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Comins MB, Kaplan U, Beam J, Navarrette A, Hixon AE. Plutonium Speciation and Oxidation State Distributions in the Presence of Citrate. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:15766-15778. [PMID: 39163648 DOI: 10.1021/acs.est.4c02803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/22/2024]
Abstract
We explored the speciation and kinetics of the Pu(VI)-citrate and Pu(III)-citrate systems (pHm = 2.5-11.0, I = 0.1 M NaCl, T = 23 °C, O2(g) < 2 ppm) using ultraviolet-visible-near-infrared (UV-vis-NIR) spectrophotometry, solvent extraction, and PHREEQC modeling. Formation constants were determined for PuO2(HcitH)(aq) (log K°1,1 = 1.09 ± 0.05) and PuO2(HcitH)(citH)3- (log K°1,2 = -0.20 ± 0.07), and evidence for (PuO2)m(citH-k)n(OH)x2m(3+k)n-x was identified under alkaline conditions. Pu(VI) species were found to be less stable in the presence of citrate than in the absence of citrate (t ≤ 168 days); the rate of reduction increased with increasing pH. The direct reduction of Pu(VI) to Pu(IV) was required to fit experimental data in the presence of citrate but did not improve the fit for Pu in the absence of citrate. We also observed increased Pu(III) stability in the presence of citrate (t ≤ 293 days), with higher concentrations of Pu(III) favored at lower pH. Finally, we provide evidence of a radiolysis-driven mechanism for the citrate-mediated reduction of plutonium that involves electron transfer from the oxidative breakdown of citrate. Our work highlights the need to investigate the redox effect of organic ligands on plutonium oxidation states under repository-relevant conditions.
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Affiliation(s)
- Matthew B Comins
- Department of Civil & Environmental Engineering & Earth Sciences, University of Notre Dame, 301 Stinson-Remick, Notre Dame, Indiana 46556, United States
| | - Ugras Kaplan
- Los Alamos National Laboratory, 1400 University Drive, Carlsbad, New Mexico 88220, United States
| | - Jeremiah Beam
- Los Alamos National Laboratory, 1400 University Drive, Carlsbad, New Mexico 88220, United States
| | - Adrianne Navarrette
- Los Alamos National Laboratory, 1400 University Drive, Carlsbad, New Mexico 88220, United States
| | - Amy E Hixon
- Department of Civil & Environmental Engineering & Earth Sciences, University of Notre Dame, 301 Stinson-Remick, Notre Dame, Indiana 46556, United States
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Bessonov AA, Shilov VP. Behavior of Plutonium(V) in the Environment. RADIOCHEMISTRY 2022. [DOI: 10.1134/s1066362222060029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
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Ram R, Kalnins C, Pownceby MI, Ehrig K, Etschmann B, Spooner N, Brugger J. Selective radionuclide co-sorption onto natural minerals in environmental and anthropogenic conditions. JOURNAL OF HAZARDOUS MATERIALS 2021; 409:124989. [PMID: 33450517 DOI: 10.1016/j.jhazmat.2020.124989] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Revised: 11/25/2020] [Accepted: 12/26/2020] [Indexed: 06/12/2023]
Abstract
Anthropogenic activities can redistribute the constituents of naturally occurring radioactive materials (NORM), posing potential hazards to populations and ecosystems. In the present study, the co-sorption of several RN from the U decay chain- 238U, 230Th, 226Ra, 210Pb and 210Po, onto common minerals associated with mining activities (chalcopyrite, bornite, pyrite and barite) was investigated, in order to identify the various factors that control long-term NORM mobility and retentivity in environmental acid-mine drainage systems and hydrometallurgical processing. The results show selective RN co-sorption to the various natural minerals, suggesting that mineral-specific mechanisms govern the variability in NORM mobility and retentivity. Both 226Ra and 210Po underwent significant sorption onto the natural minerals investigated in this study. The order of co-sorption in sulfate media for chalcopyrite and bornite was 210Po>226Ra>206Pb>210Pb>238U/230Th. Conversely, both pyrite and barite showed increased affinity for 226Ra; the order of co-sorption in sulfate media was 226Ra>210Po>206Pb/210Pb>238U/230Th for pyrite and 226Ra>206Pb/210Pb>230Th/238U/210Po for barite. Similar orders of co-sorption were observed in the nitrate media: for chalcopyrite and bornite