Résumé
<div><p>It is a matter of strategic independence for Europe to urgently find processes taking better account of environmental and economic issues, when mining and recycling rare earth elements (REE). Currently there is no economic process of this kind available and there is no waste recycling for rare earth elements at all. Moreover, 97% of the mining operations are performed in China, hence representing a major Damocles' Sword for the rest of the world's economy. On long term, mining cannot be the solution and circular economy can only start by full recycling, a policy for which Singapore is leading the effort in science needed for technology.</p></div><p>The objective of the REE-CYCLE project is on one hand to develop the fundamental understanding involved in the processing complex fluids for extraction and desextraction coupled in cascades. Replacing trial and error and experiment plans combining all possible formlation, colloidal science allows modelling taking into account chemical potential in the coexisting complex fluids; The “ienaic” approach deals with the science of controlled transfer of electrolytes between complex fluids in equilibria.<p/><p> We this has been done at three levels that will be described in this talk:</p><p> (i) by enabling, for the first time ever, the fast measurement not only of the “efficiency” but also the components of the free energy of mass transfer between complex fluids);</p><p> (ii) develop predictive models of electrolyte including entropic effects and solvent organisation beyond the classical supra-molecular “complexation” i.e. an enthalpic interaction with the first “complexant” neighbour.</p><p> (iii) by suing this knowledge to understand “synergic” as well as “antagonistic effects” that are the –yet totally unexplained- effects that are used in the vast majority of the molecular mechanisms at the basis of the efficient liquid-liquid extraction processes that have been developed since 60 years, classified in chemical engineering Handbooks in seventeen categories with different performances, without the existence of a unified theory combining nanoscience determining nanostructures and free energy in nano-domains.</p><p>In this talk, we will:</p><p>- describe a new, fast and reliable method to determine with unprecedented precision free energy of transfers, - explain the ingredients needed for modelling the transfer using Gaussian random wavelet fields or approximating polar cores as a confined droplets, and</p><p>- give a precise example demonstrating that synergy used in practice can improve yields and selectivity as well as volume of real plants by a factor of ten are mainly driven by entropic effects: two extractants are mixed in a highly curved active extractant film combining two anionic and solvating surface active agents with electronegative “complexing” groups.</p>