Mechanism of silver-influenced bacterial leaching of chalcopyrite, pyrite and a copper ore

The silver catalyzed bioleaching of chalcopyrite, pyrite and a chalcopyrite containing ore from Dexing Copper Mine (China) was investigated. It has been found that silver ions selectively accelerated the rate of copper dissolution from the ore while suppressed the iron leaching. Adding 2.0 g Ag per kg mineral, the copper recovery from chalcopyrite increased from 29.2% (without a catalyst) up to 78.4%, while the iron recovery decreased from 51.0% (no silver) to 27.4%, in the presence of microorganisms. It is believed that the enhancement of chalcopyrite bioleaching by Ag ions is attributed to the formation of an intermediate, Ag 2S, which was confirmed by X ray diffraction of the solid leach residue of chalcopyrite and the analyses of the cyclic voltammetry for CuFeS 2 electrodes in silver containing 9 K medium. The inhibition of pyrite biooxidation is owing to the formation of metallic silver on the pyrite surface instead of Ag 2S, which was detected by X ray photoelectron spectroscopy (XPS).