Inorganic Chemicals Industry ›› 2024, Vol. 56 ›› Issue (1): 33-39.doi: 10.19964/j.issn.1006-4990.2023-0302

• Research & Development • Previous Articles     Next Articles

Study on solid-liquid phase equilibrium of ternary system of Li+, Na+∥Cl--H2O at different temperatures

WANG Yanfei1,2(), YANG Chaofan1,2, CAO Di1,2, XU Shijie1,2()   

  1. 1. Tianjin Key Laboratory of Brine Chemical Engineering and Ecological Utilization of Resources, Tianjin 300457, China
    2. College of Chemical Engineering and Materials, Tianjin University of Science and Technology, Tianjin 300457, China
  • Received:2023-06-02 Online:2024-01-10 Published:2024-01-18
  • Contact: WANG Yanfei, XU Shijie E-mail:wangyanfei@tust.edu.cn;xushijie@tust.edu.cn

Abstract:

The enrichment of LiCl in brine system is high,and high-purity LiCl is widely used in industry.Because of the similar properties of Na+ and Li+,the removal of NaCl from brine has become the difficulty of producing high-purity LiCl.The solid-liquid equilibrium data of Li+,Na+∥Cl--H2O ternary system is an important basic data for the separation of LiCl and NaCl.The solid-liquid phase equilibrium relationship of ternary system of Li+,Na+∥Cl--H2O at 348.15 K,358.15 K and 363.15 K under atmospheric pressure was investigated by an isothermal dissolution equilibrium method and the equilibrium phase diagram was constructed.The results showed that the phase diagrams at different temperatures were composed of one eutectic invariant point,two single salt crystallization fields(NaCl and LiCl·H2O) and two univariate solubility curves,and it formed neither double salt nor solid solution.With the increase of the temperature,the crystallization region of NaCl was expanded slightly,while the crystal region of LiCl·H2O was changed little.LiCl had a strong salting-out effect on NaCl.The modified BET model was used to correlate the phase equilibrium data,and the correlation value was in good agreement with the experimental value,indicating that the model was more suitable for predicting phase equilibrium relation in this water-salt system at high temperature and high concentration.The density of the saturated solution of the system was measured and the apparent molar volume was calculated from the density value.The results showed that the density was decreased at first and then increased with the increase of LiCl composition,and reached the maximum at the co-saturation point.These results supplemented the thermodynamic data of Li+,Na+∥Cl--H2O system at high temperature and played a basic guiding role in the removal of Na+ and purification of LiCl.

Key words: lithium chloride, sodium chloride, solid-liquid equilibrium, fixed BET model, apparent molar volume

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