Removal of anionic dyes using magnetic Fe@graphite core-shell nanocomposite as an adsorbent from aqueous solutions.

In this study, magnetic Fe@graphite nanocomposite (Fe@G-N) with a core-shell structure was prepared by chemical vapor deposition CVD process for the adsorptive removal of anionic dyes from aqueous solutions. Fe@G-N was characterized by XRD, HRTEM, HAADF-STEM, FTIR, Raman spectroscopy, BET and zeta potential measurements, and then applied in adsorption of two kinds of anionic dyes, Acid Red 88 (AR88) and Direct Orange 26 (DO26). The effect of parameters like initial dye concentration (5-40mgL), pH solution (4-10) and temperature (20-60°C) on the adsorption process was studied. The pseudo-first-order, pseudo-second-order kinetic models and the intraparticle diffusion model were used to describe the kinetic data. A kinetic study indicated that a pseudo-second-order model agreed well with the experimental data. The experimental data were analyzed by the Langmuir and Freundlich adsorption models. Adsorption equilibrium studies showed that adsorption of AR88 and DO26 followed the Langmuir model. Thermodynamic parameters such as Gibbs free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) were also obtained and analyzed.