Effect of redox potential on chalcopyrite dissolution imposed by addition of ferrous ions

Copper is a metal with a great economic interest and about 70% is found in nature in chalcopyrite form (CuFeS2). However the chalcopyrite dissolution is a challenge for industries as well as researchers because of its slow dissolution kinetics. The control of redox potential is one factor that can help in this drawback. This study was undertaken to evaluate the role of redox potential on chalcopyrite bioleaching by addition of ferrous ions. Acid leaching with addition of ferrous ions promoted high dissolution of chalcopyrite by the maintenance of low redox potential (420 mV/Ag/AgCl). On the other hand, the copper dissolution in bacterial systems showed low copper recovery (610 mV/Ag/AgCl). XRD of solid residues showed in abiotic conditions the formation of elemental sulfur, jarosites and a significant decrease on chalcopyrite’s peaks. In bacterial conditions, only jarosites was detected as new crystalline phase. SEM analysis confirmed the results obtained by XRD. In general, the results showed conclusive evidence that the maintenance of low redox potential and the addition of ferrous ions have positively influenced the copper recovery and confirmed the literature data, which indicate a critical potential range where chalcopyrite leaching is more favorable.