Benzotriazole is part of a larger family of benzotriazoles which are widely used as antifreeze, corrosion inhibitor and UV-stabilizers in many commercial and industrial applications. It is frequently detected in urban runoff, wastewater, and receiving aquatic environments. In surface waters, benzotriazole is typically resistant to biodegradation and hydrolysis, but can be transformed via direct photolysis and photoinduced mechanisms, e.g., by reactive species formed from dissolved organic molecules. Compound-specific isotope analysis (CSIA) is a promising tool to track and quantify contaminant transformation in the environment. Due to the highly reaction-specific isotope fractionation patterns, CSIA can provide direct evidence of contaminant transformation and has the potential to provide insights into transformation mechanisms. In addition, measuring changes of isotope ratios of more than one element can help identify the relative contribution of different reaction mechanisms. Therefore, the aim of this study was to characterize the phototransformation processes of benzotriazole using multi-element CSIA. The direct photolysis of benzotriazole resulted in significant 15N fractionation, which were -3.4±0.4‰ at pH 5, -7.0±0.8‰ at pH 7 and -4.7±0.6‰ at pH 9, respectively, indicating a N-N bond fission yielding imine is the rate-limiting step. The identified transformation products of aniline, 3-aminophenol and phenazine further supported that the yield imine was rapidly stabilized via two routes: nitrogen elimination followed by hydroxylation and a dimerization process. The formation of hydroxybenzotriazole during indirect photolysis suggested an oxidative attack by OH radical on the benzene ring. The significant 13C fractionation and non-detectable 2H and 15N fractionation in the UV/H2O2 system revealed that the formation of O-C bond at the benzene ring was the rate-limiting step of the indirect photolysis. The results of this study highlight the great potential for multi-element CSIA application to track benzotriazole degradation in complex environments.

Investigation of the phototransformation mechanisms of benzotriazole in surface waters using compound-specific isotope analysis

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.