Accelerated degradation of sulfadiazine by nitrogen-doped magnetic biochar-activated persulfate: Role of oxygen vacancy

Modification using biochar as a carrier is a promising method to improve the activation of peroxymonosulfate (PMS) by magnetic nanoparticles. In this study, we provided an effective strategy to control the generation of oxygen vacancy to prepare N-doped magnetic biochar (NMB) by optimizing the heat treatment process of gas foaming. The NMB exhibited superior catalytic performance and stable recycling use in the activation of PMS to degrade sulfadiazine (SDZ). Through multiple characterization techniques and density functional theory (DFT) calculations, the mechanism of the reaction process about oxygen vacancy was explored for the first time in magnetic biochar. In addition, the degradation kinetics, recycling experiment, and removal of total organic carbon were carried out to evaluate the degradation performance of NMB/PMS system. After 15 min of reaction, the removal rate of SDZ reached 95.2%. After the fifth cycle of use, the removal rate of SDZ remained at 79.6%. In addition to SDZ, the NMB/PMS system could also efficiently remove ofloxacin, reactive brilliant red, and bisphenol A, suggesting excellent degradation reactivity for different types of pollutants. The oxygen vacancy was found to play an important role in the catalytic process probably through changing the electronic structure of the NMB catalyst and thereby activating the charge transfer to participate in the degradation. The results from this study might deepen the understanding of the activation mechanism driven by magnetic biochar and provide insights into the development of low-cost wastewater treatment technologies.