Determination of NaCl and Na2SO4 Equilibrium Solubility in Cyclohexanol and Cyclohexanone Aqueous Solutions at 323.15 K

The equilibrium solubility and physical properties (nD, η, and ρ) of NaCl and Na2SO4 in cyclohexanol and cyclohexanone aqueous solutions at 323.15 K were determined by an isothermal solution saturation method. According to the experimental data, the phase diagrams and diagrams of physical properties vs composition were plotted. The system of NaCl and Na2SO4 in cyclohexanol aqueous solution at 323.15 K can be divided into one invariant point, two univariant curves, and three crystallization regions. The physical properties of this system changed regularly with the change of the solubility of Na2SO4. The solubility of Na2SO4 and NaCl significantly reduced due to the presence of cyclohexanol in water. With the increase of the cyclohexanol content in aqueous solution in the system, the crystallization region of Na2SO4 increased obviously. The system of NaCl and Na2SO4 in cyclohexanone aqueous solution consisted of one invariant point, two univariant curves, and two crystallization regions corresponding to NaCl and Na2SO4. When Na2SO4 and NaCl were analyzed as 5.22 and 23.91 wt %, respectively, the solution reached saturation at 323.15 K. The presence of cyclohexanone in water has little effect on the solubility of Na2SO4 and NaCl. The equilibrium solids were verified by X-ray diffraction. It can be seen from the experimental results that the influence of the presence of organic impurity in water on the solubility of Na2SO4 and NaCl cannot be generalized. The measured data, especially the crystalline regions, could provide the fundamental basis, which would be of great value in designing and optimizing the crystallization process of NaCl and Na2SO4 in coal chemical high-salinity wastewater.