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Issue 20, 2005
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Molecular dynamics simulation of uranyl(VI) adsorption equilibria onto an external montmorillonite surface

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Abstract

We used molecular dynamics simulations to study the adsorption of aqueous uranyl species (UO22+) onto clay mineral surfaces in the presence of sodium counterions and carbonato ligands. The large system size (10 000 atoms) and long simulation times (10 ns) allowed us to investigate the thermodynamics of ion adsorption, and the atomistic detail provided clues for the observed adsorption behavior. The model system consisted of the basal surface of a low-charge Na-montmorillonite clay in contact with aqueous uranyl carbonate solutions with concentrations of 0.027 M, 0.081 M, and 0.162 M. Periodic boundary conditions were used in the simulations to better represent an aqueous solution interacting with an external clay surface. Uranyl adsorption tendency was found to decrease as the aqueous uranyl carbonate concentration was increased, while sodium adsorption remained constant. The observed behavior is explained by physical and chemical effects. As the ionic strength of the aqueous solution was increased, electrostatic factors prevented further uranyl adsorption once the surface charge had been neutralized. Additionally, the formation of aqueous uranyl carbonate complexes, including uranyl carbonato oligomers, contributed to the decreased uranyl adsorption tendency.

Graphical abstract: Molecular dynamics simulation of uranyl(vi) adsorption equilibria onto an external montmorillonite surface

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Publication details

The article was received on 06 Jul 2005, accepted on 18 Aug 2005 and first published on 08 Sep 2005


Article type: Paper
DOI: 10.1039/B509307D
Phys. Chem. Chem. Phys., 2005,7, 3580-3586

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    Molecular dynamics simulation of uranyl(VI) adsorption equilibria onto an external montmorillonite surface

    J. A. Greathouse and R. T. Cygan, Phys. Chem. Chem. Phys., 2005, 7, 3580
    DOI: 10.1039/B509307D

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