Liquid phase equilibria of (water + phosphoric acid + 1-butanol or butyl acetate) ternary systems at T = 308.2 K H. Ghanadzadeh a,b , A. Ghanadzadeh a, * , Kh. Bahrpaima a a Department of Chemistry, Faculty of Science, University of Guilan, Rasht, Iran b Department of Chemical Engineering, University of Guilan, Rasht, Iran article info Article history: Received 6 May 2008 Received in revised form 27 June 2008 Accepted 1 July 2008 Available online 9 July 2008 Keywords: LLE data Ternary systems UNIQUAC model Extraction processes abstract (Liquid + liquid) equilibria and tie lines for the ternary systems of (water + phosphoric acid + 1-butanol) and (water + phosphoric acid + butyl acetate) were measured at T = 308.2 K. The experimental ternary (liquid + liquid) equilibrium data were correlated with the UNIQUAC model. The reliability of the exper- imental tie lines was confirmed using Othmer–Tobias correlation. The average root-mean-square devia- tion (RMSD) values of (water + phosphoric acid + 1-butanol) and (water + phosphoric acid + butyl acetate) systems were 2.17% and 2.16%, respectively. Distribution coefficients and separation factors were measured to evaluate the extracting capability of the solvents. The results show that butyl acetate may be considered as a reliable organic solvent for the extraction of phosphoric acid from aqueous solutions. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction The precise (liquid + liquid) equilibrium (LLE) data of multi- component mixtures are important to design many chemical pro- cesses and separation operations. The LLE investigations of ternary systems have been the subject of much interest in the recent years [1–7]. Phosphoric acid is a widely used acid, which has many indus- trial applications. The pure phosphoric acid is extensively used as and additive in the food industry. Therefore, the separation and purification of phosphoric acid from aqueous solutions by solvent extraction technique are of economic importance in the chemical industry [8–10]. Liquid phase equilibrium data of (water + phosphoric acid) with organic solvents (extractants) are important and needed for the de- sign of an efficient separation operation. Many organic solvents have been investigated and reported in the literature as extractants for the extraction and purification of phosphoric acid from water. Heavy alcohols, ketones and ethers have mainly been used for extraction of phosphoric acid from aqueous solutions [11–18]. The type of solvent is one of the most important factors that influ- ences the equilibrium characteristics of the extraction of acid from aqueous solutions [19–22]. From practical and economical aspects, the search for new and suitable organic solvents for the separation of phosphoric acid from water is a current study. In this research, 1-butanol and butyl acetate were tested as organic solvents for recovery of phosphoric acid from water. The 1-butanol and butyl acetate have been used as organic solvents for the determination of LLE data for many ternary mixtures [23–25]. The focus of this study is placed on the phase behaviour of LLE for the mixtures of (water + phosphoric acid) with 1-butanol and butyl acetate at T = 308.2 K. The LLE data were correlated with the solution model of UNIQUAC, and the values of the interaction parameter were obtained. Distribution coefficients and separation factors were determined from the tie line data to establish the extracting capability of the solvents and the possibility of using these solvents for the separation of (water + phosphoric acid). 2. Experimental 2.1. Materials Analytical grade phosphoric acid, 1-butanol and butyl acetate (mass fraction purity > 0.99) were supplied by Merck. Bi-distilled water was used throughout all the experiments. 2.2. Procedure The equilibrium between liquid phases was studied in a trans- parent water thermostat at T = 308.2 K. The temperature was con- trolled within ±0.1 K. A glass cell which can contain a solution of volume from (50 to 200) cm 3 was designed. The cell was filled with known masses of heterogeneous mixtures of (water + phosphoric acid + solvent). The prepared mixtures were placed in the extrac- tion vessel, stirred for 4 h, and then left to settle for 4 h. 0021-9614/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.jct.2008.07.001 * Corresponding author. Tel./fax: +98 131 3233262. E-mail address: aggilani@guilan.ac.ir (A. Ghanadzadeh). J. Chem. Thermodynamics 40 (2008) 1666–1670 Contents lists available at ScienceDirect J. Chem. Thermodynamics journal homepage: www.elsevier.com/locate/jct