Adsorption rate of phenol from aqueous solution onto organobentonite: Surface diffusion and kinetic models

The concentration decay curves for the adsorption of phenol on organobentonite were obtained in an agitated tank batch adsorber. The experimental adsorption rate data were interpreted with diffusional models as well as first-order, second-order and Langmuir kinetic models. The surface diffusion model adjusted the data quite well, revealing that the overall rate of adsorption was controlled by surface diffusion. Furthermore, the surface diffusion coefficient increased raising the mass of phenol adsorbed at equilibrium and was independent of the particle diameter in the range 0.042–0.0126 cm. It was demonstrated that the overall rate of adsorption was essentially not affected by the external mass transfer. The second-order and the Langmuir kinetic models fitted the experimental data quite well; however, the kinetic constants of both models varied without any physical meaning while increasing the particle size and the mass of phenol adsorbed at equilibrium.

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► Phenol adsorption capacity of organobentonite decreased with temperature.
► Overall adsorption rate of phenol onto organobentonite was modeled in this work.
► External mass transport did not affect the adsorption rate of phenol.
► Adsorption rate of phenol on organobentonite was controlled by surface diffusion.
► Second-order and Langmuir kinetic models fitted the rate data reasonably well.