the order was 210Po>226Ra/206Pb/210Pb/238U/230Th compared to 226Ra>210Po/206Pb/210Pb/238U/230Th for pyrite and barite. The behavior of 210Po was found to the anomalous: in both sulfate and nitrate solutions, 210Po had little affinity for barite compared to the sulfides. Thermodynamic modeling indicated the formation of a reduced PoS(s) phase at the surface of sulfide minerals, leading to the suggestion that 210Po likely undergoes reductive precipitation on the surface of sulfide minerals. The high sorption of both 206Pb and 210Pb observed in the sulfate systems were likely as a result of co-precipitation as insoluble anglesite compared to nitrate where they mainly remained in solution. Overall, barite showed the highest affinity for 226Ra, given its propensity to sorb 226Ra (similar ionic size). Both 238U and 230Th were highly mobile in acidic sulfate and nitrate solutions. The results highlighted here identify the various constraints on the natural variability and fractionation of NORM in the environment, as well as the mineral-specific mechanisms that control co-sorption of RN. This information provides a framework for predicting RN transport within soils and ground waters with variable geochemical conditions and in metallurgical extraction processes, in order to develop effective strategies towards NORM mitigation.
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Affiliation(s)
- Rahul Ram
- School of Earth, Atmosphere and Environment, 9 Rainforest Walk, Monash University, Clayton, VIC 3168, Australia.
| | - Chris Kalnins
- Institute for Photonics and Advanced Sensing and School of Physical Sciences, University of Adelaide, Adelaide, SA, Australia
| | | | - Kathy Ehrig
- BHP Olympic Dam, Adelaide, SA 5000, Australia
| | - Barbara Etschmann
- School of Earth, Atmosphere and Environment, 9 Rainforest Walk, Monash University, Clayton, VIC 3168, Australia
| | - Nigel Spooner
- Institute for Photonics and Advanced Sensing and School of Physical Sciences, University of Adelaide, Adelaide, SA, Australia
| | - Joël Brugger
- School of Earth, Atmosphere and Environment, 9 Rainforest Walk, Monash University, Clayton, VIC 3168, Australia.
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Foster JC, Starstrom SA, DeVol TA, Powell BA, Husson SM. Functionalized Polymer Thin Films for Plutonium Capture and Isotopic Screening from Aqueous Sources. Anal Chem 2020; 92:5214-5221. [PMID: 32189504 DOI: 10.1021/acs.analchem.9b05758] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The rapid screening of plutonium from aqueous sources remains a critical challenge for nuclear nonproliferation efforts. The determination of trace-level Pu isotopes in water requires offsite sample preparation and analysis; therefore, new methods that combine plutonium purification, concentration, and isotopic screening in a fieldable detection system will provide an invaluable tool for nuclear safeguards. This contribution describes the development and characterization of thin polymer-ligand films for the isolation and concentration of waterborne Pu for direct spectroscopic analyses. Submicron thin films were prepared through spin coating onto Si wafers and consisted of combinations of polystyrene (PS) with dibenzoylmethane, thenoyltrifluoroacetone, and di(2-ethylhexyl)phosphoric acid (HDEHP). Pu uptake studies from solutions at pH from 2.3 to 6.3 indicated that only films containing HDEHP exhibited significant recovery of Pu. High alpha spectroscopy peak energy resolutions were achieved for PS-HDEHP films over a range of film thicknesses from 30 to 250 nm. A separate study was performed to evaluate uptake from a primarily Pu(V) solution where it was observed that doubling the HDEHP loading in the film increased uptake of Pu by an order of magnitude. X-ray photoelectron spectroscopy (XPS) analysis revealed that HDEHP was highly concentrated within the first few nanometers of the film at the higher loading. XPS analysis also revealed that, in the presence of water, HDEHP was stripped from the surface layer of the film at circumneutral pH. While significant losses of ligand were seen in all samples, higher loadings of HDEHP resulted in measurable amounts of ligand retained after a 12-h soak in water. Findings of this study are being used to guide the development of thin-film composite membrane-based detection methods for the rapid, fieldable analysis of Pu in water.
