298·15K下Li_2SO_4-Li_2B_4O_7-H_2O体系热力学性质的等压研究

Isopiestic Studies on the Thermodynamic Properties for Li_2B_4O_7-Li_2SO_4-H_2O System at 298.15 K

用等压法研究了Li2SO4-Li2B4O7-H2O体系的Li2SO4和Li2B4O7纯盐水溶液(离子强度范围分别为0.3577～5.6378 mol·kg-1及0.1747～2.4497mol·kg-1)及混合盐水溶液(离子强度范围为0.3118～5.5248mol·kg-1)的渗透系数,并获得了该体系渗透系数随离子强度的变化规律.用实验数据以最小二乘法求取了Li2SO4和Li2B4O7的纯盐参数及混合盐参数,拟合的标准偏差分别为0.0072和0.0188.用Pitzer模型计算的渗透系数与实验值结果取得一致,表明该模型能够较好的描述25℃下Li2SO4-Li2B4O7-H2O体系的热力学性质.实验对完善含锂、硼盐湖卤水体系的热力学模型和盐湖资源的综合开发具有重要意义.

The osmotic coefficients have been detennined for Li2B4O7 - Li2SO4 - H2O and Li2SO4 - Li2B4O7 - H2O system at 298.15K by the isopiestie method in the molality ranges of 0.3577 - 5.6378 mol·kg^-1,0.1747-2.4497 mol·kg^- 1 and in the ionic strength range of 0.3118 -5.5248 mol·kg^- 1 respectively. The studies reveal that the osmotic coefficients increase with the increasing of ion strength. Pitzer＇s single electrolyte parameters for Li2SO4 - H2 O, Li2B4 07 - H2O system and Pitzer＇ s mixing electrolyte parameters are evaluated from resent measurements by using multiple regression, with the relative standard deviations of O. 0072 and 0.0188 respectively. The osmotic coefficients values detennined experimentally and those calculated by using the model with the parameters are in reasonable agreement. It is shown that the Pitzer model can describe the system＇s thermodynamics qualities well at 298.15K.These studies are useful to extend the applications of the thermodynamic model for salt lake brine systems containing Lithium and borates.