Transformation products of contaminants of emerging concern in water by UV-based processes

Abstract

Contaminants of emerging concern (CECs) and their respective transformation products (TPs) formed following photodegradation pose considerable threats to the environment and our health. The formation of TPs during UV-LED-based degradation of three target pollutants in the EU Watch List of CECs was accessed by LC-MS-Orbitrap, and their reaction pathways were elucidated. The influence of different matrices and treatments of choice on TP formation was investigated. Results showed that matrix changes did not produce different reaction pathways during UV-A photocatalysis, although plots of TP peak areas vs. time were different for each case. A new TP was found for the antidepressant venlafaxine, (1-[2-(dimethylnitroryl)-1-(4-methoxyphenyl)ethyl]cyclohexanol. When comparing UV-A photocatalysis with UV-C photolysis, dissimilar pathways were observed due to the distinct reaction mechanisms of each process, since photocatalysis, unlike photolysis, relies on radical-based reaction routes. Different levels of confidence were obtained for each TP depending on the availability of MS2 data in the literature and of standards for comparison. All the found TPs had similar molecular masses in comparison to their respective parent compounds. Most of the TPs remained in the effluent after 6 hours of photodegradation, which highlights the importance of their control, close-monitoring, and further toxicity assessments. HIGHLIGHTS Detection of transformation products of contaminants of emerging concern in water.; Elucidation of reaction pathways for photolysis and photocatalysis.; A new transformation product found for venlafaxine.; No difference in detected compounds for tap and ultrapure water.;

Keywords

• orbitrap
• photodegradation
• transformation products
• trimethoprim
• venlafaxine