Electrochemical study of orpiment (As2S3) and realgar (As2S2) in acidic medium Article uri icon

abstract

  • Electrochemical characterizations of high purity natural crystals of orpiment (As2S3) and realgar (As2S2) were performed in the presence of a bacteria-free, acidic bacterial growth medium for Thiobacillus ferrooxidans, name M2. A carbon-paste electrode (CPE), composed of a mixture of pure mineral grains with graphite powder and silicon oil as a binder, was used for the experiments. Reproducibility of the mineral surfaces was assured by monitoring the open-circuit potential (OCP) of the initial CPE-mineral-electrolyte interface. The voltammetric study revealed that the oxidation processes for both of these arsenic-bearing minerals involves two steps: an initial oxidation of the sulfide mineral to H3AsO3 and HSO4-, followed by the oxidation of H3AsO3 to H3AsO4. The reduction processes for the two minerals, however, differ. While the reduction of orpiment occurs in a dual step process, for realgar, the process is achieved in a single step.

publication date

  • 1997-01-01