Selective ions are transferred from the aqueous phase into the organic phase thanks to complexing molecules present at the interface : extractants.

Studied systems:

-An organic phase : dodecane + monoamid: DEHiBA

-An acid aqueous phase : nitrate ions

Interfacial dynamic in liquid/liquid extraction processes probed by non linear optics

P.M. Gassin(1), G. Martin-Gassin (1) (2),D. Meyer(1), J.F. Dufreche(1) ,O. Diat (1), E. Benichou (3), P. F. Brevet (3)

(1) : Institut de Chimie Séparative de Marcoule(2) : CEA Marcoule/DRCP(3) : Laboratoire de Spectrométrie Ionique et Moléculaire, Université Lyon 1 - CNRS

Organic Phase

Aqueous Phase

Complexed Ions

Hydrated Ions

Extractants

Solvated Ions

Liquid/liquid extraction processes are used in separation processes specially concerning nuclear fuel.

What happened at the interface during extraction process ?What are characteristic times of extractants movements on the surface ?

Liquid-Liquid extraction Non Linear Optics

Interface structure

Probing Probing interface structure by by polarization resolved SHGpolarization resolved SHG

- A /2 plate rotates the incident light polarization.

- An analyzer selects the emergent light polarization

Combined SHG and interfacial tension measurements

Possible interpretation and outlook

'n_H+_22

Interface Dynamic

SHG Fluctuation signature of acid extraction

The dynamic of extraction can be view with 3 differents regimes:

1 : The SHG signal fall off because the DEHiBA adsorbes to the interface

2 : The SHG signal fluctuates. The maximum of the SHG standard deviation matches with the maximum flux across the interface

3 : Final Equilibrium state

Real time SHG evolution after introduction of DEHiBA into organic phase at t=0s

G. Martin-Gassin, PCCP submitted

Interpretation of the fluctuation stage during the extraction :

-It can be aggregate on the interface

-It can be 3D developpement of the interface: protrusion

-SHG dependence with [DEHiBA] similar to interfacial tension dependence. -No change in the polarisation signal with DEHiBA .-A possible interpretation is that DEHiBA perturbs and smoothes the sharp neat interface

-Full surface coverage is reached at nearly 200 mM of DEHIBA

? ? ? ? ? ?

CH

3

NC

H3

CH

3

CH

3

CH

3

CH

3

O

Water dipole oriented on the liquid/liquid interface

Water dipole perturbed by the DEHiBA

Interpretation:

Next step :

1) Working with a new molecule, both chromophore and extractant to enhanced SHG signal.

2) To quantify the fluctuations by analysis SHG fluctuations with autocorrelation function

3) To develop a new setup in order to mesure simultaneously SHG signal and Interfacial tension.

N

S

N

SHO

CO2H

CH3(CH2)17

Luciferine

Complexation site

ProtrusionsG.Wipff, JPC C, 2009

Protrusion, ondulations, Léontidis, JPC B, 2009

RoughnessBenjamin, CPL, 2009

Laser

Chopper

Sample in petri dish

Photon counting device

half wave plate

Analyzer

aliphatic Chains

Complexation site

SHG SHG2

SHG

I t I tg

I

( ) ( )( )

Second Harmonic Generation (SHG) is a nonlinear optical phenomenon involving the conversion of two photons at the fundamental frequency into one photon at the harmonic frequency.

In centrosymmetric bulk materials, SHG is forbidden in the electric dipole approximation. SHG is therefor surface specific at the nanometer scale.

Zoom x106

~ 1 nm

P-output SSHG intensity as a function of the input polarization angle. Lines are the fitted curve.