a ghanadzadeh gilani - Department of chemistry ,Faculty of Science ,University of Guilan ,Rasht ,Iran
sh moayedi - Department of chemistry ,Faculty of Science ,University of Guilan ,Rasht ,Iran
k karimidardashti - Department of chemistry ,Faculty of Science ,University of Guilan ,Rasht ,Iran

Liquid-liquid equilibrium data for ternary system of [water + propionic acid + ester (benzyl acetate)] were measuredand correlated at T = 308.2 K and atmospheric pressure. The solubility curve data were determined using the cloud-point titration method. The phase diagram for the ternary system shows type-1 liquid-liquid equilibrium (LLE) behavior, where the two liquid pairs (acid + water) and (acid + ester) are totally miscible and one liquid pair (water + ester) is partially miscible. The acid-base titration, the Karl-Fisher technique, and refractive index measurements were used to obtain the tie- line data. The distribution coefficients and separation factors were calculated over the biphasic area. The thermodynamic models of UNIQUAC and NRTL were utilized to correlate the experimental tie line data. The reliability of the tie line data was determined by the Othmer-Tobias equation. The results show separation factors confirm the ability of these solvent for extraction of propionic acid from water.A liquid-liquid extraction is an importamt separation technique for environmental, clinical, and industrial laboratories.

Liquid-Liquid equilibrium; Propionic acid; Ester, NRTL model