Progress in electrometallurgy research and applications

Abstract

concentrations on the kinetics of these processes. It is interesting to note that the authors did not postulate separate anodic and cathodic sites on the surfaces of the solids, as had been the case in previous publications from this source. In another general paper, Osseo-Asare2 reviewed the basic concepts of semicon­ ductor electrochemistry and the appli­ cation of these concepts to selected oxide and sulfide dissolution systems. While such concepts can be useful in explain­ ing some observations such as the rela­ tive amounts of sulfur and sulfate as products of sulfide oxidation, it remains to be seen whether semiconducting phe­ nomena are appropriate, given the im­ purities present in most naturally occur­ ring sulfide minerals. In this regard, the paper by Mishra and Osseo-Asare3 on the reduction of iron(III) and oxygen on natural pyrite specimens provides an interesting example of the need to in­ voke surface states and pinning of the Fermi level (probably by impurities in the crystal) . The lack of sensitivity to the reduction potential of the oxidant, which varied by over one volt, is also indicative of pseudometallic rather than semicon­ ductor behavior. Galvanic interaction between gold and associated sulfide minerals during the cyanidation of gold ores was studied by Lorenzen. 4