Synthesis of iron-magnetite nanocomposites for hexavalent chromium sorption

Abstract

Owing to multiple industrial applications of chromium compounds, developing chronic and highly water soluble chromium adsorption methods has gained attention. Nano-iron-magnetite nanocomposite (IM-NCs) was successfully synthesized from Eucalyptus globulus leaf extract for chromium adsorption from an aqueous solution. The occurrence of the black solution was the first physical indication of the formation of zero-valent iron. The X-ray diffraction pattern analysis confirmed the formation of the Fe/Fe3O4 nanocomposite. The FT-IR spectrum indicated the presence of Fe-O stretch, probably due to the development of iron oxides, which confirmed the oxidation of parts of the zero-valent iron to magnetite. The SEM image showed the agglomerated morphology of nanoparticles (NPs). The EDX analysis showed the existence of the expected elemental compositions of Fe and O. The UV–vis spectra showed peaks at 450 and 550 nm with a broader absorption band ranging from 350 to 650 nm, probably resulting from the octahedral ferric ions and magnetite. The BET and TEM/HRTEM image analyses yielded specific surface areas and an approximate crystallite size of 14 m2 g−1 and 19 nm, respectively. The Langmuir adsorption isotherm fitted the experimental data more than the Freundlich isotherm model. The well-fitted pseudo-second-order (PSO) model compared with the pseudo-first-order (PFO) model describes the chemisorption nature of the adsorption process. The negative free energy value confirms the spontaneity of the adsorption process. The maximum adsorption capability of the materials was 19 mg/g.