Electrochemical behaviour of the oxidative dissolution of arsenopyrite catalysed by Ag+ in 9K culture medium

Abstract Arsenopyrite (FeAsS) is the most common As-containing sulphide mineral in gold deposits. Most auriferous arsenopyrite ores are refractory necessitating pre-treatments before gold extraction. Bio-oxidation pre-treatment is simple and eco-friendly technology that has attracted significant attention in the past decade. Slow leaching kinetics of bioleaching is, however, a critical impedance to its large-scale application. The addition of metal cations has previously been found to expedite the leaching process. The electrochemical behaviour of Ag+ in the dissolution of arsenopyrite in 9 K culture medium was investigated in depth by a series of electrochemical and analytical techniques. Electrochemical results suggested that Ag+ could significantly improve the oxidative dissolution of arsenopyrite. Analytical results demonstrated that, with Ag+, only a discontinuous, porous and non-passivating film was formed on the arsenopyrite surface. The catalytic effect of silver is largely attributed to that Ag+ can enhance the oxidative dissolution of not only arsenopyrite but also the passive film by forming conducting Ag2S on the arsenopyrite surface, which explains why Ag+ can remove the passive film on the surface of arsenopyrite during bioleaching and thus effectively shorten its bioleaching period.