1
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Katheras AS, Karalis K, Krack M, Scheinost AC, Churakov SV. Stability and Speciation of Hydrated Magnetite {111} Surfaces from Ab Initio Simulations with Relevance for Geochemical Redox Processes. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:935-946. [PMID: 38133817 DOI: 10.1021/acs.est.3c07202] [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: 12/23/2023]
Abstract
Magnetite is a common mixed Fe(II,III) iron oxide in mineral deposits and the product of (anaerobic) iron corrosion. In various Earth systems, magnetite surfaces participate in surface-mediated redox reactions. The reactivity and redox properties of the magnetite surface depend on the surface speciation, which varies with environmental conditions. In this study, Kohn-Sham density functional theory (DFT + U method) was used to examine the stability and speciation of the prevalent magnetite crystal face {111} in a wide range of pH and Eh conditions. The simulations reveal that the oxidation state and speciation of the surface depend strongly on imposed redox conditions and, in general, may differ from those of the bulk state. Corresponding predominant phase diagrams for the surface speciation and structure were calculated from first principles. Furthermore, classical molecular dynamics simulations were conducted investigating the mobility of water near the magnetite surface. The obtained knowledge of the surface structure and oxidation state of iron is essential for modeling retention of redox-sensitive nuclides.
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Affiliation(s)
- Anita S Katheras
- Institute of Geological Sciences, University of Bern, CH-3012 Bern, Switzerland
| | | | - Matthias Krack
- Laboratory for Materials Simulations (LMS), Paul Scherrer Institute (PSI), CH-5232 Villigen PSI, Switzerland
| | - Andreas C Scheinost
- The Rossendorf Beamline (BM20), European Synchrotron Radiation Lab, FR-38043 Grenoble, France
- Institute of Resource Ecology, Helmholtz-Zentrum Dresden-Rossendorf, DE-01328 Dresden-Rossendorf, Germany
| | - Sergey V Churakov
- Institute of Geological Sciences, University of Bern, CH-3012 Bern, Switzerland
- Laboratory for Waste Management (LES), Paul Scherrer Institute (PSI), CH-5232 Villigen PSI, Switzerland
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2
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Kang J, Zhang G, Chen B, Chen L, Wu R, Zhou X, Hang J, Zheng C, Xia C. Excessive consumption mechanism of hydrazine in the reaction with ReO 4−: Re species evolution and ReO 2· nH 2O-catalyzed decomposition. Inorg Chem Front 2022. [DOI: 10.1039/d2qi00606e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
ReO4− is slowly reduced to ReO42− and Re(iv) species by hydrazine, and ReO2·nH2O catalyzes hydrazine decomposition.
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Affiliation(s)
- Jinyang Kang
- College of Chemistry, Sichuan University, Chengdu 610064, P. R. China
| | - Guikai Zhang
- Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Bo Chen
- College of Chemistry, Sichuan University, Chengdu 610064, P. R. China
| | - Lang Chen
- College of Chemistry, Sichuan University, Chengdu 610064, P. R. China
| | - Rulei Wu
- College of Chemistry, Sichuan University, Chengdu 610064, P. R. China
| | - Xiaoyuan Zhou
- College of Chemistry, Sichuan University, Chengdu 610064, P. R. China
| | - Jiahui Hang
- College of Chemistry, Sichuan University, Chengdu 610064, P. R. China
| | - Chengbin Zheng
- College of Chemistry, Sichuan University, Chengdu 610064, P. R. China
| | - Chuanqin Xia
- College of Chemistry, Sichuan University, Chengdu 610064, P. R. China
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3
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Williamson AJ, Lloyd JR, Boothman C, Law GTW, Shaw S, Small JS, Vettese GF, Williams HA, Morris K. Biogeochemical Cycling of 99Tc in Alkaline Sediments. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:15862-15872. [PMID: 34825817 DOI: 10.1021/acs.est.1c04416] [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: 06/13/2023]
Abstract
