In order to understand the reactivity of environmental contaminants such as Pb(II) and Sb(V), we employed Density Functional Theory (DFT) calculations using periodic slab models (PSM) for the surfaces of (1-102) α-Al2O3 and α-Fe2O3. The reactivity was measured in terms of relative adsorption energies of Pb(II) and Sb(V) ions on the (1-102) α-Al2O3 and α-Fe2O3 surfaces. Our relative adsorption energy results show that tridentate adsorption for Pb(II) and Sb(V) was the most favorable on both oxides (α-Al2O3 and α-Fe2O3), followed by bidentate corner-sharing mode. Based on the relative adsorption energy trends, we further analyzed the geometry in terms of Sb-O and Pb-O distances, O-Sb/Pb-O angles and the structural relaxations Fe/Al and O layers in the periodic slabs. Our results indicate that Sb-O (1.9 – 2.3 Å) and Pb-O (2.0 – 2.28 Å) distances depend on whether the O atom in the surface is a doubly bound oxygen or singly bound oxygen and agree well with crystal truncation rod experiments. Also, longer bonds do not necessarily mean weaker bonds as shown by projected density of states analysis. Popular models such as bond-valence that rely on the bulk parameterization cannot explain the structural distortion due to the adsorption of various ions on environmental interfaces and therefore demonstrate the need for detailed electronic structure analysis.

Reactivity of Sb(V) and Pb(II) on environmentally active (1-102) surface of hematite and alumina

249th National Meeting (2015)

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