Triclosan breakdown by Fenton-like oxidation

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 attackThis research has been supported by the Spanish MICINN through the project CTQ2008-03988 and by the CM through the project S-2009/AMB-158

Application of intensified Fenton oxidation to the treatment of hospital wastewater: Kinetics, ecotoxicity and disinfection

“…Its potential application to EPs has been studied with promising results by several authors [24][25][26]. In previous contributions, we have proved the degradation of different and highly-persistent EPs such as triclosan [25] and carbamazepine [26] using low concentrations of iron (1-2 mg L -1 ) and H 2 O 2 (25-60 mg L -1 , corresponding to the theoretical stoichiometric amount). Nevertheless, the application of Fenton oxidation to the treatment of hospital wastewaters has been scarcely studied in the literature so far.…”

“…So far, it has been successfully applied to the treatment of different industrial wastewaters such as cosmetics [20,21], pesticides [21], power plant [21], textile [22] or sawmill [23]. Its potential application to EPs has been studied with promising results by several authors [24][25][26]. In previous contributions, we have proved the degradation of different and highly-persistent EPs such as triclosan [25] and carbamazepine [26] using low concentrations of iron (1-2 mg L -1 ) and H 2 O 2 (25-60 mg L -1 , corresponding to the theoretical stoichiometric amount).…”

Improved wet peroxide oxidation strategies for the treatment of chlorophenols

“…The Fenton process is one of the most commonly used AOP for the removal of recalcitrant pollutants from wastewaters [11][12][13][14]. It has gained large attention due to the simplicity of design and setup, safe operation, high efficiency and the use of readily availability reagents.…”

Degradation of contaminants of emerging concern by UV/H2O2 for water reuse: Kinetics, mechanisms, and cytotoxicity analysis

“…2,8-DCDD, resulted from the cyclization of TCS under UV irradiation, initiated by transferring an electron from the phenolic group to OH, followed by the removal of a chlorine atom on C 2 and the subsequent recombination of C 2 and C 8 (Kliegman et al, 2013;Latch et al, 2003;Mezcua et al, 2004). The continuous attack of OH could lead to the breakdown of the ether bond (Munoz et al, 2012), generating T 161 and T 143 . The proposed structure of T 143 ([M-H] À , m/ z 142.9904, C 6 H 5 ClO 2 , 1 ppm) is supported by the fragmentation and the [MÀH] À isotopic pattern as shown in Fig.…”