Combined chemical and bacterial leaching of ultrafine ground chalcopyrite

Abstract

The changes in surface properties and the leaching of chalcopyrite CuFeS 2 after ultrafine grinding are examined. Surface area measurement and photoelectron spectroscopy (XPS) were used for characterization of the ground samples. A gradual decrease in the particle size, from 32 μm, for as received CuFeS2, to 2 μm, for the sample ground for 60 min, as well as increasing the surface area from 0.23 m 2 g −1 to 2.68 m2 g −1 for equal samples was observed. Analysis of the XPS line of sulphur S2 p electrons has shown the existence of sulphur in three different chemical forms: S 2-, So and S 6+. The ground samples exhibited a greater proportion of higher oxidation states. The samples were chemically preleached with an acid solution of Fe(III) sulphate to an equal conversion degree (ϵ cu = 25%), characterized and subsequently leached by the bacteria Thiobacillus thiooxidans. While the rate of chemical leaching is proportional to the increase in CuFeS 2 surface area, the rate of subsequent bacterial leaching is limited by 15 min grinding. The different behaviour of the samples ground for a long time may be explained by differences in the chemical composition of surface layers.