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From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
Published on: March 24, 2018
Decoding the Formation and Speciation of Emerging Halogenated Oxidation Byproducts by the UV/NHCl2 Process in the
Kun Wang1, Binghua Jing2, Chii Shang1,3
1Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR 999077, China.
Abstract:
In reverse osmosis (RO)-based potable reuse scenarios, the UV/dichloramine (NHCl2) and UV/monochloramine (NH2Cl) processes co-occur during RO permeate treatment, where bromide may also exist. However, the formation of emerging oxidation byproducts (OBPs) during the UV/NHCl2 process remains unexplored. This work, for the first time, elucidates the molecular-level formation of emerging chlorinated and brominated OBPs (Cl- and Br-OBPs) from RO permeate dissolved organic matter (rpDOM) and illustrates bromamine-induced transformation of Cl-OBPs into their brominated analogues in the UV/NHCl2 process in the presence of bromide, utilizing Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and membrane introduction mass spectrometry (MIMS). In the presence of bromide, 48 Br-OBPs and three bromochloro OBPs were generated in the UV/NHCl2 process, with some Cl-OBPs being transformed into their brominated analogues, likely due to the generation of NHBrCl (∼6 μM) and NHBr2 (∼2 μM). Compared with the UV/NHCl2 process, the number of Br-OBPs formed during the UV/NH2Cl process was 31.3% lower. The transformation of 4-aminophenol, a model compound of rpDOM, further elucidated the formation of halogenated OBPs through chlorine/bromine substitution and oxidation mechanisms. The findings provide new insights into the molecular-level transformation of halogenated OBPs during the UV/chloramine process in bromide-containing water.
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