Investigation of Chalcopyrite Leaching Kinetics by Alternative Leaching Chemicals

Abstract

Chalcopyrite (CuFeS2) is one of the most abundant sulfide minerals in the world copper deposit. It is known as a refractory sulfide mineral due to passivation during leaching process in a conventional leaching system. In this study, alternative lixiviants, MSA (methanesulfonic acid, CH4SO3) and sulfurous acid (H2SO3) were investigated to enhance leaching kinetic. In addition, alternative oxidants, hydrogen peroxide (H2O2), dichromate (Cr2O72-) and nitrate (NO3-) were also tested to study chalcopyrite leaching behavior in the presence of the oxidants in alternative lixiviants.Chalcopyrite leaching tests were conducted to choose the best performing lixiviant among MSA, sulfuric acid (H2SO4) and sulfurous acid with ferric at 75oC. Then, alternative oxidants, hydrogen peroxide, dichromate and nitrate were investigated with the selected lixiviant. The results of chalcopyrite leaching with various lixiviants exhibited that MSA showed the highest copper extraction of 47% with 30 g/L MSA and 5 g/L ferric. Then, copper extraction enhanced to above 90% with hydrogen peroxide, dichromate and nitrate in MSA medium. When chalcopyrite leaching was compared between sulfuric acid and MSA in these oxidant, MSA achieved higher copper extraction than sulfuric acid medium. The overall activation energy of MSA – H2O2 and MSA – NO3- leaching were 79.8 and 126 kJ/mol, respectively, indicating that the surface chemical reaction governs overall leaching kinetic. Meanwhile, MSA – Cr2O72- was determined to a diffusion controlled mechanism based on its activation energy of 21.7 kJ/mol. Results of residue characterization supported the reaction mechanism as K-jarosite precipitation on a leached residue from MSA – Cr2O72- system, which hindered mass transport and passivated chalcopyrite. Overall, nitrate leaching could be the more effective, economical and compatible than other alternative oxidants for copper leaching based on the comparative investigations.