Wastewater generated from the production of energetic materials, before treatment and permitted release may contain explosive compounds such as nitroguanidine (NQ) and 2,4-dinitroanisole (DNAN), both classified as insensitive munitions (IMs). Treatment of IM wastewater using zero valent metal or bimetal technology have been well-studied, particularly iron-based reagents. However, they may be limited to low pH conditions. Magnesium-based reagents can be advantageous, because they do not require low pH conditions and offer greater reduction potential. In this work, the reductive degradation of pure NQ and DNAN in water by a Mg/Cu bimetal was studied. Treatment of NQ produced two parallel reactions: nitroreduction led to the formation of aminoguanidine, or reduction of the encompassing nitramine group resulted in N-N bond cleavage to form guanidine. Additional byproducts identified were urea, cyanamide, and formamide, which were likely formed by hydrolysis of guanidine due to the alkaline pH (10-10.5) produced by the reaction of Mg and water forming Mg(OH)<sub>2</sub>. Aminoguanidine is the undesired product due to its relative toxicity, and its yield increased with lowered pH. Results of the impact of reaction conditions on the selectivity of NQ degradation products will be shown. Conversely, treatment of DNAN resulted in subsequent nitroreduction: one nitro group was reduced (ortho or para) to form 2-amino-4-nitroanisole or 4-amino-2-nitroanisole (2-ANAN or 4-ANAN), and subsequent reduction of the other nitro group formed 2,4-diaminoanisole (DAAN). DAAN was the final reduced product; however, this compound is not stable in oxygenated environments. Treatment of DAAN with Mg/Cu with supplementation of dissolved oxygen resulted in DAAN removal. Dissolved oxygen also impacted fate and mass balance of DAAN, (i.e. amount of contaminant adsorbed to bimetal reagent vs. that present in liquid phase).

Bimetal treatment of insensitive munitions 2,4-dinitroanisole (DNAN) and nitroguanidine (NQ)

2019 Fall National Meeting

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