Density, speed of sound, and surface tension of binary aqueous solutions containing ammonium based protic ionic liquids

Abstract

Density, ρ, speed of sound, u, and surface tension γ, of binary mixtures containing ethanolammonium based protic ionic liquids (PILs) and water were measured to access the influence of PIL-water interactions on physicochemical properties. Volumetric properties of PILs were evaluated at ambient pressure but at temperatures from 298.15 K to 313.15 K. Apparent molar volume and apparent molar isentropic compressibility values of ethanolammonium acetate [EAAc], ethanolammonium butanoate [EABu], and ethanolammonium hexanoate [EAHx], were calculated and commuted to determine the infinite dilution partial molar volume using Redlich-Mayer type of equation. Further, excess molar volume was also determined as a function of mole fraction. The coefficients of Redlich-Kister equation also determined and presented. Overall, the hydrophilic interactions occur between PILs and water molecules and the strength of interactions weakens as anionic chain length increases. Low surface tension values were observed for PILs with longest alkyl chain. The results indicate that hydrophobicity of alkyl chain strongly influences the interfacial properties.