Li_2B_4O_7-MgCl_2(B)-H_2O体系热力学性质的等压研究及离子相互作用模型  

Isopiestic Studies of Thermodynamic Properties and Representation with Ion-interaction Model for Li_2B_4O_7-MgCl_2(B)-H_2O System at 298.15 K

作　　者：张爱云[1] 姚燕[1] 杨吉民[1] 宋彭生[1] 

机构地区：[1]中国科学院青海盐湖研究所

出　　处：《化学学报》2004年第12期1089-1094,MJ01,共7页Acta Chimica Sinica

基　　金：国家自然科学基金 (Nos.2 9871 0 34 ;2 0 3730 84);中国科学院基础局重点基础资助项目

摘　　要：采用等压法测定了 2 98.15K下Li Mg Cl borate H2 O体系离子强度范围为 0 .0 5 81～ 0 .63 2 0mol·kg-1,MgCl2 不同离子浓度分数的等压摩尔平衡浓度、水活度 ,计算了Li2 B4O7和MgCl2 混合溶液的饱和水蒸汽压、渗透系数等热力学性质 .考虑了在不同的总硼浓度范围的硼酸 (H3 BO3 )和硼氧配阴离子 [B(OH) -4,B3 O3 (OH) -4,B4O5(OH) 2 -4]的不同生成反应平衡 .由实验结果对修正的Pitzer渗透系数方程进行了参数化研究 ,提出了一简化的参数化模型 ,减少了模型的经验参数量 ,获得了锂、镁、氯离子与硼物种组合之间、及不同硼氧配阴离子之间的组合相互作用参数 ,用该模型计算的渗透系数值与实验结果取得合理的一致性 ,从而将离子作用模型扩展到对含硼、锂、镁的复杂体系的表述 .对完善含锂。The isopiestic molalities and the water activities have been measured by isopiestic method and the water vapor pressures and the osmotic coefficients have been calculated from the measurements in the ion-strength range from 0 0581 mol·kg -1 to 0 6320 mol·kg -1 at T=298 15 K for the system Li-Mg-Cl-borate-H 2O. The formation reaction equilibria of boron species of boric acid (H 3BO 3) and borate anions [B(OH) - 4, B 3O 3(OH) - 4 and B 4O 5(OH) 2- 4] have been taken into account for the system in different total boron concentration ranges. A simplified model based on Pitzer's osmotic coefficient equations with minor modifications has been proposed by combining the same kinds of ion-interactions related to the different borate anions, which reduced the number of ion-interaction parameters from 52 in the primary model to 23 in the simplified model. The ion-interaction parameters among the groups of borate anions, Cl -, Li + and Mg 2+ for the simplified model have been estimated using the experimental data taken from this work and references. The osmotic coefficient values determined experimentally and those calculated by using the model with the parameters are in reasonable agreement. Pitzer's ion-interaction model has been extended to represent the thermodynamic properties of the complex system containing various borate anions. These studies are useful to improve the thermodynamic model for salt lake brine systems containing lithium and borates.

关 键 词：Li2B4O7-MgCl2-H2O体系 热力学性质 等压法 渗透系数 离子相互作用模型 盐湖卤水体系 

分 类 号：O642[理学—物理化学]