title: Kinetic study of the reactions between chloramine disinfectants and hydrogen peroxide: temperature dependence and reaction mechanism.
abstract: The temperature-dependent kinetics for the reaction between hydrogen peroxide and chloramine water disinfectants (NH2Cl, NHCl2, and NCl3) have been determined using stopped flow-UV/Vis spectrophotometry. Rate constants for the mono- and dichloramine-peroxide reaction were on the order of 10(-2)M(-1)s(-1) and 10(-5)M(-1)s(-1), respectively. The reaction of trichloramine with peroxide was negligibly slow compared to its thermal and photolytically-induced decomposition. Arrhenius expressions of ln(kH2O2-NH2Cl)=(17.3±1.5)-(51500±3700)/RT and ln(kH2O2-NHCl2)=(18.2±1.9)-(75800±5100)/RT were obtained for the mono- and dichloramine peroxide reaction over the temperature ranges 11.4-37.9 and 35.0-55.0°C, respectively. Both monochloramine and hydrogen peroxide were first-order in the rate-limiting kinetic step and concomitant measurements made using a chloride ion selective electrode showed that the chloride was produced quantitatively. These data will aid water utilities in predicting chloramine concentrations (and thus disinfection potential) throughout the water distribution system.
authors.affiliation: Department of Chemistry and Biochemistry, California State University at Long Beach, 1250 N. Bellflower Blvd., Long Beach, CA 90804, United States.
authors.forename: Garrett
authors.initials: G
authors.lastname: McKay
authors.forename: Brittney
authors.initials: B
authors.lastname: Sjelin
authors.forename: Matthew
authors.initials: M
authors.lastname: Chagnon
authors.forename: Kenneth P
authors.initials: KP
authors.lastname: Ishida
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Mezyk
mesh_terms: D002700:Chloramines / Q000737:chemistry*; D004202:Disinfectants / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry*; D007700:Kinetics; D008956:Models, Chemical; D013696:Temperature; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D002700:Chloramines; D004202:Disinfectants; D014874:Water Pollutants, Chemical; D006861:Hydrogen Peroxide; C030816:chloramine
keywords: Chloramination; Chloramines; Hydrogen peroxide; Kinetics; Water disinfection