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Affiliation(s)
- James C Foster
- Department of Chemical and Biomolecular Engineering, Clemson University, 127 Earle Hall, Clemson, South Carolina 29634, United States
| | - Samantha A Starstrom
- Department of Chemical and Biomolecular Engineering, Clemson University, 127 Earle Hall, Clemson, South Carolina 29634, United States
| | - Timothy A DeVol
- Department of Environmental Engineering and Earth Sciences, Clemson University, 342 Computer Court, Anderson, South Carolina 29625, United States
| | - Brian A Powell
- Department of Environmental Engineering and Earth Sciences, Clemson University, 342 Computer Court, Anderson, South Carolina 29625, United States
| | - Scott M Husson
- Department of Chemical and Biomolecular Engineering, Clemson University, 127 Earle Hall, Clemson, South Carolina 29634, United States
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Maloubier M, Emerson H, Peruski K, Kersting AB, Zavarin M, Almond PM, Kaplan DI, Powell BA. Impact of Natural Organic Matter on Plutonium Vadose Zone Migration from an NH 4Pu(V)O 2CO 3(s) Source. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:2688-2697. [PMID: 31942795 DOI: 10.1021/acs.est.9b05651] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We investigated the influence of natural organic matter (NOM) on the behavior of Pu(V) in the vadose zone through a combination of the field lysimeter and laboratory studies. Well-defined solid sources of NH4Pu(V)O2CO3(s) were placed in two 5-L lysimeters containing NOM-amended soil collected from the Savannah River Site (SRS) or unamended vadose zone soil and exposed to 3 years of natural South Carolina, USA, meteorological conditions. Lysimeter soil cores were removed from the field, used in desorption experiments, and characterized using wet chemistry methods and X-ray absorption spectroscopy. For both lysimeters, Pu migrated slowly with the majority (>95%) remaining within 2 cm of the source. However, without the NOM amendment, Pu was transported significantly farther than in the presence of NOM. Downward Pu migration appears to be influenced by the initial source oxidation state and composition. These Pu(V) sources exhibited significantly greater migration than previous studies using Pu(IV) or Pu(III) sources. However, batch laboratory experiments demonstrated that Pu(V) is reduced by the lysimeter soil in the order of hours, indicating that downward migration of Pu may be due to cycling between Pu(V) and Pu(IV). Under the conditions of these experiments, NOM appeared to both enhance reduction of the Pu(V) source as well as Pu sorption to soils. This indicates that NOM will tend to have a stabilizing effect on Pu migration under SRS vadose zone field conditions.
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Affiliation(s)
- Melody Maloubier
- Department of Environmental Engineering & Earth Sciences, Clemson University, Clemson, South Carolina 29634, United States
| | - Hilary Emerson
- Subsurface Science and Technology, Energy & Environment, Pacific Northwest National Laboratory, Richland, Washington 99354, United States
| | - Kathryn Peruski
- Department of Environmental Engineering & Earth Sciences, Clemson University, Clemson, South Carolina 29634, United States
| | - Annie B Kersting
- Glenn T. Seaborg Institute, Physical & Life Sciences, Lawrence Livermore National Laboratory, Livermore, California 94550, United States
| | - Mavrik Zavarin
- Glenn T. Seaborg Institute, Physical & Life Sciences, Lawrence Livermore National Laboratory, Livermore, California 94550, United States
| | - Philip M Almond
- Savannah River National Laboratory, Aiken, South Carolina 29808, United States
| | - Daniel I Kaplan
- Savannah River National Laboratory, Aiken, South Carolina 29808, United States
| | - Brian A Powell
- Department of Environmental Engineering & Earth Sciences, Clemson University, Clemson, South Carolina 29634, United States
- Savannah River National Laboratory, Aiken, South Carolina 29808, United States
- Department of Chemistry, Clemson University, Clemson, South Carolina 29634, United States
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