Measurements and calculations of solid-liquid equilibria in quaternary system Li₂SO₄-Na₂SO₄-K₂SO₄-H₂O at 288 K

Abstract

The isothermal dissolution equilibrium method has been used to investigate the solid and liquid equilibria of quaternary system Li₂SO₄-Na₂SO₄-K₂SO₄-H₂O at 288 K. The phase diagram and water diagram were plotted according to the experiment results. It was found that Li₂SO₄-Na₂SO₄-K₂SO₄-H₂O quaternary system contains four double salts at 288 K. There are six invariant points, twelve univariant curves and seven areas of crystallization: Li₂SO₄ H₂O, Na₂SO₄ 10H₂O, K₂SO₄, Li₂SO₄ 3Na₂SO₄ 12H₂O, Li₂SO₄ K₂SO₄, Na₂SO₄ 3K₂SO₄, 2Li₂SO₄ Na₂SO₄ K₂SO₄. Using the equilibrium solubility data of the quaternary system at 288 K, the solubility product(lnK _sp) of solid phase 2Li₂SO₄ Na₂SO₄ K₂SO₄, which is not reported was acquired. Based on the chemical model of Pitzer’s electrolyte solution theory, the solubilities for the quaternary system Li₂SO₄-Na₂SO₄-K₂SO₄-H₂O at 288 K were calculated with corresponding parameters. Compared the results of experimental measurement with those of calculation, it was showed that the calculated values had a good agreement with the experimental ones.

Keywords

Salt-water system / Phase equilibrium / Solubility / Sulfate / Pitzer’s Equation

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