Reduction of Nitroglycerin with Elemental Iron:  Pathway, Kinetics, and Mechanisms

Abstract

Nitroglycerin (NG) is a nitrate ester used in dynamites, propellants, and medicines and is therefore a common constituent in propellant-manufacturing and pharmaceutical wastewaters. In this study we investigated the reduction of NG with cast iron as a potential treatment method. NG was reduced stepwise to glycerol via 1,2- and 1,3-dinitroglycerins (DNGs) and 1- and 2-mononitroglycerins (MNGs). Nitrite was released in each reduction step and was further reduced to NH4+. Adsorption of NG and its reduction products to cast iron was minimal. A reaction pathway and a kinetic model for NG reduction with cast iron were proposed. The estimated surface area-normalized reaction rate constants for NG and NO2- were (1.65 +/- 0.30) x 10(-2) (L x m(-2) x h(-1)) and (0.78 +/- 0.09) x 10(-2) (L x m(-2) x h(-1)), respectively. Experiments using dialysis cell with iron and a graphite sheet showed that reduction of NG to glycerol can be mediated by graphite. However, reduction of NO2- mediated by graphite was very slow. NG and NO2- were also found to reduce to glycerol and NH4+ by Fe2+ in the presence of magnetite but not by aqueous Fe2+ or magnetite alone. These results indicate that in a cast iron-water system NG may be reduced via multiple mechanisms involving different reaction sites, whereas nitrite is reduced mainly by iron and/ or adsorbed Fe2+. The study demonstrates that iron can rapidly reduce NG to innocuous and biodegradable end products and represents a new approach to treat NG-containing wastewaters.

Microwave-assisted hydrolysis of nitroglycerin (NG) under mild alkaline conditions: New insight into the degradation pathway

“…This is in line with the observation made earlier by Capellos et al (1984) on the absence of the partially denitrated DNGs and MNGs from NG hydrolysis (pH 12). Likewise we did not observe the fully denitrated NG product glycerol which is known to be the final product of NG reaction with Fe(0) (Oh et al, 2004) and frequently found during biodegradation of the nitrate ester (Wendt et al, 1978;Servent et al, 1991;Meng et al, 1995;Marshall and White, 2001). When glycerol was allowed to react under the same conditions (pH 9) the chemical stayed intact indicating that glycerol is not a product of NG hydrolysis.…”

“…When nitrite was microwave heated at pH 9 the anion stayed intact indicating that the anion did not reduce to ammonia as observed during treatment of NG with Fe(0) where the three -NO 2 groups in the nitrate ester reduced to ammonia (Oh et al, 2004). The same nitrite control did not give nitrate during microwave-assisted hydrolysis, indicating that nitrite and nitrate originated from NG independently during NG hydrolysis.…”

“…Presently NG can be found in waste streams and soils of munitions manufacturing facilities and in areas adjacent to pharmaceutical plants. High concentrations of NG were found in soil at Canadian Forces training areas (Jenkins et al, 2008) and in wastewaters of US Badger Army ammunition plant (Barabo, WI, 180 mg L À1 ) and Radford Army ammunition plant (Radford, VA, 300-600 mg L À1 ) ( Oh et al, 2004). Being toxic (Pesari and Grasso, 1993) NG must thus be removed from contaminated wastewater before it reaches soil and ground water.…”

Biochar‐mediated reductive transformation of nitro herbicides and explosives

“…Similar to GAC [34,35], biochar has been proposed as an adsorbent to decrease the concentrations and bioavailability of organic and metallic pollutants [17,36,37]. The present study further suggests that biochar may also be applied to promote the degradation of organic compounds including agrochemicals, explosives, and potentially other nitrogenous compounds such as azo dyes [38] and nitrate esters [26,39]. For example, in shooting ranges, proving grounds, and other military installations where soil and groundwater are contaminated with explosives, biochar may be used to accelerate the breakdown of these compounds.…”

Phytotoxicity and uptake of nitroglycerin in a natural sandy loam soil

“…Other physico-chemical remediation technologies for the removal of NG from the environment include oxidation, composting, phytoremediation, biodegradation (Pandey et al, 2007), iron reduction (Oh et al, 2004), and sorption using nano-structured silica based materials (Saad et al, 2010). However, none of these technologies are efficacious in removing energetic residues from soil, which can pose exposure risks for human and ecological receptors, such as terrestrial plants.…”