Effective removal of azo-dye orange II from aqueous solution by zirconium-based chitosan microcomposite adsorbent

Abstract

In this study, zirconium-based chitosan (CTS@Zr) microcomposite was prepared and employed as an efficient adsorbent for the removal of orange II dye from aqueous solution. The microcomposite was characterized by BET, FT-IR, XRD, SEM and EDS. Various parameters including solution pH, contact time, temperature and initial dye concentration were systematically investigated. The results showed that the adsorption process was pH dependent and the optimum condition was at pH 2.0. Adsorption kinetics followed the pseudo-second order model and thermodynamic constant values demonstrated that the adsorption process of orange II dye onto CTS@Zr microcomposite was feasible, spontaneous (ΔG⁰ < 0) and endothermic (ΔH⁰ > 0) under the examined conditions. Equilibrium isotherms showed a good fit with Langmuir isotherm equation for the monolayer adsorption process and the maximum adsorption capacity was calculated for 926 mg g⁻¹. More importantly, the removal rate was higher than 99.4% when initial dye concentration was less 100 mg L⁻¹ (0.20 g L⁻¹ dosage), indicating that the CTS@Zr microcomposite exhibited excellent efficiency for the removal of orange II dye. Moreover, the orange II loaded CTS@Zr microcomposite adsorbent was easily regenerated by using 0.05 M NaOH within 10 min and the adsorption capacity still remained 98% after six regeneration cycles. The mechanisms of adsorption were attributed to electrostatic attraction and ligand exchange reaction between CTS@Zr and Dye–SO₃⁻ anions. Therefore, the CTS@Zr microcomposite adsorbent possesses a great potential for the removal of orange II dyes from aqueous solution.