Measurement and Correlation of Phase Diagram Data of Hydrophilic Alcohols (1-Propanol/2-Propanol) + + Salts (Na2SO4/(NH4)2SO4/NH4NO3) + Water Systems

G. Khayati and M. Shahriari

Abstract
Binodal data and the ternary liquid–liquid equilibria (LLE) was experimentally determined at 298.15 K for hydrophilic alcohols (1-propanol or 2-propanol) + salts (Na2SO4, (NH4)2SO4 or NH4NO3) + water systems. The salting-out and the phase-forming abilities of the salts and alcohols for the investigated ATPSs were discussed. The salting-out abilities of the investigated salts follow the order Na2SO4 > (NH4)2SO4 > NH4NO3, which can be indicated by the location of the binodal curves plotted in mass fraction, the effective excluded volume (EEV), the salting-out coefficient (Ks), the size of the ions, and the Gibbs free energy of hydration of the ions. The phase-separation ability of the studied hydrophilic alcohols was discussed on the basis of the dielectric constant and boiling point of the alcohols. The results show that the phase-separation capability of the system consists of different hydrophilic alcohols in the order: 1-propanol>2-propanol. Furthermore, the binodal curves of the studied systems were satisfactorily correlated by a nonlinear equation with four parameters. The reliability of the calculation method and the corresponding LLE data was successfully proved by the Othmer-Tobias equation and the Bancroft equation.

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Keywords
liquid–liquid equilibrium, aqueous two-phase system, hydrophilic alcohols, salting-out effect, phase-forming ability