A new aspect within the SMILE project is the characterization of sorption complexes on the molecular level. This is an essential basis for the correct chemical description of sorption reactions, and thus the extraction of thermodynamic parameters. The partners will specifically characterize sorption processes in those systems where data gaps are identified.
We will use modern spectroscopic, microscopic, and diffraction techniques to characterize sorption complexes and the reactions leading to their formation. A major role will be played by surface X-ray diffraction methods (Fenter (2002), Park and Fenter (2007)), which will enable determination of surface complexes with sub-Å resolution, while also characterizing changes to the mineral surface itself and its hydration structure. We will combine these techniques with X-ray spectroscopy (XANES, EXAFS), IR spectroscopy, atomic force microscopy (AFM) and interferometry (VSI), as well as luminescence spectroscopy (TRLFS).
Initial studies will focus on mica, feldspar, and hematite and their interaction with low-valent actinides, e.g. Am(III), Pu(III), and Th(IV). Additional research will then be driven by findings in these studies as well as input from titration and column experiments, and thermodynamic modelling and SCM.
Fenter, P., X-ray Reflectivity as a Probe of Mineral-Fluid Interfaces: A User Guide. Rev. Min. Geochem. 2002, 49, 149-220.
Park, C.; Fenter, P., Phasing of Resonant Anomalous X-ray Reflectivity Spectra and Direct Fourier Synthesis of Element-Specific Partial Structures at Buried Interfaces. J. Appl. Crystallogr. 2007, 40 (2), 290-301.