Triclosan breakdown by Fenton-like oxidation

Macarena Munoz,Zahara M De Pedro,Jose A Casas,Juan J Rodriguez

doi:10.1016/j.cej.2012.05.097

Macarena Munoz, Zahara M De Pedro + Show 2 more

Open Access

https://doi.org/10.1016/j.cej.2012.05.097

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Abstract

Fenton-like oxidation has proved to be highly efficient for the removal of triclosan, a highly toxic emerging water pollutant. From 10mg/L starting aqueous solutions complete conversion of triclosan was achieved in less than 1h at 25°C and around 20min at 50°C with 1mg/L Fe3+ and H2O2 at the theoretical stoichiometric amount (25mg/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 15min 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 27kJ/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.

Highlights

In recent years, there has been increasing concern regarding the emerging pollutants such as pharmaceuticals and personal care products, surfactants, flame retardants, industrial additives, steroids and hormones and disinfection by-products
This facilitates indentifying the byproducts formed in the early stages of the process. Even at these operating conditions triclosan was oxidized by hydroxyl radicals and complete conversion of this compound was achieved upon 60 min reaction time
Fenton-like oxidation has shown to be an efficient solution for the removal of triclosan, an emerging water pollutant with antimicrobial activity

Summary

Introduction

There has been increasing concern regarding the emerging pollutants such as pharmaceuticals and personal care products, surfactants, flame retardants, industrial additives, steroids and hormones and disinfection by-products. These pollutants correspond in many cases to unregulated contaminants, which may be candidates for future regulation depending on research on their potential health effects and monitoring data regarding their occurrence. These hardly biodegradable products, resistant to conventional biological treatment in sewage plants, have been found in their effluents at concentrations ranging 0.1–20 lg LÀ1.

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