High-Loading UiO-66@Polycaprolactone Electrospun Nanofibers for Equilibrium-Driven Removal of Perfluorooctanoic Acid from Water

Per and polyfluoroalkyl substances (PFAS) are a group of pollutants known as "forever chemicals" due to their persistence in the environment and their strong resistance to degradation.Many compounds in this class, such as perfluorooctanoic acid (PFOA), are highly toxic to humans. In this study, we investigated the harvesting efficiency of accumulated PFOA from freshwater samples using zirconium-based metal-organic framework (MOF), i.e. UiO-66, as the primary adsorbent with a high chemical affinity for PFOA. In an effort to enhance MOF stability and flexibility, UiO-66 gel was added into biodegradable polycaprolactone (PCL) at 5, 12, 21 and 35 wt% in addition to a pure PCL electrospun control and electric field forming fibrous composite material (PCL-UiO-66). Filtration experiments using PFOA-contaminated water showed a strong correlation between the UiO-66 content in PCL-UiO-66 and the PFOA harvesting efficiency. Post-filtration fluorine content in the filter membranes indicates the effective PFOA uptake of the PCL-UiO-66 composite. In contrast, the PFOA uptake increases linearly with the concentration of UiO-66 used in the electrospinning fabrication process. Experiments using PFOA-contaminated water showed a strong correlation where ~90% of the pollutant was removed in batch soaking. These results demonstrate the applicability of fibrous PCL-UiO-66-based filter membranes to remove traces of PFOA from freshwater with high efficiency, as a scalable water treatment technology using simple, biodegradable materials.