title: Pilot-scale treatment of RDX-contaminated soil with zerovalent iron.
abstract: Soils in Technical Area 16 at Los Alamos National Laboratory (LANL) are severely contaminated from past explosives testing and research. Our objective was to conduct laboratory and pilot-scale experiments to determine if zerovalent iron (Fe(0)) could effectively transform RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) in two LANL soils that differed in physicochemical properties (Soils A and B). Laboratory tests indicated that Soil A was highly alkaline and needed to be acidified [with H2SO4, Al2(SO4)3, or CH3COOH] before Fe(0) could transform RDX. Pilot-scale experiments were performed by mixing Fe(0) and contaminated soil (70 kg), and acidifying amendments with a high-speed mixer that was a one-sixth replica of a field-scale unit. Soils were kept unsaturated (soil water content = 0.30-0.34 kg kg(-1)) and sampled with time (0-120 d). While adding CH3COOH improved the effectiveness of Fe(0) to remove RDX in Soil A (98% destruction), CH3COOH had a negative effect in Soil B. We believe that this difference is a result of high concentrations of organic matter and Ba. Adding CH3COOH to Soil B lowered pH and facilitated Ba release from BaSO4 or BaCO3, which decreased Fe(0) performance by promoting flocculation of humic material on the iron. Despite problems encountered with CH3COOH, pilot-scale treatment of Soil B (12 100 mg RDX kg(-1)) with Fe(0) or Fe(0) + Al2(SO4)3 showed high RDX destruction (96-98%). This indicates that RDX-contaminated soil can be remediated at the field scale with Fe(0) and soil-specific problems (i.e., alkalinity, high organic matter or Ba) can be overcome by adjustments to the Fe(0) treatment.
authors.affiliation: School of Natural Resources, University of Nebraska-Lincoln, 362 Plant Sciences, Lincoln, NE 68583-0915, USA.
authors.forename: S D
authors.initials: SD
authors.lastname: Comfort
authors.forename: P J
authors.initials: PJ
authors.lastname: Shea
authors.forename: T A
authors.initials: TA
authors.lastname: Machacek
authors.forename: T
authors.initials: T
authors.lastname: Satapanajaru
mesh_terms: D004787:Environmental Pollution / Q000517:prevention & control*; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry*; D012378:Rodenticides / Q000737:chemistry*; D012987:Soil; D012989:Soil Pollutants / Q000302:isolation & purification*; D014227:Triazines / Q000737:chemistry*
chemical_list: D012378:Rodenticides; D012987:Soil; D012989:Soil Pollutants; D014227:Triazines; D007501:Iron; C009160:cyclonite