Fixed bed adsorption kinetics is analyzed to test the validity of the simplified model based on the linear driving force approximation by comparison with the exact model by using the orthogonal collocation method. The axial dispersion, the external film diffusion, and the intraparticle diffusion are considered to be the major mass transfer phenomena involved with the fixed bed adsorption kinetics in this study. It is assumed that a local equilibrium is attained at the fluid-solid interface and the equilibrium can be described by the Langmuir isotherm. A homogeneous particle diffusion model is employed to describe the intraparticle diffusion.