title: Effects of isocyanuric acid on the monochlorodimedone chlorinating rates with free chlorine and ammonia chloramine in water.
abstract: Changes in monochlorodimedone (MCD) chlorinating rates with free chlorine (mixture of HOCl and OCl-) and ammonia monochloramine (NH2Cl) in water at pH 7 by the addition of isocyanuric acid (H3Cy) were determined at room temperature. Decreases in MCD absorbance at 290nm in equimolar (0.04mM) reactions of MCD and free available chlorine solutions containing H3Cy (0.01-1.60 mM) were recorded in a stopped-flow spectrophotometer. The rates indicate second-order reactions. Since the rate with free chlorine was high (> 7.6 x 10(6) M(-1) s(-1)), the amounts of free chlorine in the solutions could be distinguished from that of chlorinated cyanurates. The chlorinating rates with chlorinated cyanurates decreased with an increase in H3Cy concentrations. Plotting the rates against the molar ratio of chlorine to H3Cy showed a linear correlation and the rates with chlorinated cyanurates (H2ClCy) was estimated at 0.5 x 10(5) M(-1) s(-1). In contrast, the rates with the NH2Cl solution containing H3Cy increased with an increase in H3Cy concentrations, increasing from 1.2 x 10 to 2.7 x 10 M(-1) s(-1) by the addition of 1.55 mM H3Cy. The DPD color development rates (OD512/t1/2/M) with free available chlorine (0.015mM) declined from 1.3 x 10(5) to 0.9 x 10(5)M(-1) by the addition of 0.61 mM H3Cy.
authors.affiliation: College of Pharmacy, Nihon University, Narashinodai, Funabashi, Japan. tachikaw@pha.nihon-u.ac.jp
authors.forename: Mariko
authors.initials: M
authors.lastname: Tachikawa
authors.forename: Chiharu
authors.initials: C
authors.lastname: Sayama
authors.forename: Kiyotaka
authors.initials: K
authors.lastname: Saita
authors.forename: Masakatsu
authors.initials: M
authors.lastname: Tezuka
authors.forename: Ryoji
authors.initials: R
authors.lastname: Sawamura
mesh_terms: D002700:Chloramines / Q000737:chemistry*; D002713:Chlorine / Q000737:chemistry*; D003485:Cyanates / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D013696:Temperature; D014874:Water Pollutants, Chemical / Q000032:analysis; D018508:Water Purification
chemical_list: D002700:Chloramines; D003485:Cyanates; D014874:Water Pollutants, Chemical; D002713:Chlorine; C030816:chloramine; C005057:isocyanic acid