Studies On The Metastable Phase Equilibrium Of The Quinary System Li⁺(K⁺ ), Na⁺//Cl, SO₄^2-, B₄O₇^2-H₂O At 273K

Zabuye Salt Lake, located in Tibet, famouses for its aboundance resources, suchas lithium, sodium, potassium, and chloride, sulfate, carbonate, and borate. In order tocomprehensive utilize the resource in the Zabuye Salt Lake, the metastable equilibriaof the quaternary system Li⁺//Cl-, SO₄^2-, B4O7^2- - H₂O and two quinary system K⁺,Na⁺//Cl-, SO₄^2-, B4O7^2- - H₂O and Li⁺, Na⁺//Cl-, SO₄^2-, B4O7^2- - H₂O were studied at273 K using an isothemal evaporation method. The solubilities, densities and pHvalues of the equilibrated solution were determined. According to the experimentaldata, the metastable equilibrium phase diagrams, the water-content diagrams, thedensity-composition diagrams and the pH-composition diagrams of the quaternarysystem were plotted; the stereo-diagram and projected phase diagrams (saturated withNa₂B4O₇, KCl or LiBO₂·8H₂O), corresponding water content diagrams,density-composition diagrams, the pH-composition diagrams and sodium, potassium(lithium) content diagrams of the both of the quinary systems were also plotted.There is no double salt or solid solution formed in the simple quaternary systemLi⁺//Cl-, SO₄^2-, B4O7^2- - H₂O. The metastable phase diagram of the system consists ofone invariant point, three univariant curves and three crystallization fields. The threecrystallization fields correspond to the single salt LiCl·H₂O, Li₂SO₄·H₂O andLiBO₂·8H₂O. Salt LiBO₂·8H₂O has the largest crystallization field, whereas saltLiCl·H₂O has the smallest crystallization field. Salt LiCl·H₂O has a strong salting-outeffect on salt Li₂SO₄·H₂O in the solution.The results show that there is no double salt or solid solution formed in thequinary system K⁺, Na⁺//Cl-, SO₄^2-, B4O7^2- - H₂O, and the metastable phase diagram ofthis system consists of three invariant points, eleven univariant curves and sixcrystallization fields. The six crystallization fields correspond to single salt NaCl,Na₂SO₄·10H₂O, Na₂B4O₇·10H₂O, KCl, K2SO₄ and K₂B4O₇·4H₂O; the projecteddiagramof this system (saturated with Na₂B4O₇) consists of three invariant points,seven univariant curves and five crystallization fields. The five crystallization fieldscorrespond to single salt Na₂SO₄·10H₂O, K₂B4O₇·4H₂O, KCl, NaCl and K2SO₄; theprojected-diagram of this system (saturated with KCl) also consists of three invariant points, seven univariant curves and five crystallization fields. The five crystallizationfields correspond to single salt Na₂SO₄·10H₂O, K₂B4O₇·4H₂O, Na₂B4O₇·10H₂O, NaCland K2SO4. In this system, the crystallizations of sodium and potassium borate areNa2B4O5(OH)4·8H₂O and K2B4O5(OH)4·2H₂O, respectively.The results show that the double salt 3Na₂SO₄·Li₂SO4·12H₂O is formed in thequinary system Li⁺, Na⁺//Cl-, SO4^2-, B4O72 - H₂O. The metastable phase diagram of thesystem has four invariant points, thirteen univariant curves and seven crystallizationfields. The seven crystallization fields correspond to single salt NaCl, Na₂SO₄·10H₂O,Na₂B4O₇·10H₂O, Li₂SO4·H₂O, LiCl·H₂O, LiBO₂·8H₂O and double salt3Na₂SO₄·Li₂SO4·12H₂O. The crystallization fields of LiCl·H₂O is smaller, while thecrystallization fields of Na₂B4O₇·10H₂O and LiBO₂·8H₂O are larger. Thus, in thecondition of metastable, it is beneficical for the precipitation of Na₂B4O₇·10H₂O andLiBO₂·8H₂O. The projected-diagram of this system (saturated with Na₂B4O₇) consistsof three invariant points, seven univariant curves and five crystallization fields. Thefive crystallization fields correspond to salt Na₂SO₄·10H₂O, Li₂SO4·H₂O,3Na₂SO₄·Li₂SO4·12H₂O, LiBO₂·8H₂O and NaCl; while, the projected-diagram of thissystem (saturated with LiBO₂·8H₂O) consists of four invariant points, five univariantcurves and four crystallization fields. The four crystallization fields correspond tosingle salt Li₂SO4·H₂O, Na₂B4O₇·10H₂O, LiCl·H₂O and NaCl.