Effect of carbon black to facilitate galvanic leaching of copper from chalcopyrite in the presence of manganese(IV) oxide

It is well known that galvanic interactions between sphalerite or pyrite and manganese (IV) oxide(MnO2) accelerate the leaching of these minerals. Because MnO2 is nobler than chalcopyrite, chalcopyrite acts as cathode to be oxidized in contact with MnO2. We investigated the feasibility of galvanic leaching of chalcopyrite concentrate using chemical reagent MnO2. Leaching experiments were performed in an erlenmeyer flask containing a sulfuric medium agitated on a magnetic stirrer at room temperature. Although the addition of MnO2 improved the leaching rate of chalcopyrite, its effect was limited. Adding carbon black significantly accelerated the kinetics of chalcopyrite leaching in the presence of MnO2, and the Cu extraction yield was 81% at MnO2/carbon black/chalcopyrite ratios of 4:1:1 in 29 h. In the absence of carbon black, the extraction was 7%. The extraction rate of Mn from MnO2 also increased. Carbon black did not affect the sulfuric acid or ferric sulfate leaching of chalcopyrite without MnO2, indicating that it could play an important role in the galvanic interaction between chalcopyrite and MnO2. The effects of several variables such as pH, dosage of MnO2 and carbon black, and temperature on the kinetics of chalcopyrite leaching were examined. (C) 2016 Elsevier B.V. All rights reserved.