Activity Coefficients of Uranyl Nitrate and Nitric Acid in Aqueous Mixtures

Ochkin, A. V.; Gladilov, D. Yu.; Nekhaevskiy, Sergey; Меркушкин, А. О.

doi:10.1016/j.proche.2016.10.013

Cited by 7 publications

(7 citation statements)

References 6 publications

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“…Predicted activity coefficients nitric acid (a, b) and uranyl nitrate (c, d) using the Pitzer paraments of Li et al, Hlushak et al, Jové Colón et al, and our results versus experimental results: (a) 0.7–1 nitric acid activity coefficients; (b) 1–4 nitric acid activity coefficients; (c) 0.45–0.70 uranyl nitrate activity coefficients; (d) 0.7–3.5 uranyl nitrate activity coefficients; (◇) = experiment data of Ochkin et al; (○) = experiment data of Davis and Davis et al; (△) = experiment data of Zongcheng et al; (×) = experiment data of Goldberg . Reprinted from ref , Copyright (1970), with permission from Elsevier.…”

Section: Mathematical Modelingmentioning

confidence: 81%

“… a Li et al b Hlushak et al c Marion et al d Kim and Frederick e Ochkin et al f Davis g Davis et al h Zongcheng et al i Goldberg …”

Section: Mathematical Modelingmentioning

confidence: 99%

“…Reprinted from ref , with the permission of AIP Publishing. Reprinted from ref , Copyright (2016), with permission from Elsevier.…”

Section: Mathematical Modelingmentioning

confidence: 99%

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Modeling of the Competition between Uranyl Nitrate and Nitric Acid upon Extraction with Tri-n-butyl Phosphate

Tan

Chang

et al. 2020

ACS Omega

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Uranium is a strategic element and plays an important role in energy resources. A H 2 O−HNO 3 − UO 2 (NO 3 ) 2 −TBP (tri-n-butyl phosphate)−diluent system is commonly used for uranium separation and purification in liquid−liquid extraction. Uranyl nitrate is promoted by the existence of nitrate at low HNO 3 concentrations but is inhibited at high HNO 3 concentrations. Considering the competitive extraction between HNO 3 and UO 2 (NO 3 ) 2 , a generic extraction model is developed. The activities of components in the aqueous phase were estimated using Pitzer models. The thermodynamic equilibrium constants and Pitzer parameters were regressed by experimental data. The resulting model was able to successfully predict uranyl nitrate, nitric acid, and water extraction over a large range of conditions (U, 0−1.8 mol/L; HNO 3 , 0−10 mol/L; TBP, 5−100 vol %) within average absolute relative deviations of 11.2, 15.7, and 23.8%, respectively. The predicted results show that water and nitric acid were extracted as di-solvates HNO 3 •(TBP) 2 •H 2 O and (TBP) 2 •2H 2 O at low nitric acid concentrations, with the formation of mono-solvates HNO 3 •TBP and HNO 3 •TBP•H 2 O as the acid concentration increased. Uranyl nitrate was shown to be rejected from the organic phase as the formation of HNO 3 •TBP and HNO 3 •TBP•H 2 O in acid was extracted at high acid concentrations.

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Section: Mathematical Modelingmentioning

confidence: 81%

“… a Li et al b Hlushak et al c Marion et al d Kim and Frederick e Ochkin et al f Davis g Davis et al h Zongcheng et al i Goldberg …”

Section: Mathematical Modelingmentioning

confidence: 99%

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Modeling of the Competition between Uranyl Nitrate and Nitric Acid upon Extraction with Tri-n-butyl Phosphate

Tan

Chang

et al. 2020

ACS Omega

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“…For example, Pitzer's equations [6] have been used in [7]. The average errors of calculated acid activities [7] from experimental ones [6] has been equal to 9.5% [8,9]. Then it is necessary to consider the interpretation the experimental data through Zdanovskii's rule and Mikulin's equations.…”

Section: Introductionmentioning

confidence: 99%

Activity Coefficients of Nitrate Uranyl and Nitric Acid in Mixed Solutions

Ochkin¹,

Меркушкин²,

Gladilov³

2022

AJAC

Self Cite

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Aqueous solutions are frequently used in chemical technology. So numerous reference books contain basic data on major properties of binary electrolyte solutions. Usually they include densities, molar or molal concentrations, activity coefficients, water activities and sometimes osmotic coefficients. Unfortunately, most solutions are mixed ones. Therefore, it is necessary to use data of binary solutions in order to calculate thermodynamic properties of mixed solutions. For example, the aqueous phase in extraction reprocessing of nuclear reactor fuel can be considered as mixed solution of nitric acid and uranyl nitrate in first approximation. Thus, in order to calculate equilibrium during extraction of uranium with TBP it is necessary to create calculations algorithm of activity coefficients of uranyl nitrate and nitric acid with different ratios of their concentrations. Usually the integration of Gibbs-Duhem equation with some conditions is used. The first ones to offer this approach were Mc Kay and Perring in 1953. Practical implementation shows that it is recommended to integrate the equation under isopiestic conditions, meaning under constant osmotic coefficients. Zdanoskiy's rule states, that the sum of ratios of molal concentrations in mixed solution to molal concentrations in binary solutions is equal to 1. Mikulin's equations for the systems that abide by Zdanovskiy's rule allow calculations of molal coefficients of activity for such systems. Molal activity coefficients of nitrate uranyl (0.1-2.0 mole/kg) and nitric acid (0-5.0 mole/kg) in mixed solutions have been calculated using Zdanovskiy's rule and Mikulin·s equations. Analytical equations were found in order to calculate these values under different concentrations. Literature data of activity coefficients for binary solutions can be combined with calculation results from equations.

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“…Encrustation mechanism could be involved in heterogeneous nucleation and agglomeration, and/or microorganisms , . In the nuclear reprocessing plant, encrustation has attracted much attention because dissolving spent nuclear fuel in a nitric acid leads to the formation of insoluble sludge mainly of zirconium molybdate hydrate (ZrMo 2 O 7 (OH) 2 (H 2 O) 2 , ZMH) . An advanced aqueous reprocessing technology named NEXT method has been developed by the Japan Atomic Energy Agency (JAEA): the key process of this method is crystallization of uranium .…”

Section: Introductionmentioning

confidence: 99%

Encrustation Prevention of Zirconium Molybdate Hydrate

et al. 2018

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In nuclear fuel reprocessing, spent nuclear fuel is dissolved by a nitric acid. It is now known that molybdenum and zirconium in fission products react to form zirconium molybdate hydrate (ZMH). ZMH adheres to the inner surface of reprocessing equipment, which affects the extraction efficiency in the subsequent extraction process. Therefore, a new prevention method of ZMH encrustation is required for stable plant operation. In this study, the encrustation amount of ZMH was investigated. Observing the deposition process, it was clarified that ZMH fine crystals were generated and agglomerated, followed by the rapid deposition. The encrustation amount of ZMH decreased as temperature or initial Mo/Zr mole ratio increased, or as the concentration of a nitric acid was reduced.

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Activity Coefficients of Uranyl Nitrate and Nitric Acid in Aqueous Mixtures

Cited by 7 publications

References 6 publications

Modeling of the Competition between Uranyl Nitrate and Nitric Acid upon Extraction with Tri-n-butyl Phosphate

Modeling of the Competition between Uranyl Nitrate and Nitric Acid upon Extraction with Tri-n-butyl Phosphate

Activity Coefficients of Nitrate Uranyl and Nitric Acid in Mixed Solutions

Encrustation Prevention of Zirconium Molybdate Hydrate

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