Solubility determination of lithium carbonate in sodium chloride solution

The solubility and solution density of Li2CO3 in NaCl solution at the molalities of (0~4.06) mol•kg-1 were determined by an isothermal dissolution equilibrium method at 278.15~358.15 K. The experimental data of lithium carbonate solubility was correlated by E-DH and Apelblat equations, with relative deviation of ±0.05. The Connaughton equation was used to correlate the solution density data with a standard deviation of less than 7×10-4. The experimental and theoretical calculations show that the solubility of Li2CO3 in NaCl-H2O system increases first and then decreases with the increase of NaCl concentration. In the temperature range of 278.15~358.15 K, the maximum solubility of Li2CO3 is obtained at NaCl concentration of ~ 0.1 mol∙kg-1. The dissolution enthalpy ΔHd, entropy ΔSd and Gibbs free energy ΔGd of Li2CO3 in aqueous NaCl solution were obtained by dissolution thermodynamic calculation. The results show that the dissolution process is a non-spontaneous process of exotherm and entropy reduction. The dissolution enthalpy and entropy increase with the increase of sodium carbonate concentration. Gibbs free energy shows minimum at 1 mol∙kg-1, and the dissolution process is an entropy controlled process. The research results provide basic data for the design of lithium carbide precipitation process for brine. © 2020, Editorial Board of "Journal of Chemical Engineering of Chinese Universities". All right reserved.