Salt-Induced Liquid–Liquid Phase Separation: Combined Experimental and Theoretical Investigation of Water–Acetonitrile–Salt Mixtures,Journal of the American Chemical Society

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Salt-Induced Liquid–Liquid Phase Separation: Combined Experimental and Theoretical Investigation of Water–Acetonitrile–Salt Mixtures
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2021-01-08 , DOI: 10.1021/jacs.0c09420
Minglun Li _{1,

2} , Bilin Zhuang _{3,

4} , Yuyuan Lu ₁ , Lijia An ₁ , Zhen-Gang Wang ₅

Affiliation

Salt-induced liquid-liquid phase separation in liquid mixtures is a common phenomenon in nature and in various applications, such as in separation and extraction of chemicals. Here, we present results of a systematic investigation of the phase behaviors in water-acetonitrile-salt mixtures using a combination of experiment and theory. We obtain complete ternary phase diagrams for nine representative salts in water-acetonitrile mixtures by cloud point and component analysis. We construct a thermodynamic free energy model by accounting for the nonideal mixing of the liquids, ion hydration, electrostatic interactions, and Born energy. Our theory yields phase diagrams in good agreement with the experimental data. By comparing the contributions due to the electrostatic interaction, Born energy, and hydration, we find that hydration is the main driving force for the liquid-liquid separation and is a major contributor to the specific ion effects. Our theory highlights the important role of entropy in the hydration driving force. We discuss the implications of our findings in the context of salting-out assisted liquid-liquid extraction and make suggestions for selecting salt ions to optimize the separation performance.

中文翻译：

盐诱导液-液相分离：水-乙腈-盐混合物的联合实验和理论研究

液体混合物中盐诱导的液-液相分离是自然界和各种应用中的常见现象，例如在化学品的分离和提取中。在这里，我们展示了结合实验和理论对水-乙腈-盐混合物中的相行为进行系统研究的结果。我们通过浊点和成分分析获得了水-乙腈混合物中九种代表性盐的完整三元相图。我们通过考虑液体的非理想混合、离子水合作用、静电相互作用和伯恩能来构建热力学自由能模型。我们的理论产生的相图与实验数据非常吻合。通过比较静电相互作用、Born 能和水合作用的贡献，我们发现水合作用是液-液分离的主要驱动力，并且是特定离子效应的主要贡献者。我们的理论强调了熵在水合驱动力中的重要作用。我们在盐析辅助液-液萃取的背景下讨论了我们的发现的意义，并就选择盐离子以优化分离性能提出了建议。

更新日期：2021-01-08

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