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X‐ray photoreduction of U(VI)‐bearing compounds
Author(s) -
MercierBion F.,
Drot R.,
Ehrhardt J. J.,
Lambert J.,
Roques J.,
Simoni E.
Publication year - 2011
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.3617
Subject(s) - uranyl , x ray photoelectron spectroscopy , chemistry , desorption , irradiation , nuclear chemistry , inorganic chemistry , adsorption , organic chemistry , chemical engineering , ion , physics , nuclear physics , engineering
Abstract During XPS analysis, the soft X‐ray‐induced reduction of metals such as Cr(VI) and Ce(IV) in oxides has been reported in the literature and some mechanisms have been proposed to explain this phenomenon. The reduction of U(VI) by the beam during X‐ray Photoelectron Spectroscopy has been already reported in the literature but only for U(VI) sorbed or precipitated onto solids with reducing properties (as micas or pyrites) for whose Fe(II) can also induce the reduction of U(VI), or onto TiO 2 whose the photocatalytic properties are well known. The objective of this paper is to investigate the effects of X‐ray beam on U(VI) bulk compounds (UO 3 , UO 2 (OH) 2 , (UO 2 ) 2 SiO 4 , UO 2 (CH 3 COO) 2 and UO 2 C 2 O 4 ). Successive U4f, U5f, C1s XPS spectra were recorded and compared as a function of the irradiation time. The XPS photoreduction of U(VI) into U(IV) is only observed for uranyl compounds containing organic matter (uranyl acetate and uranyl oxalate). Considering the evolution of the C1s signal during the X‐ray irradiation, a significant decrease of the C O component simultaneously to the U(VI) reduction is observed, which suggests a desorption of CO or other volatile organic products from the solid surface. All these results on U(VI) bulk compounds indicate the important role of organic carbon species in the photoreduction process and to explain these observations, a photoreduction mechanism has been suggested. Copyright © 2010 John Wiley & Sons, Ltd.