Competitive Adsorption of Phenolic Compounds onto Activated Carbon Fibers in Fixed Bed

Abstract

For a multicomponent competitive adsorption process, a mathematical model was built to describe the mass transfer kinetics in a fixed-bed adsorber packed with activated carbon fibers (ACFs). The effects of competitive adsorption equilibrium constants, axial dispersion, external mass transfer, and intraparticle diffusion resistances on the breakthrough curves were analyzed for weakly adsorbed and strongly adsorbed components. Experiments were carried out to remove phenolic compounds from an aqueous solution. With the equilibrium data and the intraparticle (intrafiber) diffusivities obtained from separate experiments in a batch adsorber, the axial dispersion coefficient was evaluated by fitting the experimental data of breakthrough curves with the theoretical model. The results show that the effects of intrafiber and external mass transfer resistances on the breakthrough curves can be neglected for a fixed-bed adsorber packed with ACFs, and the axial dispersion is confirmed to be the main parameter that controls the adsorption kinetics. A simpler model, based solely on a liquid phase mass balance and incorporating local equilibrium with axial dispersion, provides a good description of the adsorption process for a fixed-bed adsorber packed with ACFs.