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Wilson AD, Foo ZH, Jayasinghe AS, Stetson C, Lee H, Rollins HW, Deshmukh A, Lienhard JH. Modeling Henry's law and phase separations of water-NaCl-organic mixtures with solvation and ion-pairing. Phys Chem Chem Phys 2024; 26:749-759. [PMID: 37800279 DOI: 10.1039/d3cp02003g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/07/2023]
Abstract
Empirical measurements of solution vapor pressure of ternary acetonitrile (MeCN) H2O-NaCl-MeCN mixtures were recorded, with NaCl concentrations ranging from zero to the saturation limit, and MeCN concentrations ranging from zero to an absolute mole fraction of 0.64. After accounting for speciation, the variability of the Henry's law coefficient at vapor-liquid equilibrium (VLE) of MeCN ternary mixtures decreased from 107% to 5.1%. Solute speciation was modeled using a mass action solution model that incorporates solute solvation and ion-pairing phenomena. Two empirically determined equilibrium constants corresponding to solute dissociation and ion pairing were utilized for each solute. When speciation effects were considered, the solid-liquid equilibrium of H2O-NaCl-MeCN mixtures appear to be governed by a simple saturation equilibrium constant that is consistent with the binary H2O-NaCl saturation coefficient. Further, our results indicate that the precipitation of NaCl in the MeCN ternary mixtures was not governed by changes in the dielectric constant. Our model indicates that the compositions of the salt-induced liquid-liquid equilibrium (LLE) boundary of the H2O-NaCl-MeCN mixture correspond to the binary plateau activity of MeCN, a range of concentrations over which the activity remains largely invariant in the binary water-MeCN system. Broader comparisons with other ternary miscible organic solvent (MOS) mixtures suggest that salt-induced liquid-liquid equilibrium exists if: (1) the solution displays a positive deviation from the ideal limits governed by Raoult's law; and (2) the minimum of the mixing free energy profile for the binary water-MOS system is organic-rich. This work is one of the first applications of speciation-based solution models to a ternary system, and the first that includes an organic solute.
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Affiliation(s)
- Aaron D Wilson
- Chemical Separations Group, Idaho National Laboratory, Idaho Falls, ID 83415-2208, USA.
| | - Zi Hao Foo
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA
| | - Ashini S Jayasinghe
- Analytical Chemistry Group, Idaho National Laboratory, Idaho Falls, ID 83415-2208, USA
| | - Caleb Stetson
- Chemical Separations Group, Idaho National Laboratory, Idaho Falls, ID 83415-2208, USA.
| | - Hyeonseok Lee
- Chemical Separations Group, Idaho National Laboratory, Idaho Falls, ID 83415-2208, USA.
| | - Harry W Rollins
- Chemical Separations Group, Idaho National Laboratory, Idaho Falls, ID 83415-2208, USA.
| | - Akshay Deshmukh
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA
| | - John H Lienhard
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA
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Wilson AD, Lee H, Stetson C. Local stress within a granular molecular solvent matrix, a mechanism for individual ion hydration. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.119544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Stetson C, Prodius D, Lee H, Orme C, White B, Rollins H, Ginosar D, Nlebedim IC, Wilson AD. Solvent-driven fractional crystallization for atom-efficient separation of metal salts from permanent magnet leachates. Nat Commun 2022; 13:3789. [PMID: 35778388 PMCID: PMC9249736 DOI: 10.1038/s41467-022-31499-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Accepted: 06/18/2022] [Indexed: 11/20/2022] Open
Abstract
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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Affiliation(s)
- Caleb Stetson
- Critical Materials Institute, Idaho National Laboratory, 1955 N Fremont Ave, Idaho Falls, ID, 83415, USA
| | - Denis Prodius
- Critical Materials Institute, Ames Laboratory, US Department of Energy, Ames, IA, 50011-3020, USA
| | - Hyeonseok Lee
- Critical Materials Institute, Idaho National Laboratory, 1955 N Fremont Ave, Idaho Falls, ID, 83415, USA
| | - Christopher Orme
- Critical Materials Institute, Idaho National Laboratory, 1955 N Fremont Ave, Idaho Falls, ID, 83415, USA
| | - Byron White
- Critical Materials Institute, Idaho National Laboratory, 1955 N Fremont Ave, Idaho Falls, ID, 83415, USA
| | - Harry Rollins
- Critical Materials Institute, Idaho National Laboratory, 1955 N Fremont Ave, Idaho Falls, ID, 83415, USA
| | - Daniel Ginosar
- Critical Materials Institute, Idaho National Laboratory, 1955 N Fremont Ave, Idaho Falls, ID, 83415, USA
| | - Ikenna C Nlebedim
- Critical Materials Institute, Ames Laboratory, US Department of Energy, Ames, IA, 50011-3020, USA
| | - Aaron D Wilson
- Critical Materials Institute, Idaho National Laboratory, 1955 N Fremont Ave, Idaho Falls, ID, 83415, USA.
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Mass action model of solution activity via speciation by solvation and ion pairing equilibria. Commun Chem 2021; 4:163. [PMID: 36697558 PMCID: PMC9814931 DOI: 10.1038/s42004-021-00599-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Accepted: 10/25/2021] [Indexed: 01/28/2023] Open
Abstract
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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