Comparison of bioleaching and dissolution process of p-type and n-type chalcopyrite

In this work, bioleaching and dissolution processes of chalcopyrite from three different regions were investigated and compared mainly by leaching experiments, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and electrochemical analysis. Hall effect experiments showed that one (chalcopyrite A) belonged to p-type chalcopyrite whose carrier concentrations were high, while the other two (chalcopyrite B and C) were both n-type chalcopyrite whose carrier concentrations were low. A remarkably higher copper extraction of p-type chalcopyrite could be achieved during bioleaching by L. ferriphilum compared with n-type chalcopyrite. Redox potential in bioleaching of p-type chalcopyrite can be maintained at the appropriate range (about 380–480 mV vs. Ag/AgCl) for a longer period of time. Acid consumption in bioleaching of p-type chalcopyrite was significantly lower than that of n-type chalcopyrite. SEM analysis indicated that p-type chalcopyrite was more easily corroded by microorganism than n-type chalcopyrite. XPS analysis revealed that monosulfide (S2−), disulfide (S22−), polysulfide (Sn2−) and sulfate (SO42−) were the main intermediate species during bioleaching of both p-type and n-type chalcopyrite. Electrochemical analysis showed that the electrochemical dissolution processes of p-type and n-type chalcopyrite were similar, while the conductivity and oxidation-reduction rate of p-type chalcopyrite was significantly higher than those of n-type chalcopyrite, thus resulting in significant higher electrochemical dissolution kinetics and copper extraction. This work is potentially useful in explaining the inconsistences in chalcopyrite hydrometallurgy.