Modeling of fixed bed adsorption of phenols on granular activated carbon

Mathematical modeling of liquid phase adsorption of phenols in fixed beds of granular activated carbon was investigated. The model considered the effects of axial diffusion in the fluid, the external film and internal diffusional mass transfer resistances of the particles, and the nonlinear adsorption isotherm of Freundlich. It was shown that the analysis of a complex multicomponent adsorption system could be simplified by converting it into a pseudo single-component adsorption system. This was achieved by lumping the concentrations of the components together as one single parameter, chemical oxygen demand. The resulting model equations were solved using the orthogonal collocation method and third-order semi-implicit Runge-Kutta method combined with a step-size adjustment strategy. Excellent agreement between simulated results and pilot plant data was obtained. Also, the breakthrough profiles revealed the formation of a primary monomolecular layer on the adsorbent surface.