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

ABSTRACT

It is of great importance to separate potassium salts from carbonate-based lakes especially from the low [K+] but high [Na+] brine which were discovered over the world. Here the phase diagram of quaternary system Na+, K+//Cl-, CO32--H2O was experimentally studied at 298.15 K via method of isothermal evaporation. Results were presented to correct the previous diagram reported by Blasdale (J. Am. Chem. Soc. 1923, 45 2935). Sorts of salt appeared and their solubility during the evaporation, and plots of density vs. composition and pH values were given based on the experimental data. It was found that there were four invariant points, seven univariant curves, and five crystallization fields in the equilibrium phase diagram. To extract single-salt of potassium, certain area in the Na+, K+//Cl-, CO32--H2O diagram were chosen to be acidified by the compressed CO2, and potassium in form of KHCO3 was precipitated from the mother solution. The carbonation was able to avoid formation of NaKCO3*6H2O during evaporation of the original system Na+, K+//Cl-, CO32--H2O. Based on experiment data the region area for potassium salt extraction was determined, and this area was suitable to extracting K+ salts from brines with [Na+/K+] ratio even lower than 0.44. This strategy opened a new pathway to recovery potassium with a maximum yield of 59.88% from the carbonate-chloride based brine.