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Urs Von Gunten – 1st expert on this subject based on the ideXlab platform
oxidative treatment of Bromide containing waters formation of bromine and its reactions with inorganic and organic compounds a critical reviewWater Research, 2014Co-Authors: Michele B Heeb, Urs Von Gunten, Justine Criquet, Saskia G ZimmermannsteffensAbstract:
Bromide (Br-) is present in all water sources at concentrations ranging from similar to 10 to >1000 mu g L-1 in fresh waters and about 67 mg L-1 in seawater. During oxidative water treatment Bromide is oxidized to hypobromous acid/hypobromite (HOBr/OBr-) and other bromine species. A systematic and critical literature review has been conducted on the reactivity of HOBr/OBr- and other bromine species with inorganic and organic compounds, including micropollutants. The speciation of bromine in the absence and presence of chloride and chlorine has been calculated and it could be shown that HOBr/OBr- are the dominant species in fresh waters. In ocean waters, other bromine species such as Br-2, BrCl, and Br2O gain importance and may have to be considered under certain conditions. HOBr reacts fast with many inorganic compounds such as ammonia, iodide, sulfite, nitrite, cyanide and thiocyanide with apparent second-order rate constants in the order of 10(4)-10(9) M-1 s(-1) at pH 7. No rate constants for the reactions with Fe(II) and As(III) are available. Mn(II) oxidation by bromine is controlled by a Mn(III,IV) oxide-catalyzed process involving Br2O and BrCl. Bromine shows a very high reactivity toward phenolic groups (apparent second-order rate constants k(app) approximate to 10(3)-10(5) M-1 s(-1) at pH 7), amines and sulfamides (k(app) 10(5) -10(6)M(-1) s(-1) at pH 7) and S-containing compounds (k(app) 10(5)-10(7)M(-1) s(-1) at pH 7). For phenolic moieties, it is possible to derive second-order rate constants with a Hammett-sigma-based QSAR approach with log(k((HOBr/PhO-)))= 7.8 – 3.5 Sigma sigma. A negative slope is typical for electrophilic substitution reactions. In general, k(app) of bromine reactions at pH 7 are up to three orders of magnitude greater than for chlorine. In the case of amines, these rate constants are even higher than for ozone. Model calculations show that depending on the Bromide concentration and the pH, the high reactivity of bromine may outweigh the reactions of chlorine during chlorination of Bromide-containing waters. (C) 2013 Elsevier Ltd. All rights reserved.
bromate formation during ozonization of Bromide containing waters interaction of ozone and hydroxyl radical reactionsEnvironmental Science & Technology, 1994Co-Authors: Urs Von Gunten, Juerg HoigneAbstract:
Kinetic simulations have been tested by laboratory experiments to evaluate the major factors controlling bromate formation during ozonation of waters containing Bromide. In the presence of an organic scavenger for OH radicals, bromate formation can be accurately predicted by the molecular ozone mechanism using published reaction rate data, even for waters containing ammonium In the absence of scavengers, OH radical reactions contribute significantly to bromate formation. Carbonate radicals, produced by the oxidation of bicarbonate with OH radicals, oxidize the intermediate hypobromite to bromite, which is further oxidized by ozone to bromate. During drinking water ozonation, molecular ozone controls both the initial oxidation of Bromide and the final oxidation of bromite. OH radical reactions contribute to the oxidation of the intermediate oxybromine species. Bromate formation in advanced oxidation processes can be explained by a synergism of ozone and OH radicals.
Akiko Nishida – 2nd expert on this subject based on the ideXlab platform
organic synthesis using sodium bromate ii a facile synthesis of n bromo imides and amides using sodium bromate and hydrobromic acid or sodium Bromide in the presence of sulfuric acidBulletin of the Chemical Society of Japan, 1993Co-Authors: Shizuo Fujisaki, Satoshi Hamura, Hisao Eguchi, Akiko NishidaAbstract:
The reaction of imides and amides in water (or aqueous acetic acid) with sodium bromate and hydrobromic acid (or sodium Bromide) in the presence of sulfuric acid under mild conditions gave the corresponding N-Bromides in high yields.
Alison Butler – 3rd expert on this subject based on the ideXlab platform
characterization of vanadium bromoperoxidase from macrocystis and fucus reactivity of vanadium bromoperoxidase toward acyl and alkyl peroxides and bromination of aminesBiochemistry, 1990Co-Authors: Helena S Soedjak, Alison ButlerAbstract:
: Vanadium bromoperoxidase (V-BrPO) has been isolated and purified from the marine brown algae Fucus distichus and Macrocystis pyrifera. V-BrPO catalyzes the oxidation of Bromide by hydrogen peroxide, resulting in the bromination of certain organic acceptors or the formation of dioxygen. V-BrPO from F. distichus and M. pyrifera have subunit molecular weights of 65,000 and 74,000, respectively, and specific activities of 1580 units/mg (pH 6.5) and 1730 units/mg (pH 6) for the bromination of monochlorodimedone, respectively. As isolated, the enzymes contain a substoichiometric vanadium/subunit ratio; the vanadium content and specific activity are increased by addition of vanadate. V-BrPO (F. distichus, M. pyrifera, and Ascophyllum nodosum) also catalyzes the oxidation of Bromide using peracetic acid. In the absence of an organic acceptor, a mixture of oxidized bromine species (e.g., hypobromous acid, bromine, and triBromide) is formed. Bromamine derivatives are formed from the corresponding amines, while 5-bromocytosine is formed from cytosine. In all cases, the rate of the V-BrPO-catalyzed reaction is much faster than that of the uncatalyzed oxidation of Bromide by peracetic acid, at pH 8.5, 1 mM Bromide, and 2 mM peracetic acid. In contrast to hydrogen peroxide, V-BrPO does not catalyze formation of dioxygen from peracetic acid in either the presence or absence of Bromide. V-BrPO also uses phenylperacetic acid, m-chloroperoxybenzoic acid, and p-nitroperoxybenzoic acid to catalyze the oxidation of Bromide; dioxygen is not formed with these peracids. V-BrPO does not catalyze Bromide oxidation or dioxygen formation with the alkyl peroxides ethyl hydroperoxide, tert-butyl hydroperoxide, and cuminyl hydroperoxide.