Experimental data and thermodynamic modeling of ternary aqueous biphasic systems of EO/PO polymers–Na2SO4–H2O

• Concentration of aqueous sodium sulfate solutions by extraction has been studied.
• Experimental liquid–liquid equilibrium data were determined.
• Purely empirical equilibrium relations and also the NRTL model were fitted to the data.
• Good agreement between data and models was obtained.
• Temperature dependent NRTL model parameters were found.

Liquid–liquid extraction using thermoresponsive polymers as solvents in aqueous two phase systems followed by induced phase separation to recover the polymers is a potential technology for water–salt separations. Here we report for seven polymers on their ternary systems containing water, sodium sulfate and the (block co)poly ether. Equilibrium data were measured at 298.15 K and 313.15 K and atmospheric pressure. Empirical equations have been used to correlate the experimental equilibria for both temperatures separately and the semi-empirical NRTL model has been applied with a temperature dependent parameter to describe the complete dataset for both temperatures together. Model predictions were in good agreement with the experimental data.