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 °C and around 20 min at 50 °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 °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 °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.

► Fenton-like process is an efficient alternative for triclosan breakdown. ► Triclosan is more susceptible to OH attack than chlorophenols. ► Aromatic byproducts formed during reaction evolved rapidly to organic acids. ► All the reaction products obtained showed lower ecotoxicity values than triclosan. ► Fenton oxidation of triclosan leads to a dramatic decrease of ecotoxicity.