Effect of Chloride Salts and Bicarbonate on Solubility of CaSO4 in Aqueous Solutions at 37°C

In the study, we present the results of thermodynamic simulation of CaSO4 water-salt systems containing Ca2+, Mg2+, Na+, K+ and HCO-3 at 37°C. The results showed that the solubility of CaSO phase increased with increasing NaCl as wells as KCl concentration in the range of 0.0 to 2.0 M and 0.0 to 1.0 M, respectively. Remarkably, enhanced effect of MgCl2 on the solubility of CaSO4 phase was much larger than that of KCl or NaCl. The only exception was CaCl2, which was found to reduce solubility value of CaSO4 in aqueous solution at 37°C with the increase of CaCl2 concentration. Also, the solubility of CaSO4 phase in mixed salt solutions was investigated at 37°C. The common ion effect was the main factor on the solubility of CaSO4 in the mixed salts solution. Furthermore, CaSO4 solubility was reduced by small amounts of NaHCO3 in mixed solutions. These studies are of relevance in the estimating the changes of various salts in blood plasma and production of salt with low impurities of Ca2+ and SO42- ions, as well as estimating oceanic-containing CaSO4 uptake of CO2.