Application of the film-pore diffusion model to the sorption of phenol onto activated carbons prepared from peanut shells

Abstract

In this work, the film-pore diffusion model was applied to the adsorption of phenol onto peanut shell activated carbon in a batch stirred vessel. This two-resistance model was applied to predict the phenol concentration decay curves for different initial phenol concentrations, carbon particle sizes and dosages. The predicted concentration decay curves were compared with the experimental findings. The optimum best-fit values of the external mass-transfer coefficient and effective diffusion coefficients were found by minimizing the difference between the experimental and model-predicted phenol solution concentration. It was found that, under the experimental conditions employed in this study, the influence of the external mass-transfer resistance was low. A single value of the mass transport coefficient, kf, of (4.8 ± 1.3) × 10-3 (cm/s) described the whole range of system conditions. The difference between the corresponding values of the effective diffusivity, Deff, was not statistically significant. Consequently, a constant value of the effective pore diffusivity of (4.1 ± 0.4) × 10-6 (cm2/s) was sufficient to provide an accurate correlation of the decay concentration curve.