Nitroglycerin (NG), otherwise known as trinitroglycerin, is a compound with various uses including as a tool for mining and demolition, an ingredient for propellants and gunpowder, and as an active ingredient in medication. Thus, nitroglycerin is a common constituent in untreated wastewater effluents from NG manufacturers and pharmaceutical industries. Effective treatment of NG in such wastewater steams can be achieved by chemical reduction. Typical reductive reagents are zero valent metals (ZVMs), where zero valent iron (ZVI) is typically the state-of-the-practice technology for waste management. On the other hand, bimetal reagents are essentially enhanced ZVM systems in which the reduction process is catalyzed with the addition of a more cathodic metal, which creates an electrochemical cell. In this work, the degradation of NG was studied with a magnesium-based bimetal reagent, Mg/Cu. NG degraded via sequential denitration: initial denitration formed 1,2-dinitroglycerin and 1,3-dinitroglycerin isomers followed by 1-monoglycerin and 2-monoglycerin isomers, ultimately leading to a benign final product glycerol. The released nitrite underwent reduction in parallel leading to the formation of ammonia and nitrogen gas. Degradation kinetics were examined using a pseudo-first-order reaction model. Critical process parameters studied included bimetal reagent dose, base metal Mg to catalytic metal Cu ratio, initial pH and matrix effects (i.e. effect of solvents and wastewater matrix). The impact of these variables were also studied in pure nitrate and nitrite solutions. Furthermore, preliminary density-functional theory (DFT) calculations were performed to theoretically assess degradation pathways. Toxicological assessments of NG and NG byproducts were conducted, utilizing commercially purchased NG byproducts dissolved in water and solvent as a surrogate to untreated wastewater effluent, which indicated potential reduction in untreated effluent toxicity.

Denitration of nitroglycerin (NG) and nitrogen transformation via enhanced reduction using a magnesium-based bimetallic reagent

ACS Fall 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.