Enhanced removal of oxytetracycline by UV-driven advanced oxidation with peracetic acid: Insight into the degradation intermediates and N-nitrosodimethylamine formation potential

Abstract

In this study, UV-driven advanced oxidation with peracetic acid (PAA) was adopted to enhance the removal of oxytetracycline (OTC) as well as to lower the formation potential of N-nitrosodimethylamine (NDMA). Results implied that the combination of UV and PAA had a synergetic effect on both the removal and mineralization of OTC. OTC (≤5 mg L−1) could be completely removed in 45 min in the UV/PAA system under the conditions of an initial pH of 7.10 and a PAA dose of 5 mg L−1; additionally, 50.9% of mineralization rate of OTC was obtained. Electron paramagnetic resonance analysis and quenching experiments indicated that ·OH was the main oxidizer for the removal of OTC, while UV, PAA and carbon-centered radicals (R–C·) also participated in its removal. During the degradation of OTC, 31 kinds of degradation intermediates were traced, and 20 kinds of them were first detected in the UV/PAA system. OTC was removed through five pathways, and the hydroxylation pathway was involved in nearly the entire degradation period. The NDMA formation potential decreased by 65.8% after the reaction, and residual dimethylamine accounted for 15.1% of its total composition. The proposed UV/PAA process is a promising method not only for the removal of refractory antibiotics but also for controlling the formation of NDMA.