Economic Potential for reprocessing Copper Mine Tailings in Chile

Four copper mine tailings in Chile were investigated for their elemental and mineral composition, in order to evaluate the potential for economic reprocessing. The sample material, taken for processing had Cu-contents between 0.1 and 0.5 %. Copper was abundant in various primary (mostly chalcopyrite) and secondary (cuprite, atacamite, brochantite and chrysocolla) minerals. This report includes tests of laboratory size. Chemical sulfuric acid leaching was assessed in comparison to bioleaching. Copper bioleaching resulted in recoveries between 20 % and 70 %. For chemical leaching the recovery was 4 % to over 80 %. The recovery was strongly dependent on the mineralogical composition of the copper minerals. Secondary copper minerals were very scarcely abundant in the solid leaching residues. Using chemical leaching a very low copper recovery for one sample could be explained by the presence of the recalcitrant mineral chalcopyrite as the almost unique copper bearing mineral. In contrast, a significant copper bioleaching was found instead. Almost one third of all chalcopyrite grains showed clear signs of alteration investigated by scanning electron microscopy. Overall, the study shows that the economic potential for tailings reprocessing is strongly dependent on the composition of the valuable metals hosting minerals in connection with the applied processing technology.