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

Abstract

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 Co₃O₄, rGO and Co₃O₄@rGO composite to activate PMS for tetracycline (TC) degradation, and detected crucial factors toward highest performance of Co₃O₄@rGO/PMS system. Batch experiments exhibited a satisfactory TC degradation efficiency under Co₃O₄@rGO/PMS, complete degraded 50 mg/L TC within 20 min. Analytical tests discovered that radical active species generated by Co₃O₄/PMS and non-radical species by rGO/PMS were successfully co-existed in Co₃O₄@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 Co₃O₄@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 Co₃O₄@rGO/PMS demonstrated it as a potent and economical system to degrade TC. Overall, this study developed a novel Co₃O₄@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.

Keywords: Co(3)O(4)@rGO/PMS; Cooperation of oxidation pathway; Density functional theory; Multiple active species; Tetracycline.