Four models for the rate of adsorption in an adsorbent (slab-like, cylindrical or spherical) are presented. The parabolic profile (PP) model is obtained by assuming a parabolic intraparticle concentration profile. The shell-core (SC) model is based on a shell-core type profile. The modified shell-core (MSG) model is an extension of the SC model. And the general driving force (GDF) model is a weighted average of the PP and MSC models. Sample calculations show that the GDF model provides the best approximation.