Incorporation and retention of 99-Tc(IV) in magnetite under high pH conditions

Timothy A. Marshall, Katherine Morris, Gareth T.W. Law, J. Frederick W. Mosselmans, Pieter Bots, Stephen A. Parry, Samuel Shaw

Research output: Contribution to journalArticle

40 Citations (Scopus)
111 Downloads (Pure)

Abstract

Technetium incorporation into magnetite and its behavior during subsequent oxidation has been investigated at high pH to determine the technetium retention mechanism(s) on formation and oxidative perturbation of magnetite in systems relevant to radioactive waste disposal. Ferrihydrite was exposed to Tc(VII)(aq) containing cement leachates (pH 10.5-13.1), and crystallization of magnetite was induced via addition of Fe(II)aq. A combination of X-ray diffraction (XRD), chemical extraction, and X-ray absorption spectroscopy (XAS) techniques provided direct evidence that Tc(VII) was reduced and incorporated into the magnetite structure. Subsequent air oxidation of the magnetite particles for up to 152 days resulted in only limited remobilization of the incorporated Tc(IV). Analysis of both X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) data indicated that the Tc(IV) was predominantly incorporated into the magnetite octahedral site in all systems studied. On reoxidation in air, the incorporated Tc(IV) was recalcitrant to oxidative dissolution with less than 40% remobilization to solution despite significant oxidation of the magnetite to maghemite/goethite: All solid associated Tc remained as Tc(IV). The results of this study provide the first direct evidence for significant Tc(IV) incorporation into the magnetite structure and confirm that magnetite incorporated Tc(IV) is recalcitrant to oxidative dissolution. Immobilization of Tc(VII) by reduction and incorporation into magnetite at high pH and with significant stability upon reoxidation has clear and important implications for limiting technetium migration under conditions where magnetite is formed including in geological disposal of radioactive wastes.
Original languageEnglish
Pages (from-to)11853-11862
Number of pages10
JournalEnvironmental Science and Technology
Volume48
Issue number20
Early online date19 Sep 2014
DOIs
Publication statusPublished - 21 Oct 2014

Fingerprint

Ferrosoferric Oxide
magnetite
technetium
Technetium
X ray absorption
remobilization
oxidation
Oxidation
radioactive waste
Dissolution
incorporation
dissolution
Radioactive waste disposal
Radioactive Waste
maghemite
X ray absorption spectroscopy
ferrihydrite
air
atomic absorption spectroscopy
Crystallization

Keywords

  • technetium incorporation
  • magnetite
  • technetium retention mechanisms
  • radioactive waste disposal
  • ferrihydrite
  • crystallization

Cite this

Marshall, T. A., Morris, K., Law, G. T. W., Mosselmans, J. F. W., Bots, P., Parry, S. A., & Shaw, S. (2014). Incorporation and retention of 99-Tc(IV) in magnetite under high pH conditions. Environmental Science and Technology , 48(20), 11853-11862. https://doi.org/10.1021/es503438e
Marshall, Timothy A. ; Morris, Katherine ; Law, Gareth T.W. ; Mosselmans, J. Frederick W. ; Bots, Pieter ; Parry, Stephen A. ; Shaw, Samuel. / Incorporation and retention of 99-Tc(IV) in magnetite under high pH conditions. In: Environmental Science and Technology . 2014 ; Vol. 48, No. 20. pp. 11853-11862.
@article{6a94ac873ae746c39680ac7f7c648d72,
title = "Incorporation and retention of 99-Tc(IV) in magnetite under high pH conditions",
abstract = "Technetium incorporation into magnetite and its behavior during subsequent oxidation has been investigated at high pH to determine the technetium retention mechanism(s) on formation and oxidative perturbation of magnetite in systems relevant to radioactive waste disposal. Ferrihydrite was exposed to Tc(VII)(aq) containing cement leachates (pH 10.5-13.1), and crystallization of magnetite was induced via addition of Fe(II)aq. A combination of X-ray diffraction (XRD), chemical extraction, and X-ray absorption spectroscopy (XAS) techniques provided direct evidence that Tc(VII) was reduced and incorporated into the magnetite structure. Subsequent air oxidation of the magnetite particles for up to 152 days resulted in only limited remobilization of the incorporated Tc(IV). Analysis of both X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) data indicated that the Tc(IV) was predominantly incorporated into the magnetite octahedral site in all systems studied. On reoxidation in air, the incorporated Tc(IV) was recalcitrant to oxidative dissolution with less than 40{\%} remobilization to solution despite significant oxidation of the magnetite to maghemite/goethite: All solid associated Tc remained as Tc(IV). The results of this study provide the first direct evidence for significant Tc(IV) incorporation into the magnetite structure and confirm that magnetite incorporated Tc(IV) is recalcitrant to oxidative dissolution. Immobilization of Tc(VII) by reduction and incorporation into magnetite at high pH and with significant stability upon reoxidation has clear and important implications for limiting technetium migration under conditions where magnetite is formed including in geological disposal of radioactive wastes.",
keywords = "technetium incorporation, magnetite, technetium retention mechanisms, radioactive waste disposal, ferrihydrite, crystallization",
author = "Marshall, {Timothy A.} and Katherine Morris and Law, {Gareth T.W.} and Mosselmans, {J. Frederick W.} and Pieter Bots and Parry, {Stephen A.} and Samuel Shaw",
year = "2014",
month = "10",
day = "21",
doi = "10.1021/es503438e",
language = "English",
volume = "48",
pages = "11853--11862",
journal = "Environmental Science and Technology",
issn = "0013-936X",
publisher = "American Chemical Society",
number = "20",

