Nanopore diffusion rates for adsorption determined by pressure-swing and concentration-swing frequency response and comparison with darken's equation

Two flow-through frequency response methods of concentration-swing frequency response (CSFR) and pressure-swing frequency response (PSFR) are applied to study the adsorption of chloroethane on BPL activated carbon over a wide range of concentrations. Chloroethane at low concentrations in helium, 500 ppm(upsilon) and 10 mol %, are studied using CSFR. Two models which treat an adsorption bed with axial dispersion or a simplified well-mixed concentration have been developed for both isothermal and nonisothermal conditions. The results show that heat effects can be negligible for the CSFR method. Pure chloroethane at relatively high concentrations is studied using PSFR. The experimental data are described well by a nonisothermal nanopore diffusion model. The diffusivities obtained from these two distinct methods are identical for the same concentration. The modeling of the concentration behavior depends quite sensitively on the isotherm model and obeys Darken's equation for the D-R isotherm. The results show that the frequency response method can distinguish the importance of heat effects and the relative importance of the mass-transfer mechanisms.