Kinetic and mechanistic insights into the abatement of clofibric acid by integrated UV/ozone/peroxydisulfate process: A modeling and theoretical study.

The feasibility of integrated UV/ozone (O)/peroxydisulfate (PDS) process for abatement of clofibric acid (CA) was systematically explored in this study with focus on the kinetic simulation and oxidation mechanisms. The results indicated the UV/O/PDS process was of prominent treatment capability with pseudo-first-order rate constant of CA degradation increased by 65.9% and 86.0% compared to UV/O and UV/PDS processes, respectively. A chemical kinetic model was developed and successfully employed to predict CA elimination as well as the specific contributions of UV, hydroxyl radical (OH) and sulfate radical (SO) under different PDS dosage, pH, natural organic matters, bicarbonate and chloride conditions in UV/O/PDS process. According to quantum chemical calculation, radical addition on ortho site of isopropoxy substituent and single electron transfer were corroborated to be the dominant reaction channels for the oxidation of CA by OH and SO, respectively. Additionally, the reactive sites and transformation pathways of CA were proposed via Fukui function calculation and UPLC-Q-TOF-MS analysis. Moreover, the performance of UV/O/PDS process was further evaluated with regard to the energy demand and bromate formation. This study first proposed a kinetic model in UV/O/PDS process and elucidated the regioselectivity and products distribution of CA during oxidative treatment.