Adsorption and Desorption Kinetics of n-Octane and n-Nonane Vapors on Activated Carbon

This investigation has involved the study of the adsorption and desorption kinetics of two n -alkanes on a wood-based active carbon (BAX950). The adsorption and desorption characteristics of n -octane vapor on the activated carbon were investigated over the relative pressure ( p / p o ) range 0−0.97 for temperatures in the range 288−313 K in a static vapor system. The adsorption characteristics of n -nonane were studied over the relative pressure range 0−0.97 and temperature range 303−323 K. The adsorption and desorption kinetics were studied with different amounts of preadsorbed n -octane for set changes in relative vapor pressure ( p / p o ). The desorption kinetics were much slower than the corresponding adsorption kinetics for the same pressure step. The rate constants for adsorption increased with increasing relative pressure and surface coverage. The kinetic data for adsorption were used to calculate the activation energies for each increase in relative pressure. The activation energy was highest at low p / p o and decreased with increasing p / p o until a maximum was reached at p / p o ∼0.075. n -Nonane adsorption showed similar trends in adsorption kinetics and activation energies to the n -octane adsorption. The results are discussed in terms of diffusion in the pore structure in relation to the adsorption isotherm and mechanism.