Removal of Forever Chemicals from Aqueous Solutions through Adsorption on Swellable Organically Modified Silicas

Per- and polyfluoroalkyl substances (PFASs), also called forever chemicals, are known for their high physicochemical stability. In the last decades, these chemicals have been widely employed for numerous industrial applications. However, their persistence in the environment has increasingly raised concern regarding their potential toxicity to living organisms including humans. Hence, the need for their removal demands the development of efficient methods to reduce their environmental impact. Here, a quaternary ammonium swellable organically modified silica (QASOMS) is used for the removal of perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), and perfluorobutanesulfonic acid (PFBS) via liquid phase adsorption. Adsorption of the pollutants was quantified using an optimized quantitative liquid phase ¹⁹F NMR method. QASOMS exhibited good adsorption capacities for all three PFASs; the highest uptake was measured for PFOA and was equal to 0.635 mmol/g at a concentration of 1.89 mM. Fast adsorption kinetics were also found for all three PFASs, showing approximately 93% of PFAS removal from the aqueous solutions after 6 h of contact. Finally, host-guest interactions between the adsorbed PFAS and the surface of QASOMS were investigated via SS-NMR spectroscopy.