Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) reduction is concurrently mediated by direct electron transfer from hydroquinones and resulting biogenic Fe(II) formed during electron shuttle-amended biodegradation

Man Jae Kwon, Kevin T. Finneran

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

This study investigated multiple electron transfer pathways for hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) biodegradation in the presence of bioavailable Fe(III) and electron shuttling compounds. In order to identify the dominant electron transfer pathway for RDX biodegradation, three sets of experiments were performed including aquifer material incubations, kinetics experiments, and cell suspensions. Incubations with aquifer sediment reduced RDX most rapidly in the presence of electron shuttling compounds such as anthraquinone-2,6-disulfonate (AQDS) and purified humic substances. In addition, RDX was reduced before the onset of significant accumulation of Fe(II), suggesting that reduced shuttles transferred electrons to Fe(III) rapidly, with the resulting Fe(II) reducing RDX. This hypothesis was also supported by the kinetic experiments; the rate of electron transfer from anthrahydroquinone-2,6- disulfonate (AH2QDS) to Fe(III) was approximately 10 5 times faster than the rate of AH2QDS electron transfer to RDX. However, an alternate hypothesis considered was direct reduction of RDX by the hydroquinone prior to the onset of Fe(III) reduction. Pure culture studies with a model Fe(III)/electron shuttle reducer (G. metallireducens) were performed to determine which pathway was most dominant. The resting cell suspension experiments demonstrated that there are four possible electron transfer pathways for RDX biodegradation; however, the rates of the electron shuttle-mediated pathways were consistently the fastest. When the Fe(II)-mediated electron transfer pathway was inhibited with the Fe(II) ligand Ferrozine, the rate and extent of RDX degradation decreased, but reduction continued. This suggests that multiple electron transfer pathways [reduction by hydroquinones and Fe(II)] overlapped in the presence of Fe(III), but inhibiting the iron pathway did not limit degradation. This demonstrates that RDX is concurrently reduced by electron shuttles and Fe(II) during electron-shuttle mediated biodegradation.

Original languageEnglish
Pages (from-to)961-971
Number of pages11
JournalEnvironmental Engineering Science
Volume26
Issue number5
DOIs
Publication statusPublished - 2009 May 1
Externally publishedYes

Fingerprint

Hydroquinones
triazine
Biodegradation
biodegradation
electron
Electrons
Aquifers
Intermetallics
cyclonite
Suspensions
Ferrozine
Experiments
Humic Substances
experiment
incubation
Degradation
aquifer
Kinetics
kinetics
degradation

Keywords

  • Electron shuttling
  • Fe(III) reduction
  • Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)

ASJC Scopus subject areas

  • Environmental Chemistry
  • Waste Management and Disposal
  • Pollution

Cite this

@article{8420054800ea4b61b1c2c90a9a630d14,
title = "Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) reduction is concurrently mediated by direct electron transfer from hydroquinones and resulting biogenic Fe(II) formed during electron shuttle-amended biodegradation",
abstract = "This study investigated multiple electron transfer pathways for hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) biodegradation in the presence of bioavailable Fe(III) and electron shuttling compounds. In order to identify the dominant electron transfer pathway for RDX biodegradation, three sets of experiments were performed including aquifer material incubations, kinetics experiments, and cell suspensions. Incubations with aquifer sediment reduced RDX most rapidly in the presence of electron shuttling compounds such as anthraquinone-2,6-disulfonate (AQDS) and purified humic substances. In addition, RDX was reduced before the onset of significant accumulation of Fe(II), suggesting that reduced shuttles transferred electrons to Fe(III) rapidly, with the resulting Fe(II) reducing RDX. This hypothesis was also supported by the kinetic experiments; the rate of electron transfer from anthrahydroquinone-2,6- disulfonate (AH2QDS) to Fe(III) was approximately 10 5 times faster than the rate of AH2QDS electron transfer to RDX. However, an alternate hypothesis considered was direct reduction of RDX by the hydroquinone prior to the onset of Fe(III) reduction. Pure culture studies with a model Fe(III)/electron shuttle reducer (G. metallireducens) were performed to determine which pathway was most dominant. The resting cell suspension experiments demonstrated that there are four possible electron transfer pathways for RDX biodegradation; however, the rates of the electron shuttle-mediated pathways were consistently the fastest. When the Fe(II)-mediated electron transfer pathway was inhibited with the Fe(II) ligand Ferrozine, the rate and extent of RDX degradation decreased, but reduction continued. This suggests that multiple electron transfer pathways [reduction by hydroquinones and Fe(II)] overlapped in the presence of Fe(III), but inhibiting the iron pathway did not limit degradation. This demonstrates that RDX is concurrently reduced by electron shuttles and Fe(II) during electron-shuttle mediated biodegradation.",
keywords = "Electron shuttling, Fe(III) reduction, Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)",
author = "Kwon, {Man Jae} and Finneran, {Kevin T.}",
year = "2009",
month = "5",
day = "1",
doi = "10.1089/ees.2008.0251",
language = "English",
volume = "26",
pages = "961--971",
journal = "Environmental Engineering Science",
issn = "1092-8758",
publisher = "Mary Ann Liebert Inc.",
number = "5",

}

TY - JOUR

T1 - Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) reduction is concurrently mediated by direct electron transfer from hydroquinones and resulting biogenic Fe(II) formed during electron shuttle-amended biodegradation

AU - Kwon, Man Jae

AU - Finneran, Kevin T.

