Ozonation of bromide-containing waters: kinetics of formation of hypobromous acid and bromate

Abstract

Ozone oxidizes Br<sup>-</sup> under water treatment conditions to form HOBr. HOBr reacts further with O<sub>3</sub>, but only in its ionized form, OBr<sup>-</sup>. OBr<sup>-</sup> is oxidized not only to BrO<sub>3</sub><sup>-</sup> but also to a species that regenerates Br<sup>-</sup>. The results are consistent with the following scheme of reactions: [three chemical equations are given] where <I>k</I><sub>1</sub> = 160 ± 20 M<sup>-1</sup> s<sup>-1</sup>, <I>k</I><sub>2</sub> = 330 ± 60 M<sup>-1</sup> s<sup>-1</sup>, and <I>k</I><sub>3</sub> = 100 ± 20 M<sup>-1</sup> s<sup>-1</sup> at 20°C. Thus, a catalytic decomposition of O<sub>3</sub> via reactions 1 and 2 is observed. The maximum intermediate HOBr concentration is greater the lower the pH. In the presence of organic matter, HOBr reacts to form bromo organics. Thus, more bromoform was produced with humic acid at pH 6.1 than at pH 8.8. The range of conditions conducive to haloform formation is narrower than during chlorination.