盐效分离作用理论预测

研究了盐效分离基本原理,采用选择性溶剂化模型,利用定标粒子理论计算盐在含水体系中的标准摩尔迁移自由能。提出了将迁移自由能与相平衡中盐效应的大小结合起来,用迁移自由能理论解释相平衡中的盐效应。文中计算了盐在6种含水体系的标准摩尔迁移自由能,并与其盐效应进行了对比,研究发现在含水体系中盐效应随盐的标准摩尔迁移自由能增大而增大,因此在盐效分离过程中可以采用标准摩尔迁移自由能模型选择有效的盐作分离剂。

Theoretical prediction of separation adding salt

The principle of salt effect on separation process was studied. The Gibbs free energy of transfer of salt from water to the corresponding organic solvent at 25℃ was calculated with the solvation model and scaled particle theory. The Gibbs free energy of transfer of salt was calculated for six ternary mixtures including acetonitrileH_2Osalt, secbutyl alcoholH_2Osalt, ethyl acetateH_2Osalt, acetoneH_2Osalt, ethanolH_2Osalt and 1propanolH_2Osalt where saltingout phenomenon occurred,and compared with salt effect on VLE or LLE. In most cases, salt effect on vapour liquid equilibrium(VLE) or liquid liquid equilibrium(LLE) increased with the increase of the Gibbs free energy of transfer of salt in systems containing water. Therefore, salt can be selected by the Gibbs free energy of transfer in separation process adding salt.