Understanding galvanic interactions between chalcopyrite and magnetite in acid medium to improve copper (Bio)Leaching

Abstract

Chalcopyrite is the main ore mineral used in industrial copper extraction. However, when passivation processes occur during hydrometallurgical treatment, a large percentage of the mineral being treated is not solubilized, so the copper recovery is limited. Galvanic interactions between semiconductor minerals are the basis of many strategies to achieve a more efficient process for increasing copper dissolution. These interactions concern generally two metallic sulfides. The present study describes a new galvanic interaction between chalcopyrite-magnetite (CuFeS2-Fe3O4) in an acid microbial culture medium, used routinely in biomining processes. The electrochemical characterization of CuFeS2, Fe3O4 and a mineral containing CuFeS2-Fe3O4 is performed. Galvanic interactions are demonstrated by comparing Evans diagrams constructed from current transients obtained by imposing the potential pulses to each species studied. It is determined that CuFeS2 and Fe3O4 fulfil the role of anode and cathode, respectively, in the behavior of the corresponding mineral. Stripping voltammetry is used to quantify electro-dissolved ions; the electrooxidation of CuFeS2-Fe3O4 mineral in acid culture medium releases twice as many copper ions as pure chalcopyrite. This corroborates that the galvanic interactions prevent the formation of typical passivating components observed in chalcopyrite.