Kinetics, mechanism and mathematical modelling of extraction of citric acid with isodecanol/n-paraffins solutions of trioctylamine

Kinetic measurements of the extraction of citric acid from aqueous solutions with trioctylamine in isodecanol/n-paraffins mixtures, were carried out in a highly agitated system (750 min(-1)) at 25 degrees C. The kinetic data were interpreted (1) by a formal elementary kinetic model, and (2) by a proposed mechanism of two reactions of complexation by which (1, 1) and (1,2) acid-amine complexes are formed. In both cases very good fits between the experimental kinetic curves and calculated ones were obtained. Both of the kinetic models include equilibrium constants. The formal elementary kinetic model with the rate of the forward reaction being of the order of 0.73 with respect to the concentration of citric acid in the aqueous phase and of first order with respect to the amine concentration, and the rare of the reverse reaction as first order with respect to the concentration of the acid-amine complex, could be suitable for the analysis and design of the process in dynamic conditions. The model based on the proposed mechanism is useful in elucidating the dependence of the participation of the individual complexes on the extraction mixture composition as well as on the initial concentration of the acid in the aqueous phase. (C) 1998 Elsevier Science Ltd. All rights reserved.