Anions Enhance Rare Earth Adsorption at Negatively Charged Surfaces

Nayak, Srikanth; Lovering, Kaitlin; Bu, Wei; Uysal, Ahmet

doi:10.26434/chemrxiv.12085062

Cited by 2 publications

(2 citation statements)

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“…12,14 This suggests that the trends observed at the nanoscale interfaces in the organic phase could be related to ion-extractant interactions at the macroscopic interfaces. 18,[64][65][66] , respectively. The variation of (a) core radius of the aggregate, (b) electron density of the core, (c) the apparent hard-sphere volume fraction, and (d) aggregates per cluster are shown.…”

Section: -mentioning

confidence: 99%

Origins of Clustering of Metalate–Extractant Complexes in Liquid–Liquid Extraction

Nayak

Kumal

Liu

et al. 2021

ACS Appl. Mater. Interfaces

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Effective and energy efficient separation of precious and rare metals is very important for a variety of advanced technologies. Liquid-liquid extraction (LLE) is a relatively less energy intensive separation technique, widely used in separation of lanthanides, actinides, and platinum group metals (PGMs). In LLE, the distribution of an ion between an aqueous phase and an organic phase is determined by enthalpic (coordination interactions) and entropic (fluid reorganization) contributions. The molecular scale details of these contributions are not well understood. Preferential extraction of an ion from the aqueous phase is usually correlated with the resulting fluid organization in the organic phase, as the longer-range organization increases with metal loading. However, it is difficult to determine the extent to which organic phase fluid organization causes, or is caused by, metal loading. In this study, we demonstrate that two systems with the same metal loading may impart very different organic phase organization; and investigate the underlying molecular scale mechanism. Small angle X-ray scattering shows that the structure of a quaternary ammonium extractant solution in toluene is affected differently by the extraction of two metalates (octahedral PtCl 6 2and square-planar PdCl 4 2-), although both are completely transferred into the organic phase. The aggregates formed by the metalate-extractant complexes (approximated as reverse micelles) exhibit more long-range order (clustering) with PtCl 6 2compared to that with PdCl 4 2-. Vibrational sum frequency generation spectroscopy, and complimentary atomistic molecular dynamics simulations on model Langmuir monolayers, indicate that the two metalates affect the interfacial hydration structures differently. Further, the interfacial hydration is correlated with water extraction into the organic phase. These results support a strong relationship between the organic phase organizational structure and different local hydration present within the aggregates of metalate-extractant complexes, which is independent of metalate concentration. File list (2) download file view on ChemRxiv Origins_of_clustering_acsami_revised.pdf (1.94 MiB) download file view on ChemRxiv SI_Origins of clustering_acsami_revised.pdf (1.82 MiB)

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Section: -mentioning

confidence: 99%

Origins of Clustering of Metalate–Extractant Complexes in Liquid–Liquid Extraction

Nayak

Kumal

Liu

et al. 2021

ACS Appl. Mater. Interfaces

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Section: -mentioning

confidence: 99%

Origins of Clustering of Metalate-Extractant Complexes in Liquid-Liquid Extraction

Nayak

Kumal²,

Liu³

et al. 2021

Preprint

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Effective and energy efficient separation of precious and rare metals is very important for a variety of advanced technologies. Liquid-liquid extraction (LLE) is a relatively less energy intensive separation technique, widely used in separation of lanthanides, actinides, and platinum group metals (PGMs). In LLE, the distribution of an ion between an aqueous phase and an organic phase is determined by enthalpic (coordination interactions) and entropic (fluid reorganization) contributions. The molecular scale details of these contributions are not well understood. Preferential extraction of an ion from the aqueous phase is usually correlated with the resulting fluid organization in the organic phase, as the longer-range organization increases with metal loading. However, it is difficult to determine the extent to which organic phase fluid organization causes, or is caused by, metal loading. In this study, we demonstrate that two systems with the same metal loading may impart very different organic phase organization; and investigate the underlying molecular scale mechanism. Small angle X-ray scattering shows that the structure of a quaternary ammonium extractant solution in toluene is affected differently by the extraction of two metalates (octahedral PtCl62- and square-planar PdCl42-), although both are completely transferred into the organic phase. The aggregates formed by the metalate-extractant complexes (approximated as reverse micelles) exhibit more long-range order (clustering) with PtCl62- compared to that with PdCl42-. Vibrational sum frequency generation spectroscopy, and complimentary atomistic molecular dynamics simulations on model Langmuir monolayers, indicate that the two metalates affect the interfacial hydration structures differently. Further, the interfacial hydration is correlated with water extraction into the organic phase. These results support a strong relationship between the organic phase organizational structure and different local hydration present within the aggregates of metalate-extractant complexes, which is independent of metalate concentration.

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Anions Enhance Rare Earth Adsorption at Negatively Charged Surfaces

Cited by 2 publications

References 24 publications

Origins of Clustering of Metalate–Extractant Complexes in Liquid–Liquid Extraction

Origins of Clustering of Metalate–Extractant Complexes in Liquid–Liquid Extraction

Origins of Clustering of Metalate-Extractant Complexes in Liquid-Liquid Extraction

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