Liquid-liquid extraction General presentation

Liquid-liquid extraction is a separation technique widely used on an industrial scale, in fields as varied as conventional hydrometallurgy, the nuclear industry, petrochemicals, pharmaceuticals and the food industry. Although the principle of this technique is relatively simple, the separations it enables are in fact the result of a combination of a large number of physico-chemical phenomena.

The classification of extraction systems proposed in this first article [J 2 760] on liquid-liquid extraction is based on a macroscopic approach to useful mass transfers from a process viewpoint: non-compensated extractions, extractions with cation exchange or anion exchange. However, beyond this classification, the reader's attention is drawn to the importance of coordination phenomena, on which the formation of many extractable species of interest is largely based. In particular, in the case of metal extraction in hydrometallurgy, the relative importance of inner-sphere and outer-sphere interactions within entities formed in the organic phase is discussed within the framework of a unifying approach emphasizing the continuity of phenomena between the molecular and supramolecular scales. This enables us to identify the levers available to the engineer to design extraction systems that are selective with regard to target ions, but also to apprehend the obstacles that stand in the way.

The [J 2 761] article focuses on the thermodynamic and kinetic aspects of matter transfer between two immiscible liquid phases.

The article [J 2 762] , for its part, gives a few elements on the definition of a liquid-liquid extraction process, but is mainly devoted to the presentation of industrial reagents available to formulate an extraction solvent.

The following articles [J 2 765] and