Surface Characterization of Chalcopyrite Dissolution in Hypochlorite Medium

The surface of chalcopyrite was studied by XPS characterization for an unleached chalcopyrite, and, after being leached in an alkaline oxidant medium at room temperature, pH 12.5, and [ClO−] 0.34 M, the reaction of enargite presented high selectivity with respect to chalcopyrite, allowing the removal of arsenic from copper concentrates with high arsenic content prior to smelting. Based on the XPS analysis, the original chalcopyrite is composed of a combination of its constituents in different oxidation states, and chalcopyrite has the following stoichiometric formula: Cu(I)0.85Cu(II)0.15Fe(II)0.65Fe(III)0.35S2−1.5S22−0.17Sn0.082−. The unleached chalcopyrite on its surface presents an iron deficiency, which raises the ratio Cu/Fe up to 2, reaching the chalcopyrite Cu/Fe rate in the fifth cycle. The Cu/S ratio of chalcopyrite, 0.5, remains constant at the surface as after the peeling. Surface sulfur shows a decrease in monosulfides, increasing the Sn2−/S2− y S22−/S2− ratio. Chalcopyrite leached with ClO−/OH− media generates surface layers with the following intermediate products: Chalcopyrite → CuFe1-xS2/CuSn/Fe3+ -OH → Fe3+-OH/CuO/SO42−. Neither sulfur intermediates nor oxidized final products are passivating, allowing the chalcopyrite transformation to progress in depth with increasing reaction time.