Dechlorination of triclosan by enhanced atomic hydrogen-mediated electrochemical reduction: Kinetics, mechanism, and toxicity assessment

Abstract

Environmental-friendly and efficient technologies for the removal of halogenated organic compounds in water are highly desired. Triclosan (TCS) is a potential threat to the environment and human health, and is resistant to biodegradation. Here, a Pd/N-GR/Cu foam exhibits a much enhanced activity as the cathode for TCS degradation by electrochemical reduction. The dechlorination rate of Pd/N-GR/Cu foam is 5.50, 6.49, and 14.68 times higher than Pd/Cu, N-GR/Cu, and Cu foam, respectively. The leaching of Pd and Cu is inhibited due to the protection by cathodic currents and alkaline conditions. 2- and 1-chlorinated isomers are the main intermediates, and the final products are completely dechlorinated 2-phenoxyphenol with a small amount of further H radical addition product 6-phenoxycyclohex-3-enol. ESR spin trapping results indicate the coupling of Pd and N-GR promotes the production and utilization of atomic H*, and the contribution of atomic H* obeys the order of Pd/N-GR/Cu (68.5%) > Pd/Cu (56.6%) > N-GR/Cu (24.3%) > Cu (5.7%). The bacterial cytotoxicity and AhR activity of TCS solution after 60 min are decreased by 83.2% and 90.3%, respectively. The electrochemical reduction can be a promising option for supplementing the current technologies for TCS abatement in wastewater.