The Catalytic Action of Fe(III) in the U(IV)–U(VI) Electron Exchange Reaction

Abstract

Abstract The catalytic action of ferric ions in the U(IV)–U(VI) electron exchange reaction has been studied in the presence of a high concentration of hydrochloric acid. The exchange rate is found to be accelerated by the addition of ferric ions; the observed rate law is given by: R=k_0[U(IV)][U(VI)]+k_c[Fe(III)]_0\sqrt[U(IV)][U(VI)] An activation energy of 19.7 kcal/mol was calculated for the iron-catalyzed reaction in the U(IV)–U(VI) electron exchange reaction. This value is much smaller than that of 32.2 kcal/mol, which was found in the non-catalytic reaction. The kinetics and equilibrium of the reaction between Fe(III) and U(IV) have also been studied in order to investigate in detail the mechanism of the catalytic reaction. A one-electron-transfer mechanism producing U(V) as an intermediate is estimated from the rate law and supported by the kinetics and equilibrium studies of the Fe(III)–U(IV) reaction.