Catalytic mechanism of manganese ions and visible light on chalcopyrite bioleaching in the presence of Acidithiobacillus ferrooxidans

Abstract The bioleaching of chalcopyrite is low cost and environmentally friendly, but the leaching rate is low. To explore the mechanism of chalcopyrite bioleaching and improve its leaching rate, the effect and mechanism of manganese ions (Mn2+) and visible light on chalcopyrite mediated by Acidithiobacillus ferrooxidans (A. ferrooxidans) were discussed. Bioleaching experiments showed that when both Mn2+ and visible light were present, the copper extraction was 14.38% higher than that of the control system (without Mn2+ and visible light). Moreover, visible light and Mn2+ promoted the growth of A. ferrooxidans. Scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) analysis revealed that Mn2+ promoted the formation of extracellular polymeric substance (EPS) on the surface of chalcopyrite, changed the morphology of A. ferrooxidans, enhanced the adsorption of bacteria on chalcopyrite surface with light illumination, and thus promoted the bioleaching of chalcopyrite. UV-vis absorbance spectra indicated that Mn2+ promoted the response of chalcopyrite to visible light and enhanced the catalytic effect of visible light on chalcopyrite bioleaching. Based on X-ray photoelectron spectroscopy (XPS), the relevant sulfur speciation of chalcopyrite before and after bioleaching were analyzed and the results revealed that visible light and Mn2+ promoted chalcopyrite bioleaching by reducing the formation of passivation layer (Sn2-/S0). Investigation into electrochemical results further indicated that Mn2+ and visible light improved the electrochemical activity of chalcopyrite, thus increasing the bioleaching rate.