Solubility of Na2CO3and NaHCO3inAqueous Sodium Sulfate Solutions and Its Application toSeparating Na2CO3and Na2SO4Salt Mixtures.

Toseparate a salt mixture (mainly consisting of Na2CO3and Na2SO4) which is formedfrom the 4,4′-diaminostilbene-2,2′-disulfonic acid wastewatertreatment, the solubility data of Na2CO3andNaHCO3in Na2SO4–water solventmixtures were measured using a dynamic method over the 275–335K temperature range. The solute-free mass fraction of Na2SO4in the solvent mixtures extended from 0 to 0.25. Thesolubility of Na2CO3and NaHCO3inNa2SO4–water solvent mixtures decreasedwith addition of Na2SO4. With rising temperature,the solubility of NaHCO3increased while the solubilityof Na2CO3increased at first and then decreasedafter transition points. The experimental data were correlated withthe electrolyte nonrandom two-liquid model. The root-mean-square deviationsof solubility temperature varied from 0.35 to 1.50 K. Based on thesolubility data of this work, a new strategy for separating the Na2CO3and Na2SO4mixture wasproposed theoretically. [ABSTRACT FROM AUTHOR]