1. Thermodynamic aspect

1.1 Phase miscibility

The question of whether two liquid phases can coexist in a given system and, when this is the case, how the compounds involved share out between these two phases, is essential for the development of a liquid-liquid extraction separation process. The literature provides us with a number of data relating to the miscibility domains of binary, ternary and quaternary mixtures [47, 59] , but these are often fragmentary and therefore insufficient when faced with a concrete problem.

• In hydrometallurgy, the feed phase is always aqueous, while the extraction solvent is always organic. For economic reasons, it is virtually never permissible to modify the aqueous...