273.15K时LiCl-Li2SO4-H2O体系热力学性质的等压研究

0℃下用改进的等压设备和改进的实验方法测定了纯水溶液(LiCl 0.5～9.2mol·kg-1,Li2SO40.3～2.5mol·kg-1)以及混合水溶液(离子强度0.5～9.5mol·kg-1)的水活度和渗透系数.该体系的等水活度线与Zdanovskii规则非理想混合溶液表达式的标准偏差为0.0088,当Li2SO4溶液达到饱和后,用Zdanovskii规则扩展式计算,标准偏差为0.0027.根据Pitzer离子相互作用模型对实验数据进行了理论分析,用本文和不同来源的文献数据拟合求取了0℃下该体系的Pitzer纯盐参数和混合参数,计算值与实验值相吻合.

Isopiestic studies of thermodynamic properties in LiCl-Li2SO4-H2O system at 273.15K

The osmotic coefficients were determined for LiCl-H_2O,Li_2SO_4-H_2O and LiCl-Li_2SO_4-H_2O at 273.15K by the isopiestic method established for low temperatures using an improved equipment in the molality ranges of 0.5-9.2 mol kg~(-1),0.3-2.5 mol kg~(-1) and in the ionic strength range of 0.5-9.5 mol kg~(-1) respectively.The experimental iso-water activity lines obey the Zdanovskii rule for non-ideal mixtures well with the standard deviation of 0.008.The relations among experienced isopiestic molalities obey the extended Zdanovskii rule with the standard deviation of 0.0027 in the high ionic strength range in which the Li_2SO_4 pure solutions became saturation and were taken away from the isopiestic measurements.The parameters of Pitzer ion-interaction model were evaluated from the measured data in this work and the data in the references by using multiple regression analsis.The standard deviations between the calculated and the experimental osmotic coefficients were reported.These studies reveal that the osmotic coefficients increase with increasing of ionic strengths and with decreasing of temperatures,and those decrease with increasing of ionic concentration fractions of Li_2SO_4,and indicate Pitzer ion-interaction model can describe the thermodynamic properties for the studied systems in the wider molality ranges at low temperature.