THERMODYNAMIC INVESTIGATION OF LIQUID‒LIQUID EQUILIBRIUM IN POLYETHYLENE GLYCOL BASED AQUEOUS TWO PHASE SYSTEMS

In this work the ability of UNIQUAC model was investigated in correlating the liquid‒liquid equilibrium in aqueous two phase systems (ATPS). In this way, four different systems containing polyethylene glycol (with different molecular mass) were studied. Phase forming salts in these systems are sodium succinate, sodium formate, magnesium sulfate or sodium tartrate. The UNIQUAC interaction parameters were fitted to the experimental data. The model parameters were obtained using Shuffled Complex Evolution (SCE) optimization algorithm. The results show that the model is in good agreement with the experimental data. In all cases the error is less than 2.7%. It must be mentioned that the error for ATPS containing sodium succinate or sodium formate is 0.73% and 0.65%, respectively. The results demonstrate that all of the correlations are satisfactory in order to representing the tie lines.