Caffeine, riboflavin and curcumin amended clays for PFAS binding

Per- and polyfluoroalkyl substances (PFAS) are usually found in mixtures with other toxic compounds. Therefore, the study and design of broad acting sorbents, such as clays, is an attractive sorption solution. We previously demonstrated that clays amended with choline and carnitine could enhance PFAS sorption properties. Here, we used computations to screen from a pool of chemical compounds, which are either supplements or generally recognized as safe, and identified particular supplements that can be amended to clay and potentially improve its sorbing capacity for PFAS in acidic conditions. Simulations were initially used as a tool to identify promising amendments to the clay, while subsequently, simulations evaluated which selected amendments could potentially bind PFAS. Our results showed that caffeine-, riboflavin- and curcumin-amended clays can, in particular instances, enhance the binding of different PFAS compared to parent clays. Experiments investigated the sorption properties of the designed systems. Notably, caffeine-amended clay significantly enhanced GenX binding when compared to parent clay, with its binding capacity being increased from 0.15 mol/kg to 1.17 mol/kg. Caffeine-amended clay also enhanced binding for PFOS by 125%, compared to the parent clay, and for PFOA to a lesser extent. Additionally, riboflavin-amended clay enhanced binding for GenX, PFOA and PFOS by 120%, 23%, and 70%, respectively, compared to the parent clay. Our studies provide atomistic details into their mechanisms of action. Both the novel computational library of chemical compound-amended clays and the approach utilized, combining computations and experiments, could enhance the future design of novel amended clays for other toxins.