Synthesis of TiO2 and ZnO Nanoparticles and CTAB-Stabilized Fe3O4 nanocomposite: kinetics and thermodynamics of adsorption

In the present study, TiO2, ZnO, and CTAB-stabilized Fe3O4 nanocomposite were successfully synthesized and employed for the removal of yellow 145 dye from aqueous solutions. These nanomaterials were characterized by various techniques such as X-ray diffraction spectroscopy (XRD), Fourier transform-infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N2 adsorptions/desorption isotherms (BET). The surface area of the nanocomposite was achieved 123.76 m2 g−1 which is greater than both of TiO2 (50.12 m2 g−1) and ZnO (26.85 m2 g−1). To achieve high adsorption capacity, the effects of different operational parameters such as dye concentration, pH, dose of adsorbent (TiO2, ZnO, and nanocomposite), and contact time were separately specified. According to the results, the pseudo-second-order kinetic model was showed better agreement with the experimental data. The rate constant (k2; g mg−1 min−1) for the adsorption of yellow 145 on the synthesized TiO2, ZnO, and nanocomposite was measured 0.0279, 0.0282, and 0.0162, respectively. Gibbs free energy, enthalpy, and entropy were calculated as the thermodynamic parameters which indicated that the adsorption process is endothermic and spontaneous. Also, the equilibrium data were fitted on Langmuir, Freundlich, Temkin, and Dobinin–Radoskovich equilibrium isotherm models. Accordingly, Longmuir and Freundlich models were the best isothermal models for describing the adsorption of yellow 145 dye by nanocomposite and metal oxides, respectively. Moreover, the results showed that the adsorption capacity depends on the specific surface area. For this reason, the adsorption capacity of nanocomposites is higher than both of TiO2 and ZnO.