Effect of the salting-out agent anion nature on the phase separation of a potassium salt–potassium bis(alkyl polyoxyethylene)phosphate–water systems

Abstract

The effect the salting-out agent anion nature has on the temperature and concentration intervals of the existence of the separation area is established by analyzing the phase diagrams of pseudoternary KCl (KBr, KI, KNO₃, K₂SO₄, K₄P₂O₇)–potassium bis(alkyl polyoxyethylene)phosphate (oxyphos B)–water systems. It is concluded that the anionic salting-out capability is reduced in the order P₂O₇^4-> SO₄^2-> Cl⁻ > Br^‒> NO₇^4-> SO₃^-> I⁻. The thermodynamic parameters of phase separation used to interpret the results are calculated. The observed pattern of a change in the salting-out ability of the investigated salts relative to aqueous solutions of the surfactants is in good agreement with the lyotropic (Hofmeister) series.