Magnetic xanthate modified chitosan as an emerging adsorbent for cationic azo dyes removal: Kinetic, thermodynamic and isothermal studies

In the present study, a novel xanthate modified magnetic chitosan, with Al₂O₃/Fe₃O₄ core-shell particle as magnetic core, was synthesized, characterized and used as an efficient adsorbent for the removal of cationic azo dye models. The adsorption study demonstrated that the xanthate modification of magnetic chitosan significantly improves its adsorption activity toward methylene blue and safranin O. The optimized adsorbent dosage was obtained 0.8 mg g⁻¹ and the process was found to be optimal in the wide pH range of 4–11. The kinetic data were evaluated well utilizing the pseudo-second-order model and it was shown that the adsorption kinetics was controlled by film diffusion and intra-particle diffusion, simultaneously. Also, the equilibrium data were fitted by Langmuir (R² > 0.95) and very well correlated with Sips isotherm (R² > 0.990) model. The maximum adsorption capacities were obtained 197.8 and 169.8 mg g⁻¹ toward the methylene blue and Safranin O at 35 °C respectively. The thermodynamic analysis confirmed the endothermic, spontaneous and irreversible adsorption process.