Active liquid-liquid interfaces – ILLA

The experimental part of ILLA project is different and new because it will couple two experimental methods, one specific to the interface (Second Harmonic Generation - SHG) and one of the fundamental physical properties of liquid interfaces, the interfacial tension. Interfacial tension will reflect the average interfacial concentration of species, whereas SHG will reflect the orientation and the dynamics of the interfacial species. Interpretation of both sets of results is generally based on physical ad hoc models, without providing a microscopic picture of the interface at the molecular level, though. An important facet of the ILLA proposal is to get more realistic pictures of the studied interfaces in the presence of the different partners involved in the assisted ion transfer using all-atom based molecular dynamics (MD) simulations.

In ICSM, priority has been given to the installation of a non-linear optical (SHG) experimental bench with 90% funding from internal CEA (budget long).
With ILM team, we focused on the implementation of the experimental setup to allow the coupling of optical measurements with SHG measurements of surface tension.
With MSM team, an important early work on molecular dynamics biphasic systems involving amide ligand to the extraction of uranyl and europium has been studied and published in JPC-B.

to merge on a same system optmised for each action within the different teams

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The ILLA project gathers three complementary teams to study in synergy liquid/liquid "LL" interfaces involved in the assisted ion extraction from water to an organic "oil" phase. This biphasic process is the basis of hydrometallurgical applications of outmost importance such as metal ion extraction or recycling. By coupling specific surface experiments and molecular simulations, we investigate the characteristics of relevant LL interfaces (size, polarity, dynamics, local intermiscibility of liquids), and the concentration and ordering of "adsorbed" species (extractants, complexes, …), following four well defined and parallel tasks. The aim is to obtain detailed molecular insights into interfacial events involved in the transfer of metallic cations (e.g. Ln3+ lanthanides) from an aqueous to an oil phase upon complexation with extractant molecules (e.g. lipophilic diamides).
ILLA is a fundamental project combining for the first time synthesis of a "reporter" extractant, non linear optics spectroscopy (SHG) coupled with surface tension measurements, and simulations (molecular dynamics) on the same systems. Beyond studies on "static" planar and curved interfaces (e.g. aqueous interfaces with lanthanide salts, or extractants alone), we plan to investigate LL interfaces "in action", i.e. to follow the kinetics and spectroscopic signature of the multistep extraction processes. These studies involve experimental and theoretical developments. The results should serve as a basis for further understanding the extraction mechanism, to improve the efficiency and kinetics of existing processes, and to develop new ones. The methodological developments (e.g. "prediction" and interpretation of SHG signature, experimental set ups) will also allow to study other liquid interfaces (e.g. in phase transfer catalytic systems).