Chloramines (NHxCly) are often utilized as disinfectants in drinking water as they are a desirable alternative to free chlorine use due to lower production of harmful disinfectant by-products. Chloramines, notably monochloramine (NH2Cl ), are generated towards the final stages of their treatment process in order to prevent fouling of the reverse osmosis (RO) membranes. However, these chloramines also pass through the RO membrane to enter AOP systems. The reactivity of chloramines in AOP systems is of major concern, as they can lower the AOP efficiencies through direct UV-light absorption as well as thermally producing halogenated disinfection byproducts. The focus of this study was on the thermal chemistry between nitrogenous organic compounds found in waste water systems and NH2Cl. The reactions of NH2Cl with a suite of amino acids and nitrogenous bases were quantified using UV-visible spectroscopy in order to determine their absolute second order rate constants. To further understand the chemistry in these systems, the pH and temperature dependence of these reactions was also investigated. The temperature dependent kinetics for alanine reaction with NH2Cl gave an Arrhenius activation energy of 6.00 ± 0.06 kJ mol-1. Finally, by utilizing 15N labeled NMR we will be able to confirm the presence or absence of any chlorinated by-products at the end of these reactions. Additional compounds are being studied in order to obtain and understand the correlation between size and structure with the chemistry of these reactions.

Kinetic study of thermal monochloramine reactions with nitrogenous compounds

253rd National Meeting (2017)

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