Efficient and stable electro-Fenton treatment of antibiotics-containing wastewater over NiFe bimetal atom catalyst via flow-through micro-nanoscale spatial confinement system.

The engineering application of electro-Fenton process is subject to limited availability of •OH caused by mass transfer limitation and the short lifetime of •OH in water. In this study, an efficient electro-Fenton treatment process is developed by constructing a flow-through micro-nanoscale spatial confinement electrode with NiFe bimetal atom catalyst for oxygen reduction reaction (ORR). The NiN₄-FeN₄ active sites are anchored onto carbon nanotubes grown in the tunnel of carbonized pine wood (NiFe-NCNTs-CP). Efficient generation of •OH is achieved through 3-electron ORR over NiFe-NCNTs-CP. Because of the unique flow-through micron-nanoscale confinement environment, the concentration of accumulated •OH reaches as high as 6092 μmol L^-1 min^-1 even though the water flux is up to 236 L m^-2 h^-1 (equivalent to a retention time of 60 s). The proposed electro-Fenton system achieves 100 % removal of florfenicol, thiamphenicol, chloramphenicol, sulfamethoxazole, and tetracycline in water within just 60 s (C₀=20 mg L^-1, pH=7, 0.7 V vs SCE). The proposed continuous flow process maintains highly stable for treating actual medical wastewater within 8 days, achieving discharge standards and eliminating the antibacterial activity of medical wastewater. Furthermore, the proposed process showed a low energy consumption of only 7.35 kWh kg (COD)^-1. This study presents a highly practical electro-Fenton process for organic wastewater treatment.