(x)ZnO(1 − x)Fe₂O₃ nanocrystallines for the removal of cadmium(II) and nickel(II) from water: kinetic and adsorption studies

In this work the efficiency of mechanically prepared magnetic (x)ZnO(1 − x)Fe₂O₃ nanocrystallines for Ni(II) and Cd(II) ions removal was investigated. The produced nanoparticles were characterized using N₂ adsorption, X-ray diffraction (XRD), and magnetization techniques. Batch mode experiments were performed to evaluate the parameters of the heavy metal ions adsorption on the nanoparticles. The concentration and temperature were found to be detrimental factors in the adsorption process as the amounts adsorbed were enhanced by their increase. While Cd(II) adsorption was found to comply with the Langmuir isotherm, the adsorption of Ni(II) ions fitted both Langmuir and Freundlich isotherms. The pseudo-second-order model was the kinetics model describing the adsorption process. The adsorption process was endothermic and spontaneous as indicated by the thermodynamic study results. The positive entropy obtained may suggest increased randomness at the solid–solution interface. A mechanism for the metal ions adsorption was proposed.