Influencing mechanism of visible light and silver ions on p- and n-type chalcopyrite bioleaching

Abstract

Different effects and mechanisms of visible light and silver ions (Ag+) on the bioleaching of p- and n-type chalcopyrite (Cpy A and Cpy B, respectively) in the presence of Acidithiobacillus ferrooxidans were investigated. The semiconductor characteristics, bioleaching behaviors, surface morphologies, main phases and surface species of chalcopyrite were evaluated by Hall effect test, bioleaching tests, X-ray diffraction, scanning electron microscope and X-ray photoelectron spectroscopy. According to the results, Cpy A had a higher carrier concentration and greater carrier mobility than Cpy B, resulting in a faster dissolution rate. After 24 d of bioleaching, the copper extraction rate of Cpy A was 91.05%, which was 17.86% higher than that of Cpy B (73.19%) when light illumination and Ag+ existed together. Obviously, visible light and Ag+ promoted the bio-dissolution process of Cpy A more strongly than Cpy B, which was mainly attributed to the higher carrier mobility in Cpy A. Furthermore, charge transfer occurred more rapidly on the chalcopyrite surface when illuminated, and more Ag2S was accumulated, especially for Cpy A. As a result, the dense structure of the passivation layer was destroyed, reducing the passivation effect and promoting chalcopyrite dissolution.