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In this study, liquid–liquid equilibrium measurements were performed for the ternary (water/non-ionic surfactant/decane) systems at T = 298.15 K and atmospheric pressure. Propylene glycol mono propyl ether and ethylene glycol monobutyl ether were selected as surfactant; the first one is propylene glycol ether, while the second one is ethylene glycol ether. New experimental liquid–liquid equilibrium data were presented for the corresponding systems. Effect of salinity and surfactant structure (EO or PO functional group) on the phase behavior of such systems has been studied by both experimental measurements and thermodynamic modeling. The experimental phase behavior data were predicted by the perturbed hard sphere chain (PHSC) equation of state. In the presence of electrolyte, mean spherical approximation (MSA) term has been coupled with the PHSC EoS to account the contribution of long-range interactions. The calculated results indicate acceptable qualitative agreement of PHSC results with the experimental data. [ABSTRACT FROM AUTHOR]

In this study, liquid–liquid equilibriums are reported for different ternary systems of aqueous solutions with decane as oil and mono-ethylene glycol butyl ether (C 4 E 1 ) as surfactant. The appearing Winsor phases and their evolution are shown by drawing temperature versus surfactant weight fraction for a given ratio of aqueous solution to oil. The obtained diagrams have the well-known fishlike shape. Four parameters are used to discuss the influence of the additives: the perpendicular and horizontal asymptotes to the realms-of-existence of the Winsor III phase. The two horizontal asymptotes, i.e., the LCST (lower critical solution temperature) and UCST (upper critical solution temperature) show no significant changes upon adding chloride salts, except for the triethylphenylammonium cation as counter-ion. By contrast, significant changes of the values of these two parameters are found when the nature of the anion of sodium salts changes. The two perpendicular parameters γ 0 (minimum concentration of surfactant needed to form a Winsor III) and γ ˜ (minimum surfactant concentration needed to reach the Winsor IV phase from a Winsor III one) are only little affected by the nature of the additive. Two other parameters in relation with Winsor III area are also studied: δ reflects the vertical extent of the realms-of-existence of Winsor III versus temperature ( δ = UCST − LCST), while ξ = γ ˜ − γ 0 reflects its horizontal extension. The value of δ is affected by the nature of the anion of sodium salts and strongly increases in presence of Na 2 SO 4 , but also with sucrose as additive. The effect of additives has in general a more pronounced influence on the values of the LCST and UCST than on ξ . The results are discussed in terms of Hofmeister effects, of salting-in and salting-out and of the resulting depletion and adsorption on the interfacial film of the Winsor III middle microemulsion. [ABSTRACT FROM AUTHOR]

In this study, liquid–liquid equilibrium measurements were performed for different ternary, water (or brine)/decane or dodecane/mono-propylene glycol ether (C 3 P 1 ) or di-propylene glycol ether (C 3 P 2 ) systems in order to build the so-called fish phase diagrams (temperature as a function of surfactant for a given polar-apolar solvent mixture) and to compare them to the well-known water (or brine)/decane or dodecane/ethylene glycol mono-butyl ether (C 4 E 1 ) phase diagrams. The study is motivated by the lower toxicity of the C x P y compared to the corresponding C x E y . Toxicity is of particular importance for any use of such molecules in the environment. Like in the presence of C 4 E 1 , the formation of Winsor type I → III → II phase transitions with increasing temperature was observed for the C x P y systems. The LCST (Lower Critical Solution Temperature) and UCST (Upper Critical Solution Temperature) of the newly studied systems were determined. The values of the γ 0 parameter (in mole fraction), the minimum value of surfactant needed to form Winsor III, increased in comparison to the C 4 E 1 systems. The value of γ ˜ (in mole fraction), minimum value of surfactant needed to reach Winsor IV from Winsor III, was comparable using C 4 E 1 and C 3 P 1 , and lower in the presence of C 3 P 2 . The substitution of decane by dodecane led to a stronger water affinity of C 4 E 1 and C 3 P 2 as greater values of the LCST and UCST have been observed in the presence of dodecane. By contrast, a lower hydration of C 4 E 1 and C 3 P 1 was found when increasing the NaCl content in brine. It can be concluded that less toxic C 3 P 1 and C 3 P 2 can be envisaged as a substitute of the contested C 4 E 1 to formulate microemulsions and particularly Winsor III systems. [ABSTRACT FROM AUTHOR]

In this study, vapor-liquid and liquid-liquid equilibrium in mixtures containing glycol ether surfactant, non-polar and polar compounds are calculated using Perturbed Hard Sphere Chain (PHSC) equation of state (EoS). Pure liquid density and vapor pressure of surfactants are used for parameter estimation of glycol ether surfactants. The PHSC parameters are calculated for both ethylene glycol ether and propylene glycol ether surfactants. Glycol ether surfactant molecules are modeled as associating components by considering two association sites for each molecule. The results show that the PHSC model is capable of correlating thermodynamic behavior of binary (polar + surfactant) and (non-polar + surfactant) systems. Upper critical solution temperature (UCST) for hydrocarbon + surfactant and lower critical solution temperature (LCST) for water + surfactant systems are accurately calculated. The critical temperatures and the extent of immiscibility are in good agreement with the available experimental data. [ABSTRACT FROM AUTHOR]