Synthesis of Crystalline Pentavalent Plutonium Hydroxides

Pentavalent plutonium is among the most dominant soluble oxidation states of Pu in neutral to alkaline aqueous solutions. Predicting and modeling the chemical behavior of plutonium in aqueous solutions relevant to environmental systems and the extreme chemical environments encountered in treating high-level radioactive waste is predicated on knowledge of its solid and solution phase speciation. Under such conditions, pentavalent plutonium is considered to be a predominant species, yet very little is known about its fundamental chemistry. In this work, we report the synthesis of 3 new Pu(V)-bearing hydroxide phases Na[Pu(V)O2(OH)2(H2O)] • 2.5H2O, Na2[Pu(V)O2(OH)3] • 2H2O, and K4[(Pu(V)O2)2(OH)6] • 4H2O as single crystals isolated from alkaline conditions using mild hydrothermal methods (<200°C). Within these reactions, we achieved reduction of Pu with solid Na2O2 and KO2 and confirmed the presence of Pu(V) via Raman spectroscopy and computational support.