Electrochemical Behavior of Fe(VI)-Fe(III) System in Concentrated NaOH Solution
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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 (FeO2-), formed in solution and solid phase, was a suitable Fe(III) species for the generation of FeO42- 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) FeO42-/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. 2008 American Chemical Society.