An experimental and theoretical analysis to separate CO2 using facilitated transport membranes immobilized with different aqueous single and mixed amine solutions have been performed. The membranes containing monoethanolamine (MEA), diethanolamine (DEA), monoprotonated ethylenediamine (EDAH(+)) and piperazine (PZ), as well as aqueous blends of PZ with MEA, DEA or EDAH(+) were considered. The aqueous solution of PZ showed the highest COz permeation rate with respect to other single amine solutions. Therefore blends of PZ with MEA, DEA and EDAH(+) increased the permeance of carbon dioxide through mixed amine membranes. Facilitated transport of carbon dioxide across a liquid membrane containing aqueous single and mixed amine solutions have been numerically modeled in which the reversible reaction A (CO2)+2B (amine) double left right arrow AB (carbamate)+BH (protonated amine) occurs inside the liquid membranes. The current numerical solution predicts the facilitated factor of COz through the immobilized membrane and is based on the dimensionless, nonlinear diffusion-reaction transport problem, allowing unequal diffusivities of complexes and carrier and cases of zero and nonzero permeate side solute concentrations. In comparison with the numerically calculated results, the results obtained were found to be in well agreement although improved estimation of physicochemical parameters would substantially improve the model predictions. (c) 2008 Elsevier B.V. All rights reserved.