Kinetics and mechanism of the reaction between hypochlorous acid and bromite ion

Thomas Frank Perrone, Purdue University

Abstract

Chlorination (as HOCl) and ozonation are common methods of water treatment in the United States and O3 has been shown to rapidly oxidize Br − to BrO3− via HOBr and BrO 2−. Therefore, bromite may also be present during the chlorination of water which contains Br−, so the reaction between HOCl and BrO2− was studied in the pH range of 5–8. The reaction between HOCl and BrO2 − unexpectedly gives significant yields of ClO2. Other products include BrO3−, ClO3 −, Br−, and Cl− with a product distribution which is modulated by changing pH and initial concentration of reactants. The yield of ClO2 increases with initial BrO 2− concentration, decreasing pH and decreasing initial HOCl concentration. The yield of BrO3− increases with increasing pH. From our study of this reaction, the connectivity of the intermediate [HOCl BrO2−] has been established as HOClOBrO−. This suggests that the reactions of X(I) with X(III) such as the reaction of HOCl with ClO2 − proceeds through the intermediate HOClOClO− (and ClOClO) enroute to the formation of ClO3− and Cl−. At low initial HOCl concentrations, the kinetics of the title reaction can be predicted by the rate constants available for the HOBr/ClO2− system.

Degree

Ph.D.

Advisors

Margerum, Purdue University.

Subject Area

Analytical chemistry

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