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Yorkshire AS, Stennett MC, Walkley B, Provis JL, Townsend LT, Haigh LT, Hyatt NC, Mottram LM, Corkhill CL. Spectroscopic identification of Ca-bearing uranyl silicates formed in C-S-H systems. Sci Rep 2023; 13:3374. [PMID: 36854709 DOI: 10.1038/s41598-023-30024-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Accepted: 02/14/2023] [Indexed: 03/02/2023] Open
Abstract
Portland cement-based grouts used for radioactive waste immobilisation contain a Ca- and Si-rich binder phase, known as calcium-silicate-hydrate (C-S-H). Depending on the blend of cement used, the Ca/Si ratio can vary considerably. A range of C-S-H minerals with Ca/Si ratios from 0.6 to 1.6 were synthesised and contacted with aqueous U(VI) at 0.5 mM and 10 mM concentrations. Solid-state 29Si MAS-NMR spectroscopy was applied to probe the Si coordination environment in U(VI)-contacted C-S-H minerals and, in conjunction with U LIII-edge X-ray absorption spectroscopy analysis, inferences of the fate of U(VI) in these systems were made. At moderate or high Ca/Si ratios, uranophane-type uranyl silicates or Ca-uranates dominated, while at the lowest Ca/Si ratios, the formation of a Ca-bearing uranyl silicate mineral, similar to haiweeite (Ca[(UO2)2Si5O12(OH)2]·3H2O) or Ca-bearing weeksite (Ca2(UO2)2Si6O15·10H2O) was identified. This study highlights the influence of Ca/Si ratio on uranyl sequestration, of interest in the development of post-closure safety models for U-bearing radioactive waste disposal.
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Pan D, Zhao X, Wang P, Li P, Li Y, Wu W, Wang Z, Fan Q. Insights into sorption speciation of uranium on phlogopite: Evidence from TRLFS and DFT calculation. J Hazard Mater 2022; 427:128164. [PMID: 34991008 DOI: 10.1016/j.jhazmat.2021.128164] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 12/14/2021] [Accepted: 12/24/2021] [Indexed: 06/14/2023]
Abstract
Knowledge of the sorption speciation of uranium at mineral/water interface is essential to construct reliable retention and migration models. In this work, the sorption speciation of U(VI) at the phlogopite/water interface was studied at trace concentrations by combining batch sorption, time-resolved luminescence spectroscopy, and theoretical calculation. Batch experiments showed that the sorption of U(VI) on phlogopite was strongly dependent on pH but weakly affected by ionic strength, implying that the inner-sphere surface complexation was mainly responsible for U(VI) sorption on phlogopite. The diverse luminescence spectral characteristics indicated the formation of multiple inner-sphere surface species at the phlogopite/water interface, whose abundances varied as a function of pH. A portion of U(VI) precipitated as uranyl oxyhydroxides such as metaschoepite and becquerelite at high pH. Density functional theory calculation revealed that the bidentate complex at the edge of phlogopite (≡AlO-MgO-UO2(H2O)3) was the most favorable sorption configuration for U(VI) at acidic condition. The increasing temperature enhanced the sorption of U(VI) on phlogopite without altering the sorption species, and such enhancement in U(VI) sorption was withdrawn once the temperature decreased. These findings are essential for understanding the immobilization mechanism of U(VI) in mica-rich granitic terrains at a molecular scale and building a reliable retention model.
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Affiliation(s)
- Duoqiang Pan
- Frontiers Science Center for Rare Isotopes, Lanzhou University, Lanzhou 730000, China; School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China.
| | - Xiaodong Zhao
- School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China
| | - Peng Wang
- School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China
| | - Ping Li
- Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
| | - Yuhong Li
- School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China
| | - Wangsuo Wu
- Frontiers Science Center for Rare Isotopes, Lanzhou University, Lanzhou 730000, China
| | - Zheming Wang
- Pacific Northwest National Laboratory, Richland, WA 99352, United States
| | - Qiaohui Fan
- Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
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Wang Y, Wu J, Pu H. Effect of calcium formate as an accelerator on dilatancy deformation, strength and microstructure of cemented tailings backfill. Chemosphere 2022; 291:132710. [PMID: 34718028 DOI: 10.1016/j.chemosphere.2021.132710] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 10/09/2021] [Accepted: 10/24/2021] [Indexed: 06/13/2023]
Abstract
Recycling mining wastes to produce cemented tailings backfill (CTB) is the optimal approach to eliminate the environmental pollution caused by their accumulation. However, its low strength limits its application. Using calcium formate (CF) as an accelerator for improving its mechanical properties is of great significance to promote sustainable development. The effects of CF dosage and curing time on dilatancy deformation, compressive strength and microstructure of CTB were investigated through mechanical compression, scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) tests. The strengthening and deterioration mechanisms of CF dosage on CTB were revealed, and its engineering practicability was systematically evaluated. The results show that the variation of volumetric strain in the dilatancy deformation stage firstly increase and then decrease with the increases of CF dosage and curing time. The relationship between CF dosage and compressive strength can be characterized by quadratic polynomial, and the optimal CF dosage characterizing the superior mechanical property of CTB is between 1.60 and 1.84. The supplement of CF reduces the size and distribution of microcracks and micropores, thereby optimizing the microstructure of CTB. Nevertheless, the excessive dosages of CF deteriorate the microstructure of CTB and produce serious defects, which cannot be effectively filled by hydration products, thus weakening the strength property of CTB. This study provides an effective accelerator for improving the mechanical properties of CTB, which is of great significance to promote the recycling of tailings.
