Iron oxides for the removal of water contaminants: A theoretical approach*

The presence of metalloids and heavy metals in aqueous sources is a major concern in many countries. Several pollutants such methylated arsenicals are already associated to different human health issues, demanding new alternatives to purify water resources. One of these solutions involves the use of iron nanoparticles due to their affinity with arsenic species. We study the interaction of arsenic complexes with iron oxide surfaces at the atomic scale from first principle calculations. From the considered anionic species, a higher adsorption energy was found for the complexation of Fe3O4(001) with As(III) being 1.3 eV higher than the adsorption energy for As(V). In the case of As(III), a large partial band charge density was found, which was associated to the O-Fe bond formation, while more delocalized electron density was found in the adsorption of As(V) subspecies, with the formation of two Fe-O bonds in the most stable configuration. Finally, we envisage the sorption capacity of other iron oxide surfaces as well as the adsorption of other pollutant compounds.