1 research outputs found
Synergism by Coassembly at the Origin of Ion Selectivity in Liquid–Liquid Extraction
In liquid–liquid extraction, synergism emerges
when for
a defined formulation of the solvent phase, there is an increase of
distribution coefficients for some cations in a mixture. To characterize
the synergistic mechanisms, we determine the free energy of mixed
coassembly in aggregates. Aggregation in any point of a phase diagram
can be followed not only structurally by SANS, SAXS, and SLS, but
also thermodynamically by determining the concentration of monomers
coexisting with reverse aggregates. Using the industrially used couple
HDEHP/TOPO forming mixed reverse aggregates, and the representative
couple U/Fe, we show that there is no peculiarity in the aggregates
microstructure at the maximum of synergism. Nevertheless, the free
energy of aggregation necessary to form mixed aggregates containing
extracted ions in their polar core is comparable to the transfer free
energy difference between target and nontarget ions, as deduced from
the synergistic selectivity peak