Water-Induced Confinement of Perfluorinated Pollutants in Biobased Polyamide Nanofibrous Membranes

Perfluorooctanoic acid (PFOA), a representative per- and polyfluoroalkyl substance (PFAS), is a persistent water contaminant due to its strong C-F bonds and amphiphilic molecular nature. Here, we reveal a water-mediated adsorption mechanism in biobased poly(hexamethylene 2,5-furandicarboxylamide) (PA6F) nanofiber membranes, in which hydration induces structural densification and molecular confinement of PFOA within the fibrous network. Upon water exposure, the electrospun PA6F membrane undergoes macroscopic shrinkage driven by swelling and partial fusion of individual nanofibers, leading to a denser polymer matrix. This transformation promotes strong PFOA retention through a combination of hydrogen bonding, electrostatic interactions, and physical confinement, as supported by molecular dynamics simulations. The PA6F nanofiber membranes achieve a PFOA removal efficiency of 94.6% and an adsorption capacity of 3.92 mg g^-1 at industrially polluting concentrations. Thermal regeneration at 240 °C enables complete release of confined PFOA while preserving the polymer backbone. The recovered polymer can be reprocessed by re-electrospinning to form new nanofiber membranes that retain 93% of the original adsorption capacity after reuse. These findings provide water-mediated confinement mechanisms in more sustainable polyamide systems, establishing a closed-loop adsorption-regeneration pathway for long-term PFAS remediation in aqueous environments.