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 adsor ption and desorption characteristics of n-octane vapor on the activated car bon were investigated over the relative pressure (p/p degrees) range 0-0.97 for temperatures in the range 288-313 K in a static vapor system. The adso rption 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 s et changes in relative vapor pressure (p/p degrees). The desorption kinetic s 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 wer e used to-calculate the activation energies for each increase in relative p ressure. The activation energy was highest at low p/p degrees and decreased with increasing p/p degrees until a maximum was reached at p/p degrees sim ilar to 0.075. n-Nonane adsorption showed similar trends in adsorption kine tics and activation energies to the n-octane adsorption. The results are di scussed in terms of diffusion in the pore structure in relation to the adso rption isotherm and mechanism.