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 (IO^MgO) 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 IO^MgO 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 IO^MgO has a comparably higher Langmuir constant (KL, 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.