Theoretische Betrachtungen zur reduktiven Auflösung von Eisen(III)-oxiden

Theoretical Considerations of the reductive dissolution of iron(III) oxides At the case of equilibrium, the extent of reductive dissolution of iron(III) oxides can be obtained by the Nernst equation. At a given pH, the maximum Fe²⁺ concentration depends on the standard potential E_o of the system, which decreases with increasing stability of the oxide. Crystal imperfections as well as increasing surface area lead to an increase of the equilibrium Fe²⁺ concentration, whereas the influence of ionic replacement cannot be determined in general. The formation of stable Fe²⁺ complexes or of solid Fe²⁺ compounds results in a higher extent of reduction. From theoretical calculations it is concluded, that, for the bacterial reduction of iron oxides, the electron transfer between donor and Fe(III) precedes the protolytic dissolution of the oxide.