A STUDY OF BIOLEACHED CHALCOPYRITE SURFACES IN THE PRESENCE OF AG(I) BY VOLTAMMETRIC METHODS

The electrochemical behaviour of a massive chalcopyrite after chemical leaching, or microbial leaching using a mixed culture of mesophilic m icroorganisms (Thiobacillus ferrooxidans, Thiobacillus thiooxidans and Leptospirilum ferroxidans), were compared. Linear voltammetry was use d as the analytical technique to follow the compositional changes on t he electrodes. Preliminary tests on particulate electrodes (graphite, elemental sulphur and Ag2S) were also included to determine the electr ochemical reaction in these silver-catalysed systems. In both leaching and bioleaching, a silver sulphide coating appeared on the surface. H owever, its thickness was higher and elemental sulphur was produced on the chalcopyrite surface by the microbial leaching. These results con firmed the catalytic mechanism of the Ag+ cations on the chalcopyrite leaching, which was proposed by Miller and later reported by many rese archers. Copyright (C) 1996 Published by Elsevier Science Ltd