Experimental study of the Tibetan Dangxiong Co salt lake brine during isothermal evaporation at 25 °C

Abstract

Production of lithium carbonate from brines has become the dominate trend in the world since the beginning of the century. Dangxiong Co, located in the interior of the Tibetan Plateau, China, is a carbonate-type lithium salt lake. The lake, rich in Li, B, K and other valuable elements, is of great economic value. The concentration rules of these elements and the salt crystallization paths in the brine were studied in an isothermal evaporation experiment at 25 °C. The sequence in sedimentation of the primary salts, which crystallized from the brine during evaporation experiment at 25 °C, was halite (NaCl)—trona (Na₂CO₃·NaHCO₃·2H₂O)—zabuyelite (Li₂CO₃)—Glaserite (3K₂SO₄·Na₂SO₄)—sylvite (KCl)—borax (Na₂B₄O₇·10H₂O). This is some different from what one may conclude with the metastable phase diagram of the quinary system Na–K–CO₃–SO₄–Cl–H₂O at 25 °C. Lithium precipitation was a continuous process that occurred throughout the whole experiment. But, it was difficult to obtain high-grade lithium salt during the evaporation operation at 25 °C. Potash was precipitated as Glaserite and sylvite in the experiment with high grade, which made the Dangxiong Co salt lake brine suitable to produce potash. Borax was precipitated in the late stage. High-grade borax could be obtained from Dangxiong Co salt lake brine. The experiment results indicate that the lithium carbonate exploiting technology that is being used on the Zabuye salt lake could be applicable to the Dangxiong Co salt lake.