Photodegradation processes of oxcarbazepine under solar simulated radiation: Analysis of transformation products

Oxcarbazepine (OXC) an antiepileptic drug, has been detected in wastewater treatment plant (WWTP) effluents, surface, and groundwater in concentrations ranged from mu g L-1 to ng L-1. The presence of this drug and its transformation products (TPs) in the aquatic environment creates uncertainty concerning the potential risks to aquatic species and living beings. In this work, the removal of OXC from the water was conducted by photolysis process and heterogeneous photocatalysis using different ZnO-based catalysts. The TPs formed in both reactions were monitored by LC-MS/MS and UPLC-qTOF-MS. The results showed that the OXC was entirely degraded after 30 min of photolysis and photocatalytic reactions. The formation of the main TPs was similar in both processes: nine TPs were detected in the photolysis, while ten products were identified during the heterogeneous photo catalysis. The photolysis reaction was the main responsible for the formation of TPs in both processes, nevertheless, these TPs remained during the photolysis treatment, while its rapid decomposition was achieved in the photocatalytic process. Different degradation pathways were elucidated based on the detection of the generated products. The main degradation reactions were hydroxylation of OXC, heterocyclic ring photo-oxidation, intramolecular ring closure, and HO' radical attack, which led the destruction of the parent compound oxcarbazepine.

Automated summary

This study investigated the removal of oxcarbazepine from water through photolysis and heterogeneous photocatalysis processes, and monitored the formation of transformation products. The results showed that oxcarbazepine was completely degraded within 30 minutes using both methods.