}

Marshall, TA, Morris, K, Law, GTW, Mosselmans, JFW, Bots, P, Parry, SA & Shaw, S 2014, 'Incorporation and retention of 99-Tc(IV) in magnetite under high pH conditions', Environmental Science and Technology , vol. 48, no. 20, pp. 11853-11862. https://doi.org/10.1021/es503438e

Incorporation and retention of 99-Tc(IV) in magnetite under high pH conditions. / Marshall, Timothy A.; Morris, Katherine; Law, Gareth T.W.; Mosselmans, J. Frederick W.; Bots, Pieter; Parry, Stephen A.; Shaw, Samuel.

In: Environmental Science and Technology , Vol. 48, No. 20, 21.10.2014, p. 11853-11862.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Incorporation and retention of 99-Tc(IV) in magnetite under high pH conditions

AU - Marshall, Timothy A.

AU - Morris, Katherine

AU - Law, Gareth T.W.

AU - Mosselmans, J. Frederick W.

AU - Bots, Pieter

AU - Parry, Stephen A.

AU - Shaw, Samuel

PY - 2014/10/21

Y1 - 2014/10/21

N2 - Technetium incorporation into magnetite and its behavior during subsequent oxidation has been investigated at high pH to determine the technetium retention mechanism(s) on formation and oxidative perturbation of magnetite in systems relevant to radioactive waste disposal. Ferrihydrite was exposed to Tc(VII)(aq) containing cement leachates (pH 10.5-13.1), and crystallization of magnetite was induced via addition of Fe(II)aq. A combination of X-ray diffraction (XRD), chemical extraction, and X-ray absorption spectroscopy (XAS) techniques provided direct evidence that Tc(VII) was reduced and incorporated into the magnetite structure. Subsequent air oxidation of the magnetite particles for up to 152 days resulted in only limited remobilization of the incorporated Tc(IV). Analysis of both X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) data indicated that the Tc(IV) was predominantly incorporated into the magnetite octahedral site in all systems studied. On reoxidation in air, the incorporated Tc(IV) was recalcitrant to oxidative dissolution with less than 40% remobilization to solution despite significant oxidation of the magnetite to maghemite/goethite: All solid associated Tc remained as Tc(IV). The results of this study provide the first direct evidence for significant Tc(IV) incorporation into the magnetite structure and confirm that magnetite incorporated Tc(IV) is recalcitrant to oxidative dissolution. Immobilization of Tc(VII) by reduction and incorporation into magnetite at high pH and with significant stability upon reoxidation has clear and important implications for limiting technetium migration under conditions where magnetite is formed including in geological disposal of radioactive wastes.

AB - Technetium incorporation into magnetite and its behavior during subsequent oxidation has been investigated at high pH to determine the technetium retention mechanism(s) on formation and oxidative perturbation of magnetite in systems relevant to radioactive waste disposal. Ferrihydrite was exposed to Tc(VII)(aq) containing cement leachates (pH 10.5-13.1), and crystallization of magnetite was induced via addition of Fe(II)aq. A combination of X-ray diffraction (XRD), chemical extraction, and X-ray absorption spectroscopy (XAS) techniques provided direct evidence that Tc(VII) was reduced and incorporated into the magnetite structure. Subsequent air oxidation of the magnetite particles for up to 152 days resulted in only limited remobilization of the incorporated Tc(IV). Analysis of both X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) data indicated that the Tc(IV) was predominantly incorporated into the magnetite octahedral site in all systems studied. On reoxidation in air, the incorporated Tc(IV) was recalcitrant to oxidative dissolution with less than 40% remobilization to solution despite significant oxidation of the magnetite to maghemite/goethite: All solid associated Tc remained as Tc(IV). The results of this study provide the first direct evidence for significant Tc(IV) incorporation into the magnetite structure and confirm that magnetite incorporated Tc(IV) is recalcitrant to oxidative dissolution. Immobilization of Tc(VII) by reduction and incorporation into magnetite at high pH and with significant stability upon reoxidation has clear and important implications for limiting technetium migration under conditions where magnetite is formed including in geological disposal of radioactive wastes.

KW - technetium incorporation

KW - magnetite

KW - technetium retention mechanisms

KW - radioactive waste disposal

KW - ferrihydrite

KW - crystallization

UR - https://www.scopus.com/inward/record.uri?eid=2-s2.0-84908138352&partnerID=40&md5=b376ebf9f5219994fd52de8c808cf6e1

UR - http://pubs.acs.org/journal/esthag

U2 - 10.1021/es503438e

DO - 10.1021/es503438e

M3 - Article

VL - 48

SP - 11853

EP - 11862

JO - Environmental Science and Technology

JF - Environmental Science and Technology

SN - 0013-936X

IS - 20

ER -