四元盐水体系热力学性质和相平衡的预测

Prediction of Thermal Properties and Phase Equilibrium of the Quaternary Salt-water Systems

应用Pitzer-Simonson-Clegg热力学模型,结合二元及三元模型参数计算了包含K+,Mg2+,Na+,Cl-和NO-3离子的6个二元盐水体系和9个三元盐水体系的溶解度,模型参数分别拟合于相关体系的水活度、渗透系数及溶解度实验数据.在未考虑四元混合参数的情况下,较为准确的预测了四元盐水体系K+,Mg2+∥Cl-,NO-3-H2O,K+,Na+∥Cl-,NO-3-H2O,Mg2+,Na+∥Cl-,NO-3-H2O和K+,Na+,Mg2+∥NO-3-H2O在不同温度下的溶解度,同时预测K+,Na+∥Cl-,NO-3-H2O体系在278.15K^323.15K范围内饱和溶液的饱和蒸汽压,及其子体系KNO3-NaNO3-H2O和NaCl-NaNO3-H2O在363.15K下饱和溶液的水活度,和KCl-KNO3-H2O体系在不同温度下共饱和点组成溶液的饱和蒸汽压,模型计算结果与文献数据吻合.

This paper calculated the phase diagrams of nine ternary systems including K＋,Mg2＋,Na＋,Cl-and NO3-and their binary systems by using a Pitzer-Simonson-Clegg thermodynamic model.The binary model parameters were fitted with experimental water activity and osmotic coefficient data,and the ternary model mixture parameters were obtained by regressing the experimental solubility data of the ternary salt-water systems.All model parameters and equilibrium constants of the solid phase were expressed as the functions of temperature.Furthermore,the positions of invariant points over the range of temperature from 273.15 K to 364.15 K of the ternary system KCl-KNO3--H2O were accurately predicted,and the predicted vapor pressures over aqueous solutions which are saturated with the invariant points of this system were in good agreement with literature data.And the water activities of the saturated solution of the ternary systems KNO3-NaNO3-H2O and NaCl--NaNO3-H2O at 363.15 K were predicted and compared with experimental data.On the basis of these,we neglected the quaternary model parameters and just used the binary and ternary parameters to predict the isotherms of the quaternary systems K＋,Mg2＋ //Cl-,NO3--H2O,K＋,Na＋ //Cl-,NO3--H2O,Mg2＋,Na＋ //Cl-,NO3--H2O and K＋,Na＋,Mg2＋ //NO3--H2O,and to predict the vapor pressure of saturated solution of the system K＋,Na＋//Cl-,NO3--H2O over the temperature range from 278.15 K to 323.15 K.The predicted values were in good agreement with experimental data.