1
|
Kumar N. Uranyl (UO 22+) structuring and dynamics at graphene/electrolyte interface. Phys Chem Chem Phys 2024; 26:20799-20806. [PMID: 38958742 DOI: 10.1039/d4cp02108h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/04/2024]
Abstract
The physicochemical phenomena at the solid/electrolyte interfaces govern various industrial processes ranging from energy generation, storage, and catalysis to chemical separations and purification. Adsorption-based solid/liquid extraction methods are promising for the selective and rapid separation of nuclear (such as uranium) and other critical materials. In this study, we quantified the adsorption, complexation, and dynamics of UO22+ ions on the graphene surface in various electrolyte media (LiNO3, NaNO3 and CsNO3) using all-atom molecular dynamics simulations, in combination with network theory based subensemble analysis, enhanced sampling, and temporal analysis. We observe that the choice of background electrolyte impacts the propensity of UO22+ adsorption on the graphene surface, with LiNO3 being the most favorable at both low and high uranyl-nitrate concentrations. Even though UO22+ primarily retained its coordination with water and interacted via the outer-sphere mechanism with graphene, the interfacial segregation of NO3- increased the number of contact ion pairs (CIPs) between UO22+ and NO3- ions, and the residence times of UO22+ within the interfacial region. This study provides a fundamental understanding of the structure and dynamics of UO22+ on the solid surface necessary to design advanced adsorption-based separation methods for energy-relevant materials.
Collapse
Affiliation(s)
- Nitesh Kumar
- Department of Chemistry, Washington State University, Pullman, Washington 99163, USA.
| |
Collapse
|
2
|
Kumar N, Premadasa UI, Dong D, Roy S, Ma YZ, Doughty B, Bryantsev VS. Adsorption, Orientation, and Speciation of Amino Acids at Air-Aqueous Interfaces for the Direct Air Capture of CO 2. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:14311-14320. [PMID: 38958522 DOI: 10.1021/acs.langmuir.4c00907] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2024]
Abstract
Amino acids make up a promising family of molecules capable of direct air capture (DAC) of CO2 from the atmosphere. Under alkaline conditions, CO2 reacts with the anionic form of an amino acid to produce carbamates and deactivated zwitterionic amino acids. The presence of the various species of amino acids and reactive intermediates can have a significant effect on DAC chemistry, the role of which is poorly understood. In this study, all-atom molecular dynamics (MD) based computational simulations and vibrational sum frequency generation (vSFG) spectroscopy studies were conducted to understand the role of competitive interactions at the air-aqueous interface in the context of DAC. We find that the presence of potassium bicarbonate ions, in combination with the anionic and zwitterionic forms of amino acids, induces concentration and charge gradients at the interface, generating a layered molecular arrangement that changes under pre- and post-DAC conditions. In parallel, an enhancement in the surface activity of both anionic and zwitterionic forms of amino acids is observed, which is attributed to enhanced interfacial stability and favorable intermolecular interactions between the adsorbed amino acids in their anionic and zwitterionic forms. The collective influence of these competitive interactions, along with the resulting interfacial heterogeneity, may in turn affect subsequent capture reactions and associated rates. These effects underscore the need to consider dynamic changes in interfacial chemical makeup to enhance DAC efficiency and to develop successful negative emission and storage technologies.
Collapse
Affiliation(s)
- Nitesh Kumar
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Uvinduni I Premadasa
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Dengpan Dong
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Santanu Roy
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Ying-Zhong Ma
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Benjamin Doughty
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Vyacheslav S Bryantsev
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| |
Collapse
|
3
|
Uysal A. Aqueous Interfaces in Chemical Separations. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023. [PMID: 37917551 DOI: 10.1021/acs.langmuir.3c02170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/04/2023]
Abstract
Chemical separations play a vital role in refinery and reprocessing of critical materials, such as platinum group metals, rare earths, and actinides. The choice of separation system─whether it is liquid-liquid extraction (LLE), sorbents, or membranes─depends on specific needs and applications. In almost all separation processes, the desired metal ions adsorb or transfer across an aqueous interface, such as the solid/liquid interface in sorbents or oil/water interfaces in LLE. Despite these separation technologies being extensively used for decades, our understanding of the molecular-scale mechanisms governing ion adsorption and transport at interfaces remains limited. This knowledge gap presents a significant challenge in meeting the increasing demands for these critical materials due to their growing use in advanced technologies. Fortunately, recent advancements in surface-specific experimental and computational techniques offer promising avenues to bridge this gap and facilitate the development of next-generation separation systems. Interestingly, unanswered questions regarding interfacial phenomena in chemical separations hold great relevance to various fields, including energy storage, geochemistry, and atmospheric chemistry. Therefore, the model interfacial systems developed for studying chemical separations, such as amphiphilic molecules assembled at a solid/water, air/water, or oil/water interface, may have far-reaching implications, extending beyond separations and opening doors to addressing a wide range of scientific inquiries. This perspective discusses recent interfacial studies elucidating amphiphile-ion interactions in chemical separations of metal ions. These studies provide direct, molecular-scale information about solute and solvent behavior at aqueous interfaces, including multivalent and complex ions in highly concentrated solutions, which play key roles in LLE of critical materials.
