Insights into the degradation of fluconazole in water by some light-based AOPs

Fluconazole (FLZ), a triazole antifungal commonly detected in wastewater treatment plant (WWTP) effluents, was evaluated for its degradability using several advanced oxidation processes (AOPs). UV C irradiation (254 nm), visible light (390–800 nm), hydrogen peroxide, peroxymonosulfate (PMS), peroxydisulfate (PS), and ozone were used in the AOP experiments. The direct and apparent quantum yields of FLZ under UV C were obtained via competitive kinetics, giving values of 1.6 × 10 −2 and 2.4 × 10 −1 mol·E −1 , respectively. FLZ showed no photolysis under visible light. However, PS was photoactivated by visible radiation, enabling roughly 70% FLZ removal within 4 h with the Vis/PS system. The second-order rate constants for FLZ reactions with HO • , SO 4 •− , CO 3 •− , and O 3 were also determined as 2.8 × 10 9 , 2.5 × 10 8 , 2.6 × 10 6 , and 0.1 M −1 ·s −1 , respectively. Among all tested AOPs, the UV C /PS process exhibited the highest FLZ removal efficiency due to enhanced generation of SO 4 •− and HO • radicals. Using Q-TOF LC/MS, several transformation products formed during FLZ degradation by UV C , HO • , and SO 4 •− were identified, and degradation pathways leading to 1,2,4-triazole-1-acetic acid were proposed. Finally, FLZ removal was assessed in a WWTP effluent spiked with nine additional micropollutants from EU watch lists using UV C , UV C /H 2 O 2 , UV C /PMS, and UV C /PS systems. FLZ was found to be the most recalcitrant compound under all the oxidation conditions tested. • Fluconazole (FLZ) is a highly persistent triazole antifungal. • Under UV C , FLZ undergoes direct photolysis and self-sensitized formation of ROS. • FLZ reacts moderately fast with HO • and SO 4 •− but shows no reactivity with O 3 . • FLZ is resistant to mineralization by UV C , HO • , and SO 4 •− processes.