Measurement and thermodynamic model study on solubility equilibrium of potassium phosphate, potassium hydrogen phosphate, and potassium carbonate in aqueous systems containing the ionic liquid [Bmim]Cl at 298.15 K

Abstract Solubilities of potassium phosphate (K 3 PO 4 ), potassium hydrogen phosphate (K 2 HPO 4 ) and potassium carbonate (K 2 CO 3 ) in aqueous systems containing the ionic liquid 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) were determined by cloud-point measurements in the temperature of 298.15 K at atmospheric pressure. The solubility equilibrium data were correlated and calculated by using Extended Pitzer thermodynamic model. In addition, the new Pitzer ion interaction parameters of the mixed-electrolyte solution were obtained by using an optimization program based on Simplex Method of Nelder–Mead algorithm. Comparison of calculated results by using the new interaction parameters at 298.15 K was expressed by the relative standard deviations between the regressed solubility values and the experimental data. Results indicate that predictions of the present model are in well accordance with experimental values, which supports the reliability of the model prediction.