Triclosan breakdown by Fenton-like oxidation

Fenton-like oxidation has proved to be highly efficient for the removal of triclosan, a highly toxic emerging water pollutant. From 10 mg/L starting aqueous solutions complete conversion of triclosan was achieved in less than 1 h at 25 degrees C and around 20 min at 50 degrees C with 1 mg/L Fe3+ and H2O2 at the theoretical stoichiometric amount (25 mg/L). From the evolution of byproducts a reaction pathway has been proposed according to which oxidation of triclosan gives rise to several aromatic intermediates (mainly, p-hydroquinone of triclosan and 2,4-dichlorophenol) which evolve to short-chain organic acids. These compounds are mineralized except oxalic acid. A dramatic decrease of ecotoxicity was achieved in a relatively short time (more than 95% in 15 min at 35 degrees C). The evolution of ecotoxicity is intimately related to the disappearance of triclosan, much more toxic than the aromatic oxidation intermediates. This disappearance was successfully described by a simple pseudo-first order rate equation with an apparent activation energy value close to 27 kJ/mol. The apparent rate constant at 25 degrees C was several orders of magnitude higher than the reported in the literature for other chlorophenolic compounds indicating a higher susceptibility of triclosan to OH radical attack. (C) 2012 Elsevier B.V. All rights reserved.