Steam-Induced Mesopore Development Enhances PFAS Adsorption in Dissolved Organic Matter-Rich Waters

Abstract Activated carbons (ACs) with various pore structures were prepared via steam activation, the most commercially viable method, and their adsorption isotherms and kinetics were evaluated for PFOA, PFOS, and GenX in ultrapure water and water containing dissolved organic matter (DOM). Results showed that moderate overactivation developed more mesopores, improving PFAS adsorption in both ultrapure and DOM-rich waters, likely due to the accommodation of PFAS aggregates requiring larger pore volume. Pearson correlation analysis confirmed that mesopore volume significantly correlated with adsorption capacity and kinetics. The overactivated mesoporous AC exhibited superior adsorption of PFAS compared to lightly activated microporous AC, showing nearly doubled adsorption capacities and faster kinetics for PFOA and PFOS, despite similar surface areas and total pore volumes, and its performance was less affected by background DOM molecular weight. Pore size distribution indicated that mesopores were the primary adsorption sites, and density functional theory calculations proved that the adsorption energy for PFAS aggregates in mesopores was much lower than in other pores. Secondary activation of commercial Calgon F400 also enhanced trace PFOA/PFOS removal (∼200 ng/L) in real water. This study clarifies the critical role of mesopores in PFAS adsorption and provides a feasible strategy for designing high-performance AC adsorbents.