Kéri Annamária, Dähn Rainer, Krack Matthias, Churakov Sergey V. (2019), Characterization of Structural Iron in Smectites — An Ab Initio Based X-ray Absorption Spectroscopy Study, in Environmental Science & Technology
, 53(12), 6877-6886.
Kéri Annamária, Dähn Rainer, Krack Matthias, Churakov Sergey V. (2017), Combined XAFS Spectroscopy and Ab Initio Study on the Characterization of Iron Incorporation by Montmorillonite, in Environmental Science & Technology
, 51(18), 10585-10594.
Kéri Annamária, Osán János, Fábián Margit, Dähn Rainer, Török Szabina (2016), Combined X-ray microanalytical study of the Nd uptake capability of argillaceous rocksNd uptake study by combined X-ray microanalysis, in X-Ray Spectrometry
, 45(1), 54-62.
Clay minerals can irreversibly bind metals in waste and soil matrices under mildly acidic to basic pH conditions. The prediction of the faith of contaminants in the geosphere requires a profound and detailed knowledge of the processes at the clay-water interface. It has been demonstrated that the combination of wet chemistry experiments and advanced X-ray absorption spectroscopy (XAS) techniques is the most promising approach to investigate environmental systems. The data analysis of extended X-ray absorption fine structure (EXAFS) spectra allows in the best cases to unequivocally determine the nature of surface complexes formed at clay mineral edge sites. With advances in computational sciences it has become possible to perform molecular simulations, which can be used for the interpretation of EXAFS data for surface adsorbed species on surfaces of clay minerals. In the proposed study at least two clay minerals will be investigated, montmorillonite and illite. Both have in common that they are dioctahedral smectite 2:1 clay minerals. Their structure consists of an octahedral sheet (consisting mainly of Al atoms) attached to two tetrahedral sheets (consisting mainly of Si atoms). In dioctahedral clays two of the three octahedral positions are filled. Whereas in montmorillonite isomorphic substitution occurs predominantly in the octahedral layers, illite is exhibiting isomorphic substitution primarily in the tetrahedral sheets. Therefore, the aim of this doctoral study is to understand the retention mechanism of environmentally relevant elements, covering various oxidation states from III to VI on most common clay minerals, montmorillonite and illite, based on molecular simulations and spectroscopic measurements. More specifically the adsorption of Ni(II), Fe(II), Fe(III), Th(IV) and U(VI) onto clay mineral edge sites will be investigated to gain a deep understanding of the faith of these elements in the geosphere. The combined interpretation of the modelling results and the XAS experiment is challenging due to potentially limited accuracy of the data. An innovative approach should be developed for the systematic improvement of the simulation results and their comparison with the experiments.