Solid–Liquid Stable Phase Equilibria of the Quaternary System (Li⁺,K⁺//\({\text{SO}}_{4}^{{2 - }}\),\({\text{CO}}_{3}^{{2 - }}\)–H₂O) at 308.15 K

Solid–liquid phase equilibria of the quaternary system (Li⁺,K⁺// \({\text{SO}}_{4}^{{2 - }}\) , \({\text{CO}}_{3}^{{2 - }}\) –H₂O) and its subsystem are very important for the separation of lithium and potassium salts from the salt lake brines. In this paper, the solubilities, densities, refractive indices and pH values of the reciprocal quaternary system (Li⁺,K⁺// \({\text{SO}}_{4}^{{2 - }}\) , \({\text{CO}}_{3}^{{2 - }}\) –H₂O) at 308.15 K were determined experimentally using the isothermal dissolution method. The dry-salt diagram and water-phase diagram were plotted based on the experimental data. The stable phase diagram contains four invariant points, nine univariant curves and six crystallization regions corresponding to Li₂CO₃, Li₂CO₃⋅K₂CO₃, K₂CO₃⋅1.5H₂O, Li₂SO₄⋅H₂O, K₂SO₄, and Li₂SO₄⋅K₂SO₄. Li₂CO₃ has the largest crystallization field, whereas the Li₂CO₃⋅K₂CO₃ crystallization field is the smallest one.