Industrial & Engineering Chemistry Research, Vol.40, No.2, 668-673, 2001
Analysis of equilibrium acid distribution in the system of citric acid-water-(triisooctylamine plus methyl isobutyl ketone) using a quasi-physical approximation
Methods for predicting the equilibrium acid distribution in a reactive extraction system are proposed, and their accuracies have been tested by experimental data. Three mathematical models are formulated. The pseudo single-reaction model is derived from the idea of chemical theory of solution. Based on the theory, the equilibrium is strongly affected by chemical effects which are assumed as a single reaction with its stoichiometric coefficients as adjustable parameters. A great improvement is provided by the ideal quasi-physical approximation model which eliminates the uncertainty of the solvation reaction mechanism by postulating the chemical equilibrium in the form of physical equilibrium. The model is proven to well fit the experimental equilibrium data obtained from the system of citric acid-water-(triisoctylamine + methyl isobutyl ketone) and gives a more flexible and relatively simpler equation of equilibrium acid distribution than the models which have been published previously. A modification made by taking the nonideality of solution into account further improves the data fitting of the ideal quasi-physical approximation model for a wider range of data. The effect of temperature on the model's parameters is also discussed.