99Tc will be present in significant quantities in radioactive wastes including intermediate-level waste (ILW). The internationally favored concept for disposing of higher activity radioactive wastes including ILW is via deep geological disposal in an underground engineered facility located ∼200-1000 m deep. Typically, in the deep geological disposal environment, the subsurface will be saturated, cement will be used extensively as an engineering material, and iron will be ubiquitous. This means that understanding Tc biogeochemistry in high pH, cementitious environments is important to underpin safety case development. Here, alkaline sediment microcosms (pH 10) were incubated under anoxic conditions under "no added Fe(III)" and "with added Fe(III)" conditions (added as ferrihydrite) at three Tc concentrations (10-11, 10-6, and 10-4 mol L-1). In the 10-6 mol L-1 Tc experiments with no added Fe(III), ∼35% Tc(VII) removal occurred during bioreduction. Solvent extraction of the residual solution phase indicated that ∼75% of Tc was present as Tc(IV), potentially as colloids. In both biologically active and sterile control experiments with added Fe(III), Fe(II) formed during bioreduction and >90% Tc was removed from the solution, most likely due to abiotic reduction mediated by Fe(II). X-ray absorption spectroscopy (XAS) showed that in bioreduced sediments, Tc was present as hydrous TcO2-like phases, with some evidence for an Fe association. When reduced sediments with added Fe(III) were air oxidized, there was a significant loss of Fe(II) over 1 month (∼50%), yet this was coupled to only modest Tc remobilization (∼25%). Here, XAS analysis suggested that with air oxidation, partial incorporation of Tc(IV) into newly forming Fe oxyhydr(oxide) minerals may be occurring. These data suggest that in Fe-rich, alkaline environments, biologically mediated processes may limit Tc mobility.
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Affiliation(s)
- Adam J Williamson
- Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, Department of Earth, Atmospheric and Environmental Sciences, The University of Manchester, Manchester M13 9PL, U.K
- CENBG-Équipe Radioactivité et Environnement, UMR 5797, CNRS-IN2P3/Université de Bordeaux, 19 chemin du Solarium, CS 10120, 33175 Gradignan, France
| | - Jonathan R Lloyd
- Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, Department of Earth, Atmospheric and Environmental Sciences, The University of Manchester, Manchester M13 9PL, U.K
| | - Christopher Boothman
- Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, Department of Earth, Atmospheric and Environmental Sciences, The University of Manchester, Manchester M13 9PL, U.K
| | - Gareth T W Law
- Radiochemistry Unit, Department of Chemistry, The University of Helsinki, Helsinki 00014, Finland
| | - Samuel Shaw
- Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, Department of Earth, Atmospheric and Environmental Sciences, The University of Manchester, Manchester M13 9PL, U.K
| | - Joe S Small
- Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, Department of Earth, Atmospheric and Environmental Sciences, The University of Manchester, Manchester M13 9PL, U.K
- National Nuclear Laboratory, Risley, Warrington, Cheshire WA3 6AE, U.K
| | - Gianni F Vettese
- Radiochemistry Unit, Department of Chemistry, The University of Helsinki, Helsinki 00014, Finland
| | - Heather A Williams
- Department of Nuclear Medicine, Manchester Royal Infirmary, Oxford Road, Manchester M13 9WL, U.K
| | - Katherine Morris
- Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, Department of Earth, Atmospheric and Environmental Sciences, The University of Manchester, Manchester M13 9PL, U.K
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4
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Spontaneous redox continuum reveals sequestered technetium clusters and retarded mineral transformation of iron. Commun Chem 2020; 3:87. [PMID: 36703425 PMCID: PMC9814752 DOI: 10.1038/s42004-020-0334-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Accepted: 06/05/2020] [Indexed: 01/29/2023] Open
Abstract
The sequestration of metal ions into the crystal structure of minerals is common in nature. To date, the incorporation of technetium(IV) into iron minerals has been studied predominantly for systems under carefully controlled anaerobic conditions. Mechanisms of the transformation of iron phases leading to incorporation of technetium(IV) under aerobic conditions remain poorly understood. Here we investigate granular metallic iron for reductive sequestration of technetium(VII) at elevated concentrations under ambient conditions. We report the retarded transformation of ferrihydrite to magnetite in the presence of technetium. We observe that quantitative reduction of pertechnetate with a fraction of technetium(IV) structurally incorporated into non-stoichiometric magnetite benefits from concomitant zero valent iron oxidative transformation. An in-depth profile of iron oxide reveals clusters of the incorporated technetium(IV), which account for 32% of the total retained technetium estimated via X-ray absorption and X-ray photoelectron spectroscopies. This corresponds to 1.86 wt.% technetium in magnetite, providing the experimental evidence to theoretical postulations on thermodynamically stable technetium(IV) being incorporated into magnetite under spontaneous aerobic redox conditions.
