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Issue 40, 2011
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Speciation of uranyl ions in fulvic acid and humic acid: a DFT exploration

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Abstract

The speciation of uranyl ions in fulvic acid (FA) and humic acid (HA), based on models of larger sizes, is systematically studied using density functional theory (DFT). Four uranyl binding sites are suggested for FA and based on their energetics, the preferential binding sites are proposed. The computed binding sites include two chelating types, one through the carboxylate group and one via the hydroxo group. A systematic way to attain the possible structure for Stevenson's HA model is carried out using a combined molecular dynamics (MD) and quantum chemical approach. Calculated structures and energetics reveal many interesting features such as conformational flexibility of HA and binding of hydrophobic molecules in agreement with the experimental suggestions. Five potential binding sites are proposed for uranyl binding to HA and the calculated geometries correlate nicely with the experimental observations. Our binding energy calculations reveal that apart from uranyl binding at the carboxylate functional group, binding at other functional groups such as those involving quinone and hydroxo sites are also possible. Finally, based on our cluster calculations the strength of uranyl binding to HAs and FAs is largely influenced by neighbouring groupsviahydrogen bonding interactions.

Graphical abstract: Speciation of uranyl ions in fulvic acid and humic acid: a DFT exploration

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Publication details

The article was received on 19 Apr 2011, accepted on 19 Aug 2011 and first published on 19 Sep 2011


Article type: Paper
DOI: 10.1039/C1CP21238A
Citation: Phys. Chem. Chem. Phys., 2011,13, 18038-18046
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    Speciation of uranyl ions in fulvic acid and humic acid: a DFT exploration

    M. Sundararajan, G. Rajaraman and S. K. Ghosh, Phys. Chem. Chem. Phys., 2011, 13, 18038
    DOI: 10.1039/C1CP21238A

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