University of Nebraska, Lincoln, NE, 68583-0915, 402-472-1503
Poor waste management practices at munitions production facilities have contaminated surrounding soil and water with hazardous materials, particularly TNT (2,4,6-trinitrotoluene) and cyclonite (RDX, hexahydro-1,3,5-trinitro-1,3,5-triazine). Remediating these contaminated sites is necessary to ensure public safety. Soil cleanup by the conventional technique of incineration, however, is very expensive and often unacceptable to the public. Cost-effective and environmentally acceptable remediation treatments are needed. We determined the efficiency of an abiotic oxidative treatment (Fenton oxidation) and a reduction treatment (metal reduction) for remediating RDX-contaminated soil. Oxidation experiments evaluated the effects of H2O2, Fe2+, and initial RDX concentrations, UV light, and contaminated soil extracts on rates of RDX transformation and mineralization. Treating an aqueous solution of 20 mg 14C-RDX L-1 in the dark with Fenton reagent (1% H2O2 and 80 mg Fe2+ L-1) resulted in complete removal of RDX within 24 h. This coincided with 70 to 85% RDX mineralization. Similar results were found with aqueous extracts of RDX-contaminated soil. UV light enhanced both RDX transformation and mineralization rates. The metal reduction experiments were performed with elemental Zn or Fe in aqueous solutions of RDX, contaminated soil extracts and soil-slurries. Treating 40 mg L-1 14C-RDX with Zn (5:1 solution:metal ratio) resulted in complete destruction of RDX within 2 h. Higher transformation rates were generally observed at lower pH. Iron was also effective in reducing RDX in solution. Mineralization of RDX by Zn reduction was not observed. The metal reduction treatment was also effective in removing RDX from contaminated-soil extracts and soil-slurries. These results indicate that both abiotic oxidative and reductive treatments can effectively remediate RDX-contaminated soil and water.
munitions, RDX, cyclonite, Fenton oxidation, remediation, metal reduction
This paper is from the Proceedings of the 10th Annual Conference on Hazardous Waste Research 1995, published in hard copy and on the Web by the Great Plains/Rocky Mountain Hazardous Substance Research Center.