Perfluoroalkyl substances (PFASs) are contaminants of emerging concern characterized by incredible stability and a dual hydrophobic/hydrophilic nature. Emerging PFASs, including short chain PFASs and perfluoroethercarboxylic acids (PFECAs), are especially problematic due to limited research on their environmental and health effects. Cyclodextrins (CDs), non-toxic cyclic sugars, were used as trapping agents for PFASs. The resulting CD-PFAS host-guest complexes were studied via 19F Nuclear Magnetic Resonance (NMR) Spectroscopy. Preliminary studies of legacy PFASs were expanded to include recently discovered PFECAs. Changes in the chemical shifts of the PFAS fluorine atoms, and subsequent modeling by non-linear least squares regression analysis, led to the determination of the association constants for the 1:1 and 2:1 CD:PFAS complexes. The strength of the complex was correlated with the PFAS chain length. α-CD (six glucose units) and γ-CD (eight glucose units) both exhibited weak to moderate association constants with PFASs (less than 500 M-1 for α-CD and 2000 M-1 for γ-CD), with only 1:1 CD:PFAS interactions observed. β-CD (seven glucose units), on the other hand, exhibited very strong association constants with PFASs (102-106 M-1 depending on chain length), with 2:1 CD:PFAS interactions also present. More than 99% of PFASs were encapsulated in the presence of excess β-CD, making β-CD a promising tool for environmental remediation of PFASs. Ongoing experiments are investigating the use of β-CD in combination with carbonaceous sorbents for removal of PFASs from water.

Encapsulation of legacy and emerging perfluoroalkyl substances by cyclodextrins

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.