Apparent molar volumes, apparent isentropic compressibilities, and viscosity B-coefficients of 1-ethyl-3-methylimidazolium bromide in aqueous di-potassium hydrogen phosphate and potassium di-hydrogen phosphate solutions at T = (298.15, 303.15, 308.15, 313

Apparent molar volumes Vϕ, apparent isentropic compressibilities κϕ, and viscosity B-coefficients for 1-ethyl-3-methylimidazolium bromide (EmimBr) in aqueous di-potassium hydrogen phosphate (K2HPO4) solutions with salt weight fractions (ws = 0.00, 0.10, 0.15, and 0.20) and potassium di-hydrogen phosphate (KH2PO4) solutions with salt weight fractions (ws = 0.00, 0.04, 0.07, and 0.10) have been determined from solution density, sound velocity and viscosity measurements at temperatures over the range (298.15 to 318.15) K as function of concentration of 1-ethyl-3-methylimidazolium bromide (EmimBr). In the investigated temperature range, the relation: Vϕ0=a0+a1T+a2T2, has been used to describe the temperature dependence of the standard partial molar volumes Vϕ0. These results have, in conjunction with the results obtained in pure water, been used to deduce the standard volumes of transfer ΔVϕ0 and viscosity B-coefficients of transfer for 1-ethyl-3-methylimidazolium bromide from water to aqueous K2HPO4 and KH2PO4 solutions for rationalizing various interactions in the ternary solutions. The structure making or breaking ability of 1-ethyl-3-methylimidazolium bromide has been discussed in terms of the sign of ∂2Vϕ0∂T2. An increase in the transfer volume of 1-ethyl-3-methylimidazolium bromide with increasing phosphate salts concentration has been explained by Friedman–Krishnan co-sphere model. The activation parameters of viscous flow for the ternary solutions investigated were also determined and discussed by the application of transition state theory.

► Vϕ, κϕ and B-coefficients were obtained for aqueous EmimBr + K2HPO4/KH2PO4 solutions.
► Vϕ0 of ionic liquid EmimBr increase with the increase of temperature.
► Positive ΔtVϕ0 of EmimBr from water to the aqueous K2HPO4/KH2PO4 solutions is obtained.
► (∂2Vϕ0/∂T2)P and dB/dT values of IL in water show that EmimBr acts as a structure makers.