Study On The Thermodynamic Properties Of Lithium Chloride In Amide / Polyhydric Alcohol - Water Mixture By Electromotive Force Method

The liquid extraction plays an important role as a separation process in chemical engineering, desalination and atmospheric processes. The design and operation of industrial processes that including electrolyte solutions require the knowledge of thermodynamic properties such as activity and osmotic coefficients, excess Gibbs free energies to reflect the non-ideality of the mixtures. Thus, the research of thermodynamic properties of electrolyte within the multivariate mixed solvents system has important theoretical and application value. Our research group has devoted to the experiments of alkaline metal salts, especially for the Rb and Cs salts and organic solvent- water mixtures so as to separate and purify these salts. As an extension of our continuous work, lithium chloride and amides/polyhydric alcohols- water mixtures were selected in this article.In this article, the ion-selective electrode Li-ISE and the Ag-AgCl electrode worked as the anode and cathode, respectively. The galvanic cells without liquid junction are as follows: Li-ISE| LiCl(m), H2O| Ag-AgCl; Li-ISE| LiCl(m), PG/EG/GL(w), H2O (1-w)| Ag-AgCl; Li-ISE| LiCl(m), DMA/DMF/NMF/Urea (w), H2O (1-w)| Ag-AgCl; The abbreviation of organic solvent stated as following: DMA ---, N-dimethylacetamide PG ---,2-propylene glycol DMF ---, N-dimethylformamide EG ---thylene glycol NMF ----methylformamide GL ---lycerol Urea ---reaWhere, m is the molality of LiCl in the determined solution, w (w= 0.00,0.10,0.20, 0.30,0.40) is the mass fraction of organic solvent in the mixtures.In this article, a study of thermodynamic properties of LiCl in PG/EG/GL+ H2O and DMF/DMA/NMF/Urea+ H2O systems is reported by electromotive method at T= 298.15 K. The Pitzer model, the modified Pitzer model and the extended Debye-Hiickel equation are used to describe the non-ideal behaviors of electrolyte solution. The mean activity coefficient γ±, the osmotic coefficient 0, the standard free energy of transference △Gt0 and the standard solubility product InK0sp, m for LiCl in mixtures are caculated and discussed for the whole series of the studied systems. In addition, the primary LiCl hydration number in organic solvent -water systems is also predicted. The experiment shows that the fitting result of models is ideal.