Promotion mechanism of natural clay colloids in the adsorption of arsenite on iron oxide particles in water

The mechanism of clay colloids promoting arsenite (As-III) adsorption on iron oxide particles (Fe2O3) was studied. Fe2O3 on attapulgite (Fe/ATP) showed 8.30-fold higher adsorption capacity per unit area than the pristine Fe2O3 (0.200 mg m(2)g(-1)) at neutral condition. Compared with Fe2O3, the higher adsorption affinity of Fe/ATP to As m was obtained based on the lower adsorption energies of the formed As-III surface complexes on Fe/ATP by density functional theory (DFT) calculations. The increased As-III adsorption capacity and affinity on Fe/ATP were attributed to the enhanced Fe chemical activity in Fe/ATP where the stronger delocalization of Fe led to stronger hybridization of the Fe-3d orbital with the O-2p orbital in As m . ATP played an important role in facilitating Fe activity through electron transfer from Al and O atoms of ATP to enhance the electronic property of the loaded Fe, which was beneficial to the adsorption of As-III as electron acceptor. The introduction of ATP provided Fe2O3 with more surface activity and availability to As-III, which is of great significance for understanding the fate and transport of As-III in the coexistence water system of clay and iron oxide particles.