Effect of 1-butyl-4-methylpyridinium and 1-butyl-3-methylimidazolium halide ionic liquids on the interactions of lactic acid in the aqueous solutions of polyethylene glycol

In this study, effect of some ionic liquids on the thermodynamic and transport properties of L(+)-lactic acid in aqueous polyethylene glycol solutions have been investigated. Density, speed of sound, and viscosity of L(+)-lactic acid in the aqueous solutions of polyethylene glycol, polyethylene glycol +1-butyl-3-methylimidazolium bromide, polyethylene glycol +1-butyl-3-methylimidazolium chloride, polyethylene glycol +1-butyl-4-methylpyridinium bromide, and polyethylene glycol +1-butyl-4-methylpyridinium chloride were measured at T/K = (288.15, 298.15, 308.15 and 318.15). Infinite dilution apparent molar volumes, transfer apparent molar volume, infinite dilution apparent molar isentropic compressibility and viscosity B-coefficient of L(+)-lactic acid were calculated using experimental data and were discussed in terms of solute-solute and solute-solvent interactions. The results reveal that solute-solvent interactions were decreased with increasing temperature, size of halide anion. Also solute-solvent interactions in the presence pyridinium ionic liquids are stronger than those of imidazolium ionic liquids. The obtained results from spectroscopic reveal that λmax of imidazolium based ionic liquids were red shifted in the presence of lactic acid and this behaviour confirmed existence hydrogen bound between lactic acid and imidazolium based ionic liquids.