Subcritical (hot/liquid) water was used in a simple static (non-flowing) vessel to treat three soils from former defense sites which were contaminated with the explosives TNT (12 wt.%), or RDX (0.62 wt.%) and HMX (0.16 wt. %). Significant degradation of RDX began at 100 C, and at 125 C for TNT and HMX, with the bulk of the undergraded explosives remaining in the soil rather than in the water phase. Based on HPLC/UV analysis, intermediate degradation products formed, but quickly degraded at < 250 C. Remediations performed using a generator-powered mobile pilot-scale unit (4 to 6 kg soil) with 4-L of water at 275 C for 1 h of real soils resulted in > 99.9% destrcution of TNT and HMX, and > 99.5% desstruction of RDX. None of the mutagenic nitroso derivatives of RDX and HMX were formed. “Microtox” acute toxicity tests with Vibrio fischeri showed no significant (compared to background) residual toxicity in either the process wastewaters or leachates from the treated soils. The operation is closed-loop (no air or water emissions), and process water can be recycled without treatment. Initial cost analysis indicates that the process should be competitive with other approaches such as bioremediation.

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