PREDICTION OF ACTIVITY-COEFFICIENTS OF ELECTROLYTES IN AQUEOUS-SOLUTIONS AT HIGH-TEMPERATURES

A recently published model for the excess Gibbs energy of aqueous solu tions containing mixed electrolytes (Lu and Maurer, 1993) is extended from 298 K to temperatures up to 573 K. The extension is achieved by i ntroducing a universal relation for the influence of temperature on so me model parameters. Although parameters are still ion specific, the i nfluence of temperature on those parameters is universal. No additiona l parameters are required for describing aqueous solutions of mixed el ectrolytes. The model accurately predicts activity coefficients at hig h temperatures and at concentrations up to the solubility limit in ele ctrolyte aqueous solutions containing, for example, K+, Na+, NH4+, SO4 2-, Cl- and NO3-.