Phase equilibria for the pseudo-ternary system (NaCl + Na2SO4 + H2O) of coal gasification wastewater at T = (268.15 to 373.15) K

Abstract The pseudo-ternary system (NaCl + Na 2 SO 4  + H 2 O) of coal gasification wastewater was studied at T  = (268.15 to 373.15) K. The solubility and density of the equilibrium liquid phase were determined by the isothermal solution saturation method. The equilibrium solids were also investigated by the Schreinemaker's method of wet residues and X-ray powder diffraction (XRD). According to the experimental data, the phase diagrams were determined. It was found that there was no significant solubility difference on the NaCl-rich side between the ternary system (NaCl + Na 2 SO 4  + H 2 O) in coal gasification wastewater and in pure water. However, the solubility on the Na 2 SO 4 -rich side of coal gasification wastewater was apparently higher than that of pure water. The increase in the solubility of Na 2 SO 4 was most likely caused by the effects of other impurities apart from NaCl and Na 2 SO 4 in coal gasification wastewater. The measured data and phase equilibrium diagrams can provide fundamental basis for salt recovery in coal gasification wastewater.