The Fate of Nitroaromatic (TNT) and Nitramine (RDX and HMX) Explosive Residues in the Presence of Pure Metal Oxides

Packed beds of six different, granular, pure, metal oxide phases were loaded with explosives through controlled proximal detonation of Composition B. Composition B contains the commonly used explosives 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro 1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX). The metal oxides examined include magnetite (Fe3O4; Fe[II] and 2Fe[III]), two different hematites (Fe2O3; Fe[III]), manganese oxide (MnO; Mn[II]), pyrolusite (MnO2; Mn[IV]), and aluminum oxide (Al2O3; Al[III]). These metal oxides were selected because of their potential to promote reductive transformation of explosive compounds. Following detonation subsamples of surficial and bulk metal oxides were mixed in aqueous batches using ultraclean water and monitored for TNT, RDX, HMX, 2ADNT, and 4ADNT concentrations for 149 days. Our results suggest that, even with highly controlled detonations, the explosive residues are heterogeneously loaded to the pure mineral phases. A logarithmic equation provides the best-fit description of the temporal trends in explosive analyte concentrations in the aqueous batches. RDX behaves more conservatively than TNT but does exhibit some loss from solution over time. Batches containing detonated magnetite and manganese oxide yielded the greatest loss of TNT, RDX, and HMX from solution and the highest 2ADNT and 4ADNT concentrations in the mineral material at the end of the batch experiments. These two batches also yielded the highest concentrations of the nitroso transformation products of RDX. This result suggests that reduced valence Fe and Mn metals promote explosive compound transformation, likely serving as a source of electrons for reductive transformation.