Participation of the Halogens in Photochemical Reactions in Natural and Treated Waters

Halide ions are ubiquitous in natural waters and wastewaters. Halogens play an important and complex role in environmental photochemical processes and in reactions taking place during photochemical water treatment. While inert to solar wavelengths, halides can be converted into radical and non-radic...

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Main Authors: Yi Yang, Joseph J. Pignatello
Format: Article
Language:English
Published: MDPI AG 2017-10-01
Series:Molecules
Subjects:
Online Access:https://www.mdpi.com/1420-3049/22/10/1684
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spelling doaj-3a05671c98d9464eb2896becc80a3e332020-11-24T20:47:59ZengMDPI AGMolecules1420-30492017-10-012210168410.3390/molecules22101684molecules22101684Participation of the Halogens in Photochemical Reactions in Natural and Treated WatersYi Yang0Joseph J. Pignatello1Department of Environmental Sciences, The Connecticut Agricultural Experiment Station, 123 Huntington St., P.O. Box 1106, New Haven, CT 06504-1106, USADepartment of Environmental Sciences, The Connecticut Agricultural Experiment Station, 123 Huntington St., P.O. Box 1106, New Haven, CT 06504-1106, USAHalide ions are ubiquitous in natural waters and wastewaters. Halogens play an important and complex role in environmental photochemical processes and in reactions taking place during photochemical water treatment. While inert to solar wavelengths, halides can be converted into radical and non-radical reactive halogen species (RHS) by sensitized photolysis and by reactions with secondary reactive oxygen species (ROS) produced through sunlight-initiated reactions in water and atmospheric aerosols, such as hydroxyl radical, ozone, and nitrate radical. In photochemical advanced oxidation processes for water treatment, RHS can be generated by UV photolysis and by reactions of halides with hydroxyl radicals, sulfate radicals, ozone, and other ROS. RHS are reactive toward organic compounds, and some reactions lead to incorporation of halogen into byproducts. Recent studies indicate that halides, or the RHS derived from them, affect the concentrations of photogenerated reactive oxygen species (ROS) and other reactive species; influence the photobleaching of dissolved natural organic matter (DOM); alter the rates and products of pollutant transformations; lead to covalent incorporation of halogen into small natural molecules, DOM, and pollutants; and give rise to certain halogen oxides of concern as water contaminants. The complex and colorful chemistry of halogen in waters will be summarized in detail and the implications of this chemistry for global biogeochemical cycling of halogen, contaminant fate in natural waters, and water purification technologies will be discussed.https://www.mdpi.com/1420-3049/22/10/1684hydroxyl radicalsulfate radicalphotocatalysisatmospheric aerosolsreactive oxygen speciesreactive halogen speciesadvanced oxidation processesdissolved natural organic matterhalogenationreclaimed waters
collection DOAJ
language English
format Article
sources DOAJ
author Yi Yang
Joseph J. Pignatello
spellingShingle Yi Yang
Joseph J. Pignatello
Participation of the Halogens in Photochemical Reactions in Natural and Treated Waters
Molecules
hydroxyl radical
sulfate radical
photocatalysis
atmospheric aerosols
reactive oxygen species
reactive halogen species
advanced oxidation processes
dissolved natural organic matter
halogenation
reclaimed waters
author_facet Yi Yang
Joseph J. Pignatello
author_sort Yi Yang
title Participation of the Halogens in Photochemical Reactions in Natural and Treated Waters
title_short Participation of the Halogens in Photochemical Reactions in Natural and Treated Waters
title_full Participation of the Halogens in Photochemical Reactions in Natural and Treated Waters
title_fullStr Participation of the Halogens in Photochemical Reactions in Natural and Treated Waters
title_full_unstemmed Participation of the Halogens in Photochemical Reactions in Natural and Treated Waters
title_sort participation of the halogens in photochemical reactions in natural and treated waters
publisher MDPI AG
series Molecules
issn 1420-3049
publishDate 2017-10-01
description Halide ions are ubiquitous in natural waters and wastewaters. Halogens play an important and complex role in environmental photochemical processes and in reactions taking place during photochemical water treatment. While inert to solar wavelengths, halides can be converted into radical and non-radical reactive halogen species (RHS) by sensitized photolysis and by reactions with secondary reactive oxygen species (ROS) produced through sunlight-initiated reactions in water and atmospheric aerosols, such as hydroxyl radical, ozone, and nitrate radical. In photochemical advanced oxidation processes for water treatment, RHS can be generated by UV photolysis and by reactions of halides with hydroxyl radicals, sulfate radicals, ozone, and other ROS. RHS are reactive toward organic compounds, and some reactions lead to incorporation of halogen into byproducts. Recent studies indicate that halides, or the RHS derived from them, affect the concentrations of photogenerated reactive oxygen species (ROS) and other reactive species; influence the photobleaching of dissolved natural organic matter (DOM); alter the rates and products of pollutant transformations; lead to covalent incorporation of halogen into small natural molecules, DOM, and pollutants; and give rise to certain halogen oxides of concern as water contaminants. The complex and colorful chemistry of halogen in waters will be summarized in detail and the implications of this chemistry for global biogeochemical cycling of halogen, contaminant fate in natural waters, and water purification technologies will be discussed.
topic hydroxyl radical
sulfate radical
photocatalysis
atmospheric aerosols
reactive oxygen species
reactive halogen species
advanced oxidation processes
dissolved natural organic matter
halogenation
reclaimed waters
url https://www.mdpi.com/1420-3049/22/10/1684
work_keys_str_mv AT yiyang participationofthehalogensinphotochemicalreactionsinnaturalandtreatedwaters
AT josephjpignatello participationofthehalogensinphotochemicalreactionsinnaturalandtreatedwaters
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