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item Bradford, Scott

Submitted to: American Chemical Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 1/20/2005
Publication Date: 3/1/2005
Citation: Bradford, S.A. 2005. Concentration dependent colloid transport in saturated porous media. American Chemical Society Abstracts, San Diego, CA. 229:U646-U647.

Interpretive Summary:

Technical Abstract: series of column experiments was undertaken to explore the influence of colloid input concentration (2, 1, 0.5, and 0.25 times a reference concentration), colloid size (negatively charged 3.2 and 1.0 m carboxyl latex microspheres), and sand grain size (360, 240, and 150 m quartz sands) on transport and deposition. A similar mass of stable mono-dispersed colloids was added to each column. For a given input concentration, decreasing the sand size and increasing the colloid size resulted in increased mass retention in the sand near the column inlet and lower relative concentrations in the effluent. For a given sand and colloid, increasing the input concentration produced less deposition and higher mass recovery in the effluent, especially for coarser sands and smaller colloids. A conventional time dependent attachment (blocking) and detachment model was not consistent with this behavior because it predicted much less retention near the column inlet and similar levels of effluent mass recovery for different input concentrations in a given system (colloid and sand). A time dependent straining model (filling of straining sites) provided a better description of the effluent and deposition data, but still could not account for the observed concentration dependency. Alternatively, the straining model was refined to include a liberation term that assumed that straining was hindered at higher concentrations (collision frequencies) due to repulsive colloid (aqueous phase) -colloid (strained) interactions. Simulations that included straining, liberation, attachment, and detachment significantly improved the description of the experimental data.