273.15K下LiCl-Li_2B_4O_7-H_2O体系热力学性质的等压研究

Isopiestic Studies on Thermodynamic Properties for LiCl-Li_2B_4O_7-H_2O System at 273.15K

用等压法研究了273 15K下LiCl-Li2B4O7-H2O体系中纯盐水溶液(离子强度范围为LiCl0 2046～2 5055mol·kg-1,Li2B4O70 1295～0 3700mol·kg-1)以及混合盐水溶液(离子强度范围为0 0931～2 4911mol·kg-1)渗透系数和水活度;计算了LiCl-Li2B4O7-H2O体系的饱和蒸汽压,获得饱和蒸汽压、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LiCl和Li2B4O7纯盐参数及体系的混合盐参数,拟合的标准偏差分别为0 0077和0 026。用该模型计算的渗透系数值与实验结果取得合理的一致。同时研究结果与273 15K下LiCl-Li2SO4-H2O体系的渗透系数随离子强度变化的规律作了比较。本研究对完善低温下含锂、硼盐湖卤水体系的热力学模型和盐湖资源的综合开发利用具有重要意义。

The water activities and the osmotic coefficients have been measured for the LiCl-H_2O,Li_2B_4O_7-H_2O and LiCl-Li_2B_4O_7-H_2O systems at 273.15K by isopiestic method in the ion strength ranges of 0.2046～2.5055 mol·kg^(-1),0.1295～0.3700 mol·kg^(-1) and 0.0931～2.4911 mol·kg^(-1) respectively.The saturated vapor pressures have been calculated for the LiCl-Li_2B_4O_7-H_2O system.These studies reveal the change rules in the saturated vapor pressures and the osmotic coefficients with increasing of ion strengths.Pitzer's single electrolyte parameters for the LiCl-H_2O,Li_2B_4O_7-H_2O system and Pitzer's mixing electrolyte parameters are evaluated from resent measurements by using multiple regression method,with the standard deviations of 0.0077 and 0.026 respectively.The osmotic coefficients values determined experimentally and these calculated by using the model with the parameters are in reasonable agreement.The change rules of the osmotic coefficients with increasing of concentrations for the LiCl-Li_2B_4O_7-H_2O system were compared with these for the LiCl-Li_2SO_4-H_2O system.These studies are useful to improve the thermodynamic model for salt lake brine systems containing Lithium and Borates at low temperatures.