Iron Oxide Nanoparticles for Efficient Removal of Arsenic from Contaminated Groundwater

Abstract

Arsenic in drinking water poses severe public-health risks in many regions. Here, magnetic iron oxide nanoparticles (Fe₃O₄ NPs) were synthesized by co-precipitation and evaluated as adsorbents for arsenic removal. Crystallinity and phase were verified by X-ray diffraction (XRD); morphology by transmission electron microscopy (TEM); surface chemistry by Fourier-transform infrared spectroscopy (FTIR); and textural properties by Brunauer–Emmett–Teller (BET) analysis. The Fe₃O₄ NPs exhibited a high specific surface area (~110 m² g⁻¹) and uniform, near-spherical particles (15–20 nm). Batch adsorption experiments examined the effects of pH, contact time, and initial arsenic concentration. The maximum adsorption capacity reached 82 mg g⁻¹ at pH 7. Kinetic data were best described by a pseudo-second-order model, indicating chemisorption as the rate-limiting step, while equilibrium data followed the Langmuir isotherm, consistent with monolayer coverage on a homogeneous surface. Magnetic separability enabled facile recovery, and regeneration tests retained >75% adsorption performance after five cycles. These results demonstrate that co-precipitated Fe₃O₄ nanoparticles are efficient and reusable adsorbents for arsenic remediation, with properties that support practical recovery and repeated use. Future work should compare performance for As(III) versus As(V) and quantify the impact of competing anions in realistic groundwater matrices.