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Sockwell AK, DiBlasi NA, Hixon AE. A spectrophotometric study of the impact of pH and metal-to-ligand ratio on the speciation of the Pu(VI)-oxalate system. Phys Chem Chem Phys 2023. [PMID: 38018253 DOI: 10.1039/d3cp04010k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2023]
Abstract
The oxalate ligand is prevalent throughout the nuclear fuel cycle. While the Pu(III)- and Pu(IV)-oxalate systems are well studied due to their use in plutonium metal and PuO2 production, the effect of oxalate on Pu(VI) remains understudied. Absorption spectroscopy was employed to probe the solution behavior of the Pu(VI)-oxalate system as a function of pH (1, 3, 7) and metal-to-ligand ratio (M/L; 10 : 1-1 : 10). Peak changes in the UV-vis-NIR spectra were associated with the formation of multiple Pu(VI)-oxalate species with increasing oxalate concentration. Some insight into identification of species present in solution was gained from the limited Pu(VI)-oxalate literature and comparisons with the assumed isostructural U(VI)-oxalate system. A peak in the UV-vis-NIR spectrum at 839 nm, which corresponds to the formation of a 1 : 1 PuO2(C2O4)(aq) complex, was observed and used to determine the formation constant (log β° = 4.64 ± 0.06). A higher coordinated Pu(VI)-oxalate peak at 846 nm was tentatively assigned as the 1 : 2 complex PuO2(C2O4)22- and a preliminary formation constant was determined (log β° = 9.30 ± 0.08). The predominance of both complexes was shown in speciation diagrams calculated from the formation constants, illustrating the importance of considering the Pu(VI)-oxalate system in the nuclear fuel cycle.
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Affiliation(s)
- A Kirstin Sockwell
- Department of Civil & Environmental Engineering & Earth Sciences, University of Notre Dame, Notre Dame, IN 46556, USA.
| | - Nicole A DiBlasi
- Department of Civil & Environmental Engineering & Earth Sciences, University of Notre Dame, Notre Dame, IN 46556, USA.
| | - Amy E Hixon
- Department of Civil & Environmental Engineering & Earth Sciences, University of Notre Dame, Notre Dame, IN 46556, USA.
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Predicting degradation of organic molecules in cementitious media. PROGRESS IN NUCLEAR ENERGY 2021. [DOI: 10.1016/j.pnucene.2021.103888] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Albina P, Durban N, Bertron A, Albrecht A, Robinet JC, Erable B. Nitrate and nitrite bacterial reduction at alkaline pH and high nitrate concentrations, comparison of acetate versus dihydrogen as electron donors. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2021; 280:111859. [PMID: 33352382 DOI: 10.1016/j.jenvman.2020.111859] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 12/03/2020] [Accepted: 12/13/2020] [Indexed: 06/12/2023]
Abstract
This study assesses bacterial denitrification at alkaline pH, up to 12, and high nitrate concentration, up to 400 mM. Two types of electron donors organic (acetate) and inorganic (dihydrogen) were compared. With both types of electron donors, nitrite reduction was the key step, likely to increase the pH and lead to nitrite accumulation. Firstly, an acclimation process was used: nitrate was progressively increased in three cultures set at pH 9, 10, or 11. This method allowed to observe for the first time nitrate reduction up to pH 10 and 100 mM nitrate with dihydrogen, or up to pH 10 and 400 mM nitrate with acetate. Nitrate reduction kinetics were faster in the presence of acetate. To investigate further the impact of the type of electron donor, a transition from acetate to dihydrogen was tested, and the pH evolution was modelled. Denitrification with dihydrogen strongly increases the pH while with acetate the pH evolution depends on the initial pH. The main difference is the production of acidifying CO2 during the acetate oxidation. Finally, the use of long duration cultures with a highly alkaline pH allowed a nitrate reduction up to pH 11.5 with acetate. However, no reduction was possible in hydrogenotrophy as it would have increased the pH further. Instead, bacteria used organic matter from inoculum to reduce nitrate at pH 11.5. Therefore, considering bacterial denitrification in a context of alkaline pH and high nitrate concentration an organic electron donor such as acetate is advantageous.
