Nano-Structured Magnesium Oxide Coated Iron Ore: Its Application to the Remediation of Wastewater Containing Lead

Magnetically separable nano-structured magnesium oxide coated iron ore (IOMgO) was prepared using environmentally benign chemicals, such as iron ore (IO), magnesium(II) nitrate hexahydrate [Mg(NO₃)₂ · 6H₂O] and urea; via an easy and fast preparation method. The IOMgO was characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energydispersive X-ray spectroscopy (EDS) and alternating gradient magnetometer (AGM) analyses. The isotherm and kinetic studies indicated that IOMgO has a comparably higher Langmuir constant (K _L , 1.69 L mg⁻¹) and maximum sorption capacity (33.9 mg g⁻¹) for lead (Pb) than other inorganic media. Based on MgO amount, the removal capacity of Pb by IO^MgO was 2,724 mg Pb (g MgO)⁻¹, which was higher than that (1,980 mg g⁻¹) for flowerlike magnesium oxide nanostructures reported by Cao et al. The kinetics, FE-SEM, elemental mapping and XRD results revealed that the substitution followed by precipitation was identified as the mechanism of Pb removal and plumbophyllite (Pb₂Si₄O₁₀ ·H₂O) was the precipitated phase of Pb. A leaching test revealed that IO^MgO had negligible concentrations of leached Fe at pH 4–9. Since the base material, IO, is cheap and easily available, IO^MgO could be produced in massive amounts and used for remediation of wastewater containing heavy metals, applying simple and fast magnetic separation.