In this study, the Deshmukh-Mather (D-M) model was used to evaluate the equilibrium behaviour of CO2 + diethylaminoethanol (DEAE) + H2O, CO2 + piperazine (PZ) + H2O, and CO2 + DEAE + PZ + H2O systems. The binary interaction parameters of the model for mentioned systems were obtained by using experimental solubility data from the literature. The ability of the model to predict the concentration profiles for all chemical species present in the liquid phase at different concentrations of amine solution was tested. The excess properties such as Gibbs energy, enthalpy, and heat capacity as a function of the CO2 loading of the amine were obtained. The solution pH and activity coefficients were also investigated. The results of thermodynamic modelling indicated that the D-M model predicted the experimental data with average absolute relative deviations (AARDs) of 7.15%, 11.3%, and 8.65%, respectively, for the CO2 + DEAE + PZ + H2O, CO2 + PZ + H2O, and CO2 + DEAE + H2O systems. The model applied in this study can be used for process simulation based on the rate-based or equilibrium-stage models of CO2 absorption with DEAE + PZ solutions. (C) 2019 Elsevier B.V. All rights reserved.