Modeling transport effects of perfluorinated and hydrocarbon surfactants in groundwater by using micellar liquid chromatography

Abstract

The effects of hydrocarbon and perfluorinated surfactants, above their critical micelle concentration (CMC), on the transport of neutral environmental pollutants are compared. Reversed-phase micellar liquid chromatography is used to model the groundwater system. The octadecylsilica stationary phase serves to simulate soil particles containing organic matter, whereas the aqueous surfactant mobile phases serve to simulate groundwater containing a surfactant at varying concentrations. Sodium dodecyl sulfate and lithium perfluorooctane sulfonate are used as representatives of the hydrocarbon and perfluorinated surfactants, respectively. Benzene, mono- and perhalogenated benzenes, and polycyclic aromatic hydrocarbons are used as models for environmental pollutants. Transport effects were elucidated from the retention factor, k, and the equilibrium constant per micelle, K eq, of the model pollutants in the individual surfactants. Based on k values, the transport of the model pollutants increased in both surfactant solutions in comparison to pure water. As the concentration of the surfactants increased, the transport of the pollutants increased as well. Notably, the K eq values of the pollutants in the perfluorinated surfactant were at least an order of magnitude less than those in the hydrocarbon surfactant. Overall, these results suggest that the presence of a perfluorinated surfactant, above its CMC, increases the transport of pollutants in a groundwater system. However, the perfluorinated surfactant exhibits a lesser transport effect than the hydrocarbon surfactant.