Liquid–liquid equilibria, excess molar volume and deviations of the refractive indices at 298.15 K for mixtures of solvents used in the molybdenum extraction process

• Thermodynamic properties for solvent recycling in Mo extraction process.
• LLE data and mixture properties for the systems {Aqueous acid solution + acetylacetone + phosphonium-based ionic liquids}.
• NRTL and UNIQUAC models were used for the description of the determined LLE data.

A separation process is necessary for the recycling of the solvent and diluent from a molybdenum (Mo) acid leaching solution. Acetylacetone is a commercial Mo solvent and phosphonium-based ionic liquid (IL) that is a promising green selective solvent for Mo ions or dilutor based on the Mo extraction test. To develop a recycling process for the solvent, pseudo ternary liquid–liquid equilibria (LLE), a separation process design data set, was determined for several systems at 298.15 K: {Aqueous acid solution (AS-solution) + acetylacetone + tri-hexyltetradecyl phosphonium chloride ([P666,14][Cl])}, {AS-solution + acetylacetone + tri-hexyltetradecyl phosphonium bis(2,2,4-trimethylpentyl) phosphinate ([P666,14][TMPP])} and {AS-solution + acetylacetone + tri-hexyltetradecylphosphonium dictanamide ([P666,14][DCA])}. The experiments were carried out at atmospheric pressure using stirred and thermo-regulated cells. The experimental LLE data for the aforementioned pseudo ternary systems were correlated using the non-random two liquid (NRTL) activity coefficient model. In addition, mixture properties, namely the excess molar volume (VE) and deviations of the refractive indices (ΔR), were determined for the following binary systems at 298.15 K: {acetylacetone + [P666,14][Cl]}, {acetylacetone + [P666,14][TMPP]} and {acetylacetone + [P666,14][DCA]}. These binary data were correlated with the Redlich–Kister polynomial.