Abstract
To make clear the mechanism of intraparticle diffusion at relatively high concentration ranges, the values of intraparticle diffusivity, Diq, of tetrahydrofuran (THF) within activated carbon pellets were measured at 308 K by use of two methods, i.e. the steady-state diffusion method and the flow method for fixed-bed adsorption. The two values of Diq obtained agreed with each other fairly well. Surface and pore diffusivities were calculated from Diq based on a concept of simultaneous occurrence of transfer through pore spacings and through surfaces. The value of surface diffusivity, Ds, thus calculated was almost equal to those reported for solvent vapor-activated carbon systems in lower concentration ranges. The value of pore diffusivity, Dp, calculated was close to that evaluated from molecular diffusion theory combined with Knudsen diffusion. It became clear that breakthrough curves numerically estimated using the values of Diq, variable with the change in amount adsorbed, fitted the experimental breakthrough curves more closely than those estimated by use of the values of diffusivity assumed to be constant irrespective of amount adsorbed for specific experimental runs.
