Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

Equilibria on Na+ //Cl-, NO3-, SO42--H2O system and Na+// NO3-, SO42- - H2O system at 313.15 K are investigated used isothermal solution saturation method. The composition and physico-chemical properties (refractive index , viscosity , density and pH) of saturated solutions are determined. Phase diagram of Na+// NO3-, SO42- - H2O system includes 2 invariant points, 3 invariant curves, and 3 crystallization fields of single salts, Na2SO4, Na2SO4*NaNO3*H2O, NaNO3. Invariant points are cosaturated with (Na2SO4 + Na2SO4*NaNO3*H2O) salts and (NaNO3 + Na2SO4*NaNO3*H2O) salts, respectively. Na+ //Cl-, NO3-, SO42--H2O system consists of 5 univariant curves, 2 invariant points cosaturated with 3 salts and 4 crystallized regions. Double salt Na2SO4*NaNO3*H2O can be verified to exist in Na+ //Cl-, NO3-, SO42--H2O and Na+// NO3-, SO42- - H2O system at equilibrium conditions at 313.15 K. In addition, comparing with reported phase diagrams in different temperatures, crystallized regions of Na2SO4*NaNO3*H2O decrease with temperature increasing, and disappears at 373.15 K. Crystallized region of sodium sulfate widens while both of crystallized regions of NaNO3 and NaCl decrease with temperature growing. All the physico-chemical properties ( , , , pH) of equilibrium solutions alter with composition change of liquid phase. Phase equilibria of Na+ //C1-, SO42-, NO3- -H2O at 313.15K was also investigated by the through and intermediate translation techniques. All data and results got in our work are important to design and optimize of crystallization of high-saline wastewater in coal chemical industry, and could be used to solve inorganic salt separation from system containing above-mentioned salts.