Heavy metals in yttrium silicide electride (Y5Si3:e(-))

Materials are needed to preferentially remove heavy metal pollutants from waste streams. Here, atomic scale simulation, based on density functional theory, is used to predict encapsulation energies and electronic structures of the one-dimensional yttrium silicide electride (Y5Si3:e(-)) hosting the heavy metals such as zinc (Zn), cadmium (Cd), mercury (Hg), chromium (Cr), nickel (Ni), copper (Cu), or lead (Pb). Assuming that the metals are present as dimers in gaseous waste, encapsulation is highly exoergic for those metals with incomplete p or d electrons (Cr, Ni, Cu, and Pb). Of the heavy metals with complete d shells (Zn, Cd, and Hg), only Zn exhibits strong encapsulation. Differences in encapsulation behavior are analyzed in terms of electronic structures, electron affinities, atomic radii, and Bader charges.