Rate theory on water exchange in aqueous uranyl ion

Dang, Liem X.; Vo, Quynh N.; Nilsson, Mikael; Nguyen, Hung D.

doi:10.1016/j.cplett.2017.01.020

Cited by 7 publications

(5 citation statements)

References 18 publications

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“…In the present work we use the framework of rate theory − to separate the contributions to the dynamics of different molecular phenomena, such as ion-pairing and solvent exchange, that occur in concert with proton transfer. In the standard application of rate theory to ion-pairing one can employ a simple interionic distance as the reaction coordinate to investigate ion-pairing and solvent exchange events. − According to transition state theory (TST), when the system arrives at the transition state (the top of the free energy barrier) from the reactant state, it immediately traverses to the product state. This assumption generally does not work with the distance between reacting species as a reaction coordinate because of the strong coupling to the fluctuating solvent bath leading to significant barrier recrossing.…”

Section: Introductionmentioning

confidence: 99%

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Resolving Heterogeneous Dynamics of Excess Protons in Aqueous Solution with Rate Theory

et al. 2020

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Rate theories have found great utility across the chemical sciences by providing a physically transparent way to analyze dynamical processes. Here we demonstrate the benefits of using transition state theory and Marcus theory to study the rate of proton transfer in HCl solutions. By using long ab initio molecular dynamics simulations, we show that good agreement is obtained between these two different formulations of rate theory and how they can be used to study the pathways and lifetime of proton transfer in aqueous solution. Since both rate theory formulations utilize identical sets of molecular data, this provides a self-consistent theoretical picture of the rates of aqueous phase proton transfer. Specifically, we isolate and quantify the rates of proton transfer, ion-pair dissociation, and solvent exchange in concentrated HCl solutions. Our analysis predicts a concentration dependence to both proton transfer and ion-pairing. Moreover, our estimate of the lifetime for the Zundel species is 0.8 and 1.3 ps for 2 M and 8 M HCl, respectively. We demonstrate that concentration effects can indeed be quantified through the combination of state-of-the-art simulation and theory and provides a picture of the important correlations between the cation (hydronium) and the counterion in acid solutions.

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Section: Introductionmentioning

confidence: 99%

“…In TST, κ is assumed to be unity. However, strong nonequilibrium solvent effects can lead to κ ≪ 1, providing significant deviations from TST rates. − …”

Section: Introductionmentioning

confidence: 99%

Resolving Heterogeneous Dynamics of Excess Protons in Aqueous Solution with Rate Theory

et al. 2020

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“…Through this work, we are confidently presenting high-quality polarizable force fields for TBP and n -dodecane molecules. Together with our previously developed model for the uranyl ion, the insights into the microscopic behaviors of these molecules at the liquid/vapor and liquid/liquid interfaces gained from this study will greatly aid the elucidation of the phase transfer mechanism of the metal complexes. This study paves the way for our next effort which will be focusing on understanding the kinetics of phase transfer phenomena involved in the SX process.…”

Section: Discussionmentioning

confidence: 92%

“…Following our previous work − of rigorous reparameterization and validation, in this study, we achieved satisfactory polarizable force fields for TBP and n -dodecane by optimizing the Lennard-Jones potential parameters and the atomistic partial charges to reproduce their experimental bulk density, heat of vaporization, and dipole moment (DM). Surface and interfacial tensions of liquid/vapor and liquid/liquid interfaces were calculated and compared with literature values as means of validation for the optimized polarizable force fields.…”

Section: Introductionmentioning

confidence: 99%

Microscopic Behaviors of Tri-n-Butyl Phosphate, n-Dodecane, and Their Mixtures at Air/Liquid and Liquid/Liquid Interfaces: An AMBER Polarizable Force Field Study

