Reduction of nitroglycerin with elemental iron: pathway, kinetics, and mechanisms.
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.
Oh
Seok-Young
SY
Department of Civil and Environmental Engineering, University of Delaware, Newark, Delaware 19716, USA.
Cha
Daniel K
DK
Kim
Byung J
BJ
Chiu
Pei C
PC
D000327:Adsorption; D002849:Chromatography, Gas; D002851:Chromatography, High Pressure Liquid; D052203:Ferrosoferric Oxide; D006108:Graphite; D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D008956:Models, Chemical; D005996:Nitroglycerin / Q000737:chemistry*; D010084:Oxidation-Reduction; D010087:Oxides; D014865:Waste Disposal, Fluid / Q000379:methods*
D010087:Oxides; D006108:Graphite; D007501:Iron; D005996:Nitroglycerin; D052203:Ferrosoferric Oxide