Measurement and correlation of the saturation concentrations for single and mixed aqueous electrolyte solutions at various temperatures

Abstract

Saturation molality for a number of single and mixed aqueous electrolyte solutions containing NaCl, CaSO 4, and Na 2SO 4, was measured at atmospheric pressure over a wide range of temperature. In order to check the repeatability of the experimental data, the experiments were replicated three times and average of the results was considered as final saturation molality. Experimental data of saturation molality for single electrolyte solutions were correlated using the modified UNIFAC–Dortmund model to account for the short-range interaction. Binary interaction parameters, between water molecules and ionic species were also reported. For the long-range interactions between the ionic species in solutions, the Pitzer–Debye–Hückel (PDH) model was used. The results showed that the PDH + UNIFAC–Dortmund activity coefficient model can accurately correlate the mean ionic activity coefficients for the single aqueous systems studied at saturation molality. In case of mixed electrolyte solutions, the PDH model was used to correlate the mean ionic activity coefficients of the electrolytes. Ternary interaction parameters, between the ionic species in solution, introduced in the PDH model were also reported. The results obtained from the PDH model were in good agreement with those of data collected in this work.