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5
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Pearce CI, Moore RC, Morad JW, Asmussen RM, Chatterjee S, Lawter AR, Levitskaia TG, Neeway JJ, Qafoku NP, Rigali MJ, Saslow SA, Szecsody JE, Thallapally PK, Wang G, Freedman VL. Technetium immobilization by materials through sorption and redox-driven processes: A literature review. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 716:132849. [PMID: 32057506 DOI: 10.1016/j.scitotenv.2019.06.195] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 06/11/2019] [Accepted: 06/12/2019] [Indexed: 06/10/2023]
Abstract
The objective of this review is to evaluate materials for use as a barrier or other deployed technology to treat technetium-99 (Tc) in the subsurface. To achieve this, Tc interactions with different materials are considered within the context of remediation strategies. Several naturally occurring materials are considered for Tc immobilization, including iron oxides and low solubility sulfide phases. Synthetic materials are also considered, and include tin-based materials, sorbents (resins, activated carbon, modified clays), layered double hydroxides, metal organic frameworks, cationic polymeric networks and aerogels. All of the materials were evaluated for their potential in-situ and ex-situ performance with respect to long-term Tc uptake and immobilization, environmental impacts and deployability. Other factors such as the technology maturity, cost and availability were also considered. Given the difficulty of evaluating materials under different experimental conditions (e.g., solution chemistry, redox conditions, solution to solid ratio, Tc concentration etc.), a subset of these materials will be selected, on the basis of this review, for subsequent standardized batch loading tests.
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Affiliation(s)
- Carolyn I Pearce
- Pacific Northwest National Laboratory, Richland, WA, United States of America.
| | - Robert C Moore
- Pacific Northwest National Laboratory, Richland, WA, United States of America
| | - Joseph W Morad
- Pacific Northwest National Laboratory, Richland, WA, United States of America
| | - R Matthew Asmussen
- Pacific Northwest National Laboratory, Richland, WA, United States of America
| | - Sayandev Chatterjee
- Pacific Northwest National Laboratory, Richland, WA, United States of America
| | - Amanda R Lawter
- Pacific Northwest National Laboratory, Richland, WA, United States of America
| | | | - James J Neeway
- Pacific Northwest National Laboratory, Richland, WA, United States of America
| | - Nikolla P Qafoku
- Pacific Northwest National Laboratory, Richland, WA, United States of America
| | - Mark J Rigali
- Sandia National Laboratories, Albuquerque, NM, United States of America
| | - Sarah A Saslow
- Pacific Northwest National Laboratory, Richland, WA, United States of America
| | - Jim E Szecsody
- Pacific Northwest National Laboratory, Richland, WA, United States of America
| | | | - Guohui Wang
- Pacific Northwest National Laboratory, Richland, WA, United States of America
| | - Vicky L Freedman
- Pacific Northwest National Laboratory, Richland, WA, United States of America
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Li D, Seaman JC, Hunyadi Murph SE, Kaplan DI, Taylor-Pashow K, Feng R, Chang H, Tandukar M. Porous iron material for TcO 4- and ReO 4- sequestration from groundwater under ambient oxic conditions. JOURNAL OF HAZARDOUS MATERIALS 2019; 374:177-185. [PMID: 30999141 DOI: 10.1016/j.jhazmat.2019.04.030] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Revised: 04/01/2019] [Accepted: 04/08/2019] [Indexed: 06/09/2023]
Abstract
Technetium-99 (99Tc) is a major contaminant at nuclear power plants and several US Department of Energy sites. Its most common aqueous species, pertechnetate (TcO4-), is very mobile in the environment, and currently there are no effective technologies for its sequestration. In this work, a porous iron (pFe) material was investigated for TcO4- and perrhenate (ReO4-) sequestration from artificial groundwater. The pFe was significantly more effective than granular iron for both TcO4- and ReO4- sequestration under oxic conditions. The Tc removal capacity was 27.5 mg Tc/g pFe at pH ˜6.8, while the Re removal capacity was 23.9 mg Re/g pFe at pH ˜10.6. Tc K-edge XANES and EXAFS analyses indicated that the removed Tc species was 70-80% Tc(IV) that was likely incorporated into Fe corrosion products (i.e., Fe(OOH), Fe3O4) and 20-30% unreduced TcO4-. In contrast, the removed Re species was ReO4- only, without detectable Re(IV). In addition, the sequestered ReO4- was not extracted (<3%) by 0.1 M Na2SO4 and 1 M KI solution, which indicated that ReO4- and by chemical analogy, unreduced TcO4-, was likely incorporated into Fe corrosion products. This inexpensive pFe material may be applied to the sequestration and stabilization of 99TcO4- from contaminated environments and nuclear waste streams.
