Thermodynamic model for solvating solutions with physical interactions

A method for the correlation of phase equilibrium data for solvating, multicomponent liquid solutions is proposed. Chemical equilibrium constants are used to calculate the extent of formation of discrete solvation complexes, and the UNIFAC group-contribution theory is used to predict the physical interactions between species in solution. The method is applied to example binary and multicomponent solvating systems including a quaternary trioctylamine/acetic acid/solvent/water system from a developmental liquid extraction process that exhibit unusually complex phase equilibria. The proposed method gives a much better representation of such systems than has been reported previously. Potential shortcomings of the approach are also discussed.