EFFECT OF THE ADSORPTION-ISOTHERM ON ONE-COMPONENT AND 2-COMPONENT DIFFUSION IN ACTIVATED CARBON

Results are presented for the equilibrium adsorption isotherms of seve ral components in an activated carbon. The amount adsorbed has been me asured over a large pressure range using head space analysis. A distin ct difference between the Dubinin-Radushkevich and the Langmuir model is observed especially for heavy component adsorption (propane and hex ane). The contribution of the isotherm model to the concentration depe ndent diffusion process in the activated carbon is outlined using the Maxwell-Stefan theory. It is demonstrated that the various isotherm mo dels give a different concentration dependence for the surface diffusi on coefficient. An activated carbon membrane, a resin disk containing activated carbon particles, has been developed to measure steady-state and transient permeation. The experiments have been performed accordi ng to the Wicke-Kallenbach method. Experimental and simulated results of binary permeation of a mixture of nitrogen and propane agree well. The essential feature of concentration dependent diffusion, an oversho ot in the transient profile of the fast moving and weakly adsorbed com ponent, is predicted. The simulations of the binary permeation show, a gain, a clear effect of the isotherm model on the mass transport proce ss. (C) 1997 Elsevier Science Ltd.