ADSORPTION IN POROUS SOLIDS HAVING BIMODAL PORE SIZE DISTRIBUTION

Abstract

The effect of micropore diffusion, macropore diffusion and adsorption on the transient uptake of porous solids having bimodal pore size distribution (for example, zeolites) is theoretically investigated in this paper. Two models commonly used in the literature—the pore diffusion model and the surface diffusion model— are considered and their equivalence is discussed. The bimodal diffusion model equations are solved analytically by using a generalized integral transform method. The solutions for the micropore, macropore concentrations and the fractional uptake are presented. Since two different processes control the transient uptake, the asymptotic solutions for micropore diffusion control case and macropore diffusion control case are obtained by using perturbation methods, so that these asymptotic solutions can be compared with that when these two processes equally contribute to the transient uptake.