Facet-Dependent and Defect-Enhanced Vanadate Adsorption on Mg(Oh)2 Surface: A Combined Study of Dft Calculations and Batch Experiments

Abstract

Vanadium contamination has gained increasing attention around the world and it is urgent to develop feasible approach to tackle this growing pollution (e.g., vanadate). Herein, density functional theory (DFT) calculations combined with batch experiments were used to systematically evaluate the capacity of Mg(OH)2 to adsorb vanadate, by investigating the impacts of different exposed facet and the surface OH defect on the structure configurations, adsorption energy and the efficiency of vanadate adsorption. DFT calculations suggested that although the capacity of vanadate adsorption on the facets of Mg(OH)2 would be obviously influenced by the formation of various coordination complex (e.g, monodentate, bidentate and tridentate) on each facet, the capacity for these facets of Mg(OH)2 towards vanadate adsorption followed the order: (100) > (001). Moreover, such a vanadate adsorption was further enhanced by the presence of surface OH defect, owing to the altered densities of states (DOS) of the adsorption site. The batch experiments verified the defect-rich Mg(OH)2 was favorable to adsorb vanadate at the low-concentration and the (100) facet with small exposed area may also play a great role. This molecular-level understanding of the facet-dependent and defect-enhanced adsorption behavior of Mg(OH)2 toward vanadate provides a useful insight into designing and applying effective adsorbents for the removal of heavy metal oxyanions.

Keywords: vanadate adsorption, Mg(OH)2, facet-dependent, surface defect, DFT calculation.