Investigation of the inter-ionic interactions of an imidazolium-based ionic liquid with the aqueous solutions of tripotassium citrate and trisodium citrate through volumetric, acoustic and FTIR routes

Abstract

Volumetric, acoustic and spectroscopic characteristics of an imidazolium-based ionic liquid, 1-Butyl-3-methylimidazolium chloride ([bmim][Cl]) in water and aqueous solutions of tri-potassium citrate, K3Cit, and tri-sodium citrate, Na3Cit were studied at five different temperatures T = (298.15 K, 303.15 K, 308.15 K, 313.15Kand 318.15 K) and atmospheric pressure (0.1Mpa). The apparent molar volume,Vϕ, and apparent molar compressibility, Kϕ,S were computed from the experimental data of densities and ultrasonic speeds. The derived properties such as standard partial molar volume, Vϕ0 , partial molar compressibilities, Kϕ,S0, limiting apparent molar expansivity, Eϕ0, and their corresponding transfer volumes, ΔtrVϕ0, transfer compressibilities, ΔtrKϕ,S0, of [bmim][Cl] from water to aqueous potassium/sodium citrate solutions were also determined. The transfer properties have been used to discuss the solute-solvent interactions that exist in the solutions. The positive value of Hepler’s constant indicates that the IL has structure-making ability in the studied solutions. In addition, FTIR spectroscopy was executed on the systems. Based on these data, the predominant molecular interactions occurring between [bmim][Cl] and water and in between [bmim][Cl] and K3Cit/Na3Cit were found to be hydrogen bonds.