Influence of molecular weight of the polymer on the liquid-liquid equilibrium of the poly(ethylene glycol) plus NaNO3+H2Osystem at 298.15 K

Liquid-liquid equilibria for the poly(ethylene glycol) (PEG) + NaNO3 + H2O system, with PEG of molecular weights 2000, 6000, and 10 000, have been measured at 298.15 K. The binodal curve was fitted using a three-parameter equation, and the compositions of the tie lines at equilibrium were fitted using the Othmer-Tobias equation. These equations were used to develop a mathematical model for interpretation of the equilibrium data of these aqueous two-phase systems (ATPS's). Data on the densities and refractive indexes are also given for the solutions at equilibrium. It was found that an increase in the molecular weight of the PEG produced a displacement of the binodal curve toward the origin and increased the liquid-liquid biphasic zone. The ATPS's studied may be used in separation of iodine and other compounds.