Liquid-liquid extraction Process design

In the two previous articles "Liquid-liquid extraction – Overview" [J2760] and "Liquid-liquid extraction - Physico-chemical bases of the processes" [J2761] , we outlined the fundamental principles of liquid-liquid extraction.

This article returns to more concrete considerations by giving some elements on the definition of a liquid-liquid extraction process and presenting the main industrial reagents, i.e. extractants, diluents and phase modifiers, available on the market today to formulate an extraction solvent in the hydrometallurgy field. It should be noted that companies marketing extractants have undergone a number of restructurings over the last fifteen years, the most recent (December 2015) being the acquisition of Cytec by the Solvay group, while companies, often Chinese, have appeared on the market offering extractants that can be described as "generic" (for example, the Mextral ^® series marketed by KopperChem (China)). Such a situation naturally broadens the range of extractants on offer, but calls for caution with regard to the quality and long-term availability of these products. In addition, these companies may be able to produce custom extractants, outside the catalog, which may be of interest in certain situations. The literature describes a large number of extractants proposed by a large number of laboratories around the world for a variety of applications ranging from primary hydrometallurgy to recycling of metal resources, not forgetting nuclear power. However, few of these molecules are really intended to go beyond the stage of fundamental studies, so the inventory of commercial extractants has changed little in recent years. The same applies to diluents and phase modifiers, although product lines are emerging, such as the ELIXORE ^® diluent series, specifically formulated for liquid-liquid extraction. In conclusion, this article briefly analyses the prospects for the development of new extractants and diluents, including the use of ionic liquids.