Ozone Promotes Chloropicrin Formation by Oxidizing Amines to Nitro Compounds
Daniel L McCurry1, Amanda N Quay1, William A Mitch1
1Department of Civil and Environmental Engineering, Stanford University , Stanford, California 94305, United States.
Environmental Science & Technology
|January 12, 2016
Summary
Primary and secondary amines are key precursors to chloropicrin during ozonation and chlorination water treatment. Ozonation converts amines to nitromethane, which chlorination then transforms into chloropicrin.
Area of Science:
- Environmental Chemistry
- Water Treatment Chemistry
Background:
- Chloropicrin formation during ozonation followed by chlorination is poorly understood.
- The specific reaction pathways and precursor compounds remain largely uncharacterized.
Purpose of the Study:
- To elucidate the reaction pathway and identify precursors for chloropicrin formation during ozonation and chlorination.
- To investigate the role of different amine types (primary, secondary, tertiary) in chloropicrin synthesis.
Main Methods:
- Experiments involving methylamine, other primary amines, secondary amines, and tertiary amines subjected to ozonation and subsequent chlorination.
- Analysis of natural water samples with derivatization techniques to identify amine precursors.
- Investigating the influence of hydroxyl radical scavengers on product yields.
Main Results:
- Ozonation of methylamine yielded nitromethane, which chlorination converted to chloropicrin (∼50% yield).
- Primary and secondary amines were identified as dominant chloropicrin precursors in natural waters.
- Lysine chlorination produced dichloronitrolysine, a chloropicrin analogue, with yields influenced by radical scavenger concentrations.
Conclusions:
- Primary and secondary amines are significant precursors to chloropicrin formation in ozonation-chlorination processes.
- Halonitroalkane analogues like dichloronitrolysine may also form and their prevalence is linked to radical scavenging conditions.
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