Why the cooperation of radical and non-radical pathways in PMS system leads to a higher efficiency than a single pathway in tetracycline degradation.

Current research focused on developing multiple active species in peroxymonosulfate (PMS) system to degrade contaminants, but deepening concern lacks over why cooperation of those active species facilitated a faster degradation. Here, we employed CoO, rGO and CoO@rGO composite to activate PMS for tetracycline (TC) degradation, and detected crucial factors toward highest performance of CoO@rGO/PMS system. Batch experiments exhibited a satisfactory TC degradation efficiency under CoO@rGO/PMS, complete degraded 50 mg/L TC within 20 min. Analytical tests discovered that radical active species generated by CoO/PMS and non-radical species by rGO/PMS were successfully co-existed in CoO@rGO/PMS system, significantly improving the performance of TC removal. Subsequently, a combination of density functional theory (DFT) calculation and intermediates analysis revealed that, in CoO@rGO/PMS system, the cooperation rather than independent effect of radical and non-radical active species expanded TC degradation pathways, enhancing the degradation performance. Furthermore, decent adaptability, stability, and recyclability toward affecting factors variation of CoO@rGO/PMS demonstrated it as a potent and economical system to degrade TC. Overall, this study developed a novel CoO@rGO/PMS system with a cooperative oxidation pathway for highly efficient TC removal, and managed to clarify why this oxidation pathway achieved high efficiency through a combination of theoretical and experimental method.