Correlation of liquid-liquid equilibrium data of water + inorganic salt + alcohol systems using the MNRTL model

Abstract

The liquid-liquid equilibrium of water+salt+alcohol systems have been correlated and predicted using the MNRTL model (Chen et al., 1982). The MNRTL model uses the extended Debye-Hückel formula proposed by Pitzer (1980) to represent the contribution of long range ion-ion interactions while the NRTL local composition model is used to represent the contribution of short range interactions of all kinds. The alcohols studied were the different propanols, butanols and pentanols. The salts were NaCl, KCl and LiCl. The results show that the MNRTL model is an adequate tool to correlate and predict the equilibrium of water + NaCl or KCl + alcohol systems. However, this model is not useful in water + LiCl + alcohol systems, since it is not able to predict the important increase in the solubility of salt in organic phase, due to the formation of “solvate” alcohol-salt.