Speciation and structural study of U(IV) and -(VI) in perchloric and nitric acid solutions

Ikeda, Atsushi ; Hennig, C.*; Tsushima, Satoru*; Scheinost, A. C.*; Bernhard, G.*; Yaita, Tsuyoshi

Speciation and complex structure of U(IV) and U(VI) are studied in aqueous acidic solutions of HClO $_{4}$ and HNO $_{3}$ by means of UV-visible-NIR and X-ray absorption spectroscopies, and density functional theory (DFT) calculations. A spherical coordinating tetravalent cation of U $^{4+}$ is surrounded by 9-10 water molecules in the primary coordination sphere in 1.0 M HClO $_{4}$ , while it forms a not-well-ordered colloidal compound of UO $_{rm 2+x}$ (x = 0.2) mixture in a lower acidic concentration of 0.1 M HClO $_{4}$ . U(VI) exists as a transdioxo uranyl cation, UO $_{2}$ $^{2+}$ , and forms a 5-fold pure hydrate complex of [UO $_{2}$ (H $_{2}$ O) $_{5}$ ] $^{2+}$ in 1.0 M HClO $_{4}$ . The water molecules in the pure hydrate complexes of U(IV) and U(VI) are successively replaced by planar bidentate coordinate nitrate ions (NO $_{3}$ $^{-}$ ) as a function of increasing HNO $_{3}$ concentration. The presence of unidentate coordinate nitrate complexes or tetranitrato U(VI) complexes is less probable in the present HNO $_{3}$ system.

Language	:	English
Journal	:	Inorganic Chemistry
Volume	:	48
Number	:	15
Pages	:	p.7201 - 7210
Publication Year/Month	:	2009/07
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Paper URL	:	https://doi.org/10.1021/ic9004467
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Keywords	:	no keyword
Research Facility	:	SPring-8(大型放射光施設)
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Article of JAEA R&D Review	:
Cooperating Institute	:	Forschungszentrum Dresden-Rossendorf

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Registration No. : AA20080874
JAEA Abstracts No. : 37001119
Paper Submission No. : 6122

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