Using First-Principles DFT to Explore the Reactivity of Hydrated Oxide Surfaces

Geochemical reactions occurring at the interface between oxide surfaces and aqueous solution exert control on the transport and fate of contaminants. Molecular-level understanding of how metal ions adsorb to these surfaces is needed to understand contaminant speciation and bioavailability. Complexity arising from multiple surface stoichiometries, hydrogen bonding patterns, and varying oxygen functional group reactivities must be carefully considered. We use the interaction of lead with alumina and hematite as model systems to probe for essential factors governing the reactivity of hydrated surfaces towards contaminant ions. While geometrically isostructural, these two oxides have sharp contrasts in electronic structure. We use this fact to make comparisons between the preferred adsorption modes of Pb(II) and discuss the relationships between surface identify, structure, and reactivity.