Mineralogy and buffer identity effects on RDX kinetics and intermediates during reaction with natural and synthetic magnetite

Jennifer H. Strehlau; Matthew J. Berens; William A. Arnold

doi:10.1016/j.chemosphere.2018.09.139

Mineralogy and buffer identity effects on RDX kinetics and intermediates during reaction with natural and synthetic magnetite

Jennifer H. Strehlau, Matthew J. Berens, William A. Arnold

Research output: Contribution to journal › Article › peer-review

5 Scopus citations

Abstract

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.

Original language	English
Pages (from-to)	602-609
Number of pages	8
Journal	Chemosphere
Volume	213
DOIs	https://doi.org/10.1016/j.chemosphere.2018.09.139
State	Published - Dec 2018
Externally published	Yes

Funding

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

Funders	Funder number
National Science Foundation
University of Minnesota
Strategic Environmental Research and Development Program	ER 2618

Keywords

Explosives
Groundwater
Iron oxides
Natural attenuation
Reduction

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10.1016/j.chemosphere.2018.09.139

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title = "Mineralogy and buffer identity effects on RDX kinetics and intermediates during reaction with natural and synthetic magnetite",

abstract = "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.",

keywords = "Explosives, Groundwater, Iron oxides, Natural attenuation, Reduction",

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T1 - Mineralogy and buffer identity effects on RDX kinetics and intermediates during reaction with natural and synthetic magnetite

AU - Strehlau, Jennifer H.

AU - Berens, Matthew J.

AU - Arnold, William A.

PY - 2018/12

Y1 - 2018/12

N2 - 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.

AB - 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.

KW - Explosives

KW - Groundwater

KW - Iron oxides

KW - Natural attenuation

KW - Reduction

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SN - 0045-6535

VL - 213

SP - 602

EP - 609

JO - Chemosphere

JF - Chemosphere

ER -

Mineralogy and buffer identity effects on RDX kinetics and intermediates during reaction with natural and synthetic magnetite

Abstract

Funding

Keywords

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