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WP1 Restoration of Contaminated Sites
(415) Remediating munitions–contaminated soil with zerovalent iron and cationic surfactants.
Park, J.1, Comfort, S.1, Shea, P.1, 1 University of Nebraska-Lincoln, Lincoln, NE, USA
ABSTRACT- Differences in solubility and reactivity among high explosives (HE) make remediation of contaminated soils difficult. When Fe0 was used to treat soils containing multiple energetics, we observed high rates of RDX and TNT destruction (98%) but not HMX. Batch experiments showed that RDX was preferentially reduced over HMX during Fe0 treatment. Our objective was to enhance HMX destruction rate by using cationic surfactants to increase HMX solubility and reactivity with Fe0. HDTMA, didodecyldimethyl ammonium bromide, and didecyldimethyl ammonium bromide increased HMX solubility in an aqueous solution and in a soil slurry. Didecyl was superior in removing HE with Fe0 in a highly contaminated soil slurry. Batch experiments were conducted with Fe 0 (3–4% w/v) and varying didecyl concentration to determine optimum HE removal in soil slurries. Results showed that 4% (w/v) Fe0 + 2% (w/v) didecyl removed all of the solid–phase HE without increasing HE solubility. The equilibrium concentration of didecyl was near its critical micelle concentration (CMC) when 2% didecyl was added to the soil slurry. This indicates that the effect of didecyl on HE destruction is not limited to increasing HE solubility. We also observed that didecyl affected corrosion and oxide formation on the iron surface. Pretreating Fe0 with didecyl was superior to Fe0 alone or Fe0 + didecyl in removing HMX from aqueous solution but was less effective when solid–phase HMX was present. Reseeding experiments in which HMX was added back to the batch reactor to mimic dissolution of solid–phase HMX showed that Fe0 pretreated with didecyl was highly reactive but reaction rates were not sustainable. These results indicate that didecyl enhances destruction by Fe0 and concentrations below its CMC are most effective.
Key words: RDX, HMX, iron, surfactant
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