The importance of geochemical and mineralogical characterization of fresh Cu-Porphyry mine tailings in mineral processing plants to optimize their revalorization potential

Abstract

The existence of enormous volumes of mine tailings (MTs) deposits around the World, and specially in Chile, has generated a growing interest about the potential economic and socio-environmental benefits of reprocessing them. The present study assesses this possibility in the world class example of Mineral Valle Central (MVC), one of the few MTs reprocessing plants that has been under operation since 1992. To do so, 20 sampling points along the mineral processing plant were selected and monitored every two months from April 2018 to January 2019, generating a total of 120 samples. The multivariate statistical analysis of detailed chemical and mineralogical information confirmed the existence of two main groups, a first one corresponding to the elements (As, Ag, Fe, Cd, Co, Ni, Pb, Sb and Zn) linked to sulphides and a second one including elements mainly hosted by silicates. As expected, the first group of elements showed a general increasing tendency in their concentration along the processing plant while the second group tended to decrease their concentrations. It was observed that during the generation of the current Cu-concentrate in MVC, Co concentrations are increased as high as ten times (~0.25 g/kg) from the original concentration in the MTs entering the reprocessing plant (~0.025 g/kg). Therefore, the design and theoretical addition of new operational units to generate pyrite concentrates was evaluated. Such a de-pyritization process unit could link economic and environmental potential benefits thanks to the recovery of the Co hosted in pyrite and to the reduction of the acid generation potential of the final MTs sent to Caren MTs deposit. This exploratory study shows important environmental benefits as well as some economic potential thanks to the recovery of Co hosted in pyrite. Notwithstanding, future comprehensive Co deportment studies and a detailed technical – economical evaluation are needed to determine the economic feasibility for the construction of the proposed de-pyritization process unit.