Hydration counteracts the separation of lanthanides by solvent extraction

Li, Zheng; Binnemans, Koen

doi:10.1002/aic.16545

Cited by 26 publications

(27 citation statements)

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“…Therefore, the SX efficiency is driven by the aqueous phase speciation in NO3system, in contrast to organic phase driven SX efficiency in SCNsystems. A recent work published during the review of this manuscript supports the importance of aqueous phase effects in extraction from nitrate media 63. These results show that the ion specific effects in complex fluids require a comprehensive understanding which goes beyond Hofmeister series or similar rankings of ions.…”

supporting

confidence: 71%

Ion-specific clustering of metal–amphiphile complexes in rare earth separations

2020

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supporting

confidence: 71%

Ion-specific clustering of metal–amphiphile complexes in rare earth separations

2020

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“…53,82 The atypical selectivity of TOMA-NO 3 towards light lanthanides is hypothesized to be due to the hydration properties of the lanthanides. 59,[83][84] The major difference in the effect of chlorometalates on the organic phase structure is the higher clustering of aggregates in the case of PtCl 6 2compared to that of PdCl 4 2-(Figure 3). Given the similar metal content but different water content, these differences can be due to different geometries of PtCl 6 2and PdCl 4 2-and different hydration structures in the reverse micellar aggregates.…”

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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“…Ethylammonium nitrate (EAN) is an IL with a low melting point (12°C), making it a suitable ionic solvent for the MP phase of SX of metals, without the need for heating. Very recently, extraction of lanthanides from EAN was found to exhibit an opposite sequence across the lanthanide series compared to that from aqueous solutions by a quaternary alkylammonium nitrate extractant, showing the special role of EAN in SX of metals 26 . In this study, we explore the extraction of transition metal nitrates from EAN by TBP and show that the extraction of metals can be significantly enhanced using EAN instead of molecular solvents.…”

Section: Introductionmentioning

confidence: 93%

“…Very recently, extraction of lanthanides from EAN was found to exhibit an opposite sequence across the lanthanide series compared to that from aqueous solutions by a quaternary alkylammonium nitrate extractant, showing the special role of EAN in SX of metals. 26 In this study, we explore the extraction of transition metal nitrates from EAN by TBP and show that the extraction of metals can be significantly enhanced using EAN instead of molecular solvents. Furthermore, the extraction mechanism is discussed based on experimental characterizations.…”

Section: Introductionmentioning

confidence: 99%

Ethylammonium nitrate enhances the extraction of transition metal nitrates by tri‐n‐butyl phosphate (TBP)

Zhang

Onghena

et al. 2021

AIChE Journal

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Several molecular polar solvents have been used as solvents of the more polar phase in the solvent extraction (SX) of metals. However, the use of hydrophilic ionic liquids (ILs) as solvents has seldomly been explored for this application. Here, the hydrophilic IL ethylammonium nitrate (EAN), has been utilized as a polar solvent in SX of transition metal nitrates by tri-n-butyl phosphate (TBP). It was found that the extraction from EAN is considerably stronger than that from a range of molecular polar solvents. The main species of Co(II) and Fe(III) in EAN are likely [Co(NO 3) 4 ] 2− and [Fe(NO 3) 4 ] − , respectively. The extracted species are likely Fe(TBP) 3 (NO 3) 3 and a mixture of Co(TBP) 2 (NO 3) 2 and Co(TBP) 3 (NO 3) 2. The addition of H 2 O or LiCl to EAN reduces the extraction because the metal cations coordinate to water molecules and chloride ions stronger than to nitrate ions. This study highlights the potential of using hydrophilic ILs to enhance SX of metals.

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Hydration counteracts the separation of lanthanides by solvent extraction

Cited by 26 publications

References 20 publications

Ion-specific clustering of metal–amphiphile complexes in rare earth separations

Ion-specific clustering of metal–amphiphile complexes in rare earth separations

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

Ethylammonium nitrate enhances the extraction of transition metal nitrates by tri‐n‐butyl phosphate (TBP)

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