Electrochemical Dissolution of Iron(III) Hydroxy-Oxides: More Information About the Particles

The process of reductive dissolution of α-Fe2O3, Ba-hexaferrite, α-FeOOH, γ-Fe2O3, γ-FeOOH, and ferrihydrite can be monitored continuously by abrasive stripping voltammetry and chronoamperometry to obtain information about homogeneity of reactivity and about the particle size of the pure phases and mixtures. Phase parameters (rate constant and charge transfer coefficient) and the geometrical factor γ, which is independent on the specific surface area, can be assigned to a phase-pure sample in the given medium. Differences in reactivity of the hydroxy-oxides are documented, and the dependence of reactivity of the α-Fe2O3 samples on the preparation procedure is characterized. The electrochemical techniques can also be employed to investigate changes in the particles during phase transformations.