Capillary transport in adsorption from liquid phase on activated carbon

Two models presented here predict the kinetics of adsorption from solution. The adsorbate is considered to form a capillary separated phase inside the micropores. The transport in the adsorbed phase is modeled as capillary transport under the influences of gradients in capillary pressure. In model I the capillary separated phase is assumed to be continuous, while in model II it is assumed to be discontinuous. The effective adsorbed phase diffusion coefficient for this transport is directly related to the pore-size distribution, which can be found from the sorption isotherm. In both models the overall apparent diffusion coefficients are compared with experimental data. Both models satisfactorily predict the dependency of the diffusion coefficient on carbon loading. Model I slightly underestimates the temperature dependency of the effective diffusion coefficient, while model II gives a good prediction of the influence of temperature on the rate of adsorption.