TNT and RDX degradation and extraction from contaminated soil using subcritical water

• Published in: Chemosphere (Oxford) Vol. 119; pp. 1148 - 1152
• Main Authors: Islam, Mohammad Nazrul, Shin, Moon-Su, Jo, Young-Tae, Park, Jeong-Hun
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.01.2015
• Subjects: Chromatography, High Pressure Liquid; Chromatography, Ion Exchange; Contamination; Continuous flow; Degradation; Environmental Restoration and Remediation - methods; Explosive Agents - chemistry; Explosives; Extraction; Molecular Structure; Particle Size; RDX; Removal efficiency; Soil (material); Soil - chemistry; Soil Pollutants - analysis; Soil Pollutants - chemistry; Soil Pollutants - isolation & purification; Subcritical water; Temperature; TNT; Triazines - analysis; Triazines - chemistry; Triazines - isolation & purification; Trinitrotoluene - analysis; Trinitrotoluene - chemistry; Trinitrotoluene - isolation & purification; Water - chemistry; Water temperature; Subcritical water; Degradation; TNT; Removal efficiency; RDX
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2014.09.101

•SCWE process for the remediation of explosive contaminated soils was introduced.•The removal and degradation efficiency of TNT and RDX were presented.•1.1% of non-degraded TNT and 1.5% of RDX were found in the extracts at 175°C.•Aspects associated with explosives degradation in subcritical water were discussed. The use of explosives either for industrial or military operations have resulted in the environmental pollution, poses ecological and health hazard. In this work, a subcritical water extraction (SCWE) process at laboratory scale was used at varying water temperature (100–175°C) and flow rate (0.5–1.5mLmin−1), to treat 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) contaminated soil, to reveal information with respect to the explosives removal (based on the analyses of soil residue after extraction), and degradation performance (based on the analyses of water extracts) of this process. Continuous flow subcritical water has been considered on removal of explosives to avoid the repartitioning of non-degraded compounds to the soil upon cooling which usually occurs in the batch system. In the SCWE experiments, near complete degradation of both TNT and RDX was observed at 175°C based on analysis of water extracts and soil. Test results also indicated that TNT removal of >99% and a complete RDX removal were achieved by this process, when the operating conditions were 1mLmin−1, and treatment time of 20min, after the temperature reached 175°C. HPLC–UV and ion chromatography analysis confirmed that the explosives underwent for degradation. The low concentration of explosives found in the process wastewater indicates that water recycling may be viable, to treat additional soil. Our results have shown in the remediation of explosives contaminated soil, the effectiveness of the continuous flow SCWE process.