Dft Studies Of Cr(vi) Complex Adsorption On Hydroxylated Hematite (1102) Surfaces

摘要

The adsorption structures of Cr(VI) species on hydroxylated α-Fe_2O_3(1102) were investigated using density functional theory within a periodic slab model. A broad structural survey of H_2CrO_4, HCrO_4 and CrO_4~(2-) adsorbed on different surface sites was carried out. Chromate species adsorb on the hydroxylated surface via an outer-sphere mechanism through H-bonding and ion-dipole attraction. The most stable structure for H_2CrO_4 reveals strong H-bonding to surface and between adsorbates. For HCrO_4~-, a configuration that shows both H-bonding and Cr-O…H-O-Fe ion-dipole interaction is the most favored. In the case of CrO_4~(2-), the most favored adsorption configuration shows the complex standing on the surface with a Cr-0 bond aligned on OH, presenting the strongest Cr-O…H-O-Fe interaction. In these three species, CrO_4~(2-) displays the strongest interaction with the hydroxylated (1102) surface with no tendency toward reduction observed, in accordance with experiment.