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Affiliation(s)
- Pierre Albina
- LGC, CNRS, INPT, UPS, Université de Toulouse, Toulouse, France; LMDC, INSA/UPS Génie Civil, Université de Toulouse, 135 Avenue de Rangueil, 31077, Toulouse Cedex 04, France.
| | - Nadège Durban
- LGC, CNRS, INPT, UPS, Université de Toulouse, Toulouse, France; LMDC, INSA/UPS Génie Civil, Université de Toulouse, 135 Avenue de Rangueil, 31077, Toulouse Cedex 04, France
| | - Alexandra Bertron
- LMDC, INSA/UPS Génie Civil, Université de Toulouse, 135 Avenue de Rangueil, 31077, Toulouse Cedex 04, France
| | - Achim Albrecht
- Andra, 1-7 rue Jean-Monet, Châtenay-Malabry, 62298, France
| | | | - Benjamin Erable
- LGC, CNRS, INPT, UPS, Université de Toulouse, Toulouse, France.
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Uranyl oxalate species in high ionic strength environments: stability constants for aqueous and solid uranyl oxalate complexes. RADIOCHIM ACTA 2021. [DOI: 10.1515/ract-2020-0083] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
Uranyl ion, UO2
2+, and its aqueous complexes with organic and inorganic ligands can be the dominant species for uranium transport on the Earth surface or in a nuclear waste disposal system if an oxidizing condition is present. As an important biodegradation product, oxalate, C2O4
2−, is ubiquitous in natural environments and is known for its ability to complex with the uranyl ion. Oxalate can also form solid phases with uranyl ion in certain environments thus limiting uranium migration. Therefore, the determination of stability constants for aqueous and solid uranyl oxalate complexes is important not only to the understanding of uranium mobility in natural environments, but also to the performance assessment of nuclear waste disposal. Here we developed a thermodynamic model for the UO2
2+–Na+–H+–Cl––ClO4
––C2O4
2––NO3
––H2O system to ionic strength up to ∼11 mol•kg−1. We constrained the stability constants for UO2C2O4(aq) and UO2(C2O4)2
2− at infinite dilution based on our evaluation of the literature data over a wide range of ionic strengths up to ∼11 mol•kg−1. We also obtained the solubility constants at infinite dilution for solid uranyl oxalates, UO2C2O4•3H2O, based on the solubility data over a wide range of ionic strengths. The developed model will enable for the accurate stability assessment of oxalate complexes affecting uranium mobility under a wide range of conditions including those in deep geological repositories.
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Ruiz-Fresneda MA, Gomez-Bolivar J, Delgado-Martin J, Abad-Ortega MDM, Guerra-Tschuschke I, Merroun ML. The Bioreduction of Selenite under Anaerobic and Alkaline Conditions Analogous to Those Expected for a Deep Geological Repository System. Molecules 2019; 24:molecules24213868. [PMID: 31717840 PMCID: PMC6865132 DOI: 10.3390/molecules24213868] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2019] [Revised: 10/21/2019] [Accepted: 10/22/2019] [Indexed: 12/23/2022] Open
Abstract
The environmental conditions for the planned geological disposal of radioactive waste —including hyper-alkaline pH, radiation or anoxia—are expected to be extremely harsh for microbial activity. However, it is thought that microbial communities will develop in these repositories, and this would have implications for geodisposal integrity and the control of radionuclide migration through the surrounding environment. Nuclear waste contains radioactive isotopes of selenium (Se) such as 79Se, which has been identified as one of the main radionuclides in a geodisposal system. Here, we use the bacterial species Stenotrophomonas bentonitica, isolated from bentonites serving as an artificial barrier reference material in repositories, to study the reduction of selenite (SeIV) under simulated geodisposal conditions. This bacterium is able to reduce toxic SeIV anaerobically from a neutral to alkaline initial pH (up to pH 10), thereby producing elemental selenium (Se0) nanospheres and nanowires. A transformation process from amorphous Se (a-Se) nanospheres to trigonal Se (t-Se) nanowires, through the formation of monoclinic Se (m-Se) aggregates as an intermediate step, is proposed. The lesser solubility of Se0 and t-Se makes S. bentonitica a potential candidate to positively influence the security of a geodisposal system, most probably with lower efficiency rates than those obtained aerobically.
