The development of new technologies
for the removal of a family
of manufactured chemicals, the per- and polyfluoroalkyl substances
(PFAS), from the environment is urgently needed to safeguard public
and environmental health. Here we report a fundamental study of the
binding mechanisms driven by fluorine–fluorine and electrostatic
interactions between perfluorooctanoic acid (PFOA), an important PFAS
molecule, and three types of block copolymer sorbents containing individually
perfluoropolyether (PFPE) or quaternized ammonium groups, or both
functional segments in combination. The results show that both the
fluorine–fluorine interactions between the PFPE segment of
the block copolymer and the fluorinated tail of the PFOA as well as
electrostatic attraction between the quaternized ammonium group and
the anionic PFOA headgroup are crucial to achieve effective PFOA sorption
from aqueous solutions. The fluorine–fluorine interactions
contribute to recognition of PFOA molecules via fluorophilicity, with
fast exchange between bound and free PFOA being observed, while the
electrostatic interactions can tightly bind PFOA, thus precluding
such exchange. Both types of interaction are observed to be rapidly
established within 5 min. We show that the sorbents containing both
fluorinated and cationic groups have a higher PFOA removal efficiency
with potentially improved sorption capacity compared with the sorbents
with a single functional group and that the electrostatic attraction
is stronger and dominates the fluorine–fluorine interactions
when the sorbent is highly charged. Overall, these results provide
important insights into designing novel sorbents for rapid and efficient
PFAS removal from contaminated environments.