Reductive transformation of 2,4,6-trinitrotoluene, hexahydro-1,3,5-trinitro-1,3,5-triazine, and nitroglycerin by pyrite and magnetite

Reductive transformation of 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and nitroglycerin (NG) by pyrite (FeS2) and magnetite (Fe3O4) was investigated to determine the role of Fe(II)-bearing minerals on the fate of toxic explosives in Fe/S-rich natural environment. Results from batch experiments showed that 65% of TNT and 45% of RDX were transformed from solution in the presence of pyrite under pH 7.4 buffered conditions within 32 days. Without a buffered solution, transformation of TNT and RDX decreased. NG was continuously and rapidly transformed by pyrite under both conditions. Complete removal of NG was achieved in 32 days under buffered conditions. NH4+ was identified as a reduction product for RDX and NG in the pyrite-water system. Reductive transformation of RDX and NG by magnetite was slower than that by pyrite. The results suggest that abiotic transformation of the explosives by pyrite and magnetite may be considered when determining the fate of explosives in Fe/S-rich subsurface environments.