钠钙氯化物在乳糖水中热力学性质的确定

Determination of thermodynamic properties of calcium chloride and sodium chloride in lactose aqueous solution

在298.15 K时利用电动势法确定四元体系氯化钠-氯化钙-乳糖-水不同组成(乳糖质量分数分别为0,5%,10%和15%)时的热力学性质。利用Pitzer离子作用模型拟合实验数据,获得了氯化钠和氯化钙在乳糖水混合溶剂中的Pitzer模型参数。进一步计算了氯化钠和氯化钙从纯水到乳糖水混合溶剂中的迁移吉布斯函数。获得了氯化钠和氯化钙混合电解质在乳糖水混合溶剂中的混合参数θ(Na Ca)和ψ(Na Ca Cl)。计算了298.15 K时四元体系中氯化钠和氯化钙的平均离子活度系数。结果发现:利用Pitzer高阶静电作用模型计算混合电解质在混合溶剂中的平均离子活度系数,能获得较为满意的结果。

The thermodynamic properties of the quaternary system [ NaC1 （ mA ）-CaC12 （ mB ） -lactose-H20 ] with compositions of 0, 5%, 10% and 15% lactose were studied based on the Pitzer ion-interaction model by the electromotive force（EMF）method at 298.15 K. The Pitzer model parameters of electrolyte NaC1 and CaC12 were respectively calculated in different ratios of lactose-water mixed solvents. The free energies of transfer of sodium chloride and calcium chloride from water to lactose-water mixtures were also calculated. The results show that NaC1 has the higher Gibbs free energy in pure water than in lactose and water mixed solvents, however CaC12 has the higher Gibbs free energy in lactose and water mixed solvents. What＇s more, the Pitzer＇s mixing interaction parameters θ（NaCa） and ψ （NaCaC1） and the mean ion activity coefficients of electrolytes were determined at 298.15 K in these studied quaternary mixed electrolyte system according to the Pitzer model. The results show that the Pitzer model with higher-order electrostatic effects describes the activity coefficients of mixed electrolytes in mixed solvent systems satisfactorily.