<scp>PFAS</scp> Removal by Anion‐Exchange Block Copolymer Membranes Featuring Highly Ordered Alternating Gyroid Nanochannels

ABSTRACT 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 (G A ) nanochannels. These G A 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 G A or sponge‐like morphology.