In this research, degradation efficiency, mechanism and intermediates’ toxicities of oxcarbazepine (OXC) upon chlorination, chlorine dioxide oxidation and ozonation were investigated. Results showed that three degradation approaches followed the second-order kinetics, and ozonation had the highest removal efficiency both of OXC and DOC. Reaction intermediates were evaluated by UPLC-Q-TOF-MS. Totals of 11, 6 and 10 intermediates were detected during the oxidation processes of chlorination, chlorine dioxide oxidation and ozonation, respectively. Although three oxidation approaches had similar pathways in N-heterocyclic ring cleavage and reorganization, ozonation was much more focused on hydroxyl radical (OH•) attacking, while chlorination had significant Cl-substitution by-products. Chlorine dioxide oxidation brought about less degradation by-products than the other two approaches. The toxicities of above-mentioned oxidation intermediates by EPA TEST indicated that some of them were intended to be more toxic than OXC, especially for those from chlorination. Further test results from the eco-toxicities of oxidized mixtures to the bioluminescent marine bacterium Vibrio fischeri demonstrated the chlorinated samples could lead to the accumulation of toxic transformation products, while chlorine dioxide oxidation and ozonation had detoxication impact during these processes.
- degradation pathway
- First received 21 January 2016.
- Accepted in revised form 15 June 2016.
- © IWA Publishing 2016