醋酸离子液体[C2mim][OAc]水溶液的摩尔表面Gibbs自由能

在288.15-318.15 K温度范围内测定了不同浓度离子液体1-乙基-3-甲基咪唑醋酸盐(C₂mim]OAc])水溶液的表面张力和密度;在改进李以圭等人的溶液表面张力模型基础上,提出摩尔表面Gibbs自由能新概念,建立了摩尔表面Gibbs自由能随溶液浓度变化的线性经验方程,利用这个经验方程估算了C₂mim]OAc]水溶液的摩尔表面Gibbs自由能,并进一步预测了该溶液的表面张力,其预测值与相应的表面张力实验值高度相关并非常相似。由此可见,摩尔表面Gibbs自由能与等张比容极其类似,可能成为预测离子液体及其溶液性质的一种新的半经验方法。在指定溶液浓度下,根据溶液的摩尔表面Gibbs自由能随温度呈线性变化的规律,得到了新的Eötvös方程,与传统的Eötvös方程相比,新Eötvös方程的每一个参数都有明确的物理意义:斜率的负值是摩尔表面熵,截距是摩尔表面焓,在指定浓度的溶液中摩尔表面焓几乎不随温度变化。

Molar Surface Gibbs Free Energy of the Aqueous Solution of the Ionic Liquid [C2mim][OAc]

The values of the density and surface tension for an aqueous solution of the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate C₂mim]OAc] with various molalities were measured from 288.15 to 318.15 K with intervals of 5 K. Based on the thermodynamic model of the surface tension of a solution proposed by LI Yi-Gui et al., a new concept of the molar surface Gibbs free energy was proposed and a linear empirical equation between the molar surface Gibbs free energy and the concentration of the solution was established. Using this empirical equation, the molar surface Gibbs free energy of aqueous C₂mim]OAc] was estimated. Using the estimated molar surface Gibbs free energy, the surface tension of the solution was predicted. The predicted values and corresponding experimental values are in agreement. Thus, the molar surface Gibbs free energy may become a semi-empirical method to predict the properties of ILs and their solution parachor. From the molar Gibbs free energy, a new Eötvös equation was obtained and each parameter of the new equation has a clear physical meaning.