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Affiliation(s)
- Miguel Angel Ruiz-Fresneda
- Department of Microbiology, University of Granada, 18071 Granada, Spain; (J.G.-B.); (J.D.-M.); (M.L.M.)
- Correspondence:
| | - Jaime Gomez-Bolivar
- Department of Microbiology, University of Granada, 18071 Granada, Spain; (J.G.-B.); (J.D.-M.); (M.L.M.)
| | - Josemaria Delgado-Martin
- Department of Microbiology, University of Granada, 18071 Granada, Spain; (J.G.-B.); (J.D.-M.); (M.L.M.)
| | - Maria del Mar Abad-Ortega
- Centro de Instrumentación Científica (CIC), University of Granada, 18071 Granada, Spain; (M.d.M.A.-O.); (I.G.-T.)
| | - Isabel Guerra-Tschuschke
- Centro de Instrumentación Científica (CIC), University of Granada, 18071 Granada, Spain; (M.d.M.A.-O.); (I.G.-T.)
| | - Mohamed Larbi Merroun
- Department of Microbiology, University of Granada, 18071 Granada, Spain; (J.G.-B.); (J.D.-M.); (M.L.M.)
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Tramaux A, Azéma N, El Bitouri Y, David G, Negrell C, Poulesquen A, Haas J, Remond S. Synthesis of phosphonated comb-like copolymers and evaluation of their dispersion efficiency on CaCO3 suspensions part II: Effect of macromolecular structure and ionic strength. POWDER TECHNOL 2018. [DOI: 10.1016/j.powtec.2018.04.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Rafrafi Y, Durban N, Bertron A, Albrecht A, Robinet JC, Erable B. Use of a continuous-flow bioreactor to evaluate nitrate reduction rate of Halomonas desiderata in cementitious environment relevant to nuclear waste deep repository. Biochem Eng J 2017. [DOI: 10.1016/j.bej.2017.05.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Malgaretti P, Pagonabarraga I, Rubi JM. Entropic electrokinetics: recirculation, particle separation, and negative mobility. PHYSICAL REVIEW LETTERS 2014; 113:128301. [PMID: 25279646 DOI: 10.1103/physrevlett.113.128301] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Indexed: 05/28/2023]
Abstract
We show that when particles are suspended in an electrolyte confined between corrugated charged surfaces, electrokinetic flows lead to a new set of phenomena such as particle separation, mixing for low-Reynolds micro- and nanometric devices, and negative mobility. Our analysis shows that such phenomena arise, for incompressible fluids, due to the interplay between the electrostatic double layer and the corrugated geometrical confinement and that they are magnified when the width of the channel is comparable to the Debye length. Our characterization allows us to understand the physical origin of such phenomena, therefore, shedding light on their possible relevance in a wide variety of situations ranging from nano- and microfluidic devices to biological systems.
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Affiliation(s)
- Paolo Malgaretti
- Department de Fisica Fonamental, Universitat de Barcelona, Carrer Martí i Franqués, 08028-Barcelona, Spain
| | - Ignacio Pagonabarraga
- Department de Fisica Fonamental, Universitat de Barcelona, Carrer Martí i Franqués, 08028-Barcelona, Spain
| | - J Miguel Rubi
- Department de Fisica Fonamental, Universitat de Barcelona, Carrer Martí i Franqués, 08028-Barcelona, Spain and Department of Chemistry, Imperial College London, SW7 2AZ London, United Kingdom
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