Efficient Arsenic Removal From Groundwater Using Porous Iron Oxide Material Prepared via Iron-Embedded Cation...

In this study, porous iron oxide material (hereinafter referred to as p-FexOy), synthesized on the hard template of Indion 220Na by ion exchange between the sodium and iron ions, was used as a new and potential material for total arsenic (As) removal in real groundwater samples. The physicochemical properties of the materials were determined by advanced methods such as Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy and mapping, transmission electron microscopy, and Brunauer-Emmett-Teller analyses. Although the study focuses on total As removal to align with the Vietnam National Technical Regulation on groundwater quality, the removal mechanism is discussed in relation to As speciation and surface charge. Selective As(V) removal occurs in acidic media, whereas both As(III) and As(V) are efficiently adsorbed near the point of zero charge (pH_pzc = 7.15). The maximum adsorption capacity (Q_max) reached 0.228 mg/g at a suitable pH range of 7-9 and an adsorption equilibrium time of 60 min. The equilibrium data were best described by the Langmuir isotherm model (R² = 0.999), indicating monolayer adsorption on a homogeneous surface, while the adsorption kinetics followed the pseudo-second-order model (R² = 0.9946). These findings suggest that p-FexOy would have many potential applications in environmental remediation.