Thermodynamic study of the ternary mixed electrolyte ([EMIm]Br + LiBr + H2O) system using potentiometric measurements

• Thermodynamic properties of (([EMIm]Br + LiBr + H2O) system were studied.
• The activity coefficients of (([EMIm]Br were determined with self-made electrodes.
• The Pitzer model was applied to describe the behavior of the electrolyte studied.
• The values of thermodynamic properties were calculated using Pitzer model.
• The temperature dependence of Gibbs free energy was used to calculate the enthalpy.

Thermodynamic study of the aqueous mixed electrolyte system containing 1-ethyl-3-methyl imidazolium bromide ([EMIm]) and lithium bromide (LiBr) was performed on the galvanic cell of the type:[EMIm] -ISE | [EMIm] Br (m1), LiBr (m2), H2O | Br-ISE over total ionic strengths from 0.01 to 2.25 mol kg−1. Various series of the salt molal ratios (r = m[EMIm]Br/mLiBr = 0.1, 0.2, 1.0, 5.0) and [EMIm]Br single electrolyte solution were used at T= (298.2, 303.2, 308.2 and 313.2) K and P = 0.1 MPa. The Pitzer ion-interaction model was employed to determine the activity coefficients for the studied system. The Pitzer mixing interaction parameters were evaluated for the mixed electrolyte system. The obtained parameters were used to calculate the mean activity coefficients of the solute species, the osmotic coefficients and excess Gibbs free energies for the whole series of the mixed electrolyte systems. Furthermore, the temperature dependence of the excess Gibbs free energy was also applied to calculate the excess enthalpy for the electrolyte system.