Binbin Shao,Chenkai Hu,Hainan Zhao,Chengcheng Xiao,Erdeng Du,Anhong Cai,Jing Deng
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.
Quanfa Zhong,Wangbao Gong,Guangjun Wang,Jun Xie,Jianshu Zhao,Qinghai Jin,Xiaoming Ma,Zhangxin Wang,Di He
This study utilized Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to investigate the molecular-level transformation of dissolved organic matter (DOM) during treatment with the novel UV/dichloroisocyanurate (NaDCC) process. Comparisons were made with conventional UV/hypochlorite (NaClO) and UV/monochloramine (NH 2 Cl) processes to assess the feasibility and environmental risks of UV/NaDCC. Results showed that UV/NaDCC and UV/NaClO had comparable and stronger DOM mineralization effects than UV/NH 2 Cl. Notably, UV/NaDCC treatment more effectively reduced DOM aromaticity, fluorescence, and apparent molecular weight, producing more oxidized and saturated molecules. Kendrick mass defect (KMD) analysis indicated that demethylation and carboxylation reactions played key roles in UV/NaDCC treatment, supported by a greater number of precursor-product pairs. The UV/NaDCC system produced substantial chlorinated and N-containing byproducts (Cl-BPs and N-BPs). Among the Cl-BPs, species formed via + 2Cl reaction ( e. g. , +H 2 Cl 2 O 2 , +Cl 2 O) were dominant, similar to the UV/NaClO system. The N-BPs with higher nitrogen content ( e. g. , N3 and N4) were more abundant than in UV/NH 2 Cl. The UV/NaDCC system produced the highest concentrations of TCM and DCAN, whereas the UV/NaClO system yielded the highest concentration of DCAA. Toxicity tests revealed that UV/NaDCC effluent displayed the highest toxicity. To the best of our knowledge, this study provides the first molecular-level insight into DOM transformation in UV/NaDCC treatment, offering theoretical and practical guidance for its application.
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