Arsenite removal from groundwater by iron-manganese oxides filter media: Behavior and mechanism

Arsenic, a common contaminant in groundwater environments, usually coexists with other contaminants, for example, ammonium, iron, and manganese. In our previous studies, an iron-manganese (Fe-Mn) oxides filter media was developed for catalytic oxidation removal of ammonium, iron, and manganese. In this study, batch oxidation/adsorption kinetic experiments revealed that the filter media could easily oxidize arsenite (As(III)) to arsenate (As(V)). And the sorption kinetics was found to follow the pseudo-second-order kinetic model. X-ray powder diffraction (XRD) and Fourier transform infrared spectra (FTIR) along with X-ray photoelectron spectroscopy (XPS) were used to analyze the surface change in the Fe-Mn oxides. Based on sorption and spectroscopic measurements, the mechanism of As(III) removal by the Fe-Mn oxides filter media was found to be an oxidation coupled with sorption approach. As(III) in the aqueous solution was firstly oxidized to As(V) on the surfaces of the Fe-Mn oxides filter media. Then the converted As(V) was attracted to the Fe-Mn oxides filter media surfaces and bounded with the active sites (-OH groups), through weak intermolecular H-bondings. Our results indicated that the novel Fe-Mn oxides filter media could be applied for the simultaneous removal of ammonium, iron, manganese, and As(III) in drinking water treatment and environmental remediation. (C) 2019 Water Environment Federation