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Affiliation(s)
- Yiming Wang
- State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Xuzhou, Jiangsu, 221116, China
| | - Jiangyu Wu
- State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Xuzhou, Jiangsu, 221116, China.
| | - Hai Pu
- State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Xuzhou, Jiangsu, 221116, China; College of Mining Engineering and Geology, Xinjiang Institute of Engineering, Urumqi, Xinjiang, 830091, China
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Yorkshire AS, Stennett MC, Walkley B, O’Sullivan SE, Mottram LM, Bailey DJ, Provis JL, Hyatt NC, Corkhill CL. Spectroscopic evaluation of U VI-cement mineral interactions: ettringite and hydrotalcite. J Synchrotron Radiat 2022; 29:89-102. [PMID: 34985426 PMCID: PMC8733996 DOI: 10.1107/s1600577521011553] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Accepted: 11/02/2021] [Indexed: 06/14/2023]
Abstract
Portland cement based grouts used for radioactive waste immobilization contain high replacement levels of supplementary cementitious materials, including blast-furnace slag and fly ash. The minerals formed upon hydration of these cements may have capacity for binding actinide elements present in radioactive waste. In this work, the minerals ettringite (Ca6Al2(SO4)3(OH)12·26H2O) and hydrotalcite (Mg6Al2(OH)16CO3·4H2O) were selected to investigate the importance of minor cement hydrate phases in sequestering and immobilizing UVI from radioactive waste streams. U LIII-edge X-ray absorption spectroscopy (XAS) was used to probe the UVI coordination environment in contact with these minerals. For the first time, solid-state 27Al magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy was applied to probe the Al coordination environment in these UVI-contacted minerals and make inferences on the UVI coordination, in conjunction with the X-ray spectroscopy analyses. The U LIII-edge XAS analysis of the UVI-contacted ettringite phases found them to be similar (>∼70%) to the uranyl oxyhydroxides present in a mixed becquerelite/metaschoepite mineral. Fitting of the EXAFS region, in combination with 27Al NMR analysis, indicated that a disordered Ca- or Al-bearing UVI secondary phase also formed. For the UVI-contacted hydrotalcite phases, the XAS and 27Al NMR data were interpreted as being similar to uranyl carbonate, that was likely Mg-containing.
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Affiliation(s)
- Antonia S. Yorkshire
- Immobilization Science Laboratory, Department of Materials Science and Engineering, University of Sheffield, Sheffield S1 3JD, United Kingdom
| | - Martin C. Stennett
- Immobilization Science Laboratory, Department of Materials Science and Engineering, University of Sheffield, Sheffield S1 3JD, United Kingdom
| | - Brant Walkley
- Immobilization Science Laboratory, Department of Materials Science and Engineering, University of Sheffield, Sheffield S1 3JD, United Kingdom
- Sustainable Materials at Sheffield, Department of Chemical and Biological Engineering, University of Sheffield, Sheffield, United Kingdom
| | - Sarah E. O’Sullivan
- Immobilization Science Laboratory, Department of Materials Science and Engineering, University of Sheffield, Sheffield S1 3JD, United Kingdom
| | - Lucy M. Mottram
- Immobilization Science Laboratory, Department of Materials Science and Engineering, University of Sheffield, Sheffield S1 3JD, United Kingdom
| | - Daniel J. Bailey
- Immobilization Science Laboratory, Department of Materials Science and Engineering, University of Sheffield, Sheffield S1 3JD, United Kingdom
| | - John L. Provis
- Immobilization Science Laboratory, Department of Materials Science and Engineering, University of Sheffield, Sheffield S1 3JD, United Kingdom
| | - Neil C. Hyatt
- Immobilization Science Laboratory, Department of Materials Science and Engineering, University of Sheffield, Sheffield S1 3JD, United Kingdom
| | - Claire L. Corkhill
- Immobilization Science Laboratory, Department of Materials Science and Engineering, University of Sheffield, Sheffield S1 3JD, United Kingdom
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Baqer Y, Bateman K, Tan VMS, Stewart DI, Chen X, Thornton SF. The Influence of Hyper-Alkaline Leachate on a Generic Host Rock Composition for a Nuclear Waste Repository: Experimental Assessment and Modelling of Novel Variable Porosity and Surface Area. Transp Porous Media 2021; 140:559-80. [DOI: 10.1007/s11242-021-01702-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Abstract
