Transcript Dynamic of extraction in a liquid/liquid interface probed by

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
Non Linear Optics
Liquid-Liquid extraction
Liquid/liquid extraction processes are used in separation
processes specially concerning nuclear fuel.
Extractants
Organic Phase
Solvated Ions
Complexed
Ions
Selective ions are transferred from the aqueous
phase into the organic phase thanks to complexing
molecules present at the interface : extractants.
P=e c
0
Aqueous Phase
w
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.
(1)
E+e c
0
(2)
2w
w
: EE +...
Hydrated Ions
What happened at the interface during extraction process ?
What are characteristic times of extractants movements on the surface ?
In centrosymmetric bulk materials,
SHG is forbidden in the electric dipole
approximation. SHG is therefor
surface specific at the nanometer
scale.
~ 1 nm
Zoom x106
Studied systems:
-An organic phase : dodecane + monoamid: DEHiBA
Complexation
site
-An acid aqueous phase : nitrate ions
aliphatic
Chains
Probing interface structure by
polarization resolved SHG
- A l/2 plate rotates the incident light
polarization.
- An analyzer selects the emergent
light polarization
half wave plate
Photon counting
device
Laser
Analyzer
Chopper
Sample in petri
dish
Interface Dynamic
Interface structure
Combined SHG and interfacial tension measurements
Real time SHG evolution after introduction of
DEHiBA into organic phase at t=0s
The dynamic of extraction can
be view with 3 differents
regimes:
1 : The SHG signal fall off
because the DEHiBA
adsorbes to the interface
P-output SSHG intensity as a function of the input polarization
angle. Lines are the fitted curve.
2 : The SHG signal
fluctuates. The maximum of
the SHG standard deviation
matches with the maximum
flux across the interface
'n_H+_22
CH 3
? ?
N
H 3C
?
?
?
Water dipole
perturbed by the
DEHiBA
H 3C
H 3C
O
?
CH 3
Water dipole
oriented on the
liquid/liquid
interface
CH 3
Interpretation:
3 : Final Equilibrium state
-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
SHG Fluctuation
signature of acid extraction
G. Martin-Gassin, PCCP submitted
Possible interpretation and outlook
Interpretation of the fluctuation stage during the extraction :
Next step :
- It can be aggregate on the interface
1) Working with a new molecule, both
chromophore and extractant to enhanced
SHG signal.
- It can be 3D developpement of the interface: protrusion
2) To quantify the fluctuations by analysis
SHG fluctuations with autocorrelation
function
Protrusions
G.Wipff, JPC C,
2009
Protrusion,
ondulations,
Léontidis, JPC B,
2009
Roughness
Benjamin, CPL,
2009
3) To develop a new setup in order to
mesure simultaneously SHG signal and
Interfacial tension.
CH3(CH2)17
Complexation
site
Luciferine
g ( ) 
ISHG ( t  )ISHG ( t )
ISHG
2