Polarization dependent grazing incidence (GI) XAFS measurements of uranyl cation sorption onto mineral surfaces

Sammanfattning

Measurement of the polarization dependence of surface sensitive grazing incidence (GI) X-Ray absorption. ne structure (XAFS) spectra at the U L3 edge is applied to identify reactive U(VI) sorption sites on various mineral surfaces. We use the known polarization dependence of the dioxouranium(VI)or 'uranyl' cation, [O = U = O](2+), to experimentally determine its orientation when sorbed onto single crystal mineral surfaces (alpha-Al2O3, CaCO3). The GIXAFS signal measured at different orientations of a U(VI) sorbed alpha-Al2O3 (11-20) wafer relative to the polarization vector of the incident synchrotron radiation, epsilon, indicates that the uranyl surface species exhibit a preferred surface orientation. Analysis of the EXAFS substantiates our previous findings, identifying the reactive sorption sites as AlO6 octahedral edges on the surface. Initial results of uranyl sorbed onto freshly cleaved (10-14) surface of natural calcite indicate that uranyl cations sorb onto terrace step edges and not onto the surface plane or with an orientation of the [O = U = O](2+) unit parallel to the (10-14) surface.

Publicerad i

Physica Scripta
2005, Volym: T115, sidor: 877-881 Utgivare: IOP PUBLISHING LTD

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https://res.slu.se/id/publ/95543