Sorption dynamics and isotherm studies of methylene blue uptake on to palm kernel fibre

Abstract

The effect of temperature on the sorption of methylene blue from aqueous solution onto palm kernel fibre has been studied. Batch kinetics and isotherm studies were performed at temperatures ranging from 299 to 339 K. The kinetic data were studied in terms of the pseudo-first-order and pseudo-second-order kinetic models and the Bangham and intraparticle diffusion models. The pseudo-second-order model best described the sorption process and was employed in predicting the rate constant, equilibrium sorption capacity and the initial sorption rate with effect of temperature. In addition activation energy of sorption has also been determined based on the pseudo-second-order rate constant. The isotherm data was analyzed by the Langmuir and Freundlich isotherms. Palm kernel fibre was found to have a Langmuir monolayer capacity of 233.41 mg g−1 at 299 K. The adsorption is endothermic at ambient temperature and the computation of the thermodynamic parameters, ΔH°, ΔS° and ΔG° indicates that the sorption was favourable at all temperatures.