ABSTRACT In this study, nickel‐doped magnetite (Ni@Fe3O4) nanoparticles were successfully prepared by chemical precipitation method and used as adsorbents for the removal of cadmium ions (Cd(II)) and hexavalent chromium ions (Cr(VI)) from aqueous solutions. The surface, structural, and morphology analysis of the nanoparticles was characterized by Brunauer–Emmett–Teller (BET) surface area measurements, powder x‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Images from TEM revealed that the prepared nanoparticles were spherical in shape, with particle size ranging between 10 ± 3.3 and 58 ± 4.6 nm. The BET surface area was 49.5 ± 3.2 m2/g. The XRD results confirmed the crystalline structure of Ni@Fe3O4 nanoparticles. The results indicated an optimum operating pH 5 for Cd(II) and pH 3 for Cr(VI), where the adsorption capacity for Cd(II) was 68 ± 1.5 mg/g and for Cr(VI) was 56 ± 2.1 mg/g. Moreover, the adsorption process was spontaneous and the amount of adsorbed ions increased with an increase in temperature, suggesting an endothermic adsorption process. The kinetic data were best described by the pseudo‐second‐order kinetic model and the isotherm data fitted well with the Langmuir isotherm model. Therefore, it can be concluded that the prepared Ni@Fe3O4 nanoparticles are effective in the removal of Cd(II) and Cr(VI) and could potentially be used in wastewater treatment.
Songo et al. (Sun,) studied this question.