Surface tensