Flotation related ESCA studies on PbS surfaces

Abstract

The oxidation of galena is known to play an important role in the beneficiation of lead sulfide by xanthate flotation. We have used electron spectroscopy for chemical analysis (ESCA) to characterize the nature of chemical species on PbS surfaces exposed to air and aqueous environments. PbS samples were in the form of thin sublimed films, natural galena crystals, and commercially available powdered material. Based on these photoelectron measurements, it may be concluded that lead sulfate is the major product of oxidation of PbS in air and aqueous environments. The presence of small amounts of elemental sulfur in the early stages of oxidation suggests that the initial oxidation step may differ from the major oxidation process. Galena occurs naturally in a wide range of stoichiometries. Oxidation was initially much slower in lead rich samples. In fact, the induction period exceeds the initial conditioning period in a typical separation plant. ESCA spectra of lead-rich sulfides confirms that the first step is the oxidation of Pb to PbO. Evidence is presented indicating that the interaction between lead sulfate and xanthates may be controlled by the semiconducting properties of the material.