Role of spatial distribution of porous medium surface charge heterogeneityin colloid transport

The role of spatial distribution of porous medium patchwise chemical (charg e) heterogeneity in colloid transport in packed bed columns is investigated . Colloid transport experiments with carboxyl latex particles flowing throu gh columns packed with chemically heterogeneous sand grains were carried ou t. Patchwise chemical heterogeneity was introduced to the granular porous m edium by modifying the surface chemistry of a fraction of the quartz sand g rains via reaction with aminosilane. Colloid transport experiments at vario us degrees of patchwise charge heterogeneity and several spatial distributi ons of heterogeneity were conducted at different flow rates and background electrolyte concentrations. Colloid deposition rate coefficients were deter mined from analysis of particle breakthrough curves as a response to short- pulse colloid injections to the column inlet. Experimental colloid depositi on rate coefficients compared well with theoretical predictions based on a colloid transport model that incorporates patchwise chemical heterogeneity. The results revealed the particle deposition rate and transport behavior t o be independent of the spatial distribution of porous medium chemical hete rogeneity. It is the mean value of chemical heterogeneity rather than its d istribution that governs the colloid transport behavior in packed columns, (C) 2001 Elsevier Science B.V. All rights reserved.