Oxidation of tetracycline antibiotics by peracetic acid: Reaction kinetics, mechanism, and antibacterial activity change

Peracetic acid (PAA) is an emerging oxidant and disinfectant increasingly used in wastewater treatment. Tetracyclines (TCs) are extensively consumed antibiotics, and frequently detected in the wastewater and surface water. Herein, PAA was found to show high reactivity towards TCs for the first time. This reaction follows the second-order kinetics with the rate constant (k2,app) rapidly raised from pH 5 to 7, and then slightly increased to pH 9. Degradation of TCs by PAA was slightly influenced by water components, thus maintaining high efficiency in the real waters. Theoretical calculations revealed the electrons mainly concentrated on the B-ring of TCs, implying the B-ring as the reactive moieties for PAA oxidation. Transformation product analysis confirmed that oxidation of TCs by PAA mainly proceeded via hydroxylation and N-demethylation. Finally, PAA-promoted oxidation could remarkably reduce the antibacterial activity of TCs.