Oxidative dissolution of ruthenium dioxide hydrate by periodate ions

Abstract

The results of a kinetic study of the oxidative dissolution of ruthenium dioxide hydrate to ruthenium tetroxide by periodate ions, IO^–₄, in acidic solution are described. The kinetics of dissolution give a good fit to a ‘soft-centre’ model in which the particles of RuO^˙₂xH₂O are assumed to be monodispersed, spherical but inhomogeneous in composition, comprising a difficult-to-corrode outer shell and a more easy-to-corrode inner core. In this work metaperiodate appears to act as a two-electron oxidant. The observed kinetics fit a reaction scheme in which the rate-determining step is the reaction between a surface site and an adsorbed IO^–₄ ion and there is competitive adsorption by any IO^–₃ present. In the absence and presence of an excess of IO^–₃ ions, the overall activation energy for the corrosion reaction was determined to be 38 ± 2 and 54 ± 4 kJ mol^–1, respectively.