Adsorption of cationic dyes onto Fe@graphite core-shell magnetic nanocomposite: Equilibrium, kinetics and thermodynamics

Abstract Magnetically separable Fe@graphite core–shell nanocomposite particles (Fe@G) were synthesized by chemical vapor deposition CVD process and characterized by XRD, HRTEM, HAADF-STEM, FTIR, Raman spectroscopy, BET and zeta potential measurements. Nanocomposite was used to adsorb two cationic dyes, Basic Yellow 28 (BY28) and Basic Red 46 (BR46), from aqueous solutions. Adsorption process was investigated under different experimental conditions of pH (3–11), initial dye concentration (10–50 mg L −1 ) and temperature (20–60 °C). The adsorption kinetics were examined using pseudo-first-order, pseudo-second-order and intraparticle diffusion model. The equilibrium adsorption data were analyzed by Langmuir, Freundlich and Temkin isotherm models. The results revealed that the pseudo-second-order model and Langmuir isotherm fit the kinetics and equilibrium data, respectively. In addition, various thermodynamic parameters, such as change in free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°), were also calculated. The thermodynamic analysis showed that the adsorption of BY28 and BR46 was spontaneous and endothermic.