Liquid–liquid equilibria for trioctylamine/1-dodecanol/citric acid/water system at 303.1 and 308.1 K: Experimental data and prediction

Abstract

The present work experimentally tests the liquid–liquid equilibria (LLE) of aqueous citric acid (CA) solutions with trioctylamine (TOA) in 1-dodecanol at 303.2 and 308.2 K. A predictive model has been developed based on the experimental data. This model considers the physical dissolution of CA and complexation with TOA. At low CA concentrations, the stoichiometric ratio of acid/amine is (1:1). However, the acid/amine ratios of (1:1), (1:2), and (2:1) are present at high CA concentrations. The equilibrium constants for the different complexes were determined and compared to previous studies, which employed other organic solvents. The equilibrium constants obtained in this study are comparatively higher, making 1-dodecanol an attractive solvation medium. Also, the literature presents LLE experiments with contact times from minutes to hours. Because of this lack of consensus, this work displays experimental evidence to suggest contact and settling times required for experimental evaluation of the equilibria in liquid–liquid systems based on the standard deviation.