Studying colloid transport in porous media using a geocentrifuge
2008 (English)In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 44, no W07407Article in journal (Refereed) Published
Movement of colloids in the subsurface is a concern because mobile colloids mayenhance the transport of contaminants. The excessive time required to conduct flow andtransport experiments in porous media led to the use of centrifuges to evaluate subsurfacetransport processes. The objective of this study was to determine the suitability ofcentrifuges to study colloid transport in saturated porous media. We used a geocentrifugeto run colloid transport experiments under different centrifugal accelerations up to 20 g.Colloids of different densities were used: polystyrene (1.05 g/cm3), silica (2 g/cm3), andhematite (5.26 g/cm3). Deposition coefficients were obtained from the colloidbreakthrough curves. We used filtration theory and a theory based on sedimentationdiffusionto derive functional relationships between centrifugal acceleration and colloidand porous media properties, which allow us to predict the effect of acceleration on colloidtransport. Comparison of experimental deposition coefficients with predictions based onfiltration theory showed that filtration theory accurately predicted the behavior ofpolystyrene at higher accelerations but underpredicted colloid deposition for silica andhematite at accelerations higher than 10 g. The sedimentation-diffusion theory allows usto determine whether a system is dominated by sedimentation or diffusion, or is in atransitional state. Theoretical predictions of colloid deposition in a porous medium agreedwell with experiments, suggesting that the theory can be used to delineate whencentrifugal acceleration will alter colloid transport in flow through column studiesconducted in a centrifuge. Common subsurface colloids, such as iron oxides andaluminosilicates, can be affected at accelerations that are used in geocentrifuge transportstudies (5 to 300 g). Even colloids with low specific densities, such as polystyrene, will beaffected by centrifugal accelerations if their size is large.
Place, publisher, year, edition, pages
2008. Vol. 44, no W07407
Other Environmental Engineering
IdentifiersURN: urn:nbn:se:uu:diva-179767DOI: 10.1029/2007WR006456OAI: oai:DiVA.org:uu-179767DiVA: diva2:546192