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Molecules 2017, 22(4), 619; doi:10.3390/molecules22040619

Degradation of Methyl 2-Aminobenzoate (Methyl Anthranilate) by H2O2/UV: Effect of Inorganic Anions and Derived Radicals

1
Institut de Chimie de Clermont-Ferrand, Clermont Université, Université Blaise Pascal, F-63177 Aubière, France
2
Dipartimento di Chimica, Università di Torino, Via Pietro Giuria 5, 10125 Torino, Italy
3
Centro Interdipartimentale NatRisk, Università di Torino, Largo Paolo Braccini 2, 10095 Grugliasco (TO), Italy
Present address: Institut National de l'environnement Industriel et des Risques (INERIS), Rue Jacques Taffanel, F-60550 Verneuil-en-Halatte, France
*
Author to whom correspondence should be addressed.
Academic Editor: Pierre Pichat
Received: 24 February 2017 / Revised: 3 April 2017 / Accepted: 6 April 2017 / Published: 12 April 2017
(This article belongs to the Special Issue Photon-involving Purification of Water and Air)
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Abstract

This study shows that methyl 2-aminobenzoate (also known as methyl anthranilate, hereafter MA) undergoes direct photolysis under UVC and UVB irradiation and that its photodegradation is further accelerated in the presence of H2O2. Hydrogen peroxide acts as a source of hydroxyl radicals (·OH) under photochemical conditions and yields MA hydroxyderivatives. The trend of MA photodegradation rate vs. H2O2 concentration reaches a plateau because of the combined effects of H2O2 absorption saturation and ·OH scavenging by H2O2. The addition of chloride ions causes scavenging of ·OH, yielding Cl2· as the most likely reactive species, and it increases the MA photodegradation rate at high H2O2 concentration values. The reaction between Cl2· and MA, which has second-order rate constant k C l 2 + M A = (4.0 ± 0.3) × 108 M−1·s−1 (determined by laser flash photolysis), appears to be more selective than the ·OH process in the presence of H2O2, because Cl2· undergoes more limited scavenging by H2O2 compared to ·OH. While the addition of carbonate causes ·OH scavenging to produce CO3· ( k C O 3 + M A = (3.1 ± 0.2) × 108 M−1·s−1), carbonate considerably inhibits the photodegradation of MA. A possible explanation is that the elevated pH values of the carbonate solutions make H2O2 to partially occur as HO2, which reacts very quickly with either ·OH or CO3· to produce O2·. The superoxide anion could reduce partially oxidised MA back to the initial substrate, with consequent inhibition of MA photodegradation. Fast MA photodegradation is also observed in the presence of persulphate/UV, which yields SO4· that reacts effectively with MA ( k S O 4 + M A = (5.6 ± 0.4) × 109 M−1·s−1). Irradiated H2O2 is effective in photodegrading MA, but the resulting MA hydroxyderivatives are predicted to be about as toxic as the parent compound for aquatic organisms (most notably, fish and crustaceans). View Full-Text
Keywords: advanced oxidation processes; methyl anthranilate; methyl 2-aminobenzoate; hydrogen peroxide; photodegradation intermediates; emerging contaminants advanced oxidation processes; methyl anthranilate; methyl 2-aminobenzoate; hydrogen peroxide; photodegradation intermediates; emerging contaminants
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MDPI and ACS Style

Lanzafame, G.M.; Sarakha, M.; Fabbri, D.; Vione, D. Degradation of Methyl 2-Aminobenzoate (Methyl Anthranilate) by H2O2/UV: Effect of Inorganic Anions and Derived Radicals. Molecules 2017, 22, 619.

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