Mechanism of Enhanced Copper Recovery From Chalcopyrite in the Presence of Carbon Black Under Ambient Conditions

The formation of a passive layer during the hydrometallurgical leaching of copper from chalcopyrite leads to a relatively low copper recovery owing to the halting of the leaching efficiency. Thus, the copper recovery during chalcopyrite leaching needs to be promoted and the formation of passive layers on the mineral surface must be reduced. Organic solvents and surfactants are used to thin the passive layer, improve electron transfer through the passive layer using electrical conductors, and improve leaching through the galvanic effect. Recent research that combined the galvanic effect and enhancement of the electrical conductivity of passive layers has been intensively discussed. Therefore, in this study, we determine the effect of carbon black on the leaching mechanism of chalcopyrite in the presence of manganese dioxide and pyrite. Chalcopyrite leaching is performed using a 1 M sulfuric acid solution under ambient conditions. Inductively coupled plasma-optical emission spectrometry is used to measure the mass concentrations of the copper and iron ions, and an X-ray diffraction pattern of the solid residue after leaching is obtained. Moreover, a cyclic voltammogram is obtained by measuring the current at the working electrode, which is prepared using pure chalcopyrite and pyrite, to reveal the role of carbon black in the leaching process. The copper recovery of our CuFeS₂ + FeS₂ + MnO₂ + C system (91.6%) is significantly higher than that of a CuFeS₂ + FeS₂ system (1.0%) after 1 M sulfuric acid leaching owing to the galvanic effect. In addition, the results indicate that the electron transfer reaction associated with chalcopyrite, chalcocite, pyrite, and elemental sulfur occurs, which leads to the continuous leaching of chalcopyrite into copper minerals, including chalcopyrite and covellite. When chalcopyrite is leached in sulfuric acid with manganese dioxide, the passive layers are activated by the influence of carbon black. Carbon black served as the active site for the reaction, enhancing the effect of charge carriers and facilitating additional oxidation half-reactions. This ultimately led to improved chalcopyrite leaching and a continuous increase in copper recovery.