Liquid-liquid equilibrium of aqueous two-phase systems containing poly(propylene glycol) and salt ((NH4)2SO4, MgSO4, KCl, and KAc): experiment and correlation

Binodal data of poly(propylene glycol) PPG(400)+salt ((NH4)(2)SO4, MgSO4, and KCl)+ H2O systems were determined at T=298.15K. and binodal data of PPG(400)+KAc+H2O system was determined at T=(298.15, 308.15, and 318.15)K. Moreover, the binodal curves were fitted to Merchuk equation, and the tie-lines were fitted to both the Othmer-Tobias and Bancroft equations. The effects of temperature and salts on the binodals and tie-lines of the investigated ATPSs were also studied. Finally, the salting-out ability of salts on the polymer was obtained by fitting the Setschenow-type equation to the tie-line data to derive a salting-out coefficient (k(S)) for each salt. For potassium salts, the relative effectiveness of the anions in inducing the phase segregation in ATPSs follows the Hofmeister series. The relative salting-out effectiveness of the sulfate salts is influenced by complexation of the cations by PPG. (C) 2011 Elsevier B.V. All rights reserved.