Effect of sulfur dioxide on flotation of chalcopyrite

The mechanism of sulfur dioxide on collectorless and collector-induced flot ation of chalcopyrite was studied by cyclic voltammetry on a rotating disc electrode, and by contact angle measurements. The first step in oxidation o f chalcopyrite is the release of iron that upon hydrolysis may stay at the surface to render the surface hydrophilic. In stirred solutions, a signific ant amount of iron goes into solution to expose a copper-sulfur (Cu-S)-rich layer that leads to hydrophobicity. The Cu-S-rich layer reacts with the co llector more readily than the original chalcopyrite or the iron-covered sur face. In the absence of xanthate, the contact angles were larger when sulfu r dioxide was present, indicating removal of some of the iron oxide at the surface. When sulfur dioxide and xanthate were added together, the contact angles were lower than those with xanthate alone. These results indicate th at improved flotation may be obtained if treatment with sulfur dioxide prec edes collector addition. (C) 2000 Elsevier Science B.V. All rights reserved .