Deep geological disposal is the preferred solution for long-term storage of radioactive waste in many countries. In a deep repository, cementitious materials are widely used in the structure and buffer/backfill of the repository for the stabilisation of the hazardous materials. The cement acts as a physical barrier and also contributes chemically to waste containment by buffering the groundwater to a high pH, limiting the solubility of many radionuclides. This paper describes an experimental and modelling study which evaluates the geochemical interaction between young cement leachate (YCL, pH = 13) and a generic hard rock (in this case Hollington sandstone, representing a ‘hard’ host rock) during permeation with the leachate, as it drives mineralogical changes in the system. One-dimensional reactive transport was modelled using a mixing cell approach within the PHREEQC geochemical code to identify the essential parameters and understand and scale up the effect of variations in these parameters on the observed geochemical processes. This study also focused on the effects of variable porosity, reactive surface area and pore volume on improving the modelling of rock alteration in the system compared to conventional models that assume constant values for these properties. The numerical results showed that the interaction between the injected hyper-alkaline leachate and the sandstone sample results in a series of mineralogical reactions. The main processes were the dissolution of quartz, kaolinite and k-feldspar which was coupled with the precipitation of calcium silicate hydrate gel and tobermorite-14A (C–S–H), prehnite (hydrated silicate), saponite-Mg (smectite clay) and mesolite (Na–Ca zeolite). The simulation showed that the overall porosity of the system increased as primary minerals dissolve and no stable precipitation of the secondary C–S–H /C–A–S–H phases was predicted. The variable porosity scenario provides a better fitting to experimental data and more detailed trends of chemistry change within the column. The time and the number of moles of precipitated secondary phases were also improved which was related to greater exposure surface area of the minerals in the sandstone sample to the YCL.
Article Highlights
The drop in calcium, aluminium and silicate concentrations is mainly due to the formation of calcium silicate hydrate and zeolite minerals as secondary phases. The simulation showed that the overall porosity of the system increased as primary minerals dissolve and no stable precipitation of the secondary C–S–H /C–A–S–H phases was predicted.
The dissolution of primary minerals and the precipitation of secondary C–S–H phases had a minimal effect on the pH values, and this was controlled mainly by the initial fluid chemistry.
The variable porosity scenario provides a better fitting to experimental data and more detailed trends of chemistry change within the column.
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Xiao Y, Zhang X, Tan Z, Zeng J, Zhang D, Dong H, He Y. Facile separation of Th(IV) from aqueous solution by graphene hydrogel. J Radioanal Nucl Chem 2020; 326:379-386. [DOI: 10.1007/s10967-020-07351-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Gijbels K, Landsberger S, Samyn P, Iacobescu RI, Pontikes Y, Schreurs S, Schroeyers W. Radiological and non-radiological leaching assessment of alkali-activated materials containing ground granulated blast furnace slag and phosphogypsum. Sci Total Environ 2019; 660:1098-1107. [PMID: 30743907 DOI: 10.1016/j.scitotenv.2019.01.089] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Revised: 01/08/2019] [Accepted: 01/08/2019] [Indexed: 06/09/2023]
Abstract
Alkali-activated materials (AAMs) based on ground granulated blast furnace slag (GGBFS) and phosphogypsum (PG) were investigated in order to quantify leaching of naturally occurring radionuclides (NOR) and inorganic non-radiological elements according to an up-flow percolation column test as described in CEN/TS 16637-3. Gamma spectroscopy and neutron activation analysis (NAA) were applied for radiological characterization, inductively coupled plasma optical emission spectrometry (ICP-OES) and ion-chromatography (IC) for chemical characterization. Upon leaching, 238U, 226Ra, 210Pb, and 228Ra were retained very well. Both for 232Th and 40K, a decrease in activity concentration was observed due to leaching and their release was influenced by the use of different alkali activators, which was also the case for the leaching of non-radiological elements. Only a small amount of Al (0.5-0.8%), Ca (0.1-0.2%) and Si (0.1-0.3%) was mobilized, while highest release was observed for K (56-94%), Na (49-88%) and S (71-87%). At first glance, drinking water is not endangered by leaching of NOR following the requirements of the European Drinking Water Directive. From the results for porosity, obtained with mercury intrusion porosimetry (MIP), it was concluded that both the porosity and formation of multiple leachable and non-leachable complexes are determining factors for the release of elements from AAMs.
