Poly-cyclodextrin modified graphene oxide for PFAS removal from drinking water

Per- and polyfluoroalkyl substances (PFASs) are persistent organic pollutants of growing concern due to their widespread occurrence in drinking water and resistance to conventional remediation technologies. Granular activated carbon (GAC), the current benchmark adsorbent, exhibits limited efficiency toward short- and medium-chain PFASs and slow adsorption kinetics. Here, we report the synthesis of a graphene oxide (GO) material covalently grafted with an amino-functionalized beta-cyclodextrin polymer crosslinked with epichlorohydrin (GO-Poly-beta CD). The hybrid material was characterized and evaluated for the adsorption of a mixture of PFASs with varying chain lengths (CF)3-9 and functional groups under environmentally relevant conditions. GO-Poly-beta CD outperformed pristine GO, showing enhanced affinity for medium-chain PFAS and removal efficiencies up to 97% for PFHpA (CF)6 and PFHxS (CF)6 after only 15 min of contact. At neutral pH, PFPeA (CF)4 removal reached 44%, compared to no removal by GO, while under acidic conditions its removal increased to 80%. Notably, PFBA (CF)3, which was not removed at neutral pH, exhibited 31% removal under acidic conditions. Molecular dynamics simulations revealed a cooperative adsorption mechanism in which PFAS molecules are stabilized through pH-responsive conformational rearrangements that strengthen interactions between the hybrid material and the contaminants, primarily via van der Waals and hydrophobic forces. Compared to GAC, GO-Poly-beta CD achieved a higher overall PFAS uptake (4.0 mu g g-1vs. 1.3 mu g g-1 for GAC) within the same contact time, demonstrating its potential for rapid and efficient PFAS removal in real drinking water treatment applications.