Ozonation of ketoprofen with nitrate in aquatic environments: kinetics, pathways, and toxicity

Abstract

In this study, nitrate ion (NO₃⁻) was found to collaborate with ozone thereby accelerating the degradation of ketoprofen. NO₃⁻ was discovered to induce the generation of hydroxyl radicals (·OH), which was crucial to the decomposition of PPCPs in wastewater treatment plants. Kinetic studies on the decomposition of ketoprofen were investigated under different concentrations of NO₃⁻. The impact mechanisms and degradation by-products were experimentally determined. The results revealed that all reactions fitted the pseudo-first-order kinetic model well. The presence of NO₃⁻ had the capacity to accelerate the ozonation of ketoprofen. The reaction by-products were evaluated by UPLC-Q-TOF-MS, and a total of five intermediates generated via the ozonation of ketoprofen were assessed. The transformation pathways were concluded to be hydroxylation, nitration, and debenzophenone and ketonized reactions. Additionally, the toxicity of the by-products was evaluated by employing Chlorella and Daphnia magna.