Electrochemical behavior of Fe(VI)-Fe(III) system in concentrated NaOH solution

The electrochemical behavior of a Fe(VI)/Fe(III) system was investigated with both a SnO₂-Sb₂O₃/electrode and a powder microelectrode. Results showed that ferrite ion (FeO^2-), formed in solution and solid phase, was a suitable Fe(III) species for the generation of FeO₄^2- and for construction of a Fe(VI)/Fe(III) redox system under strong basic conditions. Solid ferrite was made by the method of molten melting a mixture of Fe₂O₃ and NaOH at 973 ± 2K. The product was confirmed to be NaFeO2 by X-ray diffraction (XRD) measurements. Ferrate (Fe(VI)) was also synthesized from ferrite (solid), Fe(OH)₃, and Fe₂O₃ using an hypochlorite oxidation method. In this method, it was demonstrated that ferrite was the most suitable material among these Fe(III) compounds for ferrate synthesis. Results also indicated: A) FeO₄^2-/FeO² - is a suitable redox system under studied experimental conditions, b) rate and the reversibility of the redox reaction between FeO₄₂ and FeO₂ were promoted markedly with the increase of temperature from 293 K to 333 K, c) the electro-oxidation of Fe02" is a fast two-electron transfer reaction on both the SnO₂-Sb₂O₃/Ti electrode and the NaFeO₂ powder microelectrode, and d) open-hearth dust of iron and steel industry could be used as a promising and valuable raw material for ferrate synthesis.