Chemical Tailoring of β-Cyclodextrin-Graphene Oxide for Enhanced Per- and Polyfluoroalkyl Substances (PFAS) Adsorption from Drinking Water

We report on the synthesis of beta-cyclodextrin (beta CD) modified graphene oxide (GO) nanosheets, having different sized alkyl linkers (GO-C-n-beta CD) and their exploitation as sorbent of perand polyfluoroalkyl substances (PFAS) from drinking water. beta CD were functionalized with a pending amino group, and the resulting precursors grafted to GO nanosheets by epoxide ring opening reaction. Loading of beta CD units in the range 12%-36% was estimated by combined XPS and elemental analysis. Adsorption tests on perfluorobutanoic acid (PFBA), a particularly persistent PFAS selected as case study, revealed a strong influence of the alkyl linker length on the adsorption efficiency, with the hexyl linker derivative GO-C-6-beta CD outperforming both pristine GO and granular activated carbon (GAC), the standard sorbent benchmark. Molecular dynamic simulations ascribed this evidence to the favorable orientation of the beta CD unit on the surface of GO which enables a strong contaminant molecules retention.