Equilibrium and kinetic studies on basic dye adsorption by oil palm fibre activated carbon

Oil palm fibre, an abundant agricultural by-product in Malaysia, was used to prepare activated carbon by physiochemical activation method. Adsorption isotherm of methylene blue onto the prepared activated carbon was determined by batch tests. The effects of various parameters such as contact time, initial methylene blue concentration and temperature were investigated, at solution pH of 6.5. The adsorption capacity was found to increase with increase in the three parameters studied. Equilibrium data were fitted to Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherms. The equilibrium data were best represented by the Langmuir isotherm, with maximum monolayer adsorption capacity of 277.78 mg/g at 30 °C. The adsorption kinetics was found to follow the pseudo-second-order kinetic model. Various thermodynamic parameters such as standard enthalpy (ΔH°), standard entropy (ΔS°) and standard free energy (ΔG°) were evaluated. Oil palm fibre-based activated carbon was shown to be a promising material for adsorption of methylene blue from aqueous solutions.