Influence of anode material on current yields during ferrate(vi) production by anodic iron dissolution Part I: Current efficiency during anodic dissolution of grey cast iron to ferrate(vi) in concentrated alkali hydroxide solutions

Abstract

Current efficiency for the oxidation of a grey cast iron anode to ferrate(vi) in 14 m NaOH was measured in the region of bubble induced convection. The maximum current yield, obtained after 180 min of electrolysis, had a value of 11% at a current density of 32 mA cm⁻² and a temperature of 20°C. The ferrate(vi) current yield increased throughout the whole current density range under study (from 1 to 36 mA cm⁻²). The iron anode was activated by cathodic prepolarization. The iron concentration in lower oxidation states in the solution after electrolysis was constant within experimental error over the whole temperature range under study. The quasisteady state anodic polarization curve for grey cast iron in the transpassive potential region was measured. This anodic polarization curve was shifted to more negative potential, at the same current density, compared to the potential of the mild steel anode.