Adsorptive removal of methyl orange from aqueous solution with crosslinking chitosan microspheres

Chitosan (CS) microspheres were successfully prepared via emulsion polymerization using biodegradable chitosan as raw material and glutaraldehyde as crosslinking agent. Micron-scale monodisperse CS microspheres were then obtained by controlling the reaction conditions. Simulated dye wastewater, containing methyl orange (MO), was examined for the adsorption dynamics and thermodynamics of CS microspheres by UV–vis spectroscopy, and the associated adsorption mechanism was preliminarily investigated. Changes in the absorbance, throw ratio, conductivity, and dissolved oxygen content of MO solution during adsorption by CS microspheres were studied, and the chemical structures of CS microspheres before and after MO adsorption were characterized by Fourier transform-infrared spectroscopy. Results showed that the prepared CS microspheres retained excellent inherent chemical stability and had strong MO adsorption capacity. CS contains many hydroxyl groups, which are involved in the adsorption of organic dye. The adsorption process had a negative value of free energy change (ΔG°); therefore, the process was a spontaneous reaction. At lower MO equilibrium concentrations, the CS microspheres had a greater capacity for adsorption.