Adsorption Characteristics and Mechanistic Study of Immobilized Chitosan-Montmorillonite Composite for Methyl Orange removal

Abstract

This work investigates the adsorption characteristics and mechanisms of immobilized chitosan-montmorillonite (CS-MT) composite for the removal of methyl orange (MO) dye. It was observed that the immobilized CS-MT has a rougher surface, lower swelling, higher adhesion strength and higher surface area than the immobilized CS. The adsorption of MO dye onto the immobilized CS-MT followed the pseudo-second-order kinetic model, whereas at equilibrium, the Langmuir model best described the MO adsorption. The maximum adsorption capacity, qm of the immobilized CS-MT at 30, 45 and 60 °C were 154.4, 82.8 and 64.9 mg g−1, respectively. The thermodynamic study showed that the process of MO adsorption onto the immobilized CS-MT was exothermic in nature. The main adsorption mechanism of MO dye on immobilized CS-MT can be assigned to electrostatic attractions, n–π stacking interaction, dipole–dipole hydrogen bonding interactions and Yoshida H-bonding. Overall, the immobilized CS-MT does not only offer relatively high adsorption capacity, but also facilitates the treatment operation reusability and easy recovery of the adsorbent.