Colloid transport in unsaturated porous media: The role of water content and ionic strength on particle straining

摘要: Abstract Packed column and mathematical modeling studies were conducted to explore the influence of water saturation, pore-water ionic strength, grain size on transport latex microspheres (1.1 μm) in porous media. Experiments carried out under chemically unfavorable conditions for colloid attachment both solid–water interfaces (SWI) air–water (AWI) using negatively charged hydrophilic colloids modifying solution chemistry with a bicarbonate buffer pH 10. Interaction energy calculations complementary batch experiments demonstrated that partitioning SWI AWI was insignificant across range strengths considered. The breakthrough curve final deposition profile measured each experiment indicating retention highly dependent suspension content, sand size. In contrast conventional filtration theory, most found deposited close inlet, hyper-exponential profiles observed. A model, accounting time- depth-dependent straining, produced reasonably good fit curves profiles. Experimental results suggest straining — low velocity regions media such as junctions primary mechanism saturated unsaturated conditions. extent stagnant flow within pore structure is enhanced decreasing leading greater amount retention. Ionic strength also contributes because number are held secondary minimum increases strength. These weakly associated prone be translated stagnation formed at grain–grain junctions, solid–water–air triple point, dead-end pores then becoming trapped.