Structure of uranium sorption complexes at montmorillonite edge sites
- 1 September 2002
- journal article
- Published by Walter de Gruyter GmbH in Radiochimica Acta
- Vol. 90 (9-11) , 653-657
- https://doi.org/10.1524/ract.2002.90.9-11_2002.653
Abstract
Summary: Extended X-ray absorption fine structure (EXAFS) spectroscopy at the uranium LIII-edge was used for determining the structural environment of aqueous uranyl sorbed onto montmorillonite. The study reveals that uranyl uptake at pH ∼5-∼7 and at an initial uranyl concentration of 5×10−5M takes place at amphoteric surface hydroxyl sites as inner-sphere complex. The measured bond distances between uranium and the equatorial oxygen atoms are in the range of 2.34 Å and 2.37 Å indicating an inner-sphere coordination. At ∼3.4 Å the presence of a U-Al backscattering pair was determined. This backscattering pair indicates that the binding of the uranyl unit to amphoteric surface hydroxyl sites occurs preferred as a bidentate inner-sphere complex on aluminol groups.Keywords
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