Degradation kinetics and mechanism of oxytetracycline by hydroxyl radical-based advanced oxidation processes

Abstract

In this study, the degradation kinetics and transformation mechanism of oxytetracycline (OTC) by UV-254nm and UV-254nm/H2O2 were investigated. The removal of OTC increased with increasing initial H2O2 dosage while excess H2O2 acted as an inhibitor of HO. The observed UV fluence based pseudo first-order rate constant of OTC (kobs, cm2mJ−1) decreased while the degradation rate at the initial 13min (µMmin−1) increased with increasing initial OTC concentrations. Presence of different water constituents in the reaction system had a different degree of influence on the degradation efficiency of OTC. Though after 10h irradiation, there was only a limited elimination of total organic carbon (TOC), successful transformation of OTC was demonstrated by the detection of thirty-one degradation byproducts in the UV/H2O2 system. Potential degradation mechanisms for OTC were proposed exhibiting five main pathways, including hydroxylation (+16Da), secondary alcohol oxidation (−2Da), demethylation (−14Da), decarbonylation (−28Da) and dehydration (−18Da). This study indicates that UV-254nm/H2O2 is an effective technology for the removal of OTC from an aquatic environment.