EFFECT OF TAPER ON DIFFUSION AND ADSORPTION IN A CYLINDRICAL PORE

The combined effects of hindered diffusion and adsorption in a single pore can be used as the basis for modeling diffusion and adsorption of macromolecules such as proteins in porous media. We examine here the influence of pore tapering, which affects both the hindrance and adsor ption effects on the overall transport rate. The governing equation is developed by averaging the continuum diffusion equation across the po re, and it is solved numerically for the case of a cylindrical pore wi th radius decreasing linearly with axial position. The effect of the t aper on axial concentration profiles is to give rise to a pronounced i nflection relative to the shape seen for a straight pore, and the net uptake rate is altered as well. These results indicate that extraction of pore structure details from solute uptake information is problemat ic, and that empirically correlated pseudocontinuum transport models m ay be more reliable.