Adaptation of Modified Shrinking Core Model for the Description of Salicylic Acid Adsorption on Olive Stones Activated Carbons

This work aimed to apply a modified shrinking core model (SCM) for describing the kinetic adsorption process of a solute in a microporous activated carbon in an agitated finite batch aqueous system. To apply the SCM, the diffusion-adsorption process in the pore of the adsorbent is transposed to a diagram of diffusion-reaction according to a mobile front. Indeed, solid adsorbent particle is assumed formed by two layers. The first layer is an inner core, not yet reached by the adsorbate, and the second layer is an outer shell, where diffusion and binding to particle sites are occurring. In this study, two mass transfer resistances are considered; the external liquid film resistance and intraparticle resistance. The developed modified SCM, applied to experimental data for the adsorption of salicylic acid onto olive stone activated carbons and a commercial one, give a more realistic prediction and shows a good accuracy in describing batch adsorption in mixed suspension. The kinetic parameters: the effective diffusivity and the mass transfer coefficient were determined. Using the estimated parameters, a parametric study was carried out to observe the effects of the particle size of adsorbent, the initial adsorbate concentration and the stirring velocity on the system kinetics.