Using Cyclodextrin Polymers to Remove PFAS and Trace Organic Contaminants from Municipal Wastewater

Trace organic contaminants (TrOCs) are groups of natural and synthetic organic compounds that are ubiquitously present in municipal wastewater and freshwater bodies. Conventional adsorbents, such as activated carbons, exhibit variable TrOCs removal efficiencies and suffer fouling by natural organic matters and inorganic constituents found in contaminated water sources. Porous crosslinked β-cyclodextrin (β-CD) polymers are promising adsorbents with demonstrated removal performances for per- and polyfluoroalkyl substances (PFAS) from contaminated water sources. We will present a new approach to access tunable β-CD adsorbents based on radical polymerization of styrene-functionalized β-CD monomers. A β-CD adsorbent bearing a cationic functional group achieved nearly 100% removal for eight anionic PFASs in nanopure water at an exceedingly low adsorbent loading of 1 mg L-1, which is at least an order of magnitude lower than that used in previous studies. Furthermore, when the β-CD adsorbents were studied in a challenging salt matrix, we observed that long-chain PFAS adsorption was controlled by a complementary interplay of hydrophobic and electrostatic interactions, whereas short-chain PFASs primarily relied on electrostatic interactions.

The adsorbents were evaluated for removing an expanded list of TrOCs, particularly PFAS and pharmaceuticals, at environmentally relevant concentrations from municipal wastewater. Batch adsorption studies show that β-CD adsorbents generally have higher adsorption affinity and faster adsorption kinetics than the benchmark adsorbents studied. Further developments of these adsorbents to approach pilot-scale testing will be presented.