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Affiliation(s)
- Katrijn Gijbels
- Hasselt University, CMK, Nuclear Technological Centre, Agoralaan, Gebouw H, 3590 Diepenbeek, Belgium.
| | - Sheldon Landsberger
- Nuclear Engineering Teaching Lab, University of Texas at Austin, Pickle Research Campus, Austin, TX 78712, USA.
| | - Pieter Samyn
- Hasselt University, IMO, Applied and Analytical Chemistry, Agoralaan, Gebouw D, 3590 Diepenbeek, Belgium.
| | - Remus Ion Iacobescu
- KU Leuven, Department of Materials Engineering, Kasteelpark Arenberg 44, 3001 Leuven, Belgium.
| | - Yiannis Pontikes
- KU Leuven, Department of Materials Engineering, Kasteelpark Arenberg 44, 3001 Leuven, Belgium.
| | - Sonja Schreurs
- Hasselt University, CMK, Nuclear Technological Centre, Agoralaan, Gebouw H, 3590 Diepenbeek, Belgium.
| | - Wouter Schroeyers
- Hasselt University, CMK, Nuclear Technological Centre, Agoralaan, Gebouw H, 3590 Diepenbeek, Belgium.
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Colmenero F, Fernández AM, Timón V, Cobos J. Becquerelite mineral phase: crystal structure and thermodynamic and mechanical stability by using periodic DFT. RSC Adv 2018; 8:24599-24616. [PMID: 35539173 PMCID: PMC9082112 DOI: 10.1039/c8ra04678f] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Accepted: 07/02/2018] [Indexed: 12/22/2022] Open
Abstract
The structure, thermodynamic and mechanical properties of becquerelite mineral, Ca(UO2)6O4(OH)6·8H2O, were studied by means of theoretical solid-state calculations based on density functional theory using plane waves and pseudopotentials. The positions of the hydrogen atoms in the unit cell of becquerelite mineral were optimized theoretically since it was not possible to determine them from X-ray diffraction data by structure refinement. The structural results, including the lattice parameters, bond lengths and X-ray powder pattern, were found to be in excellent agreement with their experimental counterparts. The fundamental thermodynamic properties of becquerelite mineral, including specific heat, entropy, enthalpy and Gibbs free energy, were then computed by performing phonon calculations at the computed optimized structure. Since the experimental values of these properties are unknown, their values were predicted. The values obtained for the isobaric specific heat and entropy of becquerelite at the temperature of 298.15 K were 148.4 and 172.3 J K−1 mol−1, respectively. The computed thermodynamic properties were combined with those of the corresponding elements in order to obtain the enthalpy and Gibbs free energy of formation as a function of temperature. The availability of these thermodynamic properties of formation allowed to determine the enthalpies and free energies and associated reaction constants of a series of reactions involving becquerelite and other uranyl containing materials. Futhermore, knowledge of these properties permitted the study of the thermodynamic stability of becquerelite with respect to a rich set of secondary phases of spent nuclear fuel, including dehydrated schoepite, schoepite, metaschoepite, studtite, metastudtite, rutherfordine and soddyite under different conditions of temperature. Becquerelite is shown to be highly stable in the presence of hydrogen peroxide. It is the second most stable phase under intermediate hydrogen peroxide concentrations (after schoepite), and the fourth most stable phase under high hydrogen peroxide concentrations (after studtite, schoepite and metaschoepite). Finally, the equation of state and elastic properties of this mineral, unknown to date, were determined. The crystal structure of becquerelite was found to be stable mechanically and dynamically. Becquerelite can be described as a brittle material exhibiting large anisotropy and large compressibility in the direction perpendicular to the sheets characterizing the structure of this layered uranyl containing material. The dependence of the elastic properties of becquerelite with respect to the strain orientation is shown to be analogous to that of schoepite mineral. The calculated bulk modulus is also very similar to that of schoepite, B ∼ 31 GPa. The full crystal structure of becquerelite mineral phase was successfully determined using theoretical solid-state methods for the first time. Additionally, a complete study of its thermodynamic and mechanical properties and stability is reported.![]()
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Affiliation(s)
| | - Ana María Fernández
- Centro de Investigaciones Energéticas
- Medioambientales y Tecnológicas (CIEMAT)
- Madrid
- Spain
| | - Vicente Timón
- Instituto de Estructura de la Materia (IEM-CSIC)
- 28006 Madrid
- Spain
| | - Joaquin Cobos
- Centro de Investigaciones Energéticas
- Medioambientales y Tecnológicas (CIEMAT)
- Madrid
- Spain
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