Low Temperature Processing of Iron Oxide Nanoflakes from Red Mud Extract toward Favorable De-arsenification of Water

Iron oxide (α-Fe₂O₃) was synthesized from red mud extract followed by hydrothermal reaction at 150 °C/6-24 h in the presence of NH₄OH. The crystallinity of α-Fe₂O₃ increased with reaction time as confirmed by X-ray Diffraction, while Fourier transform infrared spectroscopy and Raman illustrate the symmetric stretching vibration of the Fe-O bond in α-Fe₂O₃. The X-ray photoelectron spectroscopic analysis shows O 1s spectra at 530.6, 531.2, and 532 eV, signifying the lattice oxygen in Fe-O, surface oxygen defects, and oxygen in adsorbed hydroxyl groups, respectively. The morphology of α-Fe₂O₃ nanoflakes was noticed from field emission scanning electron microscopy and transmission electron microscopy. The developed particles reveal the BET surface area in the range of 136-347 m²/g. The maximum As(V) adsorption capacity of 32-41 mg/g was obtained for adsorbent dose of 0.25 g/L. The arsenic level could be lowered down to 2-3 μg/L (<10 μg/L as per WHO's limit) with contaminated real water (64 μg/L) using 0.25 g/L of sample dose within 5 min of adsorption.