Abstract

In the present work the occurrence of surface transformations triggered during chemical and biological leaching of chalcopyrite at 70 °C in basal medium were investigated with the aid of the Rietveld technique. Leaching experiments were conducted in 250 ml shake flasks at 150 rpm, contacting 1 g of a -80 # + 120# chalcopyrite concentrate with 100 ml of iron-free basal medium at pH 1.5 at 70°C. Three different conditions were used: experiment (a) in aerated conditions with basal medium inoculated with Sulfolobus metallicus (4x108 cells/ml); experiment (b) in aerated abiotic conditions; experiment (c) in abiotic conditions under N2 atmosphere. Copper and iron dissolved in solution was analyzed with atomic absorption. Samples of the initial chalcopyrite and the treated samples obtained after 16 days under the various experimental conditions were analyzed by Grazing-Incident X-ray diffraction (GID). The obtained x-ray spectra were then analyzed with the Rietveld refinement technique using the Topas software. Results showed that the initial concentrate consisted mainly of tetragonal chalcopyrite (JCPDS : 37-0471). Chalcopyrite leached under abiotic-anaerobic conditions was crystallographically unaffected. In chalcopyrite leached under aerated abiotic conditions there was evidence of surface texturization showed as preferential orientation to the crystallographical planes ( 3 1 2 ) and (1 1 6). Finally, surface texturization was also observed in chalcopyrite leached under inoculated conditions, but in this case showed as preferential orientation to the crystallographical planes ( 0 2 4 ) and ( 2 2 0). These results give a first evidence of surface texturization phenomena during dissolution of chalcopyrite at 70 °C. They suggest that chalcopyrite dissolution occurs via selective leaching of specific crystallographic planes, and this selectivity is influenced by both the chemical action of oxygen and the microorganism actvity. © (2009) Trans Tech Publications.