The removal of per- and polyfluoroalkyl substances (PFASs) from water is an emerging challenge for water quality managers. Much attention has focused on the removal of anionic perfluoroalkyl acids, but not the removal of cationic, zwitterionic, and nonionic PFASs, which may co-occur with anionic perfluoroalkyl acids in PFAS-contaminated groundwater. The objective of this research was to evaluate the performance of different types of β-cyclodextrin polymers (CDPs) for the removal of different types of PFASs from water. We designed a series of batch experiments to evaluate the performance of three CDPs, an anion exchange (AE) resin, and cation exchange (CE) resin for the removal of eleven PFASs representing long- and short-chain anionic, zwitterionic, and nonionic per- and polyfluoroalkyl substances. We measured adsorption affinity, adsorption kinetics, and the effects of pH and water matrix constituents for each of the five adsorbents. We found that a CDP with a negative surface charge rapidly removes all zwitterionic PFASs with log KD values ranging between 2.4 and 3.1, and the CE resin rapidly removes two zwitterionic PFASs with log KD values of 1.8 and 1.9. The CDPs with a positive surface charge rapidly remove all anionic PFASs with log KD values between 2.7 and 4.1, and the AE resin removes all anionic PFASs relatively slowly with log KD values between 2.0 and 2.3. All adsorbents exhibited variable removal of the nonionic PFASs and some adsorption inhibition at higher pH values and in the presence of groundwater matrix constituents. Our findings provide insight on how novel CDPs can be used for the remediation of groundwater contaminated with complex mixtures of PFASs and demonstrate the importance of evaluating remediation technologies for their potential to remove PFAS classes representing different charge states.

β-Cyclodextrin polymers with different cross-linkers and ion-exchange resins exhibit variable adsorption of anionic, zwitterionic, and nonionic PFASs

ACS Fall 2021

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