Parallel mass transport of protein in the pore fluid and on the pore wall of porous adsorbent is modeled based on the Maxwell-Stefan theory that uses chemical potential gradient as the diffusive driving force. The uptake kinetics of proteins (BSA and gamma-globulin) to anion exchanger is studied by batch adsorption. The parallel diffusion model based on the MS approach (MS-ParD model) and its simplified form, the surface diffusion model (MS-SD model), are analyzed and compared with those based on the Fick's law (F-ParD and F-SD models). It is found that the models from the MS equation and the Fick's law are quite different from each other. For the MS-ParD model, both the pore and surface diffusion coefficients are constant, while the surface or pore diffusion coefficient for the F-ParD model varies significantly with initial protein concentration. Moreover, the MS-SD model can be used to describe the uptake of a protein that shows nearly a rectangular isotherm, in which the surface diffusion contributes very small to the mass transport. In addition, an equation that describes the relationship between the surface diffusion coefficients for the MS-SD and F-SD models is proposed. It is observed that the ratio of the surface diffusion coefficients for the MS-ParD and F-ParD models for less favorably adsorbed protein can be qualitatively described by a theoretical equation. It is concluded that the MS-ParD model is superior to the F-ParD model for describing the non-ideality of adsorbed protein. (c) 2007 Elsevier B.V. All rights reserved.