KCl-PEG4000-H2O三元体系288、298、308 K相平衡测定及计算

采用等温溶解平衡法研究了288、298、308 K下三元体系KCl-PEG4000-H₂O的相平衡关系，绘制了相应的相图、密度-组成图和折射率-组成图。研究发现：288、298、308 K下，三元体系KCl-PEG4000-H₂O无分层现象，只存在固液相平衡关系，其平衡相图由不饱和液相区(L)、一固一液区(S+L)和两固一液区(2S+L)构成，且两固一液区随温度升高减小。KCl溶解度随着溶液中PEG4000含量不断增加而减小。溶液中PEG4000含量小于0.50时，盐析率受温度影响较小；含量大于0.50时，盐析率随着温度升高呈减小趋势。采用修正后的Pitzer方程进行了三元体系KCl-PEG4000-H₂O (288、298、308 K)溶解度计算，对比发现，理论计算值与实验值吻合较好。

Measurements and simulation for ternary system KCl-PEG4000-H2O at 288, 298 and 308 K

The phase equilibrium relationship of the ternary system KCl-PEG4000-H₂O at 288, 298 and 308 K was studied by isothermal dissolution equilibrium method. The corresponding phase diagram, density-composition diagram and refractive index-composition diagram were drawn. The results show that over the entire PEG 4000 composition rang studied only one liquid phase is obtained, without the biphase region formed at 288, 298 and 308 K. The phase diagram of system KCl-PEG4000-H₂O consists of one homogeneous area with unsaturated liquid (L), an equilibrium area containing the solid phase of KCl and saturated liquid phase (S+L), one area with one liquid phase and two solid phases(2S+L). The area of (2S+L) decrease with the increasing of temperature, while the areas of (L) and (S+L) increase with the increasing of temperature. The solubility of KCl decreases with the addition of PEG 4000 at 288, 298 and 308 K. When w_PEG4000 in the solution is less than 0.50, the temperature has little effect on the salting-out ratio of the system, while when w_PEG4000 is higher than 0.50, the salting-out ratio of the system decreases with the increasing of temperature. The thermodynamics calculation of equilibrium data of system KCl-PEG4000-H₂O at 288, 298 and 308 K was carried out by using the modified Pitzer equation, it can be seen from the comparison of experimental and calculation diagrams that the predictive solubilities agree well with the experimental values.