Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is known to undergo reduction mediated by ferrous iron in the presence of minerals, including magnetite. Idealized laboratory conditions may not provide representative reaction kinetics or pathways compared to field conditions. The effects of magnetite mineral morphology, the aquifer material matrix, the presence of aqueous Fe(II), and the buffer identity on RDX reduction kinetics and intermediate formation are investigated in this work. Reactions in bicarbonate buffer were substantially slower than those performed in 3-(N-morpholino)propanesulfonic acid (MOPS) buffer, and the presence of quartz and clays in magnetite-containing aquifer material resulted in slower reaction kinetics and production of additional iron oxide phases. Buffer identity also changed the rate controlling step and reaction product distribution. Conditions as close to those expected in field systems are necessary to evaluate the reaction rates and pathways of RDX in reduced groundwater systems.
Bibliographical noteFunding Information:
We thank Michael LeFrancois and Lindsey Kenyon (Arcadis), Mary Lee (Minnesota Army National Guard), Roger Walton (U.S. Army Environmental Command), and Amy Hadiaris (Minnesota Pollution Control Agency) for assistance with TCAAP aquifer material collection. Drilling was performed under the Army's Installation Restoration Program (IRP), a subset of the Defense Environmental Restoration Program. We also thank Thomas Webber (University of Minnesota) for SEM imaging and EDS mapping and R. Lee Penn for access to the XRD. This work was supported by the Strategic Environmental Research and Development Program (SERDP) as part of project ER 2618. Parts of this work were carried out in the Characterization Facility, University of Minnesota, which receives partial support from the National Science Foundation through the MRSEC program. Appendix A
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- Iron oxides
- Natural attenuation