Modeling adsorption rate of pyridine onto granular activated carbon

The overall adsorption rate of pyridine on a granular activated carbon (GAC) is modeled in this work. The concentration decay curves for pyridine adsorption on GAC were obtained in a rotating basket adsorber. The experimental data were interpreted using a diffusional model that considered external mass transport, intraparticle diffusion, and adsorption on an active site; intraparticle diffusion could be due to both pore volume and surface diffusion. Results showed that the surface diffusion represented more than 93.5% of total intraparticle diffusion, confirming that surface diffusion was the mechanism controlling the overall adsorption rate. The model considering that surface diffusion was the controlling diffusion mechanism, interpreted reasonably well the concentration decay data for pyridine adsorption at different experimental conditions. Results showed that the surface diffusion coefficient increased while raising the temperature and mass of pyridine adsorbed at equilibrium, and was independent on the particle diameter. The external mass transport did not affect the overall rate of pyridine adsorption on GAC.