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Affiliation(s)
- Dien Li
- Savannah River National Laboratory, Aiken, SC, 29808, USA.
| | - John C Seaman
- Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, 29802, USA
| | - Simona E Hunyadi Murph
- Savannah River National Laboratory, Aiken, SC, 29808, USA; Department of Physics and Astronomy, University of Georgia, Athens, GA, 30602, USA
| | | | | | - Renfei Feng
- Canadian Light Source, Saskatoon, SK, S7N 0X4, Canada
| | - Hyunshik Chang
- Hӧganäs Environmental Solutions LLC, Cary, NC, 27513, USA
| | - Madan Tandukar
- Hӧganäs Environmental Solutions LLC, Cary, NC, 27513, USA
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7
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Wang L, Song H, Yuan L, Li Z, Zhang P, Gibson JK, Zheng L, Wang H, Chai Z, Shi W. Effective Removal of Anionic Re(VII) by Surface-Modified Ti 2CT x MXene Nanocomposites: Implications for Tc(VII) Sequestration. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:3739-3747. [PMID: 30843686 DOI: 10.1021/acs.est.8b07083] [Citation(s) in RCA: 76] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Environmental contamination by 99Tc(VII) from radioactive wastewater streams is of particular concern due to the long half-life of 99Tc and high mobility of pertechnetate. Herein, we report a novel MXene-polyelectrolyte nanocomposite with three-dimensional networks for enhanced removal of perrhenate, which is pertechnetate simulant. The introduction of poly(diallyldimethylammonium chloride) (PDDA) regulates the surface charge and improves the stability of Ti2CT x nanosheet, resulting in Re(VII) removal capacity of up to 363 mg g-1, and fast sorption kinetics. The Ti2CT x/PDDA nanocomposite furthermore exhibits good selectivity for ReO4- when competing anions (such as Cl- and SO42-) coexist at a concentration of 1800 times. The immobilization mechanism was confirmed as a sorption-reduction process by batch sorption experiments and X-ray photoelectron spectroscopy. The pH-dependent reducing activity of Ti2CT x/PDDA nanocomposite toward Re(VII) was clarified by X-ray absorption spectroscopy. As the pH increases, the local environment gradually changes from octahedral-coordinated Re(IV) to tetrahedral-coordinated Re(VII). The overall results suggest that Ti2CT x/PDDA nanocomposite may be a promising candidate for efficient elimination of Tc contamination. The reported surface modification strategy might result in applications of MXene-based materials in environmental remediation of other oxidized anion pollutants.
