The corrosion inhibitor 1H-benzotriazole (pKa=8.4) can exist in two different forms in natural waters, and photochemical transformation is a potentially significant attenuation pathway for both of them. Depending on conditions, the modelled half-life times range from some days/weeks to several months. In sunlit water bodies, the acidic (neutral) form would undergo direct photolysis (accounting for up to 7% of total phototransformation) and, most notably, reaction with the hydroxyl radicals (·OH) and the triplet states of chromophoric dissolved organic matter (3CDOM*). The basic (anionic) form would undergo significant transformation with ·OH and 3CDOM*. The ·OH reactions would be more important at low dissolved organic carbon (DOC) and the 3CDOM* processes at high DOC. In the presence of highly reactive triplet-state model compounds, the two benzotriazole forms reactwith similar rate constants. In this case, they would show comparable half-life times in surface-water environments. With less reactive triplet states, the rate constant of the anionic form can be a couple of orders of magnitude higher than that of the neutral one. Under these circumstances, the neutral form could be considerablymore photostable than the anionic one at highDOC. Therefore, depending on 3CDOM*reactivity, the solution pH may or may not play an important role in the photoattenuation kinetics of 1H-benzotriazole in sunlit naturalwaters, especially at high DOC. Both forms of benzotriazole yield hydroxyderivatives as their main transformation intermediates under all the relevant photochemical reaction pathways. These intermediates could be formed via ·OH-induced hydroxylation, or upon electron abstraction followed by reaction with water. Differently from UVC irradiation data reported in previous studies, the concentration of aniline upon excitation of 1Hbenzotriazole under environmentally significant UVwavelengths was always belowthe detection limit of the analytical method used in this work (5 μmol L−1).

Photochemical transformation of benzotriazole, relevant to sunlit surface waters: Assessing the possible role of triplet-sensitised processes

FABBRI, DEBORA;MINELLA, Marco;MAURINO, Valter;MINERO, Claudio;VIONE, Davide Vittorio
2016

Abstract

The corrosion inhibitor 1H-benzotriazole (pKa=8.4) can exist in two different forms in natural waters, and photochemical transformation is a potentially significant attenuation pathway for both of them. Depending on conditions, the modelled half-life times range from some days/weeks to several months. In sunlit water bodies, the acidic (neutral) form would undergo direct photolysis (accounting for up to 7% of total phototransformation) and, most notably, reaction with the hydroxyl radicals (·OH) and the triplet states of chromophoric dissolved organic matter (3CDOM*). The basic (anionic) form would undergo significant transformation with ·OH and 3CDOM*. The ·OH reactions would be more important at low dissolved organic carbon (DOC) and the 3CDOM* processes at high DOC. In the presence of highly reactive triplet-state model compounds, the two benzotriazole forms reactwith similar rate constants. In this case, they would show comparable half-life times in surface-water environments. With less reactive triplet states, the rate constant of the anionic form can be a couple of orders of magnitude higher than that of the neutral one. Under these circumstances, the neutral form could be considerablymore photostable than the anionic one at highDOC. Therefore, depending on 3CDOM*reactivity, the solution pH may or may not play an important role in the photoattenuation kinetics of 1H-benzotriazole in sunlit naturalwaters, especially at high DOC. Both forms of benzotriazole yield hydroxyderivatives as their main transformation intermediates under all the relevant photochemical reaction pathways. These intermediates could be formed via ·OH-induced hydroxylation, or upon electron abstraction followed by reaction with water. Differently from UVC irradiation data reported in previous studies, the concentration of aniline upon excitation of 1Hbenzotriazole under environmentally significant UVwavelengths was always belowthe detection limit of the analytical method used in this work (5 μmol L−1).
566-567
712
721
Bianco, Angelica; Fabbri, Debora; Minella, Marco; Brigante, Marcello; Mailhot, Gilles; Maurino, Valter; Minero, Claudio; Vione, Davide
File in questo prodotto:
File Dimensione Formato  
STOTEN2016_BZT.pdf

Accesso riservato

Tipo di file: PDF EDITORIALE
Dimensione 2.59 MB
Formato Adobe PDF
2.59 MB Adobe PDF   Visualizza/Apri   Richiedi una copia
BZT_STOTEN2016.pdf

Accesso aperto con embargo fino al 01/01/2019

Tipo di file: POSTPRINT (VERSIONE FINALE DELL’AUTORE)
Dimensione 2.74 MB
Formato Adobe PDF
2.74 MB Adobe PDF Visualizza/Apri

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2318/1615931
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 8
  • ???jsp.display-item.citation.isi??? 8
social impact