Thermodynamic investigation of the ternary ([BMIm]Br + LiBr + H2O) system using potentiometric measurements

During recent years, ionic liquids (ILs) due to their unique physical and chemical properties have attracted great interest [1-2]. ILs have been widely used in various fields of application. The presence of ionic liquids in a process needs a deeper knowledge about the thermodynamic behavior of the mixture. In this work, thermodynamic study of the aqueous electrolyte system containing 1-buthyle-3- methyl imidazolium bromide ([BMIm]Br) and lithium bromide (LiBr) was carried out on the galvanic cell of the type: [ BMIm] -ISE│ [BMIm] Br (m1), LiBr (m2), H2O │Br-ISE on total ionic strengths from 0.01 to 2.80 mol.kg-1. Various series of the salt molal ratios (r= mLiBr / m[BMIm]Br = 10, 7.5, 5) were used at T= 298.2 K and P = 0.1 MPa. The experimental mean activity coefficients of [BMIm]Br in the aqueous solution were determined using the emf measurements in according to Nernst equation. The plot of mean activity coefficients of [BMIm]Br at various total ionic strengths for various series of salt molal ratios at T= 298.2K were shown in Figure1. The Pitzer ioninteraction model was used to analyze 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 system.