The solubilization of dodecane by polyoxyethylene (20) sorbitan monool
eate, a nonionic surfactant, was investigated as a potential means of
recovering nonaqueous-phase liquids from contaminated aquifers. Residu
al saturations of dodecane were established by injecting C-14-labeled
dodecane into water-saturated soil columns and displacing the free pro
duct with water. Flushing with a 43 g/L surfactant solution increased
the concentration of dodecane in the column effluent by 5 orders of ma
gnitude. However, effluent dodecane concentrations were considerably l
ess than the equilibrium value of 3500 mg/L measured in batch studies.
Subsequent column experiments conducted at several flow velocities an
d with periods of flow interruption confirmed the existence of rate-li
mited, rather than instantaneous, solubilization of residual dodecane.
The results of this study demonstrate the sizable capacity of surfact
ant solutions to enhance the recovery of residual dodecane, even under
conditions of rate-limited solubilization.