Interplay of physically different properties leading to challenges in separating lanthanide cations – an <i>ab initio</i> molecular dynamics and experimental study

Leung, Kevin; Ilgen, Anastasia Gennadyevna; Criscenti, Louise

doi:10.1039/d1cp00031d

Cited by 5 publications

(11 citation statements)

References 60 publications

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“…4 quantitatively depend on basis sets, the choice of implicit solvent, and other factors. Nevertheless, our qualitative conclusion that cluster-based calculations with the PCM implicit solvent significantly overestimate dimerization stability is consistent with our previous work 42 . In Sec.…”

Section: Resultssupporting

confidence: 92%

“…Finite temperature spin-polarized AIMD simulations apply projector-augmented wave-based Vienna Atomic Simulation Package (VASP) 61 – 64 , a 400 eV energy cutoff, and -point sampling of the Brillouin zone. These settings are similar to those in our previous ion desorption work 35 , 42 . Simulation cells containing silica are charge-neutral, have dimensions 14.2 × 14.2 × 26.0 Å 3 , a Si 40 O 88 slab for the reconstructed -cristobalite (001) slab, 2 Cu 2+ , and 121 H 2 O molecules.…”

Section: Methodssupporting

confidence: 70%

“…Another main focus of this work is to compare dimerization free energies on silica surfaces with those in pure water. AIMD, in conjunction with potential-of-mean-force (PMF) methods which rigorously calculate free energy changes along a reaction coordinate, has been successfully applied to estimate the acidity constants of mineral surfaces and to compare the free energies of desorption of different metal cations [36][37][38][39][40][41][42] . Here we extend these methods to dimerization reactions.…”

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confidence: 99%

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Ab initio molecular dynamics free energy study of enhanced copper (II) dimerization on mineral surfaces

Leung

Greathouse

2022

Commun Chem

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Understanding the adsorption of isolated metal cations from water on to mineral surfaces is critical for toxic waste retention and cleanup in the environment. Heterogeneous nucleation of metal oxyhydroxides and other minerals on material surfaces is key to crystal growth and dissolution. The link connecting these two areas, namely cation dimerization and polymerization, is far less understood. In this work we apply ab initio molecular dynamics calculations to examine the coordination structure of hydroxide-bridged Cu(II) dimers, and the free energy changes associated with Cu(II) dimerization on silica surfaces. The dimer dissociation pathway involves sequential breaking of two Cu2+-OH− bonds, yielding three local minima in the free energy profiles associated with 0-2 OH− bridges between the metal cations, and requires the design of a (to our knowledge) novel reaction coordinate for the simulations. Cu(II) adsorbed on silica surfaces are found to exhibit stronger tendency towards dimerization than when residing in water. Cluster-plus-implicit-solvent methods yield incorrect trends if OH− hydration is not correctly depicted. The predicted free energy landscapes are consistent with fast equilibrium times (seconds) among adsorbed structures, and favor Cu2+ dimer formation on silica surfaces over monomer adsorption.

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Section: Resultssupporting

confidence: 92%

Section: Methodssupporting

confidence: 70%

mentioning

confidence: 99%

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Ab initio molecular dynamics free energy study of enhanced copper (II) dimerization on mineral surfaces

Leung

Greathouse

2022

Commun Chem

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“…In this study, the distance from Sc 3+ /Y 3+ to the plane defined by three surface oxygen atoms (i.e., two O in AlOH and one O in SiO(H)) was selected as the reaction coordinate. A similar reaction coordinate has been shown to be able to describe the desorption processes of REEs from mineral surface (Leung et al, 2021). The outer-sphere form was taken as the final state of the desorption process.…”

Section: Constrained Aimdmentioning

confidence: 99%

Understanding the unique geochemical behavior of Sc in the interaction with clay minerals

Zhang,

Liu,

et al. 2024

American Mineralogist

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Regolith-hosted rare earth elements (REEs) deposits received great attention due to the increasing incorporation of REEs in modern technologies. In lateritic Sc deposits and ion-adsorption deposits (IADs), Sc behaves quite differently from other REEs: REEs adsorb as outer-sphere complexes on clay surface in IADs while Sc could enter the lattice of clay minerals in lateritic Sc deposits. The unique behavior of Sc has not been well understood yet. Here, by using first-principles molecular dynamics techniques, we show that the complexation mechanisms of Y 3+ and Sc 3+ on clay edge surfaces are distinctly different. Y 3+ preferentially adsorbs on Al(OH) 2 SiO site with its coordination water protonated. Sc 3+ is found to behave similarly to other first-row transition metals (e.g. Ni 2+ ) due to its smaller ionic radius and prefers adsorbing on the vacancy site, from where Sc 3+ can be readily incorporated in the clay lattice. The H 2 O ligands of Sc 3+ get deprotonated upon complexation, providing new binding sites for further enrichment of Sc 3+ . These processes prevent Sc 3+ from being leached during weathering and lead to the formation of Sc-rich clay minerals found in lateritic deposits. Based on these results, it is revealed that the small ionic radius and high affinity to enter the vacancy on edge surfaces make Sc compatible with clay minerals and are the origin of its unique geochemical behavior.

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“…Nanoscale confinement affects ion adsorption by only 1−2 kJ/mol. These divergences and confinement effects have significant impact on implicit solvent modeling of catalysis 54 and electrochemical models, 55,56 many of which currently apply ϵ r calculated at MHz-to-GHz; on low dielectric organic solvents relevant to batteries; 55−57 and ion dimerization and adorption on mineral surfaces, 58,59 especially multivalent ions. 60 Finally, we raise caveats about applying dielectric theories to electrolytes with mobile ions.…”

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confidence: 99%

Finding Infinities in Nanoconfined Geothermal Electrolyte Static Dielectric Properties and Implications on Ion Adsorption/Pairing

Leung

2023

Nano Lett.

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Infinities should naturally occur in the dielectric responses of ionic solutions relevant to many geochemical, energy storage, and electrochemical applications at a strictly zero frequency. Using molecular dynamics simulations cross-referenced with coarse-grained Monte Carlo models, using nanoslit pore models at hydrothermal conditions, and treating confined mobile charges as polarization, we demonstrate the far reaching consequences. The dielectric permittivity profile perpendicular to the slit (ϵ⊥(z)) increases, not decreases, with ionic concentration, unlike in the more widely studied megahertz-to-gigahertz frequency range. In confined electrolytes, the divergences in ϵ⊥(z) correctly describe crossovers between bulk- and surface-dominated dielectric behavior. Nanoconfinement at low ionic concentrations changes monovalent ion energetics by 1–2 kJ/mol, but no dielectric property studied so far is universally correlated to ion adsorption or ion–ion interactions. We caution that infinities signal violation of the “electrical insulator” dielectric assumption.

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Interplay of physically different properties leading to challenges in separating lanthanide cations – an ab initio molecular dynamics and experimental study

Abstract: The lanthanide elements have well-documented similarities in their chemical behavior, which makes the valuable trivalent lanthanide cations (Ln(III)) particularly difficult to separate from each other in water. In this work,...

Cited by 5 publications

References 60 publications

Ab initio molecular dynamics free energy study of enhanced copper (II) dimerization on mineral surfaces

Ab initio molecular dynamics free energy study of enhanced copper (II) dimerization on mineral surfaces

Understanding the unique geochemical behavior of Sc in the interaction with clay minerals

Finding Infinities in Nanoconfined Geothermal Electrolyte Static Dielectric Properties and Implications on Ion Adsorption/Pairing

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