Surfactant Phase Behavior with Field Degreasing Solvent

Abstract

Surfactant phase behavior data are presented for dense nonaqueous phase liquids (DNAPLs). The experimental procedures and results published in this paper led to the successful selection of a surfactant formulation that was used in a field demonstration at a site contaminated with DNAPL rich in trichloroethene (TCE). Experiments were conducted to investigate the effects of temperature, electrolyte, cosolvent, xanthan gum polymer, and surfactant hydrophobe length on surfactant phase behavior. Experimental results are presented for a field degreasing solvent that is a DNAPL from Operable Unit 2 (OU2) of Hill Air Force Base, Layton, UT. These experiments show that procedures previously developed and reported only for pure component DNAPLs such as TCE can be useful for selecting suitable surfactants for complex field DNAPLs. In addition to the usual criteria of large increases in contaminant solubilization and lowering of interfacial tensions, we identify rapid formation of microemulsions with acceptably low viscosities as an additional requirement for surfactant screening. Our results indicate that the best surfactant formulations equilibrate to low viscosity microemulsions within a few hours. Extensive soil column studies have shown that such behavior leads to DNAPL recoveries exceeding 99% without significant problems such as pore plugging and high surfactant retention.