Laboratory evaluation of custom-designed surfactants to remediate NAPL source zones

Laboratory column studies were conducted using custom-designed anionic surfactants, the branched alcohol propoxylated sulfates, to evaluate their effectiveness in removing nonaqueous phase liquids (NAPLs) from both Ottawa sand and field alluvium. Surfactant efficacy was tested at temperatures ranging between 11 and 50 degrees C for contaminants such as tetrachloroethene (PCE), weathered gasoline, and Naval Special Fuel Oil. It has been shown that use of branched alcohol propoxylated sulfates can achieve very low final NAPL saturations even with recalcitrant NAPLs, while exhibiting low induced hydraulic gradients, low microemulsion viscosity, and minimal sorption on contaminated field soils. These custom-designed surfactants are effective with both dense NAPLs (DNAPLs) and light NAPLs. Finally, these surfactants were used to create neutrally buoyant microemulsions with a PCE DNAPL. The laboratory experiments show that these custom-designed, high-performance surfactants can be tailored to optimize contaminant solubility for specific field NAPLs.