Bicarbonate enhanced removal of triclosan by copper(II) catalyzed Fenton-like reaction in aqueous solution

The antimicrobial and preservative agent triclosan (TCS) is an emerging and persistent pollutant, and is ubiquitous in the environment. Low cost and efficient removing technology for TCS in water has been the target of many researches. In this study, effective removal of TCS from water was achieved by Cu2+/H2O2 system in the presence of environmental relevant concentration of bicarbonate (HCO3-). The removal efficiency of TCS increased with the increase of HCO3- concentration from 0 to 2.0 mM, while further increase of the HCO3- concentration caused the decrease of removal efficiency. TCS (0.01 mM) could be totally removed over 120 min when HCO3- was 2.0 mM (pH 8.72) in the presence of 0.01 mM Cu2+ ions at 25.0 degrees C. In order to explore the reaction mechanism, radical scavenging technologies, molecular probe compound p-Chlorobenzoic acid (PCBA) and cyclovoltammetric (CV) experiments were employed to determine the reactive oxygen species (ROS), the steady-state concentrations of (OH)-O-center dot and Cu2+-complex, respectively. The results suggested that the Cu2+-complex formed between Cu2+ and HCO3- could catalyze H2O2 to produce and (OH)-O-center dot, which were responsible for the removal of TCS. Based on the reaction mechanism and identified intermediates of the oxidation process using TOF-LC-MS techniques, the reaction pathways for the oxidation of TCS were proposed including the cleavage of the ether bond, hydroxylation and polymerization. Finally, evaluation on the toxicity change of TCS reaction solution mediated by Cu2+/H2O2-HCO3- system with the freshwater green alga Scenedesmus obliquus showed significant detoxification of TCS. (C) 2016 Elsevier B.V. All rights reserved.