ABSTRACTCOMPARISON OF TRANSPORT EFFECTS OF PERFLUORINATED AND HYDROCARBON SURFACTANTS ON ENVIRONMENTAL CO–CONTAMINANTSByRashad Najee Simmons The use of groundwater as drinking water justifies efforts for the prevention and remediation of groundwater contamination by environmental pollutants. The inclusion of hydrocarbon surfactants (HCSs), at high concentrations, in a groundwater system has been used for groundwater remediation, and is known to increase the transport of environmental pollutants. While much information is known about HCS, little to no information is available for the perfluorinated surfactants (PFSs). The overall objective of this research was to determine the transport effects of PFSs on known environmental contaminants, in comparison to the transport effects of HCSs. Polycyclic aromatic hydrocarbons, halogenated benzene compounds, and the BTEX series of compounds (benzene, toluene, ethylbenzene, and p–xylene) were used as representatives of important classes of hydrophobic neutral environmental pollutants. A series of aromatic amines was used as representatives of cationic environmental pollutants. Reversed–phase liquid chromatography (RPLC) was used to model the groundwater system. Above their critical micelle concentration (CMC), surfactants form micelles that can act as partitioning mediums for hydrophobic neutral pollutants, increasing their transport. In the first study, the transport effects of HCSs and PFSs, above their CMC (> 20 mM), were compared in the RPLC system for representative neutral environmental pollutants. Transport effects were elucidated from retention factors, k, and the equilibrium constant per micelle of the model pollutants. The resulting data suggest that the presence of HCSs and PFSs, above the CMC, increases the transport of co–contaminants in a groundwater system. However, PFSs (18 to 103 % increase) exhibit a lesser transport effect than HCSs (32 to 247 % increase). Previous literature suggests that surfactants below their CMC have a negligible effect on the transport of hydrophobic neutral pollutants, while undergoing ion–pair formation with ionic pollutants and decreasing their transport. In the second and third studies, the transport effects of HCSs and PFSs, below their CMC (< 6 mM), were compared in the RPLC system. Transport effects were elucidated from retention factors, k, and selectivity factors, α, of the model pollutants. The resulting data suggest the presence of HCSs statistically decreases transport of neutral pollutants (4 to 13 %), while the presence of PFSs statistically increases their transport (5 to 16 %). Further results show that transport of cationic aromatic amines decreases with increasing concentration of both anionic HCSs and PFSs in RPLC system, with PFSs (99 to 100 % decrease) exhibiting a greater transport effect than HCSs (96 to 100 % decrease). Due to the differences in chemical and physical properties, PFSs exhibit different transport effects in comparison to HCSs under the same conditions. The inclusion of anionic PFSs in a groundwater system will increase the transport of neutral environmental pollutants, while decreasing the transport of cationic pollutants. An unintentional release of PFSs can lead to an increase in groundwater contamination by neutral pollutants. However, the judicious use of PFSs can be used for remediation of cationic pollutants in groundwater.
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