title: Role of halogen(I) cation-transfer mechanisms in water chlorination in the presence of bromide ion.
abstract: Bromide ion is rapidly converted to HOBr via BrCl by reaction with HOCl. The subsequent slow reactions of (HOCl, OCl-)/(HOBr, OBr-) mixtures are monitored directly by multiwavelength UV-vis absorbance methods and simultaneously by ion chromatographic measurement of ClO2-, ClO3-, and BrO3- (p[H+] 5.6-7.6). A first-order loss of HOCl is observed which is catalyzed by trace concentrations of Br- and BrCl. Chlorite ion forms first and is subsequently oxidized to ClO3-. The loss of HOBr is slower and is second-order in HOBr, so that BrO3- formation takes longer than ClO3- formation. Under the conditions of this work, the relative yield of BrO3- increases with increase in pH. The decomposition of HOCI by bromide proceeds primarily by a series of halogen(I) cation-transfer reactions with subsequent halide release. The presence of HOCI increases the BrO3- yield three-fold from HOBr decay alone.
authors.affiliation: Department of Chemistry, Purdue University, Brown Laboratory of Chemistry, West Lafayette, IN 47907-1393, USA. margerum@purdue.edu
authors.forename: Dale W
authors.initials: DW
authors.lastname: Margerum
authors.forename: HartzKaraE
authors.initials: H
authors.lastname: Huff
mesh_terms: D001965:Bromides / Q000737:chemistry*; D002412:Cations / Q000737:chemistry; D002713:Chlorine / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007477:Ions; D008956:Models, Chemical; D018508:Water Purification; D014881:Water Supply
chemical_list: D001965:Bromides; D002412:Cations; D007477:Ions; D002713:Chlorine