At the molecular level, the description of the ion transfer through an active interface is still fully opened to exploration. As mentionedin a recent paper on surfactant at LL interface, some general accepted picture of molecular conformation or orientation can bereconsidered when specific studies are carried out. Its study is essential for progressing in fundamental understanding of factorsgoverning the separation process. This is certainly a highly challenging problem that cannot be totally solved in a three year program.However, we propose an original approach coupling complementary experiments and modelling in focusing on this interfacespecifically.Liquid/liquid interface will be probed by neutron reflectivity (beamtime requested on FIGARO) in order to determine at equilibrium(controlled by chemical potential regulation) the extractant molecule distribution that will allow to extract metal cation from aqueous upto organic phase. In parallel, SAXS and SANS experiment will be performed to characterize nanoaggregation of the extractant molecules in the samethermodynamical conditions.