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Updated: Nov 2, 2025

Interfacial Molecular-level Structures of Polymers and Biomacromolecules Revealed via Sum Frequency Generation Vibrational Spectroscopy
Published on: August 13, 2019
Stoichiometry of Lanthanide-Phosphate Complexes at the Water Surface Studied Using Vibrational Sum Frequency
Ryoji Kusaka1, Masayuki Watanabe1
1Nuclear Science and Engineering Center, Japan Atomic Energy Agency (JAEA), 2-4 Shirakata, Tokai, Ibaraki 319-1195, Japan.
Abstract:
In the solvent extraction of metal ions, the transport mechanism of metal ions through the liquid-liquid organic/aqueous interface remains unclear. In this study, the adsorption process of trivalent lanthanide ions from the aqueous phase to the interface in the solvent extraction of lanthanides with di(2-ethylhexyl)phosphoric acid (HDEHP) extractant is investigated by using a model interface-water surface covered with HDEHP (air/HDEHP/aqueous interface). As a result, symmetric POO- stretch signals of HDEHP observed by vibrational sum frequency generation spectroscopy and density functional theory calculations show that the stoichiometric ratio of lanthanide-HDEHP complexes formed at the air/HDEHP/aqueous interface is 1:1. The formation of the interfacial 1:1 lanthanide-HDEHP complex could be an elementary chemical process occurring just before the transfer of lanthanide ions to the side of the organic phase.
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