Pyrite oxidation in alkaline solutions: The carbonate effect

Claudia L. Caldeira, Virginia S.T. Ciminelli, Kwadwo Asare Osseo-Asare

Research output: Chapter in Book/Report/Conference proceedingConference contribution

5 Scopus citations


An investigation of pyrite oxidation in alkaline solutions was carried out with the aid of thermodynamic modeling, kinetic experiments and infrared spectroscopy. In the presence of carbonate, Eh-pH diagrams show that soluble iron-carbonate complexes (FeCO30, FeOHCO3 - and FeCO32-) coexisting with pyrite may be formed at a pH range of 6-12. Above pH 11 and under oxidizing conditions, only Fe(OH)4- is stable, even in the presence of carbonate/bicarbonate ions. In addition to iron oxyhydroxides and soluble sulfate species, iron carbonate compounds were identified as one of the products of pyrite oxidation with the help of diffuse reflectance infrared spectroscopy. The conditions under which thermodynamic and IR analyses indicate the presence of carbonate compounds also conespond to those in which the fastest rate of pyrite oxidation in carbonate solutions was found. By expanding the Singer-Stumm model for pyrite oxidation to alkaline solutions, the oxidation of Fe(II) may be considered the rate-limiting step. We suggest that the formation of Fe(II)-CO3 soluble complexes favors the oxidation of iron, which in turn favors the overall kinetics of pyrite oxidation in carbonate solutions. The electron transfer to O2 is facilitated by the formation of a Fe(II)-CO3 complex at the pyrite surface or in solution.

Original languageEnglish (US)
Title of host publicationHydrometallurgy 2008
Subtitle of host publicationProceedings of the 6th International Symposium
Number of pages10
StatePublished - Nov 26 2008
EventHydrometallurgy 2008: 6th International Symposium - Phoenix, AZ, United States
Duration: Aug 17 2008Aug 21 2008


OtherHydrometallurgy 2008: 6th International Symposium
Country/TerritoryUnited States
CityPhoenix, AZ

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Metals and Alloys


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