Transport processes of actinides in aqueous and non-aqueous solutions

Marx, G.; Gauglitz, R.; Friehmelt, V.; Feldner, K.H.

doi:10.1016/0022-5088(86)90407-8

Cited by 6 publications

(5 citation statements)

References 8 publications

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“…2 The direct measurements of NpO 2 2+ and PuO 2 2+ utilized a capillary tube diffusion cell. 3 These results generally agree with those obtained from the simulations reported in the present work. Previous MD simulations of aqueous UO 2 2+ by Kerisit et al 22 using a force field from Wipff and co-workers 41,42 resulted in a UO 2 2+ diffusivity of 0.7659 Â 10 À9 m 2 s À1 which is somewhat higher than our predictions and the direct experimental measurements.…”

Section: Self-diffusion Coefficientssupporting

confidence: 92%

“…28 In a given charge state, the ions have very similar mobilities. Table 1 shows a comparison of simulated self-diffusivities and those determined experimentally using direct 2,3 and indirect (by measuring ionic conductivities and mobilities [4][5][6][7] ) methods. In the direct methods for UO 2 2+ and UO 2 + , diffusion current constants were measured and directly related to the diffusion coefficient via the Ilkovic equation.…”

Section: Self-diffusion Coefficientsmentioning

confidence: 99%

“…For example, theoretical models based on experimental ionic conductivity measurements have suggested that the diffusion coefficients for monocation actinyls are roughly twice that of the dication actinyls, though this is contrary to direct experimental measurements. 2,3 The residence time for water exchange of UO 2 2+ has been observed in NMR experiments to be of the order of 10 À6 s, whereas simulations 14,22 suggest that it is much faster, on the order of 10 À9 s. Recently, Kerisit et al 21 developed a new model for classical simulation of UO 2 2+ in water to accurately reproduce the residence times observed experimentally with NMR, but the first hydration shell of UO 2 2+ in their model was tighter than what has been observed experimentally. [23][24][25][26] With a goal to develop a force field for modeling actinide systems in a consistent manner, we reported a general procedure for determining intermolecular interaction parameters from quantum mechanical calculations.…”

Section: Introductionmentioning

confidence: 99%

“…Subscripts refer to uncertainties in the last digit(s); for e.g. 0.61 9 is equivalent to 0.61 AE 0.09, 0.64 10 is equivalent to 0.64 AE 0.10 Diffusion coefficient value is estimated for 0.056 molar ions from a plot of diffusion coefficient vs. concentration given in the work of Marx et al3 d Mauerhofer et al40 calculated these diffusion coefficients from ionic conductivity and ionic mobility experiments using the Nernst-Einstein relation. e Kerisit et al22 further looked at the reported experimental ionic conductivity and ionic mobility results of UO 22+ and converted them into the diffusion coefficients using the Nernst-Einstein relation.…”

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confidence: 99%

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Dynamics of actinyl ions in water: a molecular dynamics simulation study

Tiwari

Rai

Maginn

2014

Phys. Chem. Chem. Phys.

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The dynamics of actinyl ions (AnO2(n+)) in aqueous solutions is important not only for the design of advanced separation processes but also for understanding the fate of actinides in the environment. The hazardous nature of actinides makes it difficult to measure transport and thermodynamic properties experimentally, so predictive simulations are an attractive method for studying these systems. Here, we report the results of atomistic-level molecular dynamics simulations of actinyl ions (of U, Np, Pu, and Am) in their mono- and dication states in aqueous solution. Quantum mechanically derived force field parameters are used to compute self-diffusion coefficients of the actinyl ions, water exchange mechanisms, and residence times of water molecules in the first solvation shell of the actinyl ions. We find that monocation actinyl ions diffuse slightly faster than their dication counterparts. Our simulations suggest that there are two distinct water exchange mechanisms for mono and dications. An associative interchange pathway is observed for water exchange involving dication actinyls, while in monocation actinyls the exchange occurs via a dissociative mechanism. The residence time of water molecules in the first solvation shell depends on the water exchange mechanism. In the case of dications, a stiffer actinyl bond angle results in a longer residence time, while for monocations, a shorter water coordination distance leads to a longer residence time. The simulations predict much faster water exchange for UO2(2+) than what is observed experimentally with NMR, but other properties are consistent with experiments.

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Section: Self-diffusion Coefficientssupporting

confidence: 92%

Section: Self-diffusion Coefficientsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Dynamics of actinyl ions in water: a molecular dynamics simulation study

Tiwari

Rai

Maginn

2014

Phys. Chem. Chem. Phys.

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“…The experimental self diffusion coefficients of the different actinyls range from 0.55 × 10 −5 cm 2 s −1 to 0.8 × 10 −5 cm 2 s −1 . [64][65][66] Considering TIP4P water mobility is too high, the aqua ion translates more freely than it should as well. The normalization corrects this effect, and then the data agree within the error with the experimental normalized range, 0.24-0.35, 64,65 using 2.3 × 10 −5 cm 2 s −1 for water.…”

Section: B Self-diffusion Coefficientmentioning

confidence: 99%

A general study of actinyl hydration by molecular dynamics simulations using ab initio force fields

Pérez-Conesa

Torrico

Martı́nez

et al. 2019

The Journal of Chemical Physics

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A set of new ab initio force fields for aqueous [AnO 2 ] 2+/+ (An = Np(VI,V), Pu(VI), Am(VI)) has been developed using the Hydrated Ion (HI) model methodology previously used for [UO 2 ] 2+ . Except for the non-electrostatic contribution of the HI-bulk water interaction, the interaction potentials are individually parameterized. Translational diffusion coefficients, hydration enthalpies, and vibrational normal mode frequencies were calculated from the MD simulations. Physico-chemical properties satisfactorily agree with experiments validating the robustness of the force field strategy. The solvation dynamics and structure for all hexavalent actinoids are extremely similar and resemble our previous analysis of the uranyl cation. This supports the idea of using the uranyl cation as a reference for the study of other minor actinyls. The comparison between the NpO 2+ 2 and NpO + 2 hydration only provides significant differences in first and second shell distances and second-shell mean residence times. We propose a single general view of the [AnO 2 ] 2+/+ hydration structure: aqueous actinyls are amphiphilic anisotropic solutes which are equatorially conventional spherically symmetric cations capped at the poles by clathrate-like water structures.

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Remarkably High Separation of Neodymium from Praseodymium by Selective Dissolution from their Oxide Mixture using an Ionic Liquid Containing aβ‐Diketone

Sengupta,

Goyal,

Prava Mantry

et al. 2024

Chemistry A European J

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A simple, efficient, and economical method for the mutual separation of Nd and Pr was developed by the selective dissolution of Nd2O3 directly from their oxide mixtures in an ionic liquid containing 2‐thenoyltrifluoroacetone (HTTA) resulting in an unprecedented separation factor (βNd/Pr) > 500, which is 277 times more than the thus far reported βNd/Pr values. The proposed mechanism was supported by DFT computations.

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Transport processes of actinides in aqueous and non-aqueous solutions

Cited by 6 publications

References 8 publications

Dynamics of actinyl ions in water: a molecular dynamics simulation study

Dynamics of actinyl ions in water: a molecular dynamics simulation study

A general study of actinyl hydration by molecular dynamics simulations using ab initio force fields

Remarkably High Separation of Neodymium from Praseodymium by Selective Dissolution from their Oxide Mixture using an Ionic Liquid Containing aβ‐Diketone

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