Synthesis and characterization of Nanoscale Zero-Valent Iron (nZVI) as an adsorbent for the simultaneous removal of As(III) and As(V) from groundwater

Arsenic (As) is a contaminant of global concern due to its negative impact on environmental systems, where As occurs mainly as two inorganic species, arsenite (As(III)) and arsenate (As(V)). Thus the simultaneously removal of both As(III) and As(V) from groundwater is a challenging issue. In this paper, zero-valent iron nanoparticles ( n ZVI) with high surface-active sites were used to simultaneously remove both As(III) and As(V) species from groundwater with removal efficiencies >99.9% for an initial concentration 100 μg L −1 . Ion chromatography atomic fluorescence (IC-AFS) analysis indicated that during removal As(III) was oxidized to As(V), while X-ray photoelectron spectroscopy (XPS) showed that the As species were adsorbed on to the surface of n ZVI by a complexation reaction. Furthermore, thermodynamic studies of the adsorption process indicated that adsorption was a spontaneous and endothermic chemisorption process. Finally, practical removal of both As species by n ZVI from real groundwaters was demonstrated with removal efficiencies of 99.9 and 70.9% for As(V) and As(III), respectively. The presence of other coexisting ions affected the removal efficiency, with phosphate and carbonate decreasing the removal efficiencies of both As(III) and As(V) due competition with active binding sites on the surface of n ZVI. Overall, this work demonstrated that n ZVI was a promising adsorbent for the practical removal of inorganic As species from complex environmental matrices such as groundwater.