This thesis is divided into two parts. The first part describes the abiotic destruction of RDX in the presence of black carbon and hydrogen sulfide. The second part investigates the role of quaternary amines as contained in anion exchange resins, flocculation aides, and personal care products as nitrosamine precursors.
We report that RDX was rapidly destroyed by sulfides in the presence of black carbon, forming nitrite and formaldehyde. Although at least 1.2 mM sulfides were needed for the reaction to proceed, these concentrations are found in certain marine sediments, together with black carbon. Compared with in-situ remediation techniques, such as bioremediation and zero-valent iron cutoff trenches, which often generate nitrosated byproducts, this in-situ, abiotic remediation technique may be an attractive alternative. Particularly for marine bombing ranges featuring unexploded ordinance (UXO), the ability of this technique to avoid dangerous excavations is desirable.
Nitrosamines, such as N-nitrosodimethylamine (NDMA), have been noted to form during disinfection of drinking waters, particularly during chloramine disinfection. Nitrosamines have been an issue particularly for treatment facilities using quaternary amine-based polymers such as anion exchange resins and coagulants (poly(diallyldimethylammonium chloride)). Nitrosamine formation has also been associated with wastewater-impacted water supplies. Although the specific precursors within municipal wastewater effluents responsible for the NDMA formation have not been identified, the association of NDMA precursors with municipal wastewater effluents suggests a possible role for consumer products. Quaternary amines are significant constituents of consumer products, including shampoos, detergents and fabric softeners. We have found that low nitrosamine yields from quaternary amines can arise from quaternary amines themselves, not just lower order amine impurities. Polymeric and benzylated quaternary amines were more potent precursors than monomeric quaternary alkylamines. Pre-treatment of quaternary amines with ozone or free chlorine, previously demonstrated to deactivate secondary and tertiary amine precursors for nitrosamines, did not significantly reduce nitrosamine formation from quaternary amines. The nitrosamine formation pathway is unclear but experiments indicated that transformation of quaternary amines to lower order amine precursors of nitrosamines via a Hoffman elimination was not involved. Experiments suggest that the pathway may involve degradation of quaternary amines by amidogen or chloramino radicals formed from chloramines.
|School Location:||United States -- Connecticut|
|Source:||DAI-B 71/02, Dissertation Abstracts International|
|Subjects:||Organic chemistry, Environmental science, Environmental engineering|
|Keywords:||Abiotic destruction, Amines, Black carbon, Marine sediments, Nitrosamine, RDX|
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