An Experimental Study of Reaction - Coupled Flow and Mass Transport in Porous Media

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This experimental study investigates coupled processes of flow and reactive mass in porous media. Of interest are reactive transport processes that involve coupling both through density effects and heterogeneous chemical reactions that may alter the hydraulic character of the medium. The goal of this study is to contribute fundamental knowledge concerning reaction-coupled mass transport. Two and Three-dimensional experiments with flow tanks will be used to elucidate the time-space evolution of reaction fronts and fluid chemistry in porous media, and to interpret the nature of the feedbacks that exist between density-driven flow, and reactive mass transport. The experiments will involve pumping a dilute Fe(CIO4) 3 solution through a mixture of quartz sand and a small quantity of crushed calcite. The initial acidity of the solution will promote calcite dissolution and lead to the precipitation of ferric oxyhydroxide. The resultant pore plugging will result in patterning in hydraulic conductivity and reroute fluid flow through the tanks. These patterns can be documented photog raphically in two-dimensional experiments. The three-dimensional experiments are technically more challenging and require that reaction fronts be described with both in situ hydraulic conductivity measurements and electrical measurements with a permanently installed electrode array. This research builds on our studies of instabilities in variable density flows, and will contribute new knowledge in the emerging area of coupled processes and practical problems of contaminant support.