Mechanochemical sulfidization of lead oxides by grinding with sulfur

Lead oxide was co-ground with sulfur to investigate the possibility of stimulating a solid-state reaction to form lead sulfide. The formation of both lead sulfide and lead sulfate was confirmed, even without any other additive such as iron powder. The necessary conditions for sulfidizing the oxides can be explained based on thermodynamic considerations, namely a negative change in Gibbs free energy. This method can be applied to treat leaded glass by co-grinding it with sulfur to form sulfide as well as sulfate, so that current mineral processing techniques, such as flotation separation, might be used to recover lead from various kinds of leaded glass wastes.