Determination and Thermodynamic Modeling of the Ternary ([BMIm]Br + LiBr + H2O) System at T=298.2 and 308.2K

During recent years, ionic liquids due to their unique physical and chemical properties have attracted great interest [1-2]. Ionic liquids have been widely used in various fields of application. The presence of ionic liquids in a process needs a deeper knowledge about the thermodynamic behaviour of the mixtures. One method of the study of the thermodynamic properties of these mixtures is the potentiometric method [3]. In this work, thermodynamic study of the aqueous electrolyte system containing 1-buthyle-3-methyl imidazolium bromide ([BMIm]) 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 and 308.2 K and P = 0.1 MPa. The experimental mean activity coefficients of [BMIm]Br in the aqueous solution were determined by using the emf measurements in according to Nernst equation. The Pitzer ion-interaction 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 systems.