Application of thermo acoustic parameters for the evaluation of the available volume of ionic liquid,1-Butyl-3-methylimidazolium chloride in mixed solvents at different temperatures

Abstract

The available volume of 1-Butyl-3-methyl imidazolium chloride, [bmim][Cl] in pure water and aqueous solutions of potassium citrate and sodium citrate at different concentrations of solute and T = (298.15 to 318.15) K have been evaluated by making use of ultrasonic velocity and thermo acoustic parameters followed by a comparative study. The thermo acoustic parameters have been used to determine available volume, V_a for the solutions under analysis. For well understanding, the values of  found from the thermo acoustic methods was tallied with the values found from the well-defined ultrasonic method (Schaaffs method). The decrease of the available volume with an increase of the mass fraction of ionic liquid and temperature shows the existence of ion-solvent interactions of IL in the studied solutions. To the best of our knowledge, this study is a pioneering effort in the evaluation of available volume present in the investigated solutions by making use of the ultrasonic approach.

Ionic liquids are regarded as alternative green solvents [1]. They can replace volatile organic solvents in several chemical reactions [2]. The room temperature ionic liquid, 1-Butyl-3-methylimidazolium chloride ([bmim][Cl]) can be extensively used as a solvent for many organic reactions such as ion exchange reactions and chromatographic separations. It has many applications in fuel industries as an energy-efficient green material for the extractive deep desulphurization of liquid fuels [3]. Among the organic salts, citrate salts are of significant applications in chemical and biochemical processes, so produced in large quantities. It has been found that both potassium and sodium citrates are importantly used in pharmaceuticals. The citrate ion acts as an anti-coagulant as it binds the calcium ions in the blood through the formation of calcium citrate complexes. The formation of kidney stones (derived from either cysteine or uric acid) can be controlled by the use of tri-potassium citrate. Both these salts are also used in food, beverages, cosmetic, pharmaceutical industries and find use in technical applications such as buffering and emulsifying agents. In this work, the available volume of ternary aqueous solutions of tri-potassium/tri-sodium citrate with [bmim][Cl] were executed at T=( 298.15, 303.15, 308.15, 313.15, and 318.15)K and atmospheric pressure. The effect of concentrations of IL [bmim][Cl] and temperature on the solution properties of citrate salts has been studied.

The increase in density and ultrasonic velocity (Figure 1) with an increase of temperature and concentration of [bmim]Cl in water indicated the existence of intermolecular interactions which is increases with temperatures [4-6].It has been found from the Figure 2, that the available volume decreases with increase in concentration of [bmim]Cl in the solutions. This indicates the ion-solvent interaction increases with increase of solute concentration.