Degradation of ambroxol by UV/chloramine process: Kinetics, degradation pathway, and control of the risk of highly toxic disinfection by-products

Binbin Shao; Chenkai Hu; Hainan Zhao; Chengcheng Xiao; Erdeng Du; Anhong Cai; Jing Deng

doi:10.1016/j.envpol.2024.125091

Degradation of ambroxol by UV/chloramine process: Kinetics, degradation pathway, and control of the risk of highly toxic disinfection by-products

Environ Pollut. 2024 Oct 9:125091. doi: 10.1016/j.envpol.2024.125091. Online ahead of print.

Authors

Binbin Shao¹, Chenkai Hu², Hainan Zhao², Chengcheng Xiao², Erdeng Du³, Anhong Cai⁴, Jing Deng⁵

Affiliations

¹ College of Civil Engineering, Zhejiang University of Technology, Hangzhou 310023, China; Zhejiang Key Laboratory of Civil Engineering Structures & Disaster Prevention and Mitigation Technology, Hangzhou 310023, China.
² College of Civil Engineering, Zhejiang University of Technology, Hangzhou 310023, China.
³ School of Urban Construction, Changzhou University, Changzhou 213164, China.
⁴ National and Local Joint Engineering Research Center for Ecological Treatment Technology of Urban Water Pollution, College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China. Electronic address: 20230106@wzu.edu.cn.
⁵ College of Civil Engineering, Zhejiang University of Technology, Hangzhou 310023, China; Zhejiang Key Laboratory of Civil Engineering Structures & Disaster Prevention and Mitigation Technology, Hangzhou 310023, China. Electronic address: zjut_djing@163.com.

PMID: 39393762
DOI: 10.1016/j.envpol.2024.125091

Abstract

Ambroxol (AMB) is a commonly used bromine-containing organic compound in medical applications and has been frequently found in water environments, which might pose risks of forming brominated disinfection by-products (Br-DBPs) in water treatment systems. The degradation kinetics as well as the degradation mechanism of AMB in the UV/chloramine process were investigated in this study. It was determined that reactive chlorine species (RCS) and the reactive nitrogen species (RNS) were the dominant free radicals for AMB degradation. Debromination occurred mainly in the initial stage of the degradation process, with a debromination rate of 34.5% at 10 min. Four possible degradation pathways of AMB were proposed based on liquid chromatography mass spectrometry (LC-MS) analysis as well as density functional theory (DFT) calculations, meanwhile the ECOSAR model was used to predict the toxicity risk of AMB and its degradation intermediates. Furthermore, after assessing the formation of DBPs during the UV/chloramine pre-oxidation process and conducting a toxicity risk analysis based on the results, it has been verified that this method can effectively remove AMB while reducing the formation potential of DBPs in the water environment. This suggests that the UV/chloramine process shows promise for treating bromine-containing organic compounds in real-world water treatment applications.

Keywords: Ambroxol; Bromide; Disinfection by-product (DBP); Reactive radicals; Transformation products (TPs); UV/chloramine.