A model is presented to describe the rate of uptake of a species by a spherical adsorbent particle when intraparticle transport can occur by parallel diffusion through the pore space and along the surfaces of pore walls. Although the conventional shrinking core model (SCM) has been applied to such systems previously, its use is valid only when adsorption onto the pore walls is described by a rectangular isotherm. As with the SCM, the new model differs from homogeneous models by envisaging the advance of the adsorbate to be marked by a distinct inward-moving interface, but it generalizes the SCM to allow for an incompletely saturated adsorbed shell behind the front governed by any Langmuir isotherm. The model has been applied to previously published experimental data for the uptake of bovine serum albumin by chitosan beads and compared to the results obtained when the same data are analysed using the corresponding homogeneous model. The fit of the two models to the convension-time data yields comparable results, but significant differences in the predicted absorbate concentration profiles within adsorbent particles are observed, particularly at high conversions.