Effect of third component on separation behavior of water+<em>t</em>-butanol+Na₂SO₃/Na₂SO₄ system at 298±2 K

Abstract

The liquid-liquid and liquid-liquid-solid equilibria for the ternary <em>t</em>-butanol-water-Na₂SO₃/Na₂SO₄ system is reported at ambient pressure and at 298±2 K. The solubility data of solutions of Na₂SO₃/Na₂SO₄ in water, <em>t-</em>butanol and solutions of varying compositions of <em>t-</em>butanol in water are reported. The phase diagrams for the studied systems are developed and salting-out effect of salt anion has been described. The structural properties of aqueous <em>t-</em>butanol solutions and the salting-out effect of SO₃^2- and SO₄^2- ions to cause phase separation have been explained. The salting-out ability of Na₂SO₃ is higher than that of Na₂SO₄ since the Gibbs free energy of hydration (Δ<em>G</em>_hyd) of SO₄^2- (−1080 kJ mol^-1) is lower than that of SO₃^2- (−1295 kJ mol^-1) ion.