Modeling solution vapor equilibria with solvation and solute assembly

Wilson, Angela K.; Stetson, Caleb

doi:10.1016/j.molliq.2021.116272

Cited by 13 publications

(14 citation statements)

References 81 publications

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“…Gaseous DME is employed as a saturation agent to induce crystallization of transition metal or lanthanide sulfates from mixed metal salt magnet leachates. DME is not thought to interact directly with other solutes; instead, DME reduces the quantity of the free water (i.e., water that is not bound within a solvation environment) to fulfill its own hydration requirements 62 , 63 . A reduction in free water, reduced water activity, and/or liquid phase microstructuring 79 induce salt precipitation.…”

Section: Resultsmentioning

confidence: 99%

“…Regardless of the organic solvent employed, the same molar fraction of NaCl was precipitated from a saturated solution, indicating that selecting for a low molecular mass solvent is preferable to selecting for a low dielectric solvent 61 . Moreover, salts with high molar solubilities 62 – 64 require more solvent to be displaced in FC than salts with an equivalent mass but lower molar solubilities 61 . High molar solubility salts also induce liquid-liquid equilibrium (LLE) separation of the organic solvent, limiting salt crystallization.…”

Section: Introductionmentioning

confidence: 99%

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Solvent-driven fractional crystallization for atom-efficient separation of metal salts from permanent magnet leachates

et al. 2022

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This work reports a dimethyl ether-driven fractional crystallization process for separating rare earth elements and transition metals. The process has been successfully applied in the treatment of rare earth element-bearing permanent magnet leachates as an atom-efficient, reagent-free separation method. Using ~5 bar pressure, the solvent was dissolved into the aqueous system to displace the contained metal salts as solid precipitates. Treatments at distinct temperatures ranging from 20–31 °C enable crystallization of either lanthanide-rich or transition metal-rich products, with single-stage solute recovery of up to 95.9% and a separation factor as high as 704. Separation factors increase with solution purity, suggesting feasibility for eco-friendly solution treatments in series and parallel to purify aqueous material streams. Staged treatments are demonstrated as capable of further improving the separation factor and purity of crystallized products. Upon completion of a crystallization, the solvent can be recovered with high efficiency at ambient pressure. This separation process involves low energy and reagent requirements and does not contribute to waste generation.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Solvent-driven fractional crystallization for atom-efficient separation of metal salts from permanent magnet leachates

et al. 2022

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Section: Introductionmentioning

confidence: 99%

“…Among fundamental chemical principles, the concept of solvation has long been a topic of significant research, playing a central role in disciplines such as supramolecular chemistry, 1 chemical reactivity, 2 macromolecular folding, 3 and colligative properties of solutions. 4 The molecular properties of both solute and solvent must be simultaneously considered to characterize the solvation process. These properties, which include the total molecular dipole moment and those of individual chemical bonds, the hydrogen-bonding donor or acceptor capability, polarizability, and molecular shape, will all influence the types of intermolecular forces between solute and solvent.…”

Section: ■ Introductionmentioning

confidence: 99%

Solvent Organization and Electrostatics Tuned by Solute Electronic Structure: Amide versus Non-Amide Carbonyls

et al. 2022

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The ability to exploit carbonyl groups to measure electric fields in enzymes and other complex reactive environments using the vibrational Stark effect has inspired growing interest in how these fields can be measured, tuned, and ultimately designed. Previous studies have concentrated on the role of the solvent in tuning the fields exerted on the solute. Here, we explore instead the role of the solute electronic structure in modifying the local solvent organization and electric field exerted on the solute. By measuring the infrared absorption spectra of amide-containing molecules, as prototypical peptides, and contrasting them with non-amide carbonyls in a wide range of solvents, we show that these solutes experience notable differences in their frequency shifts in polar solvents. Using vibrational Stark spectroscopy and molecular dynamics simulations, we demonstrate that while some of these differences can be rationalized using the distinct intrinsic Stark tuning rates of the solutes, the larger frequency shifts for amides and dimethylurea primarily result from the larger solvent electric fields experienced by their carbonyl groups. These larger fields arise due to their stronger p-π conjugation, which results in larger C=O bond dipole moments that further induce substantial solvent organization. Using electronic structure calculations, we decompose the electric fields into contributions from solvent molecules that are in the first solvation shell and those from the bulk and show that both of these contributions are significant and become larger with enhanced conjugation in solutes. These results show that structural modifications of a solute can be used to tune both the solvent organization and electrostatic environment, indicating the importance of a solute-centric paradigm in modulating and designing the electrostatic environment in condensed-phase chemical processes.

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“…Solution speciation phenomena like solvation 1 , 2 and ion pairing 3 , 4 have been experimentally demonstrated 5 to contribute to various solution properties, thus attracting interest within emerging electrolyte theories 6 . Several research groups (ours 7 , Zivitsas 8 – 11 , Heyrokská 12 – 17 , and others 18 ) have taken the use of solution speciation a step further by directly using mass action equilibria (or processes) to model solution behavior without electrostatics. In these models the concentrations of solute species, generated by assembly processes (primarily solvation and ion pairing), are correlated to a solution’s vapor pressure (solvent activity) via Raoult’s law.…”

Section: Introductionmentioning

confidence: 99%

Mass action model of solution activity via speciation by solvation and ion pairing equilibria

2021

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Solutes and their concentrations influence many natural and anthropogenic solution processes. Electrolyte and solution models are used to quantify and predict such behavior. Here we present a mechanistic solution model based on mass action equilibria. Solvation and ion pairing are used to model speciated solute and solvent concentrations such that they correlate to a solution’s vapor pressure (solvent activity) according to Raoult’s law from dilute conditions to saturation. This model introduces a hydration equilibrium constant (Kha) that is used with either an ion dissociation constant (Kid) or a hydration modifier (m) with an experimentally determined ion dissociation constant, as adjustable parameters to fit vapor–liquid equilibrium data. The modeled solvation equilibria are accompanied by molecular dynamics (MD) studies that support a decline in the observed degree of solvation with increased concentration. MD calculations indicate this finding is a combination of a solvent that solvates multiple solutes, and changes in a solute’s solvation sphere, with the dominant factor changing with concentration. This speciation-based solution model is lateral to established electrostatics-based electrolyte theories. With its basis in mass action, the model can directly relate experimental data to the modeled solute and solvent speciated concentrations and structures.

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Modeling solution vapor equilibria with solvation and solute assembly

Cited by 13 publications

References 81 publications

Solvent-driven fractional crystallization for atom-efficient separation of metal salts from permanent magnet leachates

Solvent-driven fractional crystallization for atom-efficient separation of metal salts from permanent magnet leachates

Solvent Organization and Electrostatics Tuned by Solute Electronic Structure: Amide versus Non-Amide Carbonyls

Mass action model of solution activity via speciation by solvation and ion pairing equilibria

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