Destruction of 2,4,6‐Trinitrotoluene by Fenton Oxidation

Abstract

AbstractPast disposal practices at munitions production facilities have generated numerous acres of 2,4,6‐trinitrotoluene (TNT)‐contaminated soil. We determined the potential of the Fenton reagent (Fe2+ and H2O2) to remediate TNT contamination in water, aqueous extracts of contaminated soil, and soil‐water slurries. The effects of H2O2 and Fe2+ concentrations, solution pH, temperature, and initial TNT concentration on transformation and mineralization rates were evaluated. Treating an aqueous TNT solution (70 mg TNT L−1) with Fenton reagent (1% H2O2, 80 mg Fe2+ L−1) in the dark resulted in 100% destruction of TNT within 24 h. This coincided with 40% mineralization. Subsequent exposure to light resulted in >90% mineralization. We observed generation of 2,4,6‐trinitrobenzoic acid and 1,3,5‐trinitrobenzene within 15 min following Fenton oxidation of TNT. This indicates that initial TNT destruction likely occurs by methyl group oxidation and decarboxylation. Subsequent transformations involve nitro moiety removal with ring hydroxylation and cleavage, as evidenced by the stoichiometric recovery of TNT‐nitrogen as NO−3 and production of oxalic acid as the primary C‐containing end product. Upon exposure to light, Fe(II) was regenerated and the oxalate produced from 14C‐TNT oxidation disappeared; this coincided with a decrease in solution 14C activity. Similar observations were made when 14C‐oxalic acid was the starting substrate. Fenton oxidation was also effective in destroying TNT in aqueous extracts of contaminated soil and soil‐water slurries. Experimental data provide evidence that the Fenton reagent can effectively remediate TNT‐contaminated water and soil.