Résumé
We will report on a newly developed liquid-liquid extraction microfluidic device. We will first report of our studies of solvent chemical activities [1, 2, 3]. We will then show that, when associated with X-ray fluorescence, It enabled us to investigate the synergy effect in liquid-liquid extraction of rare earths. We will show unpublished results obtained enabling the study of both the kinetic and the equilibrium of such reactions. This approach has allowed us to determine the variation of the free energy of transfer for five rare earths mixed together in solution with iron, a non-target ion and thus at different pH and temperature. We finally will discuss these results in regards of the various terms contributing to the free energy associated with this synergy effect. [4]