Degradation of trinitroglycerin (TNG) using zero-valent iron nanoparticles/nanosilica SBA-15 composite (ZVINs/SBA-15).

Trinitroglycerin (TNG) is an industrial chemical mostly known for its clinical use in treating angina and manufacturing dynamite. The wide manufacture and application of TNG has led to contamination of vast areas of soil and water. The present study describes degradation of TNG with zero-valent iron nanoparticles (ZVINs) in water either present alone or stabilized on nanostructured silica SBA-15 (Santa Barbara Amorphous No. 15). The BET surface areas of ZVINs/SBA-15 (275.1 m2 g(-1)), as determined by nitrogen adsorption-desorption isotherms, was much larger than the non-stabilized ZVINs (82.0 m2 g(-1)). X-ray diffraction (XRD) showed that iron in both ZVINs and ZVINs/SBA-15 was present mostly in the α-Fe0 crystalline form considered responsible for TNG degradation. Transmission Electron Microscopy (TEM) showed that iron nanoparticles were well dispersed on the surface of the nanosilica support. Both ZVINs and ZVINs/SBA-15 degraded TNG (100%) in water to eventually produce glycerol and ammonium. The reaction followed pseudo-first-order kinetics and was faster with ZVINs/SBA-15 (k1 0.83 min(-1)) than with ZVINs (k1 0.228 min(-1)). The corresponding surface-area normalized rate constants, knorm, were 0.36 and 0.33 L h(-1) m(-2) for ZVINs/SBA-15 and ZVINs, respectively. The ZVINs/SBA-15 retained its original degradation efficiency of TNG after repeatedly reacting with fresh nitrate ester for five successive cycles. The rapid and efficient transformation of TNG with ZVINs/SBA-15, combined with excellent sustained reactivity, makes the nanometal an ideal choice for the clean up of water contaminated with TNG.

Degradation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) using zerovalent iron nanoparticles.

Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is a common contaminant of soil and water at military facilities. The present study describes degradation of RDX with zerovalent iron nanoparticles (ZVINs) in water in the presence or absence of a stabilizer additive such as carboxymethyl cellulose (CMC) or poly(acrylic acid) (PAA). The rates of RDX degradation in solution followed this order CMC-ZVINs > PAA-ZVINs > ZVINs with k1 values of 0.816 +/- 0.067, 0.082 +/- 0.002, and 0.019 +/- 0.002 min(-1), respectively. The disappearance of RDX was accompanied by the formation of formaldehyde, nitrogen, nitrite, ammonium, nitrous oxide, and hydrazine by the intermediary formation of methylenedinitramine (MEDINA), MNX (hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine), DNX (hexahydro-1,3-dinitroso-5-nitro-1,3,5-triazine), TNX (hexahydro-1,3,5-trinitroso-1,3,5-triazine). When either of the reduced RDX products (MNX or TNX) was treated with ZVINs we observed nitrite (from MNX only), NO (from TNX only), N2O, NH4+, NH2NH2 and HCHO. In the case of TNX we observed a new key product that we tentatively identified as 1,3-dinitroso-5-hydro-1,3,5-triazacyclo-hexane. However, we were unable to detect the equivalent denitrohydrogenated product of RDX and MNX degradation. Finally, during MNX degradation we detected a new intermediate identified as N-nitroso-methylenenitramine (ONNHCH2NHNO2), the equivalentof methylenedinitramine formed upon denitration of RDX. Experimental evidence gathered thus far suggested that ZVINs degraded RDX and MNX via initial denitration and sequential reduction to the corresponding nitroso derivatives prior to completed decomposition but degraded TNX exclusively via initial cleavage of the N-NO bond(s).

A morphological investigation of soot produced by the detonation of munitions.

The morphology of three different detonation soot samples along with other common soot materials such as carbon black, diesel soot and chimney soot was studied by elemental and proximate analysis, X-ray diffraction and electron microscopy. The goal of this study was to better define the morphology of the detonation soot in order to better assess the interactions of this type of soot with explosive residues. The detonation soot samples were obtained by the detonation of artillery 155mm projectiles filled with either pure TNT (2,4,6-trinitrotoluene) or composition B, a military explosive based on a mixture of TNT and RDX (trimethylentrinitramine). The carbon content of the soot samples varied considerably depending on the feedstock composition. Detonation soot contains less carbon and more nitrogen than the other carbonaceous samples studied, due to the molecular structure of the energetic materials detonated such as TNT and RDX. The ash concentration was higher for detonation soot samples due to the high metal content coming from the projectiles shell and to the soil contamination which occurred during the detonation. By X-ray diffraction, diamond and graphite were found to be the major crystalline carbon forms in the detonation soot. Two electron microscopy techniques were used in this study to visualise the primary particles and to try to explain the formation mechanism of detonation soot samples.