Adsorption of Reactive Blue 4 Dye onto Chitosan 10B in Aqueous Solution: Kinetic Modeling and Isotherm Analysis

Abstract

The reactive blue 4 (RB4) dye adsorption onto chitosan 10B was studied in aqueous solution as a function of contact time, dye concentrations, ionic strength, temperature and solution pHs. The dye adsorption kinetics validated a pseudo second-order model while the rate determining step followed intraparticle diffusion mechanism. The equilibrium dye adsorption isotherms were nicely fitted with the Langmuir model. The maximum amount of dye uptake onto chitosan 10B was found to be 95.24 μmol/g. The mean adsorption energy (E) from the Dubinin–Radushkevich isotherm, the activation energy (Ea) from Arrhenius equation and apparent thermodynamic parameters such as changes in standard free energy (∆G°), standard enthalpy (∆H°) and standard entropy (∆S°) indicate that the present adsorption is a spontaneous endothermic physisorption process. Desorption of RB4 from dye-loaded chitosan was tested in NaOH solution (pH 13) and the chitosan flakes can be reused.