(508e) Thermodynamic Modeling of the Water-Li+-Br--Cl--I--NO3- Quinary System

Lithium salts can be found in a wide array of applications such as lithium bromide (LiBr) found in semiconductors and absorption chillers, lithium chloride (LiCl) used in graphene and carbon nanotube development, lithium iodide (LiI) in high temperature batteries, and LiNO₃ used in thermal energy storage. Developing an accurate thermodynamic model of aqueous lithium salt systems for a broad temperature and concentration range has been a continuing problem with few successes. Because of the lithium ion's unique hygroscopic properties, the ion favors a hydrated form where water molecules can be considered to be permanently bound, and when considered, this complex chemistry can drastically improve thermodynamic modeling techniques for lithium salt solutions. Recent studies in molecular simulation show that high temperature predictions of the semi-empirical Electrolyte Non-Random Two Liquid (eNRTL) activity coefficient model have a more accurate representation of the solution activity than the Pitzer model, which diverges to infinity. By using the eNRTL model, vapor-liquid equilibrium (VLE) and solid-liquid equilibrium (SLE) data is used to obtain binary interaction parameters for each ion-ion and ion-molecule pair. The simplicity of the model allows for accurate predictions of the aqueous quinary lithium salt system up to 500 K and salt saturation.