Revealing the Molecular-Level Interactions between Cationic Fluorinated Polymer Sorbents and the Major PFAS Pollutant PFOA

Abstract

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.

Efficient Removal of Perfluorinated Chemicals from Contaminated Water Sources Using Magnetic Fluorinated Polymer Sorbents

“…The fluorogels not only show >99 % removal for PFOA but also had >80 % removal efficiency for 17 other legacy and emerging PFAS. More recently, we quantitatively investigated the contributions of fluorous and electrostatic interactions to the sorption of PFAS [14] . The sorption of PFOA by cationic PFPE‐containing polymer was significantly higher (≈100 %) compared with the non‐ionic PFPE‐containing polymer (≈15.2 %).…”

Detection and differentiation of per- and polyfluoroalkyl substances (PFAS) in water using a fluorescent imprint-and-report sensor array

“…We hypothesized that the DCL sensors might be further improved by incorporating a fluorinated building block due to the well-established partitioning of fluoroalkanes, alkanes, and water, known as the fluorous effect. 53–56 Thus, replacing building block E with the analogous fluorinated building block X (Fig. 3), which has been reported previously, 57 in DCLs within the imprint-and-report array (sensors 2-X, 3-X, and 4-X) may leverage the fluorous effect by introducing fluorine–fluorine host–guest interactions and creating tighter binding.…”

Fluorine in Medicinal Chemistry: In Perspective to COVID-19

“…Fluorinated compounds are very successful in the long history of medicinal chemistry. Fluorine has both hydrophobic and lipophobic characters, 21,25,62,63 and the judicious introduction of fluorine into a drug can productively improve its membrane permeability and cellular uptake, influence pharmacokinetic properties, and subsequently increase the therapeutic efficacy of SARS-CoV-2.…”