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Sorption of Pu(VI) onto synthesized goethite under oxidizing and normal conditions was investigated, which revealed its pH dependence on different solid/liquid ratios. Pu speciation upon sorption on the solid phase was characterized via extended X-ray absorption fine structure (EXAFS) spectroscopy, while that in solution was assessed using ultraviolet-visible (UV-Vis) spectroscopy and liquid-liquid extraction. The obtained results demonstrate differences in plutonium behavior in the studied systems. Pu(VI) remains hexavalent on the goethite surface and in solution under oxidizing conditions. While Pu(IV) is stabilized on the mineral and Pu(V) is found in solution under normal conditions. This study provides the thermodynamic descriptions of these reactions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Here we provide evidence that the formation of PuO2 nanoparticles from oxidized PuVI under alkaline conditions proceeds through the formation of an intermediate PuV solid phase, similar to NH4PuO2CO3, which is stable over a period of several months. For the first time, state‐of‐the‐art experiments at Pu M4 and at L3 absorption edges combined with theoretical calculations unambiguously allow to determine the oxidation state and the local structure of this intermediate phase. [ABSTRACT FROM AUTHOR]

In this study, the effect of light on the kinetics and speciation of plutonium at its interaction with particles of TiO2 under different light conditions is shown for the first time. It was found that sorption was followed by reduction of the plutonium to Pu(IV). In this, the reduction reaction and sorption in conditions of the presence of light proceed significantly more rapidly due to the photocatalytic activity of titanium dioxide, providing a source of electrons for the reaction. Spectral methods (XAFS and TEM) showed that plutonium forms nanoclusters with the structure of PuO2, which decorate the surface of the solid phase. [ABSTRACT FROM AUTHOR]

Plutonium partitioning and speciation was studied under the conditions of a liquid nuclear waste repository site. The dominating effect of corrosion products (Fe and Cr) oxides on plutonium partitioning was established in batch sorption tests at 150 ℃ and by using sequential extraction. Various techniques including Mössbauer spectrometry, XRD and TEM were used to characterize Fe/Cr oxide phases that form both precipitates and surface coatings which sorb plutonium. The sorption and speciation of plutonium was modeled thermodynamically using Pourbaix diagram that takes into account both surface complexation reaction and precipitation of insoluble PuO2. [ABSTRACT FROM AUTHOR]

Rücktitelbild: A Novel Metastable Pentavalent Plutonium Solid Phase on the Pathway from Aqueous Plutonium(VI) to PuO2 Nanoparticles (Angew. Keywords: Actinoidchemie; Elektronenstrukturberechnungen; Pentavalentes Plutonium; Plutoniumdioxid-Nanopartikel; Pu M4 HERFD Actinoidchemie, Elektronenstrukturberechnungen, Pentavalentes Plutonium, Plutoniumdioxid-Nanopartikel, Pu M4 HERFD. [Extracted from the article]