Volatile organic chloramines formation during ClO2 treatment

Volatile organic chloramines are reported as the disinfection byproducts during chlorination or chloramination. However, ClO2, as an important alternative disinfectant for chlorine, was not considered to produce halogenated amines. In the present work, volatile organic chloramines including (CH3)(2)NCl and CH3NCl2 were found to be generated during the reaction of ClO2 and the dye pollutants. (CH3)(2)NCl was the dominant volatile DBP to result from ClO2 treated all four dye pollutants including Methyl Orange, Methyl Red, Methylene Blue and Malachite Green, with molar yields ranging from 2.6% to 38.5% at a ClO2 to precursor (ClO2/P) molar ratio of 10. HOCl was identified and proved to be the reactive species for the formation of (CH3)(2)NCl, which implied (CH3)(2)NCl was transformed by a combined oxidation of ClO2 and hypochlorous acid. (CH3)(2)NCl concentrations in the ppb range were observed when real water samples were treated by ClO2 in the presence of the dye pollutants. The results suggest that these azo dyes are one of the significant precursors for the formation of HOCl during ClO2 treatment and that organic chloramines should be considered in ClO2 disinfection chemistry and water treatment. (C) 2020 Published by Elsevier B.V. on behalf of The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences.