Comparative study of the batch adsorption kinetics and mass transfer in phenol-sand and phenol-clay adsorption systems

Abstract

This study was aimed at evaluating the kinetics and mass transfer of phenol adsorption onto sand and clay sediments. The adsorption studies were carried out in batch mode. The results showed that the time taken to attain equilibrium in the adsorption of phenol onto sand and clay sediments are 21 and 27 h, respectively. At an equal given time, clay sediments relatively had higher adsorption of phenol than sand sediments, which can be ascribed to its large surface area and higher porosity. The kinetic data adjusted well to the pseudo-first-order and Elovich kinetic models; however, Elovich kinetic model best describe the phenol adsorption kinetics. Mass transfer models were applied to the adsorption data to evaluate the rate-limiting step in the adsorption of phenol onto the sand and clay sediments. The values of the external mass transfer coefficient and diffusion coefficient were estimated from the models. Biot number was determined using the estimated internal mass transfer (intraparticle diffusion) coefficient and the external mass transfer coefficient. From the applied models and the calculated Biot number, the results revealed that the mechanism of phenol adsorption onto sand and clay sediments was not only by intraparticle diffusion but also by film diffusion.