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Role of Carbonate Species on General Acid Catalysis of Bromide Oxidation by Hypochlorous Acid (HOCl) and Oxidation by Molecular Chlorine (Cl2)
Citation:
Brodfuehrer, S., D. Wahman, A. Alsulaili, G. Speitel, AND L. Katz. Role of Carbonate Species on General Acid Catalysis of Bromide Oxidation by Hypochlorous Acid (HOCl) and Oxidation by Molecular Chlorine (Cl2). ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 54(24):16186–16194, (2020). https://doi.org/10.1021/acs.est.0c04563
Impact/Purpose:
Revise reaction kinetics of free chlorine and bromide for use in drinking water models. Samuel H. Brodfuehrer Samuel H. Brodfuehrer
Description:
Bromide ion (Br–) oxidation kinetics have taken on renewed importance in chloramine disinfection as several seconds to several minutes of free chlorination often precedes free ammonia addition. In such systems, the potential for bromine–substituted disinfection by–products must be considered and their formation is dependent on a series of reactions including Br– oxidation by hypochlorous acid (HOCl). The rate of hypobromous acid formation from Br– oxidation by HOCl is a general acid–assisted reaction where the value of the rate constant depends on the concentration of different acids present in the matrix (hydrogen ion, carbonic acid, and bicarbonate anion, as well as any other acid). Experiments were conducted over a range of natural water conditions (carbonate and bicarbonate buffer concentrations and pH) to incorporate acid catalysis into the rate expression for conditions typical of drinking water treatment systems. The reaction rate constant for Br– oxidation by HOCl was determined to be k' (M–1 s–1) = 1,550 + 2.89x1010[H+] + 2.84x105[HCO3–] + 2.93x108[H2CO3] + 1.82x105[NH4+] + 4.76x103[HPO42–] + 2.44x106[H2PO4–] + 8.80x108[H3PO4].
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DOI: Role of Carbonate Species on General Acid Catalysis of Bromide Oxidation by Hypochlorous Acid (HOCl) and Oxidation by Molecular Chlorine (Cl2)
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