Solubility of KCl, NaCl, Na ₂ SO ₄ , and K ₂ SO ₄ in Water–Methanol: Experimental and Modeling

To measure the solubility of KCl, NaCl, Na2SO4, and K2SO4 through a methodical-analytical approach, a simple and accurate apparatus is applied. The solubility of these salt types is measured in H2O and CH3OH at 278.15 and 288.15 K. The nonelectrolyte UNIQUAC-NRF and modified nonelectrolyte UNIQUAC-NRF models are developed to correlate the salt solubility data based on the excess Gibbs free energy. In these models, the composition of short-range interaction and long-range contribution is represented through the local composition model and a Pitzer–Debye–Hückel equation, respectively. Each one of these two models has two binary adjustable parameters, which are obtained by fitting the experimental solubility data of the water–methanol–salt mixtures at 278.15 and 288.15 K. The adjustment of the parameters is essential in predicting the solubility of the salt types for H2O–CH3OH–salt mixtures at electrolyte concentrations up to the saturation point and temperatures within 283.15 to 328.15 K. The findings here indicate that these two models can accurately describe salt solubility in water–methanol–salt mixtures, only through the binary adjustable parameters.