Kinetic sorption study of Cerium (IV) on magnetite nanoparticles

Magnetite nanoparticles (Fe₃O₄) and humic acid-coated magnetite nanoparticles (Fe₃O₄/HA) were prepared by co-precipitation method for cerium ions removal from aqueous solution. The success of preparation in nanoscale was confirmed by x-ray diffraction (XRD) and transmission electron microscopy (TEM). The TEM image shows that the size of Fe₃O₄ is around 15 nm and the presence of humic acid reduces the magnetite aggregation and stabilizes the magnetite suspension. Adsorption studies with respect to various process variables such as contact time, pH, and temperature were investigated by batch technique. The sorption kinetics and isotherms of Fe₃O₄ and Fe₃O₄/HA for Ce (IV) ions show that the sorption kinetics follow the pseudo-second-order and Langmuir isotherm models for both sorbents. The maximum capacities (Q_max) of Ce (IV) onto Fe₃O₄ and Fe₃O₄/HA were found to be 160 and 280 mg/g, respectively. The thermodynamic parameters (ΔG^o, ΔH^o and ΔS^o) were calculated, and the results revealed that the sorption process of Ce (IV) ions on both Fe₃O₄ and Fe₃O₄/HA are spontaneous, endothermic for Fe₃O₄ and exothermic for Fe₃O₄/HA.