Influence of anode material on current yield during ferrate(VI) production by anodic iron dissolution .3. Current efficiency during anodic dissolution of pure iron to ferrate(VI) in concentrated alkali hydroxide solutions

The dependence of the current efficiency for the oxidation of a pure iron (99.95%) anode to ferrate(VI) ions in 14M NaOH was measured in the region of bubble induced convection for the temperature range 20 to 50 degrees C. The highest current yield obtained after 180 min electrolysis was 60% at a current density of 2.3 mA cm(-2) and a temperature of 30 degrees C. The same current yield was found at a current density of 4.5 mA cm(-2) and a temperature of 40 degrees C. The dependence of the ferrate(VI) current yields on the NaOH concentration in the electrolyte solution was studied in the range 12 to 17M. The optimum concentration was found to be 16M. The quasistationary anodic polarization curve of pure iron in the transpassive potential region was measured. Apparent oxygen evolution starts at a potential 110 mV higher than for white and grey cast iron anodes.