Isothermal Evaporations of the Brine from Tibet’s Laguocuo Salt Lake at 15 °C: Experiment and UNIQUAC Simulations

Abstract

The original composition of Laguocuo Salt Lake was found in the mirabilite area of the 15 °C isothermal phase diagrams of the Li+, Na+, K+//Cl−, SO42−-H2O system. Four phases comprise the isothermal evaporation procedure. The first stage is the unsaturated stage except for carbonate. The second stage is made up of sodium chloride, mirabilite, and borax precipitate simultaneously, where the halogenation rate is 31.58%, and the water loss rate is 68.32%. The penultimate step is the lithium salt precipitation section, where primarily NaCl, Na2SO4·10H2O, and Li2SO4·3Na2SO4·12H2O are formed, where the water loss rate is 91.38%, the halogenation rate is 7.42%, and the salt precipitation rate is 1.20%. The final stage is the eutectoid stage of lithium and potassium salts, where primarily NaCl, Li2SO4·3Na2SO4·12H2O, and 3K2SO4·Na2SO4 precipitate simultaneously. The rates of water loss, halogenation, and salt precipitation are 93.60%, 5.73%, and 0.67%, respectively. NaCl, Li2SO4·3Na2SO4·12H2O, and 3K2SO4·Na2SO4 were all precipitated through dispersion precipitation of borax with the evaporation process following precipitation. The UNIQUAC model was employed to predict the isothermal evaporation at 15 °C. The theoretical calculation and the experimental were in good agreement. The present work can offer a fundamental theoretical framework for the development and use of Laguocuo Salt Lake resources at 15 °C.