An EXAFS and TRLFS study of the sorption of trivalent actinides onto smectite and kaolinite
Authors/Editors
Research Areas
Publication Details
Output type: Journal article
Author list: Stumpf T., Hennig C., Bauer A., Denecke M., Fanghaenel T.
Publisher: De Gruyter
Publication year: 2004
Volume number: 92
Issue number: 3
Start page: 133
End page: 138
Number of pages: 6
ISSN: 0033-8230
eISSN: 2193-3405
URL: http://api.elsevier.com/content/abstract/scopus_id:2442426223
Languages: English-Great Britain (EN-GB)
Unpaywall Data
Open access status: closed
Abstract
The structure parameters of the Am aquo ion and of Am(III) sorbed onto smectite and kaolinite at varying pH are analyzed using EXAFS. An Am-O distance of 2.47-2.49 Å is found and a coordination number of 8-9 oxygen atoms is observed for the Am and its hydration sphere. Combined TRLFS TRUS (Cm(III)) and EXAFS (Am(III)) results show that An(III) sorbs onto smectite at pH 4, forming an outer-sphere complex and retains its complete primary hydration sphere. With increasing pH, inner-sphere sorption onto smectite and kaolinite occurs. The overall number of oxygen atoms coordinating the actinide ion remains about the same at pH 6, with four water molecules being replaced by oxygen atoms from the mineral surface during inner-sphere complex formation. The coordination number of sorbed Am(III) at pH 8 exhibits an apparent decrease, which may be affected by the formation of ternary OH-/Am/clay mineral surface species.
Keywords
Actinides, Clay minerals, EXAFS, Surface complexation, TRLFS
