Abstract
The phase equilibria of the quaternary system Li+, Na+//Cl‒, \({\text{HCO}}_{{\text{3}}}^{ - }\) ‒H2O at 313.15 K with CO2 pressure at 0.3 MPa were studied with the isothermal dissolution method. According to the experimental results, the dry-salt phase diagram, the water content phase diagram, and the physicochemical properties (pH and refractive indexes) diagrams were plotted. In the dry-salt phase diagram, there are two invariant points, five solubility isotherm curves, and four crystallization fields corresponding to LiCl⋅H2O, NaCl, LiHCO3 and NaHCO3. The crystallization region of LiHCO3 is the largest, while that of LiCl⋅H2O is the smallest. LiCl⋅H2O has the highest solubility and exerts a strong salting-out effect on NaCl and NaHCO3. A comparison between the phase diagrams of the systems Li+, Na+//Cl‒, \({\text{CO}}_{3}^{{2 - }}\) ‒H2O at 323.15 K and Li+, Na+//Cl‒, \({\text{HCO}}_{{\text{3}}}^{ - }\) ‒H2O at 313.15 K shows that the crystallization zones of carbonate salts (LiHCO3 and NaHCO3) change to those of bicarbonate salts (LiHCO3 and NaHCO3).The change in area of the crystallization zones for bicarbonate salts can be used to separate NaHCO3 from the lithium precipitation mother liquor with CO2 carbonation method.