Collapse
Affiliation(s)
- Ahmet Uysal
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| |
Collapse
|
4
|
Chu ZQ, Zhu RY, Su J. Theoretical insights into the coordination structures, stabilities and electronic spectra of Cm 3+ species at the gibbsite-water interface: A computational study combing ab initio molecular dynamics and wave function theory. J Colloid Interface Sci 2023; 640:727-736. [PMID: 36898179 DOI: 10.1016/j.jcis.2023.02.157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2023] [Revised: 02/20/2023] [Accepted: 02/28/2023] [Indexed: 03/07/2023]
Abstract
The information of structure and stability of actinide species is key to understand the sorption mechanism of actinides at mineral-water interface. Such information is approximately derived from experimental spectroscopic measurements and needs to be accurately obtained by a direct atomic-scale modelling. Herein, systematic first-principles calculations and ab initio molecular dynamics (AIMD) simulations are carried out to study the coordination structures and absorption energies of Cm(III) surface complexes at gibbsite-water interface. Eleven representative complexing sites are investigated. The most stable Cm3+ sorption species are predicted to be a tridentate surface complex in weakly acidic/neutral solution condition and a bidentate one in the alkaline solution condition. Moreover, luminescence spectra of the Cm3+ aqua ion and the two surface complexes are predicted based on the high-accuracy ab initio wave function theory (WFT). The results give a gradually decreasing emission energy in good agreement with experimental observation of a red shift of peak maximum with pH increasing from 5 to 11. This work is a comprehensive computational study involving AIMD and ab initio WFT methods to gain the coordination structures, stabilities, and electronic spectra of actinide sorption species at the mineral-water interface, thus providing important theoretical support for geological disposal of actinide waste.
Collapse
Affiliation(s)
- Zhao-Qin Chu
- College of Chemistry, Sichuan University, Chengdu 610064, PR China
| | - Ru-Yu Zhu
- College of Chemistry, Sichuan University, Chengdu 610064, PR China
| | - Jing Su
- College of Chemistry, Sichuan University, Chengdu 610064, PR China.
| |
Collapse
|
5
|
Poulin-Ponnelle C, Duvail M, Dumas T, Berthon C. Contribution of Molecular Dynamics in pNMR for the Structural Determination of An V and An VI Complexes in Solution. Inorg Chem 2022; 61:15895-15909. [PMID: 36166623 DOI: 10.1021/acs.inorgchem.2c02040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In this study, we propose to use classical molecular dynamics (MD) coupled with 1H NMR spectroscopy to study the conformations of different actinyl AnVI (An = U, Np, and Pu) and AnV (An = Np) complexes with tetra-ethyl dyglicolamide (TEDGA) ligands in order to have a better representation of such complexes in solution. Molecular dynamics simulations showed its effectiveness in interpreting the experiments by the calculation of geometric factors needed for the determination of magnetic properties of these complexes. We demonstrated that different conformations of the AnV and AnVI complexes with TEDGA exist in solution with different coordination modes, which is experimentally confirmed by 1H NMR and EXAFS spectroscopies. Furthermore, MD simulations provide additional insights into the structures of complexes in solution since conformations with fast exchanges, which are not accessible from NMR experiments, have been observed by MD simulations.
Collapse
Affiliation(s)
| | - Magali Duvail
- ICSM, Univ. Montpellier, CEA, CNRS, ENSCM, Bagnols sur Cèze 30207, France
| | - Thomas Dumas
- LILA, Univ. Montpellier, CEA, Bagnols sur Cèze 30207, France
| | - Claude Berthon
- LILA, Univ. Montpellier, CEA, Bagnols sur Cèze 30207, France
| |
Collapse
|
6
|
Kumar N, Clark AE. Unexpected inverse correlations and cooperativity in ion-pair phase transfer. Chem Sci 2021; 12:13930-13939. [PMID: 34760180 PMCID: PMC8549775 DOI: 10.1039/d1sc04004a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Accepted: 09/16/2021] [Indexed: 11/21/2022] Open
Abstract
Liquid/liquid extraction is one of the most widely used separation and purification methods, where a forefront of research is the study of transport mechanisms for solute partitioning and the relationships that these have to solution structure at the phase boundary. To date, organized surface features that include protrusions, water-fingers, and molecular hinges have been reported. Many of these equilibrium studies have focused upon small-molecule transport – yet the extent to which the complexity of the solute, and the competition between different solutes, influence transport mechanisms have not been explored. Here we report molecular dynamics simulations that demonstrate that a metal salt (LiNO3) can be transported via a protrusion mechanism that is remarkably similar to that reported for H2O by tri-butyl phosphate (TBP), a process that involves dimeric assemblies. Yet the LiNO3 out-competes H2O for a bridging position between the extracting TBP dimer, which in-turn changes the preferred transport pathway of H2O. Examining the electrolyte concentration dependence on ion-pair transport unexpectedly reveals an inverse correlation with the extracting surfactant concentration. As [LiNO3] increases, surface adsorbed TBP becomes a limiting reactant in correlation with an increased negative surface charge induced by excess interfacial NO3−, however the rate of transport is enhanced. Within the highly dynamic interfacial environment, we hypothesize that this unique cooperative effect may be due to perturbed surface organization that either decreases the energy of formation of transporting protrusion motifs or makes it easier for these self-assembled species to disengage from the surface. A forefront of research in separations science (specifically liquid–liquid extraction) is the study of transport mechanisms for solute partitioning, and the relationships that these have to solution structure at the phase boundary.![]()
Collapse
Affiliation(s)
- Nitesh Kumar
- Department of Chemistry, Washington State University Pullman Washington 99164 USA
| | - Aurora E Clark
- Department of Chemistry, Washington State University Pullman Washington 99164 USA.,Pacific Northwest National Laboratory Richland Washington 99354 USA
| |
Collapse
|
7
|
Zemb T, Clark A. Special Issue on Hierarchical Organization in Solvent Extraction. SOLVENT EXTRACTION AND ION EXCHANGE 2021. [DOI: 10.1080/07366299.2021.1972562] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- Thomas Zemb
- Institut de Chimie Séparative de Marcoule, France
| | - Aurora Clark
- Department of Chemistry, Washington State University, Pullman, USA
| |
Collapse
|