Date of Award
Master of Science
Geological and Environmental Sciences
Dr. Daniel P. Cassidy
Dr. Duane R. Hampton
Dr. Donald M. Reeves
Surfactant, Saponin, NAPL, contamination, push-pull
Masters Thesis-Open Access
Laboratory studies were conducted on Quillaja saponins and nine other surfactants commonly used to remove non-aqueous phase liquids (NAPLs) from soils and aquifers. The NAPL contaminant tested was diesel fuel. Static batch reactors containing an aged diesel-contaminated soil was treated with saponins and nine other commercially available surfactants to determine how much diesel fuel could be removed with the pore fluids after 1 day and 10 days of contact time. Of all the surfactants tested, saponins achieved the greatest removal of diesel fuel after 1 day and 10 days. There was large disparity in the diesel fuel removed by the other nine surfactants tested, which suggests a high degree of specificity controlled by the soil, rather than the NAPL itself. The amount of diesel fuel removed was much greater after 10 days than after 1 day, which demonstrates the importance of allowing contact time after introducing surfactants into a NAPL contaminated system, especially one with little or no mixing.
Column studies were then conducted with saponins as the only surfactants, with and without co-injection with hydrogen peroxide (H2O2). Because mixing has been shown to enhance contact between NAPL and surfactants, and therefore NAPL removal, H2O2 was tested as a co-injectate that could provide mixing in the pores of the columns because of its tendency to auto-decomposition to O2 gas on soils. Columns were used to simulate a Push-Pull application of surfactants, which is increasingly being used for small NAPL contaminated sites (e.g., gasoline stations). The columns were charged with Ottawa sand (20-30 mesh) that had been artificially contaminated with diesel fuel and mixed every month over a year-long period. Two doses of saponins were injected (500 times and 1000 times the critical micelle concentration) alone and with a 5% H2O2 solution. When injected alone, the higher dose of saponins achieved greater NAPL removal than the lower dose. For both saponin doses tested, NAPL removal was significantly enhanced when co-injected with H2O2. The greatest removal achieved was when a solution of saponins 1000 times the CMC was injected in a 5% hydrogen peroxide solution. The results suggest that injecting saponins with low concentrations of H2O2 has the potential to enhance surfactant-enhanced NAPL recovery in Push-Pull applications in the field.
Holada, Charles E., "Evaluation of Non-Ionic Surfactants with and without Hydrogen Peroxide for the In-Situ Remediation of NAPL Contaminants" (2017). Masters Theses. 920.