Effect of temperature and molar mass of polymer on liquid-liquid equilibria of aqueous two-phase system containing poly ethylene glycol di-methyl ether and ammonium sulfate and application of this system in separation of lactic acid

The liquid-liquid equilibrium (LLE) of {polyethylene glycol di-methyl ether 2000 {(PEGDME2000) + (NH4)2SO4 +H2O} system has been determined experimentally at T = (298.15, 308.15 and 318.15) K and atmospheric pressure (≈85 kPa). To investigate the effect of molar mass of the polymer on the tie-lines, similar measurements were also made at T = 298.15 K on this two-phase system consisting of the PEGDME with molar masses of 250 and 500 g mol−1. Finally the effect of molar mass of polymer on the binodals was studied by measuring LLE of this system at T = 298.15 K for molar masses of 250, 500 and 2000 g mol−1. Moreover, the effect of temperature on the binodal curves and the tie-lines for the investigated aqueous two-phase system has been studied. The binodal data were also obtained for (polyethylene glycol 2000 + ammonium sulfate + water) system at 298.15 K. Binodal theory was also used in order to study the effect of polymer molar mass, temperature and also type of polymer on the solution-out ability of polymer. Two empirical equations were used for reproducing the experimental binodal results. The tie-line data were correlated by using Setschenow type equation, and osmotic virial model. The use of this system for separation of lactic acid was also examined. The effects of tie-line length and temperature on the lactic acid separation were also searched. Finally, the equation proposed by Diamond-Hsu was used to the correlating of the lactic acid experimental distribution coefficients in the studied two-phase system.