PY - 2009/5/1

Y1 - 2009/5/1

N2 - This study investigated multiple electron transfer pathways for hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) biodegradation in the presence of bioavailable Fe(III) and electron shuttling compounds. In order to identify the dominant electron transfer pathway for RDX biodegradation, three sets of experiments were performed including aquifer material incubations, kinetics experiments, and cell suspensions. Incubations with aquifer sediment reduced RDX most rapidly in the presence of electron shuttling compounds such as anthraquinone-2,6-disulfonate (AQDS) and purified humic substances. In addition, RDX was reduced before the onset of significant accumulation of Fe(II), suggesting that reduced shuttles transferred electrons to Fe(III) rapidly, with the resulting Fe(II) reducing RDX. This hypothesis was also supported by the kinetic experiments; the rate of electron transfer from anthrahydroquinone-2,6- disulfonate (AH2QDS) to Fe(III) was approximately 10 5 times faster than the rate of AH2QDS electron transfer to RDX. However, an alternate hypothesis considered was direct reduction of RDX by the hydroquinone prior to the onset of Fe(III) reduction. Pure culture studies with a model Fe(III)/electron shuttle reducer (G. metallireducens) were performed to determine which pathway was most dominant. The resting cell suspension experiments demonstrated that there are four possible electron transfer pathways for RDX biodegradation; however, the rates of the electron shuttle-mediated pathways were consistently the fastest. When the Fe(II)-mediated electron transfer pathway was inhibited with the Fe(II) ligand Ferrozine, the rate and extent of RDX degradation decreased, but reduction continued. This suggests that multiple electron transfer pathways [reduction by hydroquinones and Fe(II)] overlapped in the presence of Fe(III), but inhibiting the iron pathway did not limit degradation. This demonstrates that RDX is concurrently reduced by electron shuttles and Fe(II) during electron-shuttle mediated biodegradation.

AB - This study investigated multiple electron transfer pathways for hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) biodegradation in the presence of bioavailable Fe(III) and electron shuttling compounds. In order to identify the dominant electron transfer pathway for RDX biodegradation, three sets of experiments were performed including aquifer material incubations, kinetics experiments, and cell suspensions. Incubations with aquifer sediment reduced RDX most rapidly in the presence of electron shuttling compounds such as anthraquinone-2,6-disulfonate (AQDS) and purified humic substances. In addition, RDX was reduced before the onset of significant accumulation of Fe(II), suggesting that reduced shuttles transferred electrons to Fe(III) rapidly, with the resulting Fe(II) reducing RDX. This hypothesis was also supported by the kinetic experiments; the rate of electron transfer from anthrahydroquinone-2,6- disulfonate (AH2QDS) to Fe(III) was approximately 10 5 times faster than the rate of AH2QDS electron transfer to RDX. However, an alternate hypothesis considered was direct reduction of RDX by the hydroquinone prior to the onset of Fe(III) reduction. Pure culture studies with a model Fe(III)/electron shuttle reducer (G. metallireducens) were performed to determine which pathway was most dominant. The resting cell suspension experiments demonstrated that there are four possible electron transfer pathways for RDX biodegradation; however, the rates of the electron shuttle-mediated pathways were consistently the fastest. When the Fe(II)-mediated electron transfer pathway was inhibited with the Fe(II) ligand Ferrozine, the rate and extent of RDX degradation decreased, but reduction continued. This suggests that multiple electron transfer pathways [reduction by hydroquinones and Fe(II)] overlapped in the presence of Fe(III), but inhibiting the iron pathway did not limit degradation. This demonstrates that RDX is concurrently reduced by electron shuttles and Fe(II) during electron-shuttle mediated biodegradation.

KW - Electron shuttling

KW - Fe(III) reduction

KW - Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)

UR - http://www.scopus.com/inward/record.url?scp=67249119947&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=67249119947&partnerID=8YFLogxK

U2 - 10.1089/ees.2008.0251

DO - 10.1089/ees.2008.0251

M3 - Article

VL - 26

SP - 961

EP - 971

JO - Environmental Engineering Science

JF - Environmental Engineering Science

SN - 1092-8758

IS - 5

ER -