Adsorption of reactive dye onto cross-linked chitosan/oil palm ash composite beads

摘要

Adsorption of reactive dye from aqueous solution onto cross-linked chitosan/oil palm ash composite beads (CC/OPA) was investigated in a batch system.Kinetic and isotherm studies were carried out by considering the effects of various parameters,such as initial concentration (50-500 mg/L),contact time,pH (2-13),and temperature (30,40,50 °C).It was found that the dye uptakes were much higher in acidic solutions than those in neutral and alkaline conditions.Langmuir,Freundlich,Redlich-Peterson,and Temkin isotherms were used to analyze the equilibrium data at different temperatures.The Redlich-Peterson isotherm fits the experimental data significantly better than the other isotherms.Adsorption kinetics data were tested using pseudo-first-order and pseudo-second-order models.Kinetic studies showed that the adsorption followed a pseudo-second-order model.The pseudo-first-order and pseudo-second-order rate constants for different initial concentrations were evaluated and discussed.Thermodynamic parameters such as standard Gibbs free energy (DELTA G°),standard enthalpy (DELTA H°),and standard entropy (DELTA S°) were evaluated by applying the Van't Hoff equation.The thermodynamics of reactive dye adsorption onto cross-linked chitosan/oil palm ash composite beads indicates its spontaneous and endothermic nature.