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Physica B: Condensed Matter 385-386, 2 (2006) 935-937
Arsenic uptake by gypsum and calcite: Modeling and probing by neutron and x-ray scattering
Alejandro Fernandez-Martinez 1, 2, Gabriel J. Cuello 1, Gabriela Roman-Ross 2, Mark R. Johnson 1, Fabrizio Bardelli 3, 4, Xavier Turrillas 5, Laurent Charlet 2

Here we report on two structural studies performed on As-doped gypsum (CaSO4 2H2O) and calcite (CaCO3), using neutron (D20-ILL) and x-ray (ID11-ESRF) diffraction data and EXAFS (BM8-ESRF). The aim of this study is to determine whether As gets into the bulk of gypsum and calcite structures or is simply adsorbed on the surface. Different mechanisms of substitution are used as hypotheses. The combined Rietveld analysis of neutron and x-ray diffraction data shows an expansion of the unit cell volume proportional to the As concentration within the samples. DFT-based simulations confirm the increase of the unit cell volume proportional to the amount of carbonate or sulphate groups substituted. Interpolation of the experimental Rietveld data allows us to distinguish As substituted within the structure from that adsorbed on the surface of both minerals.
1 :  Institut Laue-Langevin (ILL)
2 :  Laboratoire de géophysique interne et tectonophysique (LGIT)
CNRS : UMR5559 – Institut de recherche pour le développement [IRD] – LCPC – OSUG – INSU – Université de Savoie – Université Joseph Fourier - Grenoble I
Consiglio Nazionale delle Ricerche – INFM – Università degli studi Roma III – UNIVERSITÀ DEGLI STUDI DI TRENTO
4 :  European Synchrotron Radiation Facility (ESRF)
5 :  Instituto Ciencias COnstruccion Eduardo Torroja (ICC)

Planète et Univers/Interfaces continentales, environnement

Arsenic – Minerals – Simulation – Diffraction – EXAFS
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