KBr-K_(2)SO_(4)-H_(2)O体系在318.15 K下的热力学性质和相平衡预测研究

Thermodynamic Properties and Phase Equilibrium Prediction ofKBr-K_(2)SO_( 4)-H_(2)O System at 318.15 K

本文采用电动势法对318.15 K下三元体系KBr-K_(2)SO_(4)-H_(2)O的热力学性质进行研究。首先,测定了KBr-H_(2)O溶液中KBr的电动势,线性回归出电极响应斜率κ和电极常数E 0,结果表明实验所用离子选择性电极具有良好的能斯特响应。然后,对318.15 K下三元体系KBr-K_(2)SO_(4)-H_(2)O混合溶液中KBr的平均活度系数进行了研究,绘制了离子强度I及离子强度分数y b与KBr的平均活度系数关系图,由图可得,当离子强度I一定,随着离子强度分数y b增大,KBr平均活度系数逐渐减小,且减小的趋势越来越大。当离子强度分数y b是个定值时,KBr平均活度系数随着离子强度I的增大而减小。应用活度系数数据通过多元线性回归拟合出该温度条件下Pitzer模型混合离子作用参数θBr,SO_(4)和ψK,Br,SO_(4),并计算了混合溶液中K_(2)SO_(4)的平均活度系数、渗透系数Φ,水活度a w,超额吉布斯自由能G E。应用拟合的Pitzer混合离子相互作用参数和Pitzer模型计算了该三元体系在318.15 K下的溶解度数据,并对计算结果和其他温度下已经报道的KBr-K_(2)SO_(4)-H_(2)O三元体系的共饱和点处的溶解度数据进行比较,对比结果表明,溶解度计算结果可靠,拟合的离子相互作用参数具有较好的精度,可用于计算相关体系的热力学参数和相平衡的预测。

In this work,the thermodynamic properties of ternary system KBr-K_(2)SO_(4)-H_(2)O at 318.15 K were studied by cell potential method.First,the cell potential values of KBr in KBr-H_(2)O single salt system were measured,the electrode response slope k and the electrode constant E 0 were fitted with linear regression,and the results showed that the selective electrode used in the experiment has good Nernst response.Then,the mean activity coefficients of KBr in ternary system KBr-K_(2)SO_(4)-H_(2)O at 318.15 K was studied,the relationship diagram between ionic strength I,ionic strength fraction y b and the mean activity coefficients of KBr was drawn.According to the diagram,when ionic strength I is constant,the mean activity coefficients of KBr gradually decreases with the increasing of ionic strength fraction y b,and the trend of decreasing becomes larger and larger.When the ionic strength fraction y b is a constant value,the mean activity coefficients of KBr decreases with the increase of ionic strength I.The Pitzer mixed ion interaction parametersθBr,SO_(4)andψK,Br,SO_(4)at this temperature were obtained by using activity coefficient data and multiple linear regression,furthermore,the mean activity coefficients of K_(2)SO_(4),permeability coefficientΦ,water activity a w and excess Gibbs free energy G E in the system were also calculated.And then,the solubility data of the ternary system KBr-K_(2)SO_(4)-H_(2)O at 318.15 K were predicted calculated by using the fitted Pitzer mixed ion interaction parameters fitted in this work and Pitzer model,The calculated results were compared with the solubility data at the invariant point of KBr-K_(2)SO_(4)-H_(2)O ternary system reported at different temperatures.The results show that the calculated results are reliable.The fitted ionic interaction parameters have good accuracy and can be used to calculate the thermodynamic parameters and predict the solubility of related systems.