中科院长春应化所的Yuyuan Lu课题组和美国加州理工学院Zhen-Gang Wang等合作，通过实验和理论研究准确描绘了水-乙腈-盐混合物的相图。相关论文发表在2021年1月8日出版的《美国化学会志》上。

该研究通过结合实验和理论系统性地考察了水-乙腈-盐混合物的相行为。通过云点和组分分析，研究人员绘制出九种代表性的盐在水-乙腈混合物中的完整三元相图。研究人员还建立了一个热力学自由能模型，其中考虑了液体非理想混合、离子水合、静电相互作用和波恩能等因素。研究表明，理论预测产生的相图与实验数据非常相符。

通过比较静电相互作用、波恩能和水合作用的贡献，研究人员发现，水合作用是促进液-液相分离的主要推动力，也是导致特定离子效应的主要原因。这一理论强调了熵在水合驱动力中的重要性。最后，研究人员还讨论了这些发现在盐析辅助液-液萃取中的意义，并为优化分离效率给出了选择盐离子的建议。

据了解，液体混合物中盐诱导的液-液相分离是一种在自然界和应用场合中常见的现象，例如在化合物的分离和萃取中。

附：英文原文

Title: Salt-Induced Liquid–Liquid Phase Separation: Combined Experimental and Theoretical Investigation of Water–Acetonitrile–Salt Mixtures

Author: Minglun Li, Bilin Zhuang, Yuyuan Lu, Lijia An, Zhen-Gang Wang

Issue&Volume: January 8, 2021

Abstract: 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.

DOI: 10.1021/jacs.0c09420

Source: https://pubs.acs.org/doi/10.1021/jacs.0c09420