Removal of TNT and RDX from water and soil using iron metal

Contaminated water and soil at active or abandoned munitions plants is a serious problem since these compounds pose risks to human health and can be toxic to aquatic and terrestrial life. Our objective was to determine if zero-valent iron (Fe⁰) could be used to promote remediation of water and soil contaminated with 2,4,6-trinitrotoluene (TNT) and hexahyro-1,3,5-trinitro-1,3,5-triazine (RDX). As little as 1% Fe⁰ (w/v) removed 70 mg TNT litre^-1 from aqueous solution within 8 h and removed 32 mg RDX litre^-1 within 96 h. Treating slurries (1:5 soil:water) of highly, contaminated soil (5200 mg TNT and 6400 mg RDX kg^-1 soil) from the former Nebraska Ordnance Plant (NOP) with 10% Fe⁰ (w/w soil) reduced CH₃CN-extractable TNT and RDX concentrations below USEPA remediation goals (17.2 mg TNT and 5.8 mg RDX kg^-1). Sequential treatment of a TNT-contaminated solution (70 mg TNT litre^-1 spiked with ¹⁴C-TNT) with Fe⁰ (5% w/v) followed by H₂O₂ 1% v/v) completely destroyed TNT and removed about 94% of the ¹⁴C from solution, 48% of which was mineralized to ¹⁴CO₂ within 8 h. Fe⁰-treated TNT also was more susceptible to biological mineralization. Our observations indicate that Fe⁰ alone, Fe⁰ followed by H₂O₂, or Fe⁰ in combination with biotic treatment can be used for effective remediation of munitions-contaminated water and soil.