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

Abstract

Per-and polyfluoroalkyl substances (PFAS) are persistent organic pollutants of major concern due to their widespread occurrence in drinking water and resistance to conventional remediation technologies. Granular activated carbon (GAC), the current benchmark sorbent, shows limited efficiency for short-and medium-chain PFAS and suffers from slow adsorption kinetics. Here, we report the synthesis of graphene oxide (GO) covalently grafted with an amino-derived β-cyclodextrin polymer crosslinked with epichlorohydrin (GO-Poly-βCD). The material was characterized and tested for the adsorption of a mixture of PFAS of different chain lengths (CF)3-9 and functional groups, under environmentally relevant conditions. GO-Poly-βCD outperformed pristine GO, showing enhanced selectivity for medium-chain PFAS and removal efficiencies up to 97% for PFHpA (CF)6 and PFHxS (CF)6 after only 15 minutes of contact time. At neutral pH, PFPeA (CF)4 was removed by 44% compared to 0% for GO, while at acidic pH its removal efficiency increased to 80%. Notably, PFBA (CF)3, which was not removed at neutral pH, reached 31% removal under acidic conditions. Molecular dynamics simulations revealed a cooperative adsorption mechanism in which PFAS are stabilized through pH-responsive structural conformation changing that enhances the interaction between the hybrid material and the contaminants, mainly through van der Waals forces and hydrophobic effects. Compared to GAC, GO-Poly-βCD achieved higher overall PFAS uptake (4.0 µg/g vs. 1.3 µg/g for GAC) within the same contact time, highlighting its potential for rapid and efficient PFAS remediation in real drinking water treatment applications.