四元体系KCl-K_(2)SO_(4)-KBO_(2)-H_(2)O在298.15 K的Pitzer模型研究

Pitzer Thermodynamic Modeling of Boron Species in the QuaternarySystem KCl-K_(2)SO_(4)-KBO_(2)-H_(2)O at 298.15 K

在Pitzer电解质溶液理论的基础上采用两种模型计算了KCl-K_(2)SO_(4)-KBO_(2)-H_(2)O体系及其子体系的溶解度。模型I假设溶液中只有一种硼物种B(OH)4-,模型II假设溶液中有4种硼物种,分别对应于B(OH)_(3)、B(OH)_(4)^(-)、B_(3)O_(3)(OH)_(4)^(-)和B_(4)O_(5)(OH)_(4)^(2-)。模型I与模型II的溶解度计算结果接近,且与实验值吻合较好。采用模型II计算了上述体系溶液中的硼物种和OH-的浓度。各硼物种的浓度主要受溶液中总硼浓度的影响,而很少受KCl和K_(2)SO_(4)的影响。计算结果说明在计算偏硼酸钾溶液体系溶解度时,可近似认为溶液中硼物种只有B(OH)_(4)^(-)。模型II可用于计算含偏硼酸钾体系的pH值。本文的计算结果可为复杂偏硼酸钾体系模型的构建提供理论基础。

The solubilities in the quaternary system KCl-K_(2)SO_(4)-KBO_(2)-H_(2)O and its subsystems were calculated with two models on the basis of the Pitzer electrolyte solution theory.The first model(model I)assumes that there is only one boron ions B(OH)_(4)^(-)in the solution.The second model(model II)assumes that there are four boron species corresponding to B(OH)_(3),B(OH)_(4)^(-),B_(3)O_(3)(OH)_(4)^(-)and B_(4)O_(5)(OH)_(4)^(2-)in the solution.The calculated solubility data with model I and II,which are nearly the same,agreed with the experimental data.The concentrations of boron species and OH-in the above systems were also calculated with model II.The concentrations of different boron species were mainly affected by the total boron concentration in the solution,but rarely affected by the concentration of KCl and K_(2)SO_(4).The calculated results show that the assumption of only one boron species B(OH)_(4)^(-)in the solution can be used for the solubility calculation.The model II can be used to describe the pH values in the systems containing potassium metaborate.The calculated results in this study can supply theoretical basis for the development of universal thermodynamic models for complicated brine systems containing potassium metaborate.