Unlocking dual-pathway peroxydisulfate activation mechanism in single atom Fe-based catalytic membranes for wastewater purification.

Carbon-based catalytic membrane processes (CMPs) have emerged as promising technologies for wastewater decontamination, but challenges such as limited catalytic activity remain. This study developed a high-efficiency peroxydisulfate-based CMP (SAFe@GF/PDS) for aniline (AN) degradation via nonradical pathways, incorporating single-atom Fe sites with pyrrolic-N2O2 coordination geometry. Under a single-pass mode at a membrane flux of 3906.3 LMH, the system achieved > 90 % AN removal and maintained > 80 % efficiency in natural waters, demonstrating robust environmental adaptability. Mechanistic investigations elucidated that the well-designed mesoporous structure enabled optimal exposure of active sites, where monoatomic Fe sites and CC moieties predominantly generated metastable complexes PDS* (50.3 % contribution) and 1O2 (47.8 % contribution), respectively. This dual-channel activation mechanism, synergistically enhanced by electron-transfer-promoting O-CO groups, facilitated efficient AN degradation through four complementary reaction pathways while simultaneously minimizing toxic byproduct formation. By adjusting Fe, N, and KOH doping ratios, a quantitative structure-activity relationship for high-performance BC-SACs was established. Precise control of Fe doping amount was essential to maximize FeNx density while avoiding clusters formation. Modulation of surface functional groups, namely increasing electron-donating COC groups and synergistic O-species (Fe-O, OC-O) while suppressing electron-withdrawing amide groups was benifical. Fabrication of hierarchical porous structures with high specific surface area and large pore volume was vital to optimize mass transport. This work presented a new class of high-efficiency catalytic membranes and offered theoretical insights for the rational design of functional materials for sustainable wastewater treatment.