Mechanochemical Sulfidization of Nonferrous Metal Oxides by Grinding with Sulfur and Iron

Co-grinding nonferrous metal (Cu, Pb, and Zn) oxides with sulfur and iron stimulate solid-state reactions to form nonferrous metal sulfides and iron oxide. The sulfidizing reaction proceeds with an increase in grinding time and is almost complete after 180 min of grinding. The necessary conditions to sulfidize the oxides can be explained on the basis of thermodynamic considerations. A larger negative change in Gibbs free energy accompanies the defined sulfidizing reaction than the formation of iron sulfides. By using the novel sulfidizing process, it is expected that current mineral processing technologies such as flotational and magnetic separations might be used to recover metals from various kinds of wastes or to purify contaminated wastes when the heavy metals contained, such as lead, cadmium, etc., are sulfidized and removed.