Synthesis of Fe3O4@NiO core-shell nanocomposite by the precipitation method and investigation of Cr(VI) adsorption efficiency

In this work, Fe3O4@NiO core-shell nanocomposite was synthesized by precipitation method and various techniques were used to obtain its specifications. According to TEM images, the average NiO shell thickness was about 5 nm and well matched to the crystallite size obtained from XRD. The morphology and purity of the nanocomposite were investigated by SEM and EDX techniques, respectively. According to the BET method, the specific surface area was equal to 27 m(2) g(-1). The efficiency of the synthesized Fe3O4@ NiO nanocomposite to Cr (VI) removal from aqueous solutions was investigated. The results showed that the Fe3O4@ NiO nanocomposite could be considered as an effective adsorbent to remove Cr(VI). The effect of parameters such as Cr(VI) concentration, dosage of Fe3O4@NiO nanocomposite, pH and time on Cr(VI) adsorption was investigated. In addition, experimental data were analyzed with various isotherm and kinetic models. The investigation of the adsorption isotherm indicated that, among various 2-parameter models, it is most consistent and compatible with Langmuir adsorption isotherm (qm = 6.88 mg g(-1)). However, regarding 3-parameter isotherms, it is most consistent with the Sips isotherm (R-2 = 0.997). Moreover, the results revealed that adsorption kinetics in this process complies with the Ho pseudo-second-order kinetics.