition of dithiophosphate collector was required to control tetrahedrite flotation during copper roughing. However, size by size analysis showed that tetrahedrite flotation increased during scavenging due to further collector addition which was required to recover coarser chalcopyrite bearing particles. The production of separate rougher and scavenger concentrates enriched in chalcopyrite and tetrahedrite respectively, became an attractive option. It was found that oxidative treatment was required to adequately control tetrahedrite flotation. This treatment was applied to a final, low volume concentrate stream containing large quantities of tetrahedrite. In order to further enhance selectivity, fundamental work is aimed at establishing the relative ease of oxidation of chalcopyrite and tetrahedrite as well as the influence of oxidation on the stability of the adsorbed hydrophobic species. A flowsheet embracing these various concepts is proposed.