Comparative studies of sulfadiazine sodium degradation performance and mechanisms in the systems of persulfate with and without activation

Biogas residue biochar (BRBC) was prepared from biogas residue (BR), and the removal activity of biochar-driven peroxydisulfate (PDS) and PDS direct oxidation of sulfadiazine sodium (SD-Na) were comparatively investigated. The optimized degradation efficiency of SD-Na could reach 95.5% in BRBC/PDS system while 46.9% in PDS alone system. The results show that surface-bound radicals, 1O2, and π−π* shake-up were all related to the properties of BRBC/PDS system. While in PDS alone system, mediated electron transfer was confirmed to be responsible for the elimination of SD-Na. The degradation intermediates and pathways of SD-Na in different systems were analyzed by density functional theory (DFT) calculations and ultra-performance liquid chromatography with time-of-flight mass spectrometry (UPLC-TOF-MS). This study provides insight into the oxidative degradation of the electron-rich organic pollutants in the systems of persulfate with and without biochar activation.