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Title: Observation of a Rare Earth Ion–Extractant Complex Arrested at the Oil–Water Interface During Solvent Extraction

Abstract

Selective extraction of metal ions from a complex aqueous mixture into an organic phase is used to separate toxic or radioactive metals from polluted environments and nuclear waste, as well as to produce industrially relevant metals, such as rare earth ions. Selectivity arises from the choice of an extractant amphiphile, dissolved in the organic phase, which interacts preferentially with the target metal ion. The extractant-mediated process of ion transport from an aqueous to an organic phase takes place at the aqueous–organic interface; nevertheless, little is known about the molecular mechanism of this process despite its importance. Although state-of-the-art X-ray scattering is uniquely capable of probing molecular ordering at a liquid–liquid interface with subnanometer spatial resolution, utilizing this capability to investigate interfacial dynamical processes of short temporal duration remains a challenge. We show that a temperature-driven adsorption transition can be used to turn the extraction on and off by controlling adsorption and desorption of extractants at the oil–water interface. Lowering the temperature through this transition immobilizes a supramolecular ion–extractant complex at the interface during the extraction of rare earth erbium ions. Under the conditions of these experiments, the ion–extractant complexes condense into a two-dimensional inverted bilayer, which is characterized on themore » molecular scale with synchrotron X-ray reflectivity and fluorescence measurements. Raising the temperature above the transition leads to Er ion extraction as a result of desorption of ion–extractant complexes from the interface into the bulk organic phase. XAFS measurements of the ion–extractant complexes in the bulk organic phase demonstrate that they are similar to the interfacial complexes.« less

Authors:
; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science - Office of Basic Energy Sciences - Chemical Sciences, Geosciences, and Biosciences Division
OSTI Identifier:
1392570
DOE Contract Number:  
AC02-06CH11357
Resource Type:
Journal Article
Journal Name:
Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces and Biophysical Chemistry
Additional Journal Information:
Journal Volume: 118; Journal Issue: 36; Journal ID: ISSN 1520-6106
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English

Citation Formats

Bu, Wei, Yu, Hao, Luo, Guangming, Bera, Mrinal K., Hou, Binyang, Schuman, Adam W., Lin, Binhua, Meron, Mati, Kuzmenko, Ivan, Antonio, Mark R., Soderholm, L., and Schlossman, Mark L. Observation of a Rare Earth Ion–Extractant Complex Arrested at the Oil–Water Interface During Solvent Extraction. United States: N. p., 2014. Web. doi:10.1021/jp505661e.
Bu, Wei, Yu, Hao, Luo, Guangming, Bera, Mrinal K., Hou, Binyang, Schuman, Adam W., Lin, Binhua, Meron, Mati, Kuzmenko, Ivan, Antonio, Mark R., Soderholm, L., & Schlossman, Mark L. Observation of a Rare Earth Ion–Extractant Complex Arrested at the Oil–Water Interface During Solvent Extraction. United States. doi:10.1021/jp505661e.
Bu, Wei, Yu, Hao, Luo, Guangming, Bera, Mrinal K., Hou, Binyang, Schuman, Adam W., Lin, Binhua, Meron, Mati, Kuzmenko, Ivan, Antonio, Mark R., Soderholm, L., and Schlossman, Mark L. Thu . "Observation of a Rare Earth Ion–Extractant Complex Arrested at the Oil–Water Interface During Solvent Extraction". United States. doi:10.1021/jp505661e.
@article{osti_1392570,
title = {Observation of a Rare Earth Ion–Extractant Complex Arrested at the Oil–Water Interface During Solvent Extraction},
author = {Bu, Wei and Yu, Hao and Luo, Guangming and Bera, Mrinal K. and Hou, Binyang and Schuman, Adam W. and Lin, Binhua and Meron, Mati and Kuzmenko, Ivan and Antonio, Mark R. and Soderholm, L. and Schlossman, Mark L.},
abstractNote = {Selective extraction of metal ions from a complex aqueous mixture into an organic phase is used to separate toxic or radioactive metals from polluted environments and nuclear waste, as well as to produce industrially relevant metals, such as rare earth ions. Selectivity arises from the choice of an extractant amphiphile, dissolved in the organic phase, which interacts preferentially with the target metal ion. The extractant-mediated process of ion transport from an aqueous to an organic phase takes place at the aqueous–organic interface; nevertheless, little is known about the molecular mechanism of this process despite its importance. Although state-of-the-art X-ray scattering is uniquely capable of probing molecular ordering at a liquid–liquid interface with subnanometer spatial resolution, utilizing this capability to investigate interfacial dynamical processes of short temporal duration remains a challenge. We show that a temperature-driven adsorption transition can be used to turn the extraction on and off by controlling adsorption and desorption of extractants at the oil–water interface. Lowering the temperature through this transition immobilizes a supramolecular ion–extractant complex at the interface during the extraction of rare earth erbium ions. Under the conditions of these experiments, the ion–extractant complexes condense into a two-dimensional inverted bilayer, which is characterized on the molecular scale with synchrotron X-ray reflectivity and fluorescence measurements. Raising the temperature above the transition leads to Er ion extraction as a result of desorption of ion–extractant complexes from the interface into the bulk organic phase. XAFS measurements of the ion–extractant complexes in the bulk organic phase demonstrate that they are similar to the interfacial complexes.},
doi = {10.1021/jp505661e},
journal = {Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces and Biophysical Chemistry},
issn = {1520-6106},
number = 36,
volume = 118,
place = {United States},
year = {2014},
month = {9}
}