First-Principles Study of Adsorption of Hazardous Atoms on the Silica Surface

Abstract

In this study, the adsorption of hazardous atoms including lead on the silica surface (SiO2 [001]) was investigated using the first-principles method within the framework of density functional theory (DFT). We performed the full structural optimization and found the most stable configuration. Four different sites were considered for the surface of silica, as well as four different sites for the surface of silica with an Al atom, and the adsorption energy along with the equilibrium geometry was determined. When the absorption energy was calculated at the four positions, the surface of silica and the surface of silica with Al had the same higher absorption at the first site (-6.66 eV and -9.11 eV). The value of the absorption energy indicates that a strong chemical bond has been formed between the lead and the surface. The maximum values for the absorption energy of the lead atoms were -6.93 eV for the silica surface and -9.11 eV for the silica surface with the Al atom. Furthermore, the structure added by aluminum with the ratio of 1:5 to build a similar structure of a zeolite crystal. Which provided more absorption energy. The value of the absorption energy indicates that a strong chemical bond has been formed between the lead and the surface. The density of state (DOS) is shown that the bandgap was 2.78 eV for the silica surface and 2.65 eV for the silica surface with Al atoms. The addition of the lead atom reduced the width of the bandgap due to the creation of a trapping layer within the bandgap.