Rapid and Efficient Removal of Ultrashort- and Short-Chain PFAS from Contaminated Water by Pyrogenic Carbons: A Strategy via Polypyrrole Nanostructured Coating

The global concern of per- and polyfluoroalkyl substance (PFAS) contamination has gradually shifted from long- to ultrashort- and short-chain PFAS, but the widely used pyrogenic carbons (PCs) are almost ineffective at removing such hydrophilic pollutants. Herein, a polypyrrole (PPy) nanostructured coating strategy was proposed to modify PCs (PPy@P-BC) for rapid and efficient removal of ultrashort- and short-chain PFAS from water. Static batch tests revealed that the sorption rate constant and sorption capacity of PFAS (C2-C6) on PPy@P-BC are at least 38 times and 5 times greater than those on undecorated PCs and benchmark materials of granular activated carbon, respectively, and their sorption equilibrium time is within 300 s. The outstanding sorption performance of PPy@P-BC is maintained in dynamic column tests (>3120 bed volumes) and different types of real water contaminated by 36 PFAS, including 11 previously identified emerging PFAS (removal >95.3%). PPy@P-BC also exhibited excellent regeneration and reusability. The following dual-drive mechanisms for PFAS removal were identified based on experimental results and density functional theory (DFT) calculations: (i) electrostatic attraction between amino functional groups (especially -NH^•+-) on the nanostructured PPy coating and anionic PFAS and (ii) pore filling facilitated by the well-preserved porous structure via construction of the nanostructured coating. Overall, these results provide a promising solution to address the ultrashort- and short-chain PFAS crisis.