(610a) Selective Removal of Selenate from Selenate-Sulphate Water Solution By Adsorption on Dispersed Single Atoms on [012] Al2O3 Surface: An Ab-Initio Study

Consumption of selenium higher than 400µg/day can lead to selenosis which has neurotoxic effects such as lethargy, dizziness, motor weakness and burning and prickling in the extremities. The most common source of high doses of selenium is drinking water, where inorganic selenium is present in selenate (Se(VI)) and selenite (Se(IV)) forms. While both selenium anions are similarly toxic to humans, selenate (Se(VI)) is harder to remove because it has a more stable structure, and is similar to its more prevalent co-contaminant cousin – sulfate. Aluminium oxide is a promising adsorbent for removing selenium oxo-anions from water. However, adsorption of selenate on the Alumina surface occurs in the outer sphere and is controlled by the surface water Hydrogen bonding network, which makes the adsorption non-selective. Here, we investigate the adsorption of selenate and sulphate on nine transition metal single-atom sites dispersed in [012] Al₂O₃ surface using density functional theory to determine if the inclusion of a single atom can induce selenate adsorption selectively over sulphate. Additionally, we elucidate the relative effects of geometric and water network effects from chemical bonding effects. We use a hybrid solvent method which includes implicit and explicit solvation and van der Waals forces, to compare adsorption energies in inner vs. outer sphere configuration. We find that V and Ge Single Atom in Al₂O₃ adsorb selenate exothermically in inner sphere configuration at neutral pH, while this process is endothermic for pure Al₂O₃ surface. We correlate the adsorption energies with physical quantities including bond strength, surface water re-configuration, pH, solvation bond distances, etc. to understand the find the other significant surface phenomenon affecting the adsorption besides the water network.