Liquid-liquid demixing of Tergitol solutions by sodium salts

The salting out effect of different inorganic (Na2CO3, Na2SO3, Na2S2O3, Na2SO4, Na2HPO4) and organic (C2H3Na2O2, C4H4Na2O6, C6H5Na3O7) sodium-based salts has been demonstrated in aqueous solutions of the non-ionic surfactant Tergitol NP10. To do that, the solubility curves of the systems (Tergitol NP10 + salt + H2O) were determined by the cloud point method at T = 298.15 K and 0.1 MPa. Additionally, a polynomial and three different exponential equations, including the most frequently used Merchuk model, were employed to describe the binodal curves. These data, together with the tie-lines, the tie-line length and the slopes of the tie-lines, allowed full characterization of the phase behaviour of the systems. Finally, Bancroft, Othmer-Tobias, and Setschenow empirical equations were employed to shed light on the thermodynamic consistency of the experimental tie-line data.