Aniline–Peroxide-Initiated Cyclodextrin-Containing Monoliths for Scalable PFAS Removal from Water

Abstract

Per- and polyfluoroalkyl substances (PFASs) are a class of persistent environmental contaminants that cause negative health effects. These health concerns and impending regulations motivate demand for PFAS removal technologies. Such technologies must be capable of high-throughput, continuous-flow operation, and maintaining treatment performance at large-scales in municipal and industrial treatment systems. Many PFAS remediation technologies rely on particle-based sorbents, which are subject to mass-transfer limitations in large-scale flow-through systems that can limit PFAS removal performance. Recently, we introduced monolithic sorbents for PFAS removal based on styrene-functionalized β-cyclodextrin polymers whose porosity can reduce these mass-transfer limitations. The first monolith formulations were prepared by photoinitiating polymerization within flow-through columns, which limited the monolith’s practical scalability. Here, we address this limitation by using a redox initiation process at room temperature, which is compatible with the high internal phase emulsion and enables scalable fabrication across column dimensions. Mercury porosimetry revealed a bimodal pore size distribution and a larger characteristic maximum pore size in the redox-initiated monoliths compared to the monomodal pore size distribution observed in the photoinitiated materials. Chemical composition and batch adsorption performance remained consistent across redox-initiated monoliths scaled to 36 times the original monolith cross-sectional area. Redox-initiated monoliths outperformed photoinitiated monoliths in flow-through columns, showing later breakthrough of the short-chain PFAS, perfluorobutanoic acid. We also evaluated the PFAS removal performance of scaled redox-initiated monoliths in columns of increasing diameters (0.5, 1, and 1.5 cm). Their performance was consistent across scales, indicating that redox-initiated monoliths with larger cross-sectional areas maintain their promising sorption performance.