Mechanism of Water Oxidation by Ferrate(VI) at pH 7-9

The kinetics of water oxidation by K2FeO4 has been reinvestigated by UV/Vis spectrophotometry from pH 7-9 in 0.2 m phosphate buffer. The rate of reaction was found to be second-order in both [FeO42-] and [H+]. These results are consistent with a proposed mechanism in which the first step involves the initial equilibrium protonation of FeO42- to give FeO3(OH)(-), which then undergoes rate-limiting O-O bond formation. Analysis of the O-2 isotopic composition for the reaction in (H2O)-O-18 suggests that the predominant pathway for water oxidation by ferrate is intramolecular O-O coupling. DFT calculations have also been performed, which support the proposed mechanism.