Mutual Solubilities of Water and the [Cnmim][Tf2N] Hydrophobic Ionic Liquids

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• 作者：Mara G. Freire ; Pedro J. Carvalho ; Ramesh L. Gardas ; Isabel M. Marrucho ; Lu&iacute ; s M. N. B. F. Santos ; Jo&atilde ; o A. P. Coutinho
• 刊名：Journal of Physical Chemistry B
• 出版年：2008
• 出版时间：February 14, 2008
• 年：2008
• 卷：112
• 期：6
• 页码：1604 - 1610
• 全文大小：77K
• 年卷期：v.112,no.6(February 14, 2008)
• ISSN：1520-5207

文摘

Ionic liquids (ILs) have recently garnered increased attention because of their potential environmental benefitsas "green" replacements over conventional volatile organic solvents. While ILs cannot significantly volatilizeand contribute to air pollution, even the most hydrophobic ones present some miscibility with water posingenvironmental risks to the aquatic ecosystems. Thus, the knowledge of ILs toxicity and their water solubilitymust be assessed before an accurate judgment of their environmental benefits and prior to their industrialapplications. 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 compoundsis surprisingly large, ranging from 0.17 to 0.36 in mole fraction, while the solubility of these ILs in water ismuch lower ranging from 3.2 × 10^-5 to 1.1 × 10^-3 in mole fraction, in the temperature and pressure conditionsstudied. From the experimental data, the molar thermodynamic functions of solution and solvation such asGibbs energy, enthalpy, and entropy at infinite dilution were estimated, showing that the solubility of theseILs in water is entropically driven. The predictive capability of COSMO-RS, a model based on unimolecularquantum chemistry calculations, was evaluated for the description of the binary systems investigated providingan acceptable agreement between the model predictions and the experimental data both with the temperaturedependence and with the ILs structural variations.