Nanoconfined iron-based catalysts activate peroxymonosulfate via electron transfer and radical pathways for efficient bisphenol A removal.

In this study, a nanoconfinement strategy was employed to encapsulate nano-Fe(III) (Fe2O3-in-CNT) for the rapid degradation of bisphenol A (BPA) through PMS-mediated Fenton-like reaction. Specifically, compared with the surface coated Fe2O3 on the CNT (Fe2O3-out-CNT), the Fe2O3-in-CNT demonstrated 3.07 times higher kobs value toward the degradation of BPA. Comprehensive experimental analyses reveal that the Fe2O3-in-CNT exhibits superior electron transfer capacity and chemical reactivity, which stems from the strengthened interaction between CNT and nanoconfined Fe2O3. Mechanistic investigations identified a profound transition: although the electron transfer process (ETP) was the main pathway for pollutant degradation in the Fe2O3-in-CNT/PMS and Fe2O3-out-CNT/PMS systems, the nanoconfined architecture triggers a dual-mechanism by uniquely facilitating the generation of sulfate radicals (SO4•-). In addition, the possible degradation pathways of BPA were proposed by high-performance liquid chromatograph triple quadrupole mass spectrometer (LC-MS/MS). Meanwhile, Fe2O3-in-CNT demonstrated exceptional longevity and minimal metal leaching in continuous-flow fixed bed experiments due to the physical shielding of the CNT channels. This study deepens the insights into nanoconfined catalysis and provides a high-performance, sustainable strategy for the detoxification of persistent organic pollutants in complex aquatic environments.