Historical assessment of metal recovery potential from old mine tailings: A study case for porphyry copper tailings, Chile

The metal mining activity has been the source of large volumes of tailings that must be stored in tailings storage facilities (TSFs). Since tailings might contain residual valuable metals, these are often subject of assessment studies aimed to find a feasible way to reprocessing. One of these TSFs was built and operated during the 1930's for the exploitation of a giant porphyry copper deposit in Chile, a deposit that is still under exploitation today. For these old tailings a historical assessment was varied out about the copper recovery potential in a reprocessing scenario by flotation. Based on theoretical concepts and available historical operational data, it can be shown that the main reason for the relatively high copper grades found in these tailings are the corresponding high grades of the processed ores, instead of being the result of an inefficient past technology of flotation with consequential low recoveries. Conversely, the former flotation circuit was optimal concerning the recovery of copper sulphides favoured by the less restrictive high copper content of these sulphides. Consistently, it is argued for the study case that the main advances in flotation circuits have focused on improving selectivity without sacrificing recovery, due to the changes in the mineralogy of the exploited ores. These are relevant facts for a reprocessing scenario, indicating a low copper recovery potential if the current conventional flotation technology is considered; thus other and/or newer processing technologies could be more efficient for recovery of the remaining copper. There are hydrometallurgical potential alternatives for reprocessing but limitations are expected in relation to milling size of the tailings material. The present findings may apply elsewhere, due to the high representativeness of the present study case.