Ozonation of carbamazepine and its main transformation products: product determination and reaction mechanisms

Matilda Kråkström,Narendra Kumar,Tapio Salmi,Leif Kronberg,Pasi Tolvanen,Patrik Eklund,Soudabeh Saeid

doi:10.1007/s11356-020-08795-0

Matilda Kråkström, Narendra Kumar + Show 5 more

Open Access

https://doi.org/10.1007/s11356-020-08795-0

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Abstract

Carbamazepine (CBZ) is a recalcitrant pharmaceutical often detected in wastewater and in the environment. CBZ can be removed from wastewater through advanced oxidation treatment methods such as ozonation. In this study, CBZ and its transformation product 1-(2-benzaldehyde)-(1H,3H)-quinazoline-2,4-dione (BQD) were ozonated, and the formation and transformation of their ozonation products were investigated using liquid chromatography coupled to ion trap mass spectrometry and high-resolution mass spectrometry as well as nuclear magnetic resonance (NMR). The main products, 1-(2-benzaldehyde)-4-hydro-(1H,3H)-quinazoline-2-one (BQM) and BQD were quantified using isolated standards and LC-UV. Of the original CBZ concentration, 74% was transformed into BQM and 83% of BQM was further transformed into BQD. Both products are more stable than CBZ and could still be detected after 240 min of ozonation. Another major product, 2,2′-azanediyldibenzaldehyde (TP225) was for the first time identified using NMR. Twelve further CBZ products were identified.

Highlights

Carbamazepine (CBZ), an antiepileptic pharmaceutical, has a tricyclic dibenzazepine structure consisting of two benzene rings fused to an azepine group
The third aim of this study was to ozonate BQD, the major transformation formed during the ozonation of CBZ, in order to determine its stability in comparison with CBZ and to identify the products which are formed from BQD
BQM reacted through direct ozonation to form BQD

Summary

Introduction

Carbamazepine (CBZ), an antiepileptic pharmaceutical, has a tricyclic dibenzazepine structure consisting of two benzene rings fused to an azepine group. Carbamazepine, along with other pharmaceuticals, enters the aquatic environment via wastewater treatment plants (WWTPs). The concentration of CBZ in effluent water from WWTPs is often higher than in the influent leading to a negative removal rate (Björnelius et al 2018; UNESCO and HELCOM 2017; Vieno et al 2006). This is believed to be due to the deconjugation of CBZ that takes place in WWTPs (Verlicchi et al 2012). The half-life has been found to be much longer: the half-lives of CBZ in a Swedish lake and in the Baltic Sea are both around 3.5 years (Björnelius et al 2018; Zou et al 2015)

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