Isothermal model, estimation diffusivity dependence

The rate of contaminant adsorption onto activated carixm particles is controlled by two parallel diffusion mechanisms of pore and surface diffusion, which operate in different manners and extents depending upon adsorption temperature and adsorbate concentration. The present study showed that two mechanisms are separated successfully using a stepwise linearization technique incorporated with adsorption diffusion model. Surface and pore diffiisivities were obtained based on kinetic data in two types of adsorbers and isothermal data attained from batch bottle technique. Furthermore, intraparticle diffiisivities onto activated carbon particles were estimated by traditional breakthrough curve method and final results were compared with those obtained by more rigorous stepwise linearization technique. 

The expressions for the FRFs for the isothermal micropore and pore-surface diffusion models were obtained for constant diffusion coefficients. If this assumption is not met, that is, if the concentration dependence of the diffusion coefficient has to be taken into account, the value estimated from the maximum of the — Imag(Fi p(diffusion coefficient corresponding to the steady-state concentration. 

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