Oxidation of ibuprofen in water by UV/O3 process: Removal, byproducts, and degradation pathways

Abstract

Owing to the huge consumption of ibuprofen (IBP), its risk of exposure in water is of concern. The UV/O3 process has advantages in IBP degradation compared with the single UV and O3 processes. To promote the utilization of UV/O3, further exploration is necessary. In this study, the degradation mechanisms, byproduct security and cost of the UV/O3 process were investigated. Degradation kinetics showed that adding of UV irradiation into 0.6 mg/L of O3 increased the IBP degradation rate by 10 times, subsequently achieving a superior mineralization result. When the pH values changed (4.0–10.0) or humic acid existed in water, the UV/O3 efficiency was less affected compared with that of O3 process, which mainly attributed to the promotion of HO formation during UV/O3. Eleven byproducts with OH/COOH groups were identified in UV/O3, most of which contained 2–6 carbons. Ozonation produced the same types of byproducts, but the byproducts from UV irradiation were aromatics. Toxicity evaluation indicated that the 4′-(2-Methylpropyl)acetophenone formed in the UV process had stronger bioaccumulation potential than IBP, and some byproducts produced in the O3 and UV/O3 processes were more harmful based on the oral rate LD50 values. Because the byproduct transformations in UV/O3 accomplished within 10 min compared with the 100 min in the separate processes, the UV/O3 technology could better ensure byproduct security. In addition, the cost of UV/O3 was most acceptable among the three technologies under the same IBP degradation target. The UV/O3 technology had the promotion potential in IBP wastewater treatment.