Combined time-resolved laser fluorescence spectroscopy and extended X-ray absorption fine structure spectroscopy study on the complexation of trivalent actinides with chloride at T = 25-200 °C

• Verfasst von: Skerencak-Frech, Andrej [VerfasserIn]
• Verfasst von: Fröhlich, Daniel R. [VerfasserIn]
• Verfasst von: Rothe, Jörg [VerfasserIn]
• Verfasst von: Dardenne, Kathy [VerfasserIn]
• Verfasst von: Panak, Petra [VerfasserIn]
• Titel: Combined time-resolved laser fluorescence spectroscopy and extended X-ray absorption fine structure spectroscopy study on the complexation of trivalent actinides with chloride at T = 25-200 °C
• Verf.angabe: Andrej Skerencak-Frech, Daniel R. Fröhlich, Jörg Rothe, Kathy Dardenne, and Petra J. Panak
• E-Jahr: 2014
• Jahr: January 2, 2014
• Umfang: 8 S.
• Fussnoten: Gesehen am 28.10.2020
• Titel Quelle: Enthalten in: Inorganic chemistry
• Ort Quelle: Washington, DC : American Chemical Society, 1962
• Jahr Quelle: 2014
• Band/Heft Quelle: 53(2014), 2, Seite 1062-1069
• ISSN Quelle: 1520-510X
• DOI: doi:10.1021/ic4025603
• Datenträger: Online-Ressource
• Sprache: eng
• K10plus-PPN: 1736846817

Abstract

The complexation of trivalent actinides (An(III)) with chloride is studied in the temperature range from 25 to 200 °C by spectroscopic methods. Time-resolved laser fluorescence spectroscopy (TRLFS) is applied to determine the thermodynamic data of Cm(III)-Cl- complexes, while extended X-ray absorption fine structure spectroscopy (EXAFS) is used to determine the structural data of the respective Am(III) complexes. The experiments are performed in a custom-built high-temperature cell which is modified for the respective spectroscopic technique. The TRLFS results show that at 25 °C the speciation is dominated mainly by the Cm3+ aquo ion. Only a minor fraction of the CmCl2+ complex is present in solution. As the temperature increases, the fraction of this species decreases further. Simultaneously, the fraction of the CmCl2+ complex increases strongly with the temperature. Also, the CmCl3 complex is formed to a minor extent at T > 160 °C. The conditional stability constant log β′2 is determined as a function of the temperature and extrapolated to zero ionic strength with the specific ion interaction theory approach. The log β°2(T) values increase by more than 3 orders of magnitude in the studied temperature range. The temperature dependency of log β°2 is fitted by the extended van’t Hoff equation to determine ΔrH°m, ΔrS°m, and ΔrC°p,m. The EXAFS results support these findings. The results confirm the absence of americium(III) chloride complexes at T = 25 and 90 °C ([Am(III)] = 10-3 m, [Cl-] = 3.0 m), and the spectra are described by 9-10 oxygen atoms at a distance of 2.44-2.48 Å. At T = 200 °C two chloride ligands are present in the inner coordination sphere of Am(III) at a distance of 2.78 Å.