CORRELATION AND PREDICTION OF MINERAL SOLUBILITIES IN THE RECIPROCAL SALT SYSTEM (NA+,K+)(CL-,SO4(2-))-H2O AT 0-100-DEGREES-C

A simplified version of the extended UNIQUAC Debye-Huckel model is used for correlation and prediction of mineral solubilities in the reciprocal salt system (Na+, K+)(Cl-, SO42-)-H2O at temperatures from 0 to 100-degrees-C. In this work the model is modified in order to contain only binary parameters with no concentration dependence. The UNIQUAC-Debye-Huckel g(E)-model is used for calculation of both ionic- and water-activities in aqueous solutions containing two or more of the four ions Na+, K+, Cl- and SO42- at concentrations from infinite dilution to saturation and temperatures from 0 to 100-degrees-C. In addition to the activity coefficient model, an expression for calculation of solubility products for various salts in the reciprocal salt system is presented. The results show that the extended UNIQUAC model is able to give a good representation of ternary solubility diagrams and a fair representation of vapor-liquid data, in the whole concentration range from infinite dilution to saturation, using the same set of interaction parameters. Furthermore, it is shown that the model is able to predict solid-liquid equilibria in the quaternary system (Na+, K+)(Cl-, SO42-)-H2O over a broad temperature range.