Salt effect on aqueous two-phase system composed of nonylphenyl ethoxylate non-ionic surfactant

Phase diagrams of detergent-based aqueous two-phase systems composed of nonylphenyl ethoxylate (4- C₉H₁₉C₆H₄(OCH₂CH₂)₉OH, NP-9) non-ionic surfactant and various salt solutions were studied experimentally at 298.15 K. The salts used were magnesium sulfate, sodium sulfate and sodium chloride. The salting-out power of salts in these systems were determined and this power can be arranged with respect to the cations as Mg²⁺>Na⁺ and anions as SO₄²⁻>Cl⁻. The experimental results of the phase diagrams were correlated using DH-NRTL model. It was found that, this model represent the experimental liquid–liquid equilibrium data of the surfactant aqueous two-phase systems with good accuracy.