THE LEACHING OF SULFIDE MINERALS IN CHLORIDE MEDIA

Recent studies on the ferric chloride and cupric chloride leaching of chalcopyrite, galena and sphalerite are reviewed. Although the chloride leaching of chalcopyrite concentrates has been proven at the demonstration plant scale, the leaching reaction is difficult. In contrast, galena dissolves rapidly in FeCl3 media, and both the leaching rate and lead solubility increase significantly with increasing chloride concentration. The hydrometallurgical treatment of lead concentrates seems to be technically feasible. The sphalerite leaching rate is strongly affected by its solid solution iron content and leaching processes for iron-rich zinc concentrates could probably be developed. The importance of intermediate sulphide phases and insoluble reaction products on the leaching of sulphides is discussed. In addition, it is postulated that at least part of the elemental sulphur reaction product is formed via the oxidation of dissolved H2S. The ability of chloride leaching processes to generate elemental sulphur while leaving pyrite largely unaffected makes them especially useful for the treatment of pyritic complex sulphides. Thus, recent chloride leaching technologies for complex sulphides are also reviewed.