Liquid-liquid equilibria for (volatile fatty acids + water + alcohol ethoxylates): Experimental measurement of pseudo-ternary systems

Experiments were conducted to establish the phase diagrams for ternary systems containing (acetic acid or propionic acid or butyric acid + water + alcohol ethoxylate surfactant) at 308.15 K and ambient pressure. Results indicated that the systems belong to Type 1 Treybal classification with water-surfactant binary pair exhibiting partial miscibility. The liquid-liquid equilibrium data were used to determine the ability of the surfactant to extract the acids from aqueous solutions. The calculated distribution coefficients and separation factors indicated that the effectiveness of the surfactant to extract acids follow the trend: butyric acid > propionic acid > acetic acid. The effectiveness of the surfactant to extract butyric acid from aqueous solutions is similar to previously studied environmentally-friendly solvents with added benefit of being non-inhibitory to microbial growth and metabolism. These characteristics of the alcohol ethoxylate used in this study could be exploited for the development of an extractive butyric acid fermentation process.