The UMR-PRU model, which has been successfully tested in the past to the predictions of different type of phase equilibrium and thermodynamic properties in binary and multicomponent systems, is applied in this work to phase equilibria in mixtures containing CO2 and organic acids. New interaction parameters are determined by fitting only binary vapor-liquid equilibrium data and then they are used to predict the vapor-liquid, solid-gas and solid-liquid-gas equilibria in CO2/organic acid systems. Furthermore, the UMR-PRU model with the newly derived interaction parameters is applied to the prediction of the phase equilibrium in ternary mixtures consisting of CO2, organic acids and water. Satisfactory results are obtained in all cases. (C) 2011 Elsevier B.V. All rights reserved.