Document Type : Regular Article
Chemical Engineering Department, Faculty of Engineering, Shomal University, P. O. Box: 731, Amol, Mazandaran, Iran
Chemical Engineering Department, Faculty of Engineering, Shomal University, PO Box 731, Amol, Mazandaran, Iran
Faculty of Chemical Engineering, Babol University of Technology, PO Box, 484, Babol, Iran
Department of Chemical and Environmental Engineering, Faculty of Engineering, University of Nottingham Malaysia Campus, Semenyih, Selangor Darul Ehsan, Malaysia
In this study, the liquid-liquid equilibrium (LLE) in the aqueous two-phase system (ATPS) formed by polyethylene glycol (PEG1500 and PEG6000) and magnesium sulfate is investigated. The experimental measurements were performed at temperature of 298.15 K and pH values of 3.60, 5.00, 6.67. Densities and refractive indices of the mixtures were first measured to obtain the compositions from the plotted tie lines. The effects of pH and molecular mass of polymers on the binodal curve, tie lines length (TLL) and slope of tie line (STL) have been examined. It was found the pH values and molecular weight rise the heterogeneous region for each system. The binodal curve was fitted to the Merchuk and the Pirdashti equations. The Othmer-Tobias as well as the Bancroft equations were subsequently selected to correlate the compositions of the tie lines at equilibrium where the fitted parameters are derived. In addition, the Guan’s equation was utilized to correlate the experimental binodal curves. Finally, the effectively excluded volume (EEV) was determined and the values were found to increase with pH.