Enhanced Cu(II)-mediated fenton-like oxidation of antimicrobials in bicarbonate aqueous solution: Kinetics, mechanism and toxicity evaluation

Increasing attention has been attracted in developing new technologies to remove chlorofene (CF) and dichlorofene (DCF), which were active agents in antimicrobials for general cleaning and disinfecting. This study investigated the significant influences of bicarbonate (HCO3-) on the degradation of CF and DCF in the Cu(II)-mediated Fenton-like system Cu2+/H2O2. Our results indicate that HCO3- may play a dual role to act 1) as a ligand to stabilize Cu(II), forming soluble [Cu-II(HCO3-)(S)](+) species to catalyze H2O2 producing hydroxyl radical (center dot OH) and superoxide ion (O-2(-center dot)) and 2) as a center dot OH scavenger. Furthermore, the reaction kinetics, mechanisms, and intermediates of CF and DCF were assessed. The apparent rate constants of CF and DCF were enhanced by a factor of 8.5 and 5.5, respectively, in the presence of HCO3- at the optimized concentration of 4 mM. Based on the intermediate identification and frontier electron densities (FEDs) calculations, the associated reaction pathways were tentatively proposed, including C-C scission, single or multiple hydroxylation, and coupling reaction. In addition, significant reduction in the aquatic toxicity of CF and DCF was observed after treatment with Cu2+/H2O2-HCO3- system, evaluated by Ecological Structure Activity Relationships (ECOSAR) program. These findings provide new insights into Cu(II)-mediated reactions to better understand the environmental fate of organic contaminants in carbonate-rich waters. (C) 2019 Elsevier Ltd. All rights reserved.