Surfactant phase behavior with field degreasing solvent

Surfactant phase behavior data are presented for dense nonaqueous phase liq uids (DNAPLs). The experimental procedures and results published in this pa per led to the successful selection of a surfactant formulation that was us ed in a field demonstration at a site contaminated with DNAPL rich in trich loroethene (TCE). Experiments were conducted to investigate the effects of temperature, electrolyte, cosolvent, xanthan gum polymer, and surfactant hy drophobe length on surfactant phase behavior. Experimental results are pres ented 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 proced ures previously developed and reported only for pure component DNAPLs such as TCE can be useful for selecting suitable surfactants for complex field D NAPLs. In addition to the usual criteria of large increases in contaminant solubilization and lowering of interfacial tensions, we identify rapid form ation of microemulsions with acceptably low viscosities as an additional re quirement for surfactant screening. Our results indicate that the best surf actant formulations equilibrate to low viscosity microemulsions within a fe w 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.