Degradation of norfloxacin by hydroxylamine enhanced fenton system: Kinetics, mechanism and degradation pathway

This study demonstrated a fast and efficient degradation of a typical antibiotic norfloxacin (NOR) in a hydroxylamine enhanced Fenton (HA-Fenton) system, which showed a higher catalytic activity over a wider pH range (3.0-9.0). The removal efficiency of NOR was 96% at following conditions: 10 mg/L NOR, 10 mM Fe2+, 1.0 mM H2O2, 0.4 mM HA and pH 5.0. The degradation rate of NOR in the HA-Fenton system (0.23 min(-1)) was 10.9 times of that (0.021 min(-1)) in Fenton system. The addition of HA to Fenton system accelerated the conversion of Fe3+ to Fe2+, leading to the high concentration of $OH in the HA-Fenton system. Ten degradation transformation products were detected by ultra-performance liquid chromatography tandem quadrupole time of flight mass spectrometer (UPLC-QTOF-MS), consequently, three main degradation steps were proposed, including defluorination, quinolone group transformation, and defluorination and piperazinyl ring opening. Further analyses of NO3-, NO2- and F- after the reaction indicated that defluorination process was the crucial degradation step. The HA-Fenton system might offer an efficient alternative for degradation of antibiotics in wastewater. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

This study demonstrated a fast and efficient degradation of the antibiotic norfloxacin in a hydroxylamine enhanced Fenton system, proposing three main degradation steps including defluorination, quinolone group transformation, and defluorination and piperazinyl ring opening. The crucial degradation step was identified as the defluorination process.