Vibrational Spectroscopy of Gas–Liquid Interfaces

Baumler, Stephen M.; Allen, Heather C.

doi:10.1016/b978-0-12-813641-6.00005-4

Cited by 13 publications

(13 citation statements)

References 59 publications

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“…Details of experimental methods have been explained in previous publications. [1][2][3][4] Here, some important points are summarized for completeness. , where λ is the wavelength and  is the incidence angle.…”

Section: Experimental Methodsmentioning

confidence: 99%

Anions Enhance Rare Earth Adsorption at Negatively Charged Surfaces

Nayak

Lovering

et al. 2020

J. Phys. Chem. Lett.

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Section: Experimental Methodsmentioning

confidence: 99%

Anions Enhance Rare Earth Adsorption at Negatively Charged Surfaces

Nayak

Lovering

et al. 2020

J. Phys. Chem. Lett.

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“…VSFG is a surface-specific, second order non-linear spectroscopic technique that probes the orientational order of the dipoles near the interface. [76][77][78][79][80] Figure 5a shows the VSFG spectra in the -OH stretch region for different aqueous subphase conditions. VSFG spectrum of the bare air/water interface, a well-studied reference, shows a peak at ~3700 cm -1 , corresponding to the dangling ("free") -OH of interfacial water.…”

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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“…Details of experimental methods have been explained in previous publications. [1][2][3][4] Here, some important points are summarized for completeness. VSFG Experiments.…”

Section: Experimental Methodsmentioning

confidence: 99%

Anions Enhance Rare Earth Adsorption at Negatively Charged Surfaces

Nayak¹,

Lovering²,

Bu³

et al. 2020

Preprint

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Anions are expected to be repelled from negatively charged surfaces. At aqueous interfaces, however, ion-specific effects can dominate over direct electrostatic interactions. Using multiple in situ surface sensitive experimental techniques, we show that surface affinity of SCN- ions are so strong that they can adsorb at a negatively charged floating monolayer at the air/aqueous interface. This extreme example of ion-specific effects may be very important for understanding complex processes at aqueous interfaces, such as chemical separations of rare earth metals. Adsorbed SCN- ions at the floating monolayer increase the overall negative charge density, leading to enhanced trivalent rare earth adsorption. Surface sensitive X-ray fluorescence measurements show that the surface coverage of Lu3+ ions can be triple of the apparent surface charge of the floating monolayer in the presence of SCN-. Comparison to NO3- samples show that the effects are strongly dependent to the character of the anion, providing further evidence to ion-specific effects dominating over electrostatics.

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Vibrational Spectroscopy of Gas–Liquid Interfaces

Cited by 13 publications

References 59 publications

Anions Enhance Rare Earth Adsorption at Negatively Charged Surfaces

Anions Enhance Rare Earth Adsorption at Negatively Charged Surfaces

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

Anions Enhance Rare Earth Adsorption at Negatively Charged Surfaces

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