Formation Mechanisms of Nitro Products from Transformation of Aliphatic Amines by UV/Chlorine Treatment

Formation of nitrogenous disinfection byproducts fromaliphaticamines is a widespread concern owing to the serious health risks associatedwith them. However, the mechanisms of transforming aliphatic aminesand forming nitro products in the UV/chlorine process have rarelybeen discussed, which are investigated in this work. Initially, secondaryamines (R1R2NH) are transformed into secondaryorganic chloramines (R1R2NCl) via chlorination.Subsequently, radicals, such as HO center dot and Cl center dot, are foundto contribute predominantly to such transformations. The rate constantsat which HO center dot, Cl center dot, and Cl-2 (center dot-) react with R1R2NCl are (2.4-5.1) x10(9), (1.5-3.8) x 10(9), and (1.2-6.1)x 10(7) M-1 s(-1),respectively. Consequently, R1R2NCl are transformedinto primary amines (R1NH2/R2NH2) and chlorinated primary amines (R1NHCl/R2NHCl and R1NCl2/R2NCl2) by excess chlorine. Furthermore, primarily driven by UVphotolysis, chlorinated primary amines can be transformed into nitroalkaneswith conversion rates of similar to 10%. Dissolved oxygen and free chlorineplay crucial roles in forming nitroalkanes, and post-chlorinationcan further form chloronitroalkanes, such as trichloronitromethane(TCNM). Radicals are involved in forming TCNM in the UV/chlorine process.This study provides new insights into the mechanisms of transformingaliphatic amines and forming nitro products using the UV/chlorineprocess. This study elucidates the roles of radicalsin transformingsecondary amines and the mechanism of forming nitro products usingthe UV/chlorine advanced oxidation process.

Automated summary

This study provides new insights into the mechanisms of transforming aliphatic amines and forming nitro products using the UV/chlorine process.