Résumé
Ion-exchange resins (IERs) can effectively remove per- and polyfluorinated alkyl substances (PFAS) from water through electrostatic interactions between the negatively charged PFAS and the positively charged anion-exchange functional groups on the resins. To mimic this behavior while developing anion-exchange adsorbents with high PFAS adsorption capacity, nanostructured block copolymer (BCP) membranes were fabricated with a high areal density of accessible ion-exchange sites by forming N-methylpyridinium-containing alternating gyroid (GA) nanochannels. These GA nanochannels, with physical continuity across the entire anion-exchange membrane (AEM) thickness, allowed for easy and homogeneous penetration of long-chain PFAS molecules (specifically perfluorooctanoic acid (PFOA)) throughout the entire membrane thickness, leading to a high potential adsorption capacity. In contrast, in analogous BCP AEMs with a nominally microporous and disordered sponge-like morphology, PFOA molecules mainly accumulate near the top and bottom surfaces. Our results also show that ion exchange is the primary mechanism of PFAS uptake since a lack of adsorption of PFOA molecules was observed on (neutral) pyridine-containing BCP membranes, regardless of whether they had a GA or sponge-like morphology.