Remediating RDX‐Contaminated Water and Soil Using Zero‐Valent Iron

Soil and water contaminated with RDX (hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine) pose a serious threat to the environment and human health. Our objective was to determine the potential for using zero‐valent iron (Fe0) to remediate RDX‐contaminated water and soil. Mixing an aqueous solution of 32 mg RDX L−1 (spiked with 14C‐labeled RDX) with 10 g Fe0 L−1 resulted in complete RDX destruction within 72 h. Nitroso derivatives of RDX accounted for approximately 26% of the RDX transformed during the first 24 h; these intermediates disappeared within 96 h and the remaining 14C products were water soluble and not strongly sorbed by iron surfaces. When RDX‐contaminated soil (30 mg RDX kg−1 spiked with 14C‐RDX) was treated with a single amendment of Fe0 (20 g kg−1 soil) in a static soil microcosm, more than 60% of the initial 14C‐RDX was recovered as 14CO2 after 112 d. Treating surface and subsurface soils containing 3600 mg RDX kg−1 with 50 g Fe0 kg−1 at a constant soil water content (0.35–0.40 kg H2O kg−1 soil) resulted in a 52% reduction in extractable RDX following 12 mo of static incubation. A second Fe0 addition at 12 mo further reduced the initial extractable RDX by 71% after 15 mo. These results support the use of zero‐valent iron for in situ remediation of RDX‐contaminated soil.