Neglected solid phase pentavalent plutonium carbonate in the environment

KPuO₂CO₃ solid phase precipitation from hexavalent plutonium (Pu(VI)) solution is discussed herein. The kinetic process of Pu(V)/potassium carbonate formation is widely investigated under constant control of Pu concentration in different oxidation states, redox potentials, and pH values. Synchrotron-based X-ray diffraction, X-ray absorption spectroscopy, high-resolution transmission electron microscopy, and scanning electron microscopy with energy-dispersive X-ray spectroscopy are employed for solid phase analysis. The crystal structure of KPuO₂CO₃ is specified via the Rietveld method and extended X-ray absorption fine structure fitting. The stability area of Pu(V) potassium carbonate is discussed and a moderated Pourbaix diagram is presented.