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首页> 外文期刊>Environmental Science & Technology >Reactivity of BrCi, Br_2, BrOCI, Br_2O, and HOBr Toward Dimethenamid in Solutions of Bromide + Aqueous Free Chlorine
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Reactivity of BrCi, Br_2, BrOCI, Br_2O, and HOBr Toward Dimethenamid in Solutions of Bromide + Aqueous Free Chlorine

机译：BrCi，Br_2，BrOCI，Br_2O和HOBr在溴化物+游离氯水溶液中对二甲烯酰胺的反应性

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摘要

HOBr, formed via oxidation of bromide by free available chlorine (FAC), is frequently assumed to be the sole species responsible for generating brominated disinfection byproducts (DBPs). Our studies reveal that BrCl, Br_2, BrOCI, and Br_2O can also serve as brominating agents of the herbicide dimethenamid in solutions of bromide to which FAC was added. Conditions affecting bromine speciation (pH, total free bromine concentration ([HOBr]_T), [CT], and [FAC]_0) were systematically varied, and rates of dimethenamid bromination were measured. Reaction orders in [HOBr]_T ranged from 1.09 (±0.17) to 1.67 (±0.16), reaching a maximum near the pK, of HOBr. This complex dependence on [HOBr]_T implicates Br_2O as an active brominating agent. That bromination rates increased with increasing [Ol~-], [FAC]_0 (at constant [HOBr]_t), and excess bromide (where [Br~-]_0> [FAC]_0) implicate BrCl, BrOCI, and Br_2, respectively, as brominating agents. As equilibrium constants for the formation of Br_2O and BrOCl (aq) have not been previously reported, we have calculated these values (and their gas-phase analogues) using benchmark-quality quantum chemical methods [CCSD(T) up to CCSDTQ calculations plus solvation effects]. The results allow us to compute bromine speciation and hence second-order rate constants. Intrinsic brominating reactivity increased in the order: HOBr Br_2O < BrOCl ≈ Br_2 < BrCl. Our results indicate that species other than HOBr can influence bromination rates under conditions typical of drinking water and wastewater chlorination.
机译：通常认为溴化氢是通过游离氯（FAC）氧化溴化物而形成的HOBr，是产生溴化消毒副产物（DBP）的唯一物质。我们的研究表明，在添加了FAC的溴化物溶液中，BrCl，Br_2，BrOCI和Br_2O还可作为除草剂二甲亚胺的溴化剂。系统地改变了影响溴形态的条件（pH，总游离溴浓度（[HOBr] _T]，[CT]和[FAC] _0），并测量了二甲萘胺的溴化速率。 [HOBr] _T中的反应阶数为1.09（±0.17）至1.67（±0.16），在HOBr的pK附近达到最大值。这种对[HOBr] _T的复杂依赖性意味着Br_2O作为活性溴化剂。溴化速率随[Ol〜-]，[FAC] _0（在恒定[HOBr] _t不变）和过量的溴化物（其中[Br〜-] _ 0> [FAC] _0）增加而增加，意味着BrCl，BrOCI和Br_2，分别作为溴化剂。由于先前尚未报道过形成Br_2O和BrOCl（aq）的平衡常数，因此我们使用基准质量的量子化学方法[CCSD（T）直至CCSDTQ计算加溶剂化计算了这些值（及其气相类似物）效果]。结果使我们能够计算出溴的形态，从而计算出二阶速率常数。内在溴化反应性按以下顺序增加：HOBr Br_2O

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  • 来源
    《Environmental Science & Technology》 |2013年第3期|1330-1338|共9页
  • 作者

    John D. Sivey; J. Samuel Arey; Peter R. Tentscher; A. Lynn Roberts;

  • 作者单位

    Department of Geography and Environmental Engineering, Johns Hopkins University, 313 Ames Hall 3400 North Charles Street Baltimore, Maryland 21218, United States,Department of Chemistry, Towson University, Smith Hall 543 8000 York Road Towson, Maryland 21252, United States;

    Environmental Chemistry Modeling Laboratory, Swiss Federal Institute of Technology at Lausanne (EPFL) 1015 Lausanne, Switzerland,Department of Environmental Chemistry, Swiss Federal Institute of Aquatic Science and Technology (Eawag) 8600 Dubendorf, Switzerland;

    Environmental Chemistry Modeling Laboratory, Swiss Federal Institute of Technology at Lausanne (EPFL) 1015 Lausanne, Switzerland;

    Department of Geography and Environmental Engineering, Johns Hopkins University, 313 Ames Hall 3400 North Charles Street Baltimore, Maryland 21218, United States;

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