Freire Mara G, Carvalho Pedro J, Gardas Ramesh L, Marrucho Isabel M, Santos Luís M N B F, Coutinho João A P
CICECO, Departamento de Química, Universidade de Aveiro, Aveiro, Portugal.
J Phys Chem B. 2008 Feb 14;112(6):1604-10. doi: 10.1021/jp7097203. Epub 2008 Jan 18.
Ionic liquids (ILs) have recently garnered increased attention because of their potential environmental benefits as "green" replacements over conventional volatile organic solvents. While ILs cannot significantly volatilize and contribute to air pollution, even the most hydrophobic ones present some miscibility with water posing environmental risks to the aquatic ecosystems. Thus, the knowledge of ILs toxicity and their water solubility must be assessed before an accurate judgment of their environmental benefits and prior to their industrial applications. In this work, the mutual solubilities for [C2-C8mim][Tf2N] (n-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) and water between 288.15 and 318.15 K at atmospheric pressure were measured. Although these are among the most hydrophobic ionic liquids known, the solubility of water in these compounds is surprisingly large, ranging from 0.17 to 0.36 in mole fraction, while the solubility of these ILs in water is much lower ranging from 3.2 x 10(-5) to 1.1 x 10(-3) in mole fraction, in the temperature and pressure conditions studied. From the experimental data, the molar thermodynamic functions of solution and solvation such as Gibbs energy, enthalpy, and entropy at infinite dilution were estimated, showing that the solubility of these ILs in water is entropically driven. The predictive capability of COSMO-RS, a model based on unimolecular quantum chemistry calculations, was evaluated for the description of the binary systems investigated providing an acceptable agreement between the model predictions and the experimental data both with the temperature dependence and with the ILs structural variations.
离子液体（ILs）近来受到越来越多的关注，因为它们作为传统挥发性有机溶剂的“绿色”替代品具有潜在的环境效益。虽然离子液体不会显著挥发并造成空气污染，但即使是疏水性最强的离子液体也与水有一定的混溶性，这对水生生态系统构成环境风险。因此，在准确判断其环境效益以及进行工业应用之前，必须评估离子液体的毒性及其水溶性。在这项工作中，测量了[C2 - C8mim][Tf2N]（正烷基 - 3 - 甲基咪唑双（三氟甲基磺酰）亚胺）与水在288.15至318.15 K、常压下的互溶性。尽管这些是已知的疏水性最强的离子液体，但水在这些化合物中的溶解度惊人地大，摩尔分数范围为0.17至0.36，而在研究的温度和压力条件下，这些离子液体在水中的溶解度要低得多，摩尔分数范围为3.2×10⁻⁵至1.1×10⁻³。根据实验数据，估算了无限稀释时溶液和溶剂化的摩尔热力学函数，如吉布斯自由能、焓和熵，结果表明这些离子液体在水中的溶解度是由熵驱动的。评估了基于单分子量子化学计算的COSMO - RS模型对所研究二元体系的预测能力，该模型预测值与实验数据在温度依赖性和离子液体结构变化方面均达成了可接受的一致性。
