Fe-N-C heterogeneous Fenton-like catalyst for the degradation of tetracycline: Fe-N coordination and mechanism studies

Fe-N-C materials have received increasing attention, due to its distinctive catalytic activity. However, the Fe-N coordination number dependence of catalytic ability and mechanism for H₂O₂ activation remain elusive. Herein, a series of Fe-N-C heterogeneous Fenton-like catalysts with different Fe-N coordination number were prepared for tetracycline degradation. The results demonstrated that samples with Fe-N₄ structure exhibited high activity. The excellent performance was mainly ascribed to the high adsorption capacity and the formation of superoxide radicals (^•O₂⁻) catalyzed by Fe linked to pyridinic nitrogen. The intermediates and degradation pathways of tetracycline degradation by Fe-N-C/H₂O₂ system were analyzed by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Furthermore, we applied our Fe-N-C catalysts to treat simulated pharmaceutical wastewater with high tetracycline degradation capacity despite high concentrations of organic matter such as oxalic acid and various ionic interferences. Our work reveals the dependence of the activation H₂O₂ on the Fe-N coordination environment and the degradation mechanism of these catalysts. It provides insights into the prospects for tuning the catalyst in practical applications.