308.15K下NaCl-CaCl2-H2O体系热力学性质的等压研究

Thermodynamics properties for the aqueous system (NaCl-CaCl_2-H_2O) at 308.15 K by using isopiestic method

采用等压法研究了308.15K下NaCl-H2O、CaCl2-H2O和NaCl-CaCl2-H2O体系离子强度分别为0.5666～5.9265molkg-1、0.3943～5.5573molkg-1和0.6524～16.6631molkg-1的等压平衡浓度和水活度,计算了渗透系数及饱和蒸汽压,获得了该体系渗透系数和饱和蒸汽压随离子强度的变化规律.应用Pitzer离子相互作用模型,用实验数据用多元线性回归拟合了308.15K下该体系的NaCl和CaCl2的纯盐参数β(0)、β(1)、Cφ分别为0.3181、1.5346、-0.0014和0.07972、0.3067、0.00075,拟合标准偏差分别为0.00072、0.0049;混合离子作用参数θNa,Ca、ψNa,Ca,Cl分别为0.06821、-0.0076,拟合标准偏差为0.0063和0.0064.用Pitzer模型计算的渗透系数与实验结果吻合.本研究为含钠钙海卤水体系热力学模型建立提供了重要的热力学基础数据.

The isopiestic molalities and water activities for the systems （NaCl-H2O）,（CaCl2-H2O） and （NaCl-CaCl2-H2O） were measured at 308.15 K by the isopiestic method in the ranges of 0.5666-5.9265 mol kg-1,0.3943-5.5573 mol kg-1,and 0.6524-16.6631 mol kg-1,respectively.The osmotic coefficients and the saturated vapor pressures were calculated for the （NaCl-CaCl2-H2O） system.The change behaviors of the osmotic coefficients and the saturated vapor pressure for the ternary system versus the changes of ion strengths were demonstrated.Pitzer＇s single electrolyte parameters β（0）,β（1）,Cφ for NaCl and CaCl2 are 0.3181,1.5346,-0.0014 and 0.07972,0.3067,0.00075 with standard deviations of 0.00072 and 0.0049,and Pitzer＇s mixing ion-interaction parameters of θNa,Ca,ψ Na,Ca,Cl corresponding to 0.06821,-0.0076 with standard deviations of 0.0063 and 0.0064 for the system （NaCl-CaCl2-H2O） were obtained by using multivariant linear regression method.The osmotic coefficient values determined experimentally and these calculated by using Pitzer model with the parameters fitted are in good agreement.The thermodynamic data obtained in this study is essential to construct the complex thermodynamic model for the type of containing sodium and calcium seawater and brine system.