Dodecane solubilization by low concentration TX-100 in saturated porous media at different pore-water velocity under continuous flow and flow interruption conditions was investigated with the use of one-dimensional flow column. Under continuous flow condition, TX-100 adsorbed onto the porous media surface, especially partitioned onto the NAPL-water interface and further into the NAPL phase induced the retardation and shouldering in TX-100 BTCs. In addition, the dynamic solubilization of dodecane based on the aggregate formation mechanism under continuous flow condition showed significantly preferential flow. The increased pore-water velocity obtained an enhanced dodecane transport efficiency, which could augment the preferential flow during the aggregate transport process. For flow interruption condition, the peaks in dodecane elution curve illustrated that dodecane solubilization by TX-100 at sub- and hyper-CMC concentrations was a rate-limited process. The high pore-water velocity with a large dodecane transport efficiency induced a higher peak both in dodecane elution curve and TX-100 BTCs at the same duration of flow interruption. In addition, the redistribution of TX-100 adsorbed on the quartz sand media surface, especially partitioned on the NAPL-water interface and further into the NAPL phase into the aqueous solution participated in dodecane solubilization process and therefore incurred the normalized concentration peaks in TX-100 BTCs. These results will promote our understanding of the solubilization mechanism of high partitioned surfactant used in SEAR technology at low concentration and will be informative for improving the performance of high partitioned surfactant in industrial application.
 

preferential flow, rate-limited solubilization, redistribution, porous media, SEAR