Study on the Effect of Complex Organics on the Phase Equilibrium of the Multicomponent Salt Systems in the High Saline Wastewater of Coal Chemical Industry

Abstract

In the coal chemical industry, the solubility and physical parameters of inorganic salts in saline wastewater need to be studied to solve the pipeline scaling problem in the resource utilization process of saline wastewater. In this paper, the effects of organic substances (phenol, alcohols, oils) on the solubility, density, pH, and equilibrium solid phase of Na⁺, Mg²⁺//Cl^––H₂O were investigated by isothermal dissolution equilibrium method at 303.15–333.15 K. Results showed that the phase diagram of this ternary system consisted of one cosaturation point, two solubility curves, and three crystallization zones. Heating had no obvious effect on the overall solubility of the Na⁺, Mg²⁺//Cl^––H₂O ternary system under the interfering substances. Meanwhile, a larger MgCl₂ crystallization zone was observed at the higher temperature indicating the change in solubility of MgCl₂ is greater than that of NaCl. The density and pH of the system all increased with the warming. The density of the ternary system increased with the solubility of MgCl₂ increasing and reached its maximum at the cosaturation point X. pH of the ternary system decreased with the increase of MgCl₂ solubility and reached the minimum at the cosaturation point G of the binary system of MgCl₂ + H₂O.