Enhanced adsorption efficiency of graphene oxide by electrostatic field for Hg(II) removal from water

A novel method to enhance the adsorption of Hg2+ by graphene oxide (GO) based on external electrostatic field was investigated by using molecular dynamics simulations. The mechanism of enhancement of adsorption performance was revealed by calculating and analyzing radial distribution function, coordinated water molecules around Hg2+, interaction energy, potential of mean force, mean residence time and density distribution of water around GO with electrostatic field. The results show that the presence of electrostatic field will increase the activity of Hg2+ ions by reducing coordination water number around Hg2+, increase the electrostatic attraction between Hg2+ and GO, and reduce the energy barrier for Hg2+ to be overcome in the process of approaching GO. In addition, electrostatic field will enhance adsorption of Hg2+ by functional groups, especially improve adsorption capacity of epoxy groups. Moreover, electrostatic field can increase the number density of water near the surface of GO, but may not be conducive to the complexation of Hg2+ with GO surface. The results of this article are helpful to understand the internal mechanism of the electrostatic field affecting the adsorption of Hg2+ ions by GO, which will provide a new approach to optimize the technology of removing heavy metal ions in water. (C) 2021 Elsevier B.V. All rights reserved.