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Remediating Munitions‐Contaminated Soil with Zerovalent Iron and Cationic Surfactants
Author(s) -
Park J.,
Comfort S. D.,
Shea P. J.,
Machacek T. A.
Publication year - 2004
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2004.1305
Subject(s) - trinitrotoluene , solubility , cationic polymerization , chemistry , aqueous solution , environmental remediation , reactivity (psychology) , bromide , bentonite , inorganic chemistry , contamination , chemical engineering , explosive material , organic chemistry , medicine , ecology , alternative medicine , pathology , engineering , biology
Soils contaminated from military operations often contain mixtures of HMX (octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine), RDX (hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine), and TNT (2,4,6‐trinitrotoluene) rather than a single explosive. Differences among explosives in solubility and reactivity make developing a single remediation treatment difficult. When Fe 0 was used to treat a munitions‐contaminated soil, we observed high rates of destruction for RDX and TNT (98%) but not HMX. Our objective was to determine if HMX destruction by Fe 0 could be enhanced by increasing HMX solubility by physical (temperature) or chemical (surfactants) means. To determine electron acceptor preference, we treated RDX and HMX with Fe 0 in homogeneous solutions and binary mixtures. Increasing aqueous temperature (20 to 55°C) increased HMX solubility (2 to 22 mg L −1 ) but did not increase destruction by Fe 0 in a contaminated soil slurry that also contained RDX and TNT. Batch experiments using equal molar concentrations of RDX and HMX demonstrated that RDX was preferentially reduced over HMX by Fe 0 By testing various surfactants, we found that the cationic surfactants (HDTMA [hexadecyltrimethylammonium bromide], didecyl, and didodecyl) were most effective in increasing HMX concentration in solution. Didecyl and HDTMA were also found to be highly effective in facilitating the transformation of HMX by Fe 0 Using HDTMA or didecyl solutions (3%, w/v) containing solid‐phase HMX, we observed that 100% of the added HMX was transformed by Fe 0 in the didecyl matrix and 60% in the HDTMA matrix. These results indicate that cationic surfactants can increase HMX solubility and facilitate Fe 0 –mediated transformation kinetics but HMX destruction rates will be slowed when RDX is present.