Plutonium(VI) sorption to manganese dioxide.

Redox-active metal oxides may strongly affect the environmental behavior and mobility of actinides . Manganese oxides are relatively common redox-active soil components, which have a high surface area and which some studies show sorb plutonium selectively over other mineral phases .' For plutonium, oxidation states that could exist in the environment include +111 to +VI, with Pu(IV) being predominant in the insoluble phase. Plutonium(V), and to a lesser extent Pu(VI), are the stable Pu oxidation states in solution under environmental conditions .Z We are using synthetic 6-Mn02 because it is most similar to the common natural manganese oxide mineral birnessite . Previously, we have shown that Pu(V) is oxidized to Pu(VI) in solution by 8-Mn02, then very effectively sorbed to the mineral . We are now studying Pu(VI) sorption to synthetic 8-Mn02 in detail to determine its sorption mechanisms and sorption capacity