Thermodynamics and phase diagram of the salt lake brine system at 298.15 K: V. Model for the system Li+, Na+, K+, Mg2+/Cl−, SO42−–H2O and its applications

As one of a series of papers related to thermodynamics and phase equilibrium for the “Salt Lake Brine System”, the present paper deals with the system Li+, Na+, K+, Mg2+/Cl−, SO42−–H2O. In order to describe thermodynamics and phase equilibrium of the title system, the Pitzer ion interaction model of aqueous electrolyte was applied. In addition to Pitzer parameters for single electrolytes for the entire range of concentration up to the saturation, the mixing parameters for pairwise ions including ion Li+, such as (Li+,Na+), (Li+,K+), (Li+,Mg2+), and for triple ions (Li+,Na+,Cl−), (Li+,Na+,SO42−),… and (Cl−,SO42−,Li+) etc are also needed. We managed to obtain reasonable Pitzer parameters for single electrolytes and the osmotic coefficient of LiCl–NaCl–H2O solutions were determined in our lab. All our data together with those published were fitted to acquire the needed parameters. The model has been extended to the system including ion Ca2+in our recent work. rameterized model of Pitzer has been applied in many aspects in our work. The calculation of thermodynamic properties of brines, prediction of solubilities for the title system and its subsystems with Li-salts, and predicting the sequences of salt precipitation during the evaporation of brines at 298.15 K etc are presented in the paper.