Kinetics and degradation mechanism of clofibric acid and diclofenac in UV photolysis and UV/H₂O₂ reaction

Abstract

In this study, we investigated the removal of the selected pharmaceuticals, clofibric acid and diclofenac, using UV photolysis and UV/H₂O₂ reactions. The degradation of diclofenac during UV photolysis reaction was faster than that of clofibric acid. Diclofenac was mainly removed by photolysis reaction; clofibric acid was more sensitive to OH radical. More effective removals of clofibric acid and diclofenac were observed when H₂O₂ was added in the UV photolysis reaction. The competition kinetics showed that the second-order rate constant between the OH radical and the pharmaceuticals was 5.57 × 10⁹ M⁻¹ s⁻¹ for clofibric acid and 2.45 × 10⁹ M⁻¹ s⁻¹ for diclofenac, respectively. The major reaction intermediates during the UV photolysis and UV/H₂O₂ reactions of clofibric acid were 4-chlorophenol and hydroquinone, and these intermediates were degraded as phenol with further reaction.

Keywords:

• Competition kinetics
• OH radical
• Hydroquinone
• Phenol
• Mineralization

Acknowledgments

This research was supported by the International Research & Development Program of the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (MEST) of Korea (No. 2012K1A3A1A12054908).