In order to study the influence of 2-(1-piperazinyl)-ethylamine (PZEA) as a promoter on the solubility of CO2 in aqueous monoethanolamine (MEA) solution, the equilibrium solubility of CO2 (mole CO2/mole blend solution) in MEA+PZEA aqueous solutions were measured experimentally using a vapor-liquid equilibrium (VLE) equipment at constant total blend concentration of 2.5 mol dm(-3) in temperatures ranging from 30 to 50 degrees C and initial partial pressures between 30 and 70 kPa. The response surface methodology (RSM) based on central composite design (CCD) was used to explore the relationship between three independent parameters (1: molar ratio of PZEA to MEA, 2: initial partial pressure of CO2 (P-co2), 3: temperature) on the CO2 loading capacity. Analysis of variance (ANOVA) showed a good agreement between experimental data and statistical model. The maximum CO2 loading capacity occurred at 0.8 (2M PZEA + 0.5 M MEA) molar ratio of PZEA to MEA. (C) 2015 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.