A thermodynamic model for the extraction of lithium from chloride brines containing aluminium and magnesium

The equilibrium constants for the extraction of lithium chloride, magnesium chloride and aluminium chloride by 1-hexanol and isopentyl alcohol were determined. For the joint distribution of the three salts between aqueous and organic solutions, a computer calculation based on a thermodynamic multicomponent electrolyte solution approach was applied. The coextraction of water was also taken into account. Predictions for the selective extraction of lithium were tested against experimental data, and reasonable agreement was found at low concentrations. The discrepancies observed at high chloride concentrations were ascribed to ion-pairing in the organic phase and to water co-extraction, possibly also to cation—cation interactions on the organicphase.