Computational Insight into the Mechanism of Arsenous Acid Adsorption on Magnetite (311) Surface

Abstract

Adsorption is the preferred technique for removal of toxic arsenous acid (As(OH)3) from groundwater. The method can be made more economically feasible by the use of magnetically recyclable adsorbents. Given this, there are a few reports on the successful use of magnetite as an adsorbent of arsenous acid. However, none of these investigations attempt to give any mechanistic insight into the molecular-level interactions between the magnetite surface and arsenous acid in the presence of solvent molecules. Understanding the mechanism involved is critical for the development of better adsorbents of As(OH)3. The present paper investigates this issue by employing classical molecular dynamics simulations for adsorption of arsenous acid in the water on the magnetite (311) surface. Radial distribution function analysis reveals that interactions between (a) Fe (of magnetite) and O (of arsenous acid) and (b) O (of magnetite) and H (of arsenous acid) dominate the adsorption interactions at the molecular level. The adsorption isotherm and equilibrium constant have also been calculated and reported. Copyright © 2019 American Chemical Society.