Freezing degradation of the anticonvulsant oxcarbazepine by bromate in water ice under sunlight irradiation

Heyang Sun; Liwen Zhang; Deming Dong; Wenming Zhang; Zhiyong Guo

doi:10.1016/j.scitotenv.2023.165014

Freezing degradation of the anticonvulsant oxcarbazepine by bromate in water ice under sunlight irradiation

Sci Total Environ. 2023 Oct 10:894:165014. doi: 10.1016/j.scitotenv.2023.165014. Epub 2023 Jun 20.

Authors

Heyang Sun¹, Liwen Zhang¹, Deming Dong¹, Wenming Zhang², Zhiyong Guo³

Affiliations

¹ Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin Provincial Key Laboratory of Water Resources and Environment, College of New Energy and Environment, Jilin University, Changchun 130012, China.
² Dept. of Civil and Environmental Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada.
³ Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin Provincial Key Laboratory of Water Resources and Environment, College of New Energy and Environment, Jilin University, Changchun 130012, China. Electronic address: zyguo@jlu.edu.cn.

PMID: 37343881
DOI: 10.1016/j.scitotenv.2023.165014

Abstract

Ice plays a crucial role in contaminant transformation in seasonally ice-covered waters. In this study, the characteristics and mechanisms of an emerging contaminant oxcarbazepine (OXC) degradation by a disinfection by-product bromate ( [Formula: see text] ) in ice were explored via combined experiments and theoretical calculations. Results showed that 74.0 % and 86.4 % of OXC was degraded by [Formula: see text] in ice after 140 min in dark and 120 min under solar irradiation, respectively, while the reaction was negligible in water. The oxidation-reduction potential of [Formula: see text] solution at 1000 μmol L^-1 was 56.9 % higher than that at 50 μmol L^-1. The oxidation-reduction potential of [Formula: see text] solution at pH 2 was 14.8 %-109.5 % higher than those at other pH values. Enhanced OXC degradation by [Formula: see text] in ice could be attributed to increased [Formula: see text] oxidation capacity resulting from locally elevated [Formula: see text] and H⁺ concentrations. Hypobromous acid (HOBr), •OH, and Br• generated by direct photolysis under solar irradiation further promoted the OXC degradation in ice. Br• formed by the direct photolysis of accumulated HOBr under solar irradiation caused the generation of bromine-containing degradation products. Bromine-containing degradation products possessed higher potential toxicities, which could contribute to increase the secondary pollution of water environment.

Keywords: Direct photolysis; Disinfection by-product; Free radical; Molecular structure; Pharmaceutical.