The possible reduction pathways of 2,4,6-trinitrotoluene (TNT) by sulfide under simulated anaerobic conditions

To predict the final fate of 2,4,6-trinitrotoluene (TNT) and its intermediates in an anaerobic fermentative solution containing reduced sulfur species and to provide a basis for the adoption of remediation methods, we investigated the pathways of TNT (TNT₀ = 50 mg/L) reduction by Na₂S at 30 ± 1 °C in an acetic acid–sodium bicarbonate buffer. Liquid chromatography/mass spectrometry (LC/MS) was used to identify TNT metabolites at different reaction times. The law of growth and decline of TNT and its metabolites was determined with time. The LC/MS result, combined with the physicochemical characteristics of related products and information from the literature, indicated possible TNT conversion pathways. Sulfide can initiate both nitroreduction and denitration of TNT simultaneously. Nitroreduction led to the accumulation of primary intermediates 4-hydroxylaminodinitrotoluene and 4-aminodinitrotoluene, whereas denitration resulted in the production of unidentified substances with molecular weight less than that of TNT. Also, polyreaction between the above intermediates formed many unidentified substances. Humification was concluded to be the best choice for remediation of TNT-contaminated soil and water due to the formation of intermediates with stable, intact aromatic systems. However, the denitration pathway of TNT offered the possibility of mineralization.