Vo¹,

Dang

Nguyen³

et al. 2018

J. Phys. Chem. B

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In solvent extraction processes for recovering metal ions from used nuclear fuel, as well as other industrial applications, a better understanding of the metal complex phase transfer phenomenon would greatly aid ligand design and process optimization. We have approached this challenge by utilizing the classical molecular dynamics simulations technique to gain visual appreciation of the vapor/liquid and liquid/liquid interface between tri-n-butyl phosphate (TBP) and n-dodecane with air and water. In this study, we successfully reparameterized polarizable force fields for TBP and n-dodecane that accurately reproduced several of their thermophysical properties such as density, heat of vaporization, and dipole moment. Our models were able to predict the surface and interfacial tension of different systems when compared to experimental results that were also performed by us. Through this study, we gained atomistic understanding of the behaviors of TBP and n-dodecane at the interface against air and water, useful in further computational studies of such systems. Finally, our studies indicate that the initial configuration of a simulation may have a large effect on the final result.

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“…Consider that NMR which has a distance dependent signal perturbation. 21,67,70 Although the distance at which NMR begins to measure the dynamic exchange of H 2 O is not necessarily known, the computational residence time is generally defined as being strictly between the first and second solvation shells. Strong ion-dipole interactions of UO 2+ 2 with water, 71 and polarization across solvation shells is largely responsible for the long residence times.…”

Section: Interfacial Slab and Identification Of Truly Interfacial Molecules Analysismentioning

confidence: 99%

Uranyl Speciation in the Presence of Specific Ion Gradients at the Electrolyte/Organic Interface

Kumar

Servis

Clark

2021

Solvent Extraction and Ion Exchange

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Uranyl (UO2+ 2 ) speciation at the liquid/liquid interface is an essential aspect of the mech?anism that underlies its extraction as part of spent nuclear fuel reprocessing schemes and environmental remediation of contaminated legacy waste sites. Of particular importance is a detailed perspective of how changing ion concentrations at the liquid interface alter the distribu?tion of hydrated uranyl ion and its interactions with complexing electrolyte counterions relative to the bulk aqueous solution. In this work, classical molecular dynamics simulations have ex?amined uranyl in bulk LiNO3(aq) and in the presence of a hexane interface. UO2+ 2 is observed to have both direct coordination with NO− 3 and outer-sphere interactions via solvent-separated ion-pairing (SSIP), whereas the interaction of Li+ with NO− 3 (if it occurs) is predominantly as a contact ion-pair (CIP). The variability of uranyl interactions with nitrate is hypothesized to prevent dehydration of uranyl at the interface, and as such the cation concentration is un?perturbed in the interfacial region. However, Li+ loses waters of solvation when it is present in the interfacial region, an unfavorable process that causes a Li+ depletion region. Although significant perturbations to ion-ion interactions, solvation, and solvation dynamics are observed in the interfacial region, importantly, this does not change the association constants of uranyl with nitrate. Thus, the experimental association constants, in combination with knowledge of the interfacial ion concentrations, can be used to predict the distribution of interfacial uranyl nitrate complexes. The enhanced concentration of uranyl dinitrate at the interface, caused by excess adsorbed NO− 3 , is highly relevant to extractant ligand design principles as such nitrate complexes are the reactants in ligand complexation and extraction events. File list (2) download file view on ChemRxiv Uranyl_complexation_and_solvation_in_nitrate_f.pdf (1.59 MiB) download file view on ChemRxiv Uranyl_complexation_and_solvation_in_nitrate_SI.pdf (4.00 MiB)

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Rate theory on water exchange in aqueous uranyl ion

Cited by 7 publications

References 18 publications

Resolving Heterogeneous Dynamics of Excess Protons in Aqueous Solution with Rate Theory

Resolving Heterogeneous Dynamics of Excess Protons in Aqueous Solution with Rate Theory

Microscopic Behaviors of Tri-n-Butyl Phosphate, n-Dodecane, and Their Mixtures at Air/Liquid and Liquid/Liquid Interfaces: An AMBER Polarizable Force Field Study

Uranyl Speciation in the Presence of Specific Ion Gradients at the Electrolyte/Organic Interface

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