Solution Thermodynamics of some Imidazolium-based Ionic Liquids in Water and Aliphatic Alcohols

Abstract

Abstract The solubilities of imidazolium-based ionic liquids [C4mim][PF6], [C6mim][PF6] and [C6mim][BF4] in water, ethanol, n-propanol, n-butanol, iso-butanol and n-pentanol have been determined from 278.15 K to 323.15 K with 5.0 K intervals by using UV-vis spectroscopy. It is shown that the characteristics of ionic liquids and solvents have significant effect on the solubilities. An increase in the alkyl chain length of the alcohol resulted in a decrease in the solubility. By increasing the alkyl chain length on the cation of the ionic liquids, the solubility increased in the alcohols but decreased in water. The nature of anion was shown to have a great impact on the solubility both in the alcohols and in water. The solution thermodynamic parameters of the ionic liquids and the thermodynamic parameters of transfer for the ionic liquids from water to the alcohols were calculated from the solubility data at different temperatures. The results has been discussed from the differences in the ionic liquid–ionic liquid, ionic liquid–water and ionic liquid–alcohol interactions.