Redox and hydrolysis properties of plutonium ions in aqueous solution

Oxydizing and reducing properties of plutonium species in non complexing aqueous solution are reviewed. The usual oxydation numbers are + III to + VI. The dismutation of Pu(IV) and Pu(V) is of great importance and as a consequence, the reader must bear in mind that the four oxydation degree can be present simultaneously in a given solution. Nevertheless, plutonium at a single oxydation state is obtained by a chemical reaction or electrochemically. Hydrolysis, which in fact is a particular case of complex formation between the ions of plutonium and OH-, predominate over Pu(IV) and to a less degree over Pu(VI), Pu(III) and Pu(V). Polynuclear species arise from the two oxydation degrees (VI) and (IV). This phenomenon which is limited to the formation of bi or trinuclear species with the Pu(VI) ions is of special concern with the Pu(IV) ions. For the latter polymers of high molecular masses have been observed. Numerical values of hydrolysis constants are given