An AFM and cyclic voltammetry study of sulphide mineral oxidation

The oxidation of sulfide minerals, such as galena (PbS), in aqueous solutions is of critical importance for effective flotation. Despite attempts over many decades, a comprehensive understanding on the formation of oxidation species at the surface is lacking. Much controversy over the oxidation products exists. A number of oxidation pathways have been proposed and experimental evidence for the formation of elemental sulfur, metal polysulfide, metal-deficient lead sulfide and sulfate have been shown and argued. It is the purpose of this work to provide a clear understanding the oxidative species present at an electrochemical oxidized galena surface at pH 5. Utilizing a novel experimental system that combines cyclic voltammetry, Atomic Force Microscopy imaging and Raman spectroscopy, the formation of microscopic islands of elemental sulfur at low anodic potentials are detected. At higher anodic potentials a sulfur layer is formed. The formation of a hydrophobic sulfur layer at the galena surface explains the self induced floatability of this mineral