Thermodynamic modeling and phase diagram prediction of salt lake brine systems II. Aqueous Li+-Na+-K+-SO42− and its subsystems

Abstract

Predicted result of complete structure phase diagram of Li 2 SO 4 -Na 2 SO 4 -H 2 O system at temperature ranging from eutectic point 251.19–373.15 K: P1, P2, P3, P4, P5 are Transition points of three solid co-saturated in the ternary system. • Thermodynamic model of aqueous Li+-Na+-K+-SO 4 2− systems across entire temperature range. • Predicting the polythermal full structure phase diagram of ternary and quaternary aqueous system.. • The multi-objective optimization method to obtain solid constants and liquid parameters. It is still a challenging task to accurately and temperature-continuously express the thermodynamic properties and phase equilibrium behaviors of the salt-lake brine with multi-component, multi-temperature and high concentration. The essential subsystem of sulfate type brine, aqueous Li + -Na + -K + -SO 4 2− and its subsystems across a temperature range from 250 K to 643 K are investigated with the improved comprehensive thermodynamic model. Liquid parameters ( Δ g IJ , Δ h IJ , and Δ C p , I J ) associated with the contributions of Gibbs energy, enthalpy, and heat capacity to the binary interaction parameters, i . e . the temperature coefficients of eNRTL parameters formulated with a Gibbs Helmholtz expression, are determined via multi-objective optimization method. The solid constants Δ f G k ° ( 298.15 ) and Δ f H k ° ( 298.15 ) of 11 solid species occurred in the quaternary system are rebuilt from multi-temperature solubilities. The modeling results show the accurate representation of (1) solution properties and binary phase diagram at temperature ranges from eutectic points to 643 K; (2) isothermal phase diagrams for Li 2 SO 4 -Na 2 SO 4 -H 2 O, Li 2 SO 4 -K 2 SO 4 -H 2 O and Na 2 SO 4 -K 2 SO 4 -H 2 O ternary systems. The predicted results of complete structure and polythermal phase diagram of ternary systems and the isothermal phase diagrams of quaternary system excellently match with the experimental data.