Thermodynamic modeling of solvent extraction equilibria

Solvent extraction is an important technique in extractive metallurgy and is used for separation and purification of metals, such as the rare-earth elements, the platinum group metals, copper, nickel and cobalt. The technique is based on the preferential distribution of metal ions between two immiscible liquid phases. In order to develop efficient solvent extraction processes, it is important to know the influence of different parameters (temperature, concentration of extractant, salt concentration and metal concentration in the feed phase) on the distribution equilibria. This is in general done by empirical or chemical models that are based only in experimental extraction data. The objective of this PhD project is to develop and validate a thermodynamic model for solvent extraction of metal ions. Such a thermodynamic model is a mathematical model of the distribution ratio, and it correlates the distribution ratio to reaction enthalpy values and the activity coefficient of each component in the two phases.