Cobalt-catalysed bicarbonate-activated peroxide as a promising system for the advanced oxidation of epirubicin in wastewaters

Epirubicin (EPI) is a common cytostatic drug often found as a pollutant in hospital wastewater. While many studies have focused on the degradation kinetics of its epimer, doxorubicin (DOX), none have reported the kinetics of EPI degradation. Herein, we report a new cost-efficient, environmentally friendly system for the advanced degradation of EPI consisting of cobalt-catalysed bicarbonate-activated peroxide. We propose a new kinetic model for EPI degradation that shows the hydroperoxyl radical is the most important reactive oxygen species (ROS) involved in the degradation process. Seven degradation products are identified using high-performance liquid chromatography coupled with mass spectrometry (HPLC-MS). The effect of surfactants, commonly found in wastewaters, is also investigated and the presence of the cationic surfactant hexadecylpyridinium chloride (CPC) in the reaction medium leads to a 6.1-fold increase in the degradation rate. Modelling the reaction kinetics using the Piszkiewicz model unveils the rate constant for the micellar degradation of EPI to be 4.66 × 10^‐3 s^‐1. The ecotoxicity study of the degradation products shows a dramatic decrease in both acute and chronic toxicity. Although the level of mineralisation of the products is less than 10%, this method is still suitable as a pre-treatment of wastewaters. The same system is successfully used for the degradation of DOX, mitoxantrone, and quinizarin. In the case of DOX, a rate constant of 3.74 × 10^‐2 s^‐1 is obtained, the highest reported so far. © 2024 Elsevier Ltd. All rights reserved.