DFT Study of Antimony(V) Oxyanion Adsorption on α-Al₂O₃(1102)

Density functional theory (DFT) calculations using periodic slab models are carried out to study the reactivity of aqueous Sb(OH) 6 – on model α-Al 2 O 3 (11̅02) surfaces. The strength of inner-sphere (specific) adsorption between Sb(OH) 6 – and surface models is ranked using DFT adsorption energies, E ads . Trends in E ads in terms of surface structure, adsorbing functional group identity, and oxyanion coordination to the surface are determined and analyzed in terms of geometry and electronic structure. The results show that not all Sb–O surf interactions involve the same type of Sb and O orbital interactions, which explains why trends in E ads cannot be rationalized by universal Sb–O bond length–bond strength relationships. The DFT results show a preference for Sb(V) bidentate and tridentate geometries in which Sb bonds through the corners of AlO 6 groups in the surface. Less favorable adsorption involving edge sites is associated with adsorption-induced surface relaxations of oxygen groups from deeper layers of the surface.