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Affiliation(s)
- Lin Wang
- Laboratory of Nuclear Energy Chemistry and Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics , Chinese Academy of Sciences , Beijing 100049 , China
| | - Huan Song
- Laboratory of Nuclear Energy Chemistry and Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics , Chinese Academy of Sciences , Beijing 100049 , China
- School of Chemistry and Chemical Engineering and Hunan Key Laboratory for the Design and Application of Actinide Complexes , University of South China , Hengyang 421001 , China
| | - Liyong Yuan
- Laboratory of Nuclear Energy Chemistry and Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics , Chinese Academy of Sciences , Beijing 100049 , China
| | - Zijie Li
- Laboratory of Nuclear Energy Chemistry and Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics , Chinese Academy of Sciences , Beijing 100049 , China
| | - Peng Zhang
- Laboratory of Nuclear Energy Chemistry and Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics , Chinese Academy of Sciences , Beijing 100049 , China
| | - John K Gibson
- Chemical Sciences Division , Lawrence Berkeley National Laboratory (LBNL) , Berkeley , California 94720 , United States
| | - Lirong Zheng
- Beijing Synchrotron Radiation Facility, Institute of High Energy Physics , Chinese Academy of Sciences , Beijing 100049 , China
| | - Hongqing Wang
- School of Chemistry and Chemical Engineering and Hunan Key Laboratory for the Design and Application of Actinide Complexes , University of South China , Hengyang 421001 , China
| | - Zhifang Chai
- Laboratory of Nuclear Energy Chemistry and Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics , Chinese Academy of Sciences , Beijing 100049 , China
- Engineering Laboratory of Advanced Energy Materials , Ningbo Institute of Industrial Technology, Chinese Academy of Sciences , Ningbo , Zhejiang 315201 , China
| | - Weiqun Shi
- Laboratory of Nuclear Energy Chemistry and Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics , Chinese Academy of Sciences , Beijing 100049 , China
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8
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Newsome L, Morris K, Cleary A, Masters-Waage NK, Boothman C, Joshi N, Atherton N, Lloyd JR. The impact of iron nanoparticles on technetium-contaminated groundwater and sediment microbial communities. JOURNAL OF HAZARDOUS MATERIALS 2019; 364:134-142. [PMID: 30343175 DOI: 10.1016/j.jhazmat.2018.10.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Revised: 08/31/2018] [Accepted: 10/02/2018] [Indexed: 06/08/2023]
Abstract
Iron nanoparticles are a promising new technology to treat contaminated groundwater, particularly as they can be engineered to optimise their transport properties. Technetium is a common contaminant at nuclear sites and can be reductively scavenged from groundwater by iron(II). Here we investigated the potential for a range of optimised iron nanoparticles to remove technetium from contaminated groundwater, and groundwater/sediment systems. Nano zero-valent iron and Carbo-iron stimulated the development of anoxic conditions while generating Fe(II) which reduced soluble Tc(VII) to sparingly soluble Tc(IV). Similar results were observed for Fe(II)-bearing biomagnetite, albeit at a slower rate. Tc(VII) remained in solution in the presence of the Fe(III) mineral nano-goethite, until acetate was added to stimulate microbial Fe(III)-reduction after which Tc(VII) concentrations decreased concomitant with Fe(II) ingrowth. The addition of iron nanoparticles to sediment microcosms caused an increase in the relative abundance of Firmicutes, consistent with fermentative/anoxic metabolisms. Residual bacteria from the synthesis of the biomagnetite nanoparticles were out-competed by the sediment microbial community. Overall the results showed that iron nanoparticles were highly effective in removing Tc(VII) from groundwater in sediment systems, and generated sustained anoxic conditions via the stimulation of beneficial microbial processes including Fe(III)-reduction and sulfate reduction.
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Affiliation(s)
- Laura Newsome
- Williamson Research Centre and Research Centre for Radwaste Disposal, School of Earth & Environmental Sciences, University of Manchester, Manchester, M13 9PL, UK.
| | - Katherine Morris
- Williamson Research Centre and Research Centre for Radwaste Disposal, School of Earth & Environmental Sciences, University of Manchester, Manchester, M13 9PL, UK
| | - Adrian Cleary
- Williamson Research Centre and Research Centre for Radwaste Disposal, School of Earth & Environmental Sciences, University of Manchester, Manchester, M13 9PL, UK
| | - Nicholas Karl Masters-Waage
- Williamson Research Centre and Research Centre for Radwaste Disposal, School of Earth & Environmental Sciences, University of Manchester, Manchester, M13 9PL, UK
| | - Christopher Boothman
- Williamson Research Centre and Research Centre for Radwaste Disposal, School of Earth & Environmental Sciences, University of Manchester, Manchester, M13 9PL, UK
| | - Nimisha Joshi
- Williamson Research Centre and Research Centre for Radwaste Disposal, School of Earth & Environmental Sciences, University of Manchester, Manchester, M13 9PL, UK
| | - Nick Atherton
- Sellafield Ltd. Land Quality, Sellafield, Seascale, Cumbria, CA20 1PG, UK
| | - Jonathan R Lloyd
- Williamson Research Centre and Research Centre for Radwaste Disposal, School of Earth & Environmental Sciences, University of Manchester, Manchester, M13 9PL, UK
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Masters-Waage NK, Morris K, Lloyd JR, Shaw S, Mosselmans JFW, Boothman C, Bots P, Rizoulis A, Livens FR, Law GTW. Impacts of Repeated Redox Cycling on Technetium Mobility in the Environment. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:14301-14310. [PMID: 29144125 DOI: 10.1021/acs.est.7b02426] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Technetium is a problematic contaminant at nuclear sites and little is known about how repeated microbiologically mediated redox cycling impacts its fate in the environment. We explore this question in sediments representative of the Sellafield Ltd. site, UK, over multiple reduction and oxidation cycles spanning ∼1.5 years. We found the amount of Tc remobilised from the sediment into solution significantly decreased after repeated redox cycles. X-ray Absorption Spectroscopy (XAS) confirmed that sediment bound Tc was present as hydrous TcO2-like chains throughout experimentation and that Tc's increased resistance to remobilization (via reoxidation to soluble TcO4-) resulted from both shortening of TcO2 chains during redox cycling and association of Tc(IV) with Fe phases in the sediment. We also observed that Tc(IV) remaining in solution during bioreduction was likely associated with colloidal magnetite nanoparticles. These findings highlight crucial links between Tc and Fe biogeochemical cycles that have significant implications for Tc's long-term environmental mobility, especially under ephemeral redox conditions.
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Affiliation(s)
- Nicholas K Masters-Waage
- Centre for Radiochemistry Research, School of Chemistry, The University of Manchester , M13 9PL, Manchester, United Kingdom
- Research Centre for Radwaste Disposal and Williamson Research Centre, School of Earth and Environmental Sciences, The University of Manchester , M13 9PL, Manchester, United Kingdom
| | - Katherine Morris
- Research Centre for Radwaste Disposal and Williamson Research Centre, School of Earth and Environmental Sciences, The University of Manchester , M13 9PL, Manchester, United Kingdom
| | - Jonathan R Lloyd
- Research Centre for Radwaste Disposal and Williamson Research Centre, School of Earth and Environmental Sciences, The University of Manchester , M13 9PL, Manchester, United Kingdom
| | - Samuel Shaw
- Research Centre for Radwaste Disposal and Williamson Research Centre, School of Earth and Environmental Sciences, The University of Manchester , M13 9PL, Manchester, United Kingdom
| | - J Frederick W Mosselmans
- Diamond Light Source Ltd ., Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom
| | - Christopher Boothman
- Research Centre for Radwaste Disposal and Williamson Research Centre, School of Earth and Environmental Sciences, The University of Manchester , M13 9PL, Manchester, United Kingdom
| | - Pieter Bots
- Research Centre for Radwaste Disposal and Williamson Research Centre, School of Earth and Environmental Sciences, The University of Manchester , M13 9PL, Manchester, United Kingdom
| | - Athanasios Rizoulis
- Research Centre for Radwaste Disposal and Williamson Research Centre, School of Earth and Environmental Sciences, The University of Manchester , M13 9PL, Manchester, United Kingdom
| | - Francis R Livens
- Centre for Radiochemistry Research, School of Chemistry, The University of Manchester , M13 9PL, Manchester, United Kingdom
| | - Gareth T W Law
- Centre for Radiochemistry Research, School of Chemistry, The University of Manchester , M13 9PL, Manchester, United Kingdom
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10
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Saslow SA, Um W, Pearce CI, Engelhard MH, Bowden ME, Lukens W, Leavy II, Riley BJ, Kim DS, Schweiger MJ, Kruger AA. Reduction and Simultaneous Removal of 99Tc and Cr by Fe(OH) 2(s) Mineral Transformation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:8635-8642. [PMID: 28695732 DOI: 10.1021/acs.est.7b02278] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Technetium (Tc) remains a priority remediation concern due to persistent challenges, including mobilization due to rapid reoxidation of immobilized Tc, and competing comingled contaminants, e.g., Cr(VI), that inhibit Tc(VII) reduction and incorporation into stable mineral phases. Here Fe(OH)2(s) is investigated as a comprehensive solution for overcoming these challenges, by serving as both the reductant, (Fe(II)), and the immobilization agent to form Tc-incorporated magnetite (Fe3O4). Trace metal analysis suggests removal of Tc(VII) and Cr(VI) from solution occurs simultaneously; however, complete removal and reduction of Cr(VI) is achieved earlier than the removal/reduction of comingled Tc(VII). Bulk oxidation state analysis of the final magnetite solid phase by XANES shows that the majority of Tc is Tc(IV), which is corroborated by XPS measurements. Furthermore, EXAFS results show successful, albeit partial, Tc(IV) incorporation into magnetite octahedral sites. Cr XPS analysis indicates reduction to Cr(III) and the formation of a Cr-incorporated spinel, Cr2O3, and Cr(OH)3 phases. Spinel (modeled as Fe3O4), goethite (α-FeOOH), and feroxyhyte (δ-FeOOH) are detected in all reacted final solid phase samples analyzed by XRD. Incorporation of Tc(IV) has little effect on the spinel lattice structure. Reaction of Fe(OH)2(s) in the presence of Cr(III) results in the formation of a spinel phase that is a solid solution between magnetite (Fe3O4) and chromite (FeCr2O4).
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Affiliation(s)
- Sarah A Saslow
- Pacific Northwest National Laboratory , 902 Battelle Boulevard, Richland, Washington 99354, United States
| | - Wooyong Um
- Pacific Northwest National Laboratory , 902 Battelle Boulevard, Richland, Washington 99354, United States
| | - Carolyn I Pearce
- Pacific Northwest National Laboratory , 902 Battelle Boulevard, Richland, Washington 99354, United States
| | - Mark H Engelhard
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory , Richland, Washington 99354, United States
| | - Mark E Bowden
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory , Richland, Washington 99354, United States
| | - Wayne Lukens
- Lawrence Berkeley National Laboratory , 1 Cyclotron Road, Berkeley, California 94720, United States
| | - Ian I Leavy
- Pacific Northwest National Laboratory , 902 Battelle Boulevard, Richland, Washington 99354, United States
| | - Brian J Riley
- Pacific Northwest National Laboratory , 902 Battelle Boulevard, Richland, Washington 99354, United States
| | - Dong-Sang Kim
- Pacific Northwest National Laboratory , 902 Battelle Boulevard, Richland, Washington 99354, United States
| | - Michael J Schweiger
- Pacific Northwest National Laboratory , 902 Battelle Boulevard, Richland, Washington 99354, United States
| | - Albert A Kruger
- United States Department of Energy, Office of River Protection , P.O. Box 450, Richland, Washington 99352, United States
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Smith FN, Um W, Taylor CD, Kim DS, Schweiger MJ, Kruger AA. Computational Investigation of Technetium(IV) Incorporation into Inverse Spinels: Magnetite (Fe3O4) and Trevorite (NiFe2O4). ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:5216-5224. [PMID: 27049925 DOI: 10.1021/acs.est.6b00200] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Iron oxides and oxyhydroxides play an important role in minimizing the mobility of redox-sensitive elements in engineered and natural environments. For the radionuclide technetium-99 (Tc), these phases hold promise as primary hosts for increasing Tc loading into glass waste form matrices, or as secondary sinks during the long-term storage of nuclear materials. Recent experiments show that the inverse spinel, magnetite [Fe(II)Fe(III)2O4], can incorporate Tc(IV) into its octahedral sublattice. In that same class of materials, trevorite [Ni(II)Fe(III)2O4] is also being investigated for its ability to host Tc(IV). However, questions remain regarding the most energetically favorable charge-compensation mechanism for Tc(IV) incorporation in each structure, which will affect Tc behavior under changing waste processing or storage conditions. Here, quantum-mechanical methods were used to evaluate incorporation energies and optimized lattice bonding environments for three different, charge-balanced Tc(IV) incorporation mechanisms in magnetite and trevorite (∼5 wt % Tc). For both phases, the removal of two octahedral Fe(II) or Ni(II) ions upon the addition of Tc(IV) in an octahedral site is the most stable mechanism, relative to the creation of octahedral Fe(III) defects or increasing octahedral Fe(II) content. Following hydration-energy corrections, Tc(IV) incorporation into magnetite is energetically favorable while an energy barrier exists for trevorite.
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Affiliation(s)
- Frances N Smith
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99354, United States
| | - Wooyong Um
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99354, United States
- Pohang University of Science and Technology (POSTECH), Pohang, South Korea
| | - Christopher D Taylor
- Fontana Corrosion Center, Materials Science and Engineering, The Ohio State University , Columbus Ohio 43210, United States
- Strategic Research and Innovation, DNV GL , Dublin Ohio 43017, United States
| | - Dong-Sang Kim
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99354, United States
| | - Michael J Schweiger
- Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99354, United States
| | - Albert A Kruger
- United States Department of Energy, Office of River Protection, P.O. Box 450, Richland, Washington 99352, United States
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Brookshaw DR, Pattrick RAD, Bots P, Law GTW, Lloyd JR, Mosselmans JFW, Vaughan DJ, Dardenne K, Morris K. Redox Interactions of Tc(VII), U(VI), and Np(V) with Microbially Reduced Biotite and Chlorite. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2015; 49:13139-13148. [PMID: 26488884 DOI: 10.1021/acs.est.5b03463] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Technetium, uranium, and neptunium are contaminants that cause concern at nuclear facilities due to their long half-life, environmental mobility, and radiotoxicity. Here we investigate the impact of microbial reduction of Fe(III) in biotite and chlorite and the role that this has in enhancing mineral reactivity toward soluble TcO4(-), UO2(2+), and NpO2(+). When reacted with unaltered biotite and chlorite, significant sorption of U(VI) occurred in low carbonate (0.2 mM) buffer, while U(VI), Tc(VII), and Np(V) showed low reactivity in high carbonate (30 mM) buffer. On reaction with the microbially reduced minerals, all radionuclides were removed from solution with U(VI) reactivity influenced by carbonate. Analysis by X-ray absorption spectroscopy (XAS) confirmed reductive precipitation to poorly soluble U(IV) in low carbonate conditions and both Tc(VII) and Np(V) in high carbonate buffer were also fully reduced to poorly soluble Tc(IV) and Np(IV) phases. U(VI) reduction was inhibited under high carbonate conditions. Furthermore, EXAFS analysis suggested that in the reaction products, Tc(IV) was associated with Fe, Np(IV) formed nanoparticulate NpO2, and U(IV) formed nanoparticulate UO2 in chlorite and was associated with silica in biotite. Overall, microbial reduction of the Fe(III) associated with biotite and chlorite primed the minerals for reductive scavenging of radionuclides: this has clear implications for the fate of radionuclides in the environment.
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Affiliation(s)
- Diana R Brookshaw
- Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, School of Earth, Atmospheric and Environmental Sciences, The University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom
| | - Richard A D Pattrick
- Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, School of Earth, Atmospheric and Environmental Sciences, The University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom
| | - Pieter Bots
- Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, School of Earth, Atmospheric and Environmental Sciences, The University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom
| | - Gareth T W Law
- Centre for Radiochemistry Research, School of Chemistry, The University of Manchester , Manchester M13 9PL, United Kingdom
| | - Jonathan R Lloyd
- Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, School of Earth, Atmospheric and Environmental Sciences, The University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom
| | - J Fredrick W Mosselmans
- Diamond Light Source Ltd., Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
| | - David J Vaughan
- Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, School of Earth, Atmospheric and Environmental Sciences, The University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom
| | - Kathy Dardenne
- Karlsruhe Institute of Technology, Institut fur Nukleare Entsorgung , D-76021 Karlsruhe, Baden-Württemberg, Germany
| | - Katherine Morris
- Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, School of Earth, Atmospheric and Environmental Sciences, The University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom
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Marshall TA, Morris K, Law GTW, Mosselmans JFW, Bots P, Parry SA, Shaw S. Incorporation and retention of 99-Tc(IV) in magnetite under high pH conditions. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2014; 48:11853-11862. [PMID: 25236360 DOI: 10.1021/es503438e] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
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.
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Affiliation(s)
- Timothy A Marshall
- Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, School of Earth, Atmospheric and Environmental Sciences, The University of Manchester , Manchester, M13 9PL, United Kingdom
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