Low pressure UV/H2O2 treatment for the degradation of the pesticides metaldehyde, clopyralid and mecoprop - Kinetics and reaction product formation.

Autor: Semitsoglou-Tsiapou S; Department of Civil and Environmental Engineering, Imperial College London, London, UK; Wetsus, European Centre of Excellence for Sustainable Water Technology, Leeuwarden, The Netherlands. Electronic address: s.semitsoglou-tsiapou12@imperial.ac.uk., Templeton MR; Department of Civil and Environmental Engineering, Imperial College London, London, UK., Graham NJ; Department of Civil and Environmental Engineering, Imperial College London, London, UK., Hernández Leal L; Wetsus, European Centre of Excellence for Sustainable Water Technology, Leeuwarden, The Netherlands., Martijn BJ; PWN Technologies, Velserbroek, The Netherlands., Royce A; Trojan Technologies, London, Ontario, Canada., Kruithof JC; Wetsus, European Centre of Excellence for Sustainable Water Technology, Leeuwarden, The Netherlands.
Jazyk: angličtina
Zdroj: Water research [Water Res] 2016 Mar 15; Vol. 91, pp. 285-94. Date of Electronic Publication: 2016 Jan 12.
DOI: 10.1016/j.watres.2016.01.017
Abstrakt: The degradation kinetics of three pesticides - metaldehyde, clopyralid and mecoprop - by ultraviolet photolysis and hydroxyl radical oxidation by low pressure ultraviolet hydrogen peroxide (LP-UV/H2O2) advanced oxidation was determined. Mecoprop was susceptible to both LP-UV photolysis and hydroxyl radical oxidation, and exhibited the fastest degradation kinetics, achieving 99.6% (2.4-log) degradation with a UV fluence of 800 mJ/cm(2) and 5 mg/L hydrogen peroxide. Metaldehyde was poorly degraded by LP-UV photolysis while 97.7% (1.6-log) degradation was achieved with LP-UV/H2O2 treatment at the maximum tested UV fluence of 1000 mJ/cm(2) and 15 mg/L hydrogen peroxide. Clopyralid was hardly susceptible to LP-UV photolysis and exhibited the lowest degradation by LP-UV/H2O2 among the three pesticides. The second-order reaction rate constants for the reactions between the pesticides and OH-radicals were calculated applying a kinetic model for LP-UV/H2O2 treatment to be 3.6 × 10(8), 2.0 × 10(8) and 1.1 × 10(9) M(-1) s(-1) for metaldehyde, clopyralid and mecoprop, respectively. The main LP-UV photolysis reaction product from mecoprop was 2-(4-hydroxy-2-methylphenoxy) propanoic acid, while photo-oxidation by LP-UV/H2O2 treatment formed several oxidation products. The photo-oxidation of clopyralid involved either hydroxylation or dechlorination of the ring, while metaldehyde underwent hydroxylation and produced acetic acid as a major end product. Based on the findings, degradation pathways for the three pesticides by LP-UV/H2O2 treatment were proposed.
(Copyright © 2016 Elsevier Ltd. All rights reserved.)
Databáze: MEDLINE
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