An XAS study of silver species evolution in silver-catalysed chalcopyrite bioleaching

he catalysing effect of Ag + or Ag nanoparticle (AgNp)on chalcopyrite (bio)leaching at 30 °C was studied in this paper, and the change of Ag speciation was investigated by Ag K-edge X-ray Absorption Near-edge Spectroscopy (XANES). The solution studies indicate that the addition of 0.2% Ag (fraction of Ag to chalcopyrite)can effectively improve the dissolution of chalcopyrite in both bioleaching and chemical leaching. Further increasing the silver concentration to 1% only marginally increase the rate of chalcopyrite dissolution compared with the rate with 0.2% Ag added. No obvious difference has been found between the catalytic effect of Ag + and AgNp (Silver Nanoparticle). XRD studies indicate the formation of jarosite, elemental sulfur in both bioleaching and chemical leaching. However, the speciation of Ag in the residual cannot be confirmed by XRD analysis. Ag k-edge XANES spectra show that Ag + or AgNp have completely changed to Ag 2 S within 7 days in both bioleaching and chemical leaching process. In-situ XANES analysis shows that the Ag + or AgNp changed to Ag 2 S very rapidly in the absence of Fe 3+ . In contrast, AgCl was firstly detected with the presence of 3 g/L Fe 3+ , which only partially changed to Ag 2 S in about 36 h, which is likely because the stability of Ag 2 S was decreased by Fe 3+ .