Network modeling of the intraparticle convection and diffusion of molecules in porous particles packed in a chromatographic column

A pore network model (cubic lattice network) is constructed to represent th e porous structure in a column packed with porous chromatographic particles . Expressions are developed and used to determine, through the utilization of the pore network model, the intraparticle interstitial fluid velocity an d pore diffusivity of a solute as the pore connectivity, n(T), of the porou s medium is varied from 2.6 to 6.0. The results show that the intraparticle interstitial velocity and the pore diffusivity increase significantly as t he value of the pore connectivity, n(T), increases, and clearly indicate th at the pore connectivity, n(T), plays a key role in determining the mass tr ansport properties of a porous medium and, therefore, it is an extremely im portant parameter in the characterization and construction of porous partic les. Furthermore, the results show that the intraparticle interstitial flui d velocity, upsilon(p,i) is many times larger than the diffusion velocity, upsilon(DA), of the solute within the porous medium, and the ratio upsilon( p,i)/upsilon(DA) increases significantly as the pore connectivity, n(T), in creases. The results of this work indicate that the pore network model coul d allow one, for a given porous medium, solute and interstitial column flui d velocity, to determine the values of the intraparticle interstitial fluid velocity, upsilon(p,i), and pore diffusivity, D-p, of the solute in an a p riori manner. The values of upsilon(p,i) and D-p could then be employed in the macroscopic models that describe the dynamic behavior of chromatographi c separations in columns packed with porous particles. (C) 1998 Elsevier Sc ience B.V. All rights reserved.