Fabrication and characterization of nanostructured MgO·Fe₂O₃ composite by mechanical milling as efficient adsorbent of heavy metals

Nanocrystalline magnesium ferrite is synthesized by high-energy ball milling of α-Fe₂O₃ and MgO powders and annealed at 700, 800 and 900 °C temperatures. The Prolonged mechanical milling process has reduced the average crystallite size of MgFe₂O₄ to the nanometer range as confirmed by the X-ray diffraction analysis. Along with MgFe₂O₄ phases of α-Fe₂O₃ and metallic Fe were highlighted by the Rietveld XRD refinements. The scanning electron microscopy micrographs of as-milled MgO-Fe₂O₃ showed cauliflower-like nanostructure with narrower size distribution (≈75 nm). Furthermore, nitrogen adsorption BET analysis demonstrated flatter rather than cylindrical shaped pores with an average pore diameter in the range 24.7–66.3 nm and decreased surface area from 13.45 to 2.23 m²/g, as a function of annealing temperature. This is consistent with the increased crystallite size values obtained from XRD analysis. The magnetic study indicated a ferromagnetic behavior with low coercivity (68.68 Oe), remanence (0.840 emu/g) and saturation magnetization of 6.517 emu/g. The variation of magnetization as a function of temperature signified cations redistribution within the spinel phase MgFe₂O₄. The as-obtained nanopowders were tested for heavy metal removal from aqueous solutions where the data revealed improved ions removal by low temperature annealed nanoparticles especially for Ni⁺² and Cd⁺² indicating their potential for contaminants removal.