Peroxymonocarbonate as a green oxidant for the efficient degradation of tetracycline

Peroxymonocarbonate (PMC), a green in situ oxidant formed from the reaction between hydrogen peroxide (H2O2) and bicarbonate (HCO3⁻), has demonstrated promising potential for the degradation of organic pollutants, although its underlying mechanisms remain not fully elucidated. In this study, the degradation efficiency and mechanistic pathways of PMC toward tetracycline (TC) were systematically investigated. Compared to H2O2 alone, PMC exhibited significantly enhanced TC degradation, with a first-order rate constant (k) of 0.0181 min⁻¹, approximately 10 times higher than that of H2O2 alone. Key factors affecting the degradation efficiency, such as anions, cations, pH, humic acid, and different water matrices, were thoroughly examined. Electron paramagnetic resonance (EPR) analysis confirmed the generation of free radicals, while non-radical oxidation pathways were also suggested. Among the reactive oxygen species, ·OH and CO3·⁻ are the primary species driving TC degradation, while ¹O2 and ·O2⁻ act as secondary contributors. Three potential degradation pathways were proposed based on liquid chromatography-mass spectrometry (LC-MS) analysis and density functional theory (DFT) calculations, and the corresponding toxicity predicted using ecological structure-activity relationship (ECOSAR) model. This study provides new insights into the application of environmentally benign oxidants for antibiotic removal and highlights the potential of PMC in water treatment practices.