A fixed-bed adsorption column was modeled mathematically using a plug-flow heterogeneous surface diffusion model (PFHSDM) representing the axial dispersed plug-flow, external mass transfer, adsorption equilibrium on the fluid-particle interface, and intraparticle diffusion. The equations were solved simultaneously using the Newton-Raphson method and the finite element method. The external mass transfer coefficients and the surface diffusion coefficients of octanoic acid and dodecanoic acid onto activated carbon were determined respectively from the PFHSDM on a singlecomponent adsorption. THe longer molecular dimension of the anionic surfactant led to a faster external mass transfer rate onto the activated carbon, but a slower surface diffusion rate inside its narrow pores. Using the extended Langmuir isotherm for binary component adsorption, the estimated kinetic coefficients of the two anionic surfactants agreed remarkably well with those of the single-component adsorption. Also they were applied to a differential column batch reactor system to predict the concentration level required for the optimal design and operation of the system.