Dispersion and polydispersity effects in the transport of xanthan in porous media

Recent experimental work on the flow of xanthan through nonadsorbing porous media has demonstrated a clear surface exclusion effect in which larger molecular weight species propagate faster than smaller fractions through the pore structure. Effluent measurements in these experiments include an assay for total polymer concentration and intrinsic viscosity of the produced solutions. Assuming zero hydrodynamic dispersion, these results may be analyzed using simple surface exclusion models to obtain the original molecular weight distribution (MWD) of the native polymer. In this paper, we model the transport of polymer through porous media using a multicomponent representation of the MWD, including the effects of hydrodynamic dispersion and surface exclusion. These calculations indicate that the data in such experiments are more difficult to interpret than the simple surface exclusion models alone would suggest. As a result of our calculations, supplementary experiments, necessary to clarify the interpretation, are suggested. © 1989 American Chemical Society.