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Publication Citation: Pb(II) Adsorption on Isostructural Hydrated Alumina and Hematite (0001) Sur faces: A DFT Study

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Author(s): Sara E. Mason; Christopher R. Iceman; Kunaljeet Tanwar; Thomas P. Trainor; Anne M. Chaka;
Title: Pb(II) Adsorption on Isostructural Hydrated Alumina and Hematite (0001) Sur faces: A DFT Study
Published: January 20, 2009
Abstract: The persistence of lead (Pb) in contaminated topsoil is ranked as one of the most serious environmental issues in the U.S. and other countries. Adsorption of Pb at the aqueous interface of nanoscale metal oxide and metal (oxy)hydroxide particles is perhaps the most significant process responsible for controlling contaminant sequestration and mobility, but is poorly understood. Experimental studies of absorption of Pb onto bulk minerals has indicated significant differences in reactivity, but the molecular basis for these differences has remained elusive due to the challenges of observing and modeling the complex chemistry that exists at the water-oxide interface. In this work we present a detailed {\it ab initio} theoretical investigation aimed at understanding the fundamental physical and chemical characteristics of Pb adsorption onto the (0001) surface of two common minerals, $\alpha$--Al$_{2}$O$_{3}$ and $\alpha$--Fe$_{2}$O$_{3}$. The results of our periodic density functional theory (DFT) calculations show that Pb(II) binds more strongly (by $\approx$30\%) to hematite than to isostructural alumina with the same fully hydroxylated surface stoichiometry due to stabilization of the Pb-O covalent interactions by the partially occupied Fe d-band. Site preference for Pb(II) adsorption on alumina is shown to depend strongly on the cost to disrupt highly stable hydrogen bonding networks on the hydrated surface, but is less of a factor for the stronger Pb-hematite interaction.
Citation: Journal of Physical Chemistry C
Volume: 113
Pages: pp. 2159 - 2170
Keywords: Density functional theory; Aluminum oxide; Iron oxide; Water; Lead
Research Areas: Biological Physics
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