青海一里平盐湖卤水Li-Na-K-Mg-Cl-SO_4-H_2O体系25℃时渗透系数、活度系数和饱和度的预测

PREDICTION OF OSMOTIC AND ACTIVITY COEFFICIENTS AND SATURATION DEGREES OF A SALT LAKE BRINE YILIPING, QINGHAI Li-Na-K-Mg-Cl-SO_4-H_2O SYSTEM AT 25℃

将Ritrer离子作用模型的应用扩展到中国富含锂的一里平盐湖卤水Li－Na-K-Mg－Cl-SO4－H2O体系，综合1990－1997年作者对该体系的含锂三元次级体系25℃时的活度系数和渗透系数的研究结果和文献数据，给出了该体系的Pitzer离子作用模型参数；计算了溶解平衡常数；预测了青海一里平盐湖晶间卤水中离子和盐的活度系数、卤水的渗透系数、水活度、蒸汽压以及盐类的饱和度；揭示了卤水在蒸发和稀释过程中上述热力学性质随离子强度变化的规律，用离子强度与盐类饱和度的关联图（I-ln（K’／K）图）分析了该卤水的折盐顺序。计算结果表明，一旦平盐湖晶间因水在25℃时只有石盐饱和，与野外观测结果相一致；用参数化的Pitzer离子作用模型预测该卤水多组分体系的热力学性质和溶解平衡是可行的。

The Pitzer ion interaction model is extended for a natural salt lake brine with high Li concentrations: a Li-Na-K-Mg-CI-SO4-H2O system at 25℃. The model parameters, resulting fromour previous studies on the osmotic and activity coefficients for a number of subsystems containing activities at 25 in 1990-1997, together with those in literatures, were obtained. The dissolution eqnilibrium constants were evaluated. The achvity coefficients of ions and salts, osmotic coefficients,activities of water, vapor pressures and saturation degrees in the interstitial brine of the Qinghai Yiliping salt lake were calculated using the model, relationships between these thermodynamicproperties and the change in ionic strengths were established. The crystallization sequences of saltsfrom the brine during the brine evaporation was analyzed on the basis of the correlation of totalionic strengths with saturation degrees of different salts (Pin(K' / K)). The results indicate that themineral which precipitates out naturally from the Yiliping brine is halite at 25t, which is inagreement with the observation on the field. The prediction of the thermodynamic properties of the brine using the parameterized Pitzer model is satisfactory. These studies are important in theestablishment of chemical models for salt lakes, the development of solution chemistry andgeochemistry, and the comprehensive utilization of salt lake resources.