Bioleaching of two different chalcopyrite ores in chloride media

Abstract

Chalcopyrite is the most abundant copper mineral and its bioleaching has been the subject of several studies due to its refractory nature when submitted to hydrometallurgical processes. Moreover, the growing worldwide demand for copper requires the processing of low-grade ores or mining tailings for which hydrometallurgical processes are a cost-effective alternative. New approaches have shown that the use of chloride ions in chalcopyrite leaching can positively contribute to its dissolution. In this regard, the present work assessed the bioleaching of two chalcopyrite ores—containing 0.34% Cu (copper ore 1) and 1.79% Cu (copper ore 2) by the extreme thermophilic archaea Sulfolobus acidocaldarius. In addition, the effect of different NaCl concentrations (0.25 − 1.0 mol/L) on copper extraction were investigated. In the experiments with the copper ore 1, the copper extractions were higher in the abiotic experiments (from 83 to 90%) than in the biotic experiments (62–80%) for all NaCl concentrations investigated. On the other hand, the experiments with the copper ore 2 showed similar results (around 83% Cu extractions) in all abiotic tests carried out in the presence of chloride and also in the biotic experiments with 0.25 and 0.50 mol/L NaCl concentrations. However, a 97% copper extraction was observed in the biotic experiment carried out with 1.0 mol/L NaCl. Regardless of the type of ore, the lowest copper dissolutions (less than 55%) were obtained in the experiments in the absence of both microorganism and chloride. The XRD analyses of the solid residues of the bioleaching experiments did not reveal the presence of Fe(III)-precipitates such as jarosite.