Photolysis of model emerging contaminants in ultra-pure water: Kinetics, by-products formation and degradation pathways

The photolysis of five frequent emerging contaminants (Benzotriazole, Chlorophene, N,N-diethyl-m-toluamide or DEET, Methylindole, and Nortriptyline HCl) was investigated in ultrapure water under monochromatic ultraviolet radiation at 254 nm and by a combination of UV and hydrogen peroxide. The resul...

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Bibliographic Details
Published in:Water research (Oxford) 2013-02, Vol.47 (2), p.870-880
Main Authors: Benitez, F. Javier, Acero, Juan L., Real, Francisco J., Roldan, Gloria, Rodriguez, Elena
Format: Article
Language:English
Subjects:
acute toxicity
Aliivibrio fischeri - drug effects
Aliivibrio fischeri - growth & development
Anti-Infective Agents, Local - analysis
Anti-Infective Agents, Local - chemistry
Anti-Infective Agents, Local - toxicity
Antidepressive Agents, Tricyclic - analysis
Antidepressive Agents, Tricyclic - chemistry
Antidepressive Agents, Tricyclic - toxicity
Applied sciences
Benzotriazole
Byproducts
Combined UV/H2O2 treatment
Contaminants
deet
DEET - analysis
DEET - chemistry
Degradation
Degradation pathway
Dichlorophen - analogs & derivatives
Dichlorophen - analysis
Drinking water and swimming-pool water. Desalination
Emerging contaminants
Exact sciences and technology
Free Radical Scavengers - chemistry
high performance liquid chromatography
hydrochloric acid
hydrogen peroxide
Hydrogen Peroxide - chemistry
Hydrogen-Ion Concentration
Identification of by-products
Insect Repellents - analysis
Insect Repellents - chemistry
Insect Repellents - toxicity
ionization
Kinetics
Liquid chromatography
mass spectrometry
Models, Chemical
Nortriptyline - analysis
Nortriptyline - chemistry
Nortriptyline - toxicity
Oxidants - chemistry
oxidation
Oxidation-Reduction
Pathways
Photolysis
Pollution
Quantum yields
Skatole - toxicity
tert-Butyl Alcohol - chemistry
Toxicity
toxicity testing
Triazoles - analysis
Triazoles - toxicity
ultraviolet radiation
Ultraviolet Rays
UV radiation
Vibrio fischeri
Water - chemistry
Water Pollutants, Chemical - analysis
Water Pollutants, Chemical - chemistry
Water Pollutants, Chemical - toxicity
Water Purification - methods
Water treatment and pollution
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Summary:The photolysis of five frequent emerging contaminants (Benzotriazole, Chlorophene, N,N-diethyl-m-toluamide or DEET, Methylindole, and Nortriptyline HCl) was investigated in ultrapure water under monochromatic ultraviolet radiation at 254 nm and by a combination of UV and hydrogen peroxide. The results revealed that the photolysis rates followed first-order kinetics, with rate constant values depending on the nature of the specific compound, the pH, and the presence or absence of the scavenger tert-butanol. Quantum yields were also determined and values in the range of 53.8 × 10−3 − 9.4 × 10−3 mol E−1 for Benzotriazole, 525 × 10−3 − 469 × 10−3 mol E−1 for Chlorophene, 2.8 × 10−3 − 0.9 × 10−3 mol E−1 for DEET, 108 × 10−3 − 165 × 10−3 mol E−1 for Methylindole, and 13.8 × 10−3 − 15.0 × 10−3 mol E−1 for Nortriptyline were obtained. The study also found that the UV/H2O2 process enhanced the oxidation rate in comparison to direct photolysis. High-performance liquid chromatography coupled to electrospray ionization quadrupole time-of-flight mass spectrometry (HPLC-ESI-QTOF-MS) technique was applied to the concentrations evaluation and further identification of the parent compounds and their by-products, which allowed the proposal of the degradation pathways for each compound. Finally, in order to assess the aquatic toxicity in the photodegradation of these compounds, the Vibrio fischeri acute toxicity test was used, and the results indicated an initial increase of this parameter in all cases, followed by a decrease in the specific case of Benzotriazole, DEET, Methylindole, and Chlorophene. ► Photolysis of five emerging contaminants (EC) was investigated. ► First-order rate constants and quantum yields were determined for each EC. ► The combined UV/H2O2 process provided a significant increase in the reaction rates. ► Intermediates were identified and the degradation pathways were proposed. ► Toxicity measurements showed an initial increase, followed by a decrease.
ISSN:0043-1354
1879-2448
DOI:10.1016/j.watres.2012.11.016