Selective oxidation of tetracyclines by peroxymonosulfate in livestock wastewater: Kinetics and non-radical mechanism

Abstract

Tetracyclines (TCs) discharged from livestock wastewater have received worldwide concerns owing to their potential threats to the ecosystem and human health. Advanced oxidation processes always exhibit low efficiency to remove TCs in livestock wastewater due to the radical scavenging by water matrices. Herein, we report selective elimination of TCs by peroxymonosulfate (PMS) in livestock wastewater. A kinetic model was developed to describe the rapid degradation of TCs by PMS in the real livestock wastewater. The radical scavenging study and electron paramagnetic resonance (EPR) technique excluded the contribution of radical species (e.g., SO4−) in the PMS-promoted oxidation of TCs. Theoretical calculations revealed the electrophilic attacks of PMS most likely located on the B-ring of TCs. Transformation product analysis further elucidated that hydroxylation dominated in the PMS-promoted oxidation of TCs, and N-demethylation also significantly contributed to chlorotetracycline (CTC) oxidation by PMS. These results demonstrate a promising strategy to eliminate TCs in livestock wastewater, because PMS shows specific reactivity towards TCs, and thus suffers less interference from the complicated water matrices.