The absorption of carbon dioxide in aqueous solutions of piperazine (PZ) in a high pressure Jerguson cell was studied at high gas loadings (1.06-2.77) mol(co2)/mol(PZ). Because of its cyclic and diamine characteristics, the reactivity and solubility of piperazine are higher than in other secondary amines. The solubility of CO2 in aqueous solutions of piperazine was measured at (313 and 343) K for (0.3 and 1.2) M piperazine up to a pressure of 7400 kPa. The Electrolyte-NRTL model was used to correlate the solubility of CO2 in aqueous solutions of piperazine. Eight adjustable ionic pair interaction parameters were estimated allowing for the correlation of the available experimental solubility data with an average deviation of 1-2% in CO2 partial pressure. The model was tested by predicting published experimental literature data for both low and high gas loadings. (C) 2010 Elsevier B.V. All rights reserved.