influence of the molecular weight of polymer on the poly vinyl pyrrolidone and zinc sulfate phase diagram of aqueous two-phase systems

The study obtained the liquid – liquid equilibrium (lle) for aqueous two-phase systems (atpss) containing poly (vinyl pyrrolidone) (pvp) (10000, 24000, and 40000) and zinc sulfate at 298.15 k. the phase area is expanded according to the increased molecular weight of the polymer. density and refractive indices were employed as the physical properties for obtaining phase composition and end of tie-line evaluations. the effect of molecular weight is discussed in relation to binodal curve, tie-line length (tll), and slope of tie line (stl) determinations. following the increase in polymer molecular weight value, the tll increased and stl slightly decreased. accordingly, pirdashti’s equation was used to correlate binodal curve evaluations of these systems. furthermore, tie-line data points were correlated by othmer-tobias, hand, and bancroft equations. finally, the study determined the effective excluded volume (eev) of salt into the pvp aqueous solution.