Measurement and correlation of phase diagram data for polyoxyethylene (10) lauryl ether and potassium hydroxide/potassium carbonate/potassium phosphate aqueous two-phase systems at 298.15 K

The phase diagrams for the systems containing polyoxyethylene (10) lauryl ether (POELE10) and three salts (KOH, K2CO3 and K3PO4) have been determined experimentally. Three experiential equations were used to correlate the binodal data. The liquid–liquid equilibrium data of these systems were obtained by experimental method and calculated method using lever rule. The tie-line data were correlated by using Othmer-Tobias and Bancroft and simple Setschenow-type equations. Furthermore, the effect of salt on the binodal curve for the studied systems has been discussed by means of salting-out coefficient, effective excluded volume (EEV) and Gibbs free energy of hydration of the ions (ΔGhyd). It was found that the salts composed of anion with a higher valence are better salting-out agents than those with a lower valence. The order of salting-out abilities of salts is K3PO4 > K2CO4 > KOH for the investigated systems. Finally, the phase-separation ability of POELE10 is more powerful compared with that of other polymers and two-phase can easily form at the lower concentration, which indicates that lower cost is a remarkable advantage of POELE10–salt ATPSs.