LDH-Enhanced Degradation of PFASs: Influence of Reactant Configurations within Nanoconfined Spaces on Hydrated Electron Transport

Hydrated electron (eaq–) reduction is an efficient pathway for degrading per- and polyfluoroalkyl substances (PFASs). Nanoconfined spaces can shield eaq– from quenchers in bulk solution and shorten diffusion distances, thereby enhancing utilization efficiency. However, the role of eaq– precursors and PFASs configurations within nanoconfined domains in governing eaq– transport remains unclear. In this study, polyindole (Pind) was synthesized within layered double hydroxide (LDH) interlayers as an eaq– precursor, while perfluorooctanoic acid (PFOA) was simultaneously enriched through electrostatic interaction. Although the eaq– yield increased with Pind loading, the PFOA degradation rate followed a unimodal trend, reaching a maximum at 27.2% Pind loading, where complete degradation was achieved within 3 h. Molecular dynamics simulations revealed stronger hydrophobic interactions among Pind molecules than between Pind and PFOA, leading to a configuration where PFOA surrounded Pind aggregates. With increasing Pind loading, this arrangement forced more eaq– to travel longer distances to attack C–F bonds, reducing their utilization efficiency despite higher overall yields. This “yield-transport” self-antagonism underscores the critical role of nanoconfined configurations in eaq– transport and utilization efficiency and provides mechanistic insights for the rational design and optimization of nanoconfinement systems.