Removal of reactive green 19 dye using chitosan beads

Abstract

The adsorption of reactive green 19 (RG19) on chitosan beads was studied in batch system. Various experimental parameters were studied, including initial dye concentration (50 - 500 mg/L), contact time, pH of solution (2 - 13) and temperature (25 - 50 °C). The experimental data were analyzed using Langmuir and Freundlich isotherm model. The result showed a better fit to the Langmuir isotherm model, claiming a homogeneous surface of chitosan beads produced. Pseudo-first-order, pseudo-second-order kinetic were used to analyze the kinetic data. It was found that the kinetic data fitted well with the pseudo-second-order kinetic model, which suggest that the adsorption is controlled by the chemisorptions process. Thermodynamic studies were carried out and various thermodynamic parameters, such as Gibbs energy (ΔG°), entalphy change (ΔH°), entrophy change (ΔS°) and activation energy (Ea) were calculated. The results reveal that RG19 has a good affinity towards chitosan beads and the adsorption process was spontaneous and endothermic. Since the low value of Ea and ∆G° indicates that process is more towards physisorption mechanism, it is concluded that the adsorption of RG19 onto chitosan beads are taking the combination route of physical and chemisorptions.