DFT study of Sb(III) and Sb(V) adsorption and heterogeneous oxidation on hydrated oxide surfaces

This study reports on density functional theory (DFT) modeling of antimony adsorption at model environmental interfaces. Both Sb(III) and Sb(V) surface complexes were studied on hydrated alumina and hematite, at varying adsorption sites and with varying distal Sb coordination. We calculate the DFT reaction energies of a number of hypothetical heterogeneous interconversion reactions of Sb surface complexes with gas-phase water and oxygen, which predict that an octahedral Sb(V) surface complex is overall the most favorable. Additionally, the results suggest that several different heterogeneous pathways starting from distinct metastable Sb surface complexes are possible, including an antimonyl (SbO) surface complex. A total of 28 Sb surface complexes are found through DFT geometry optimizations, the structural and energetic details of which are reported to guide future experimental studies and to form a basis for ongoing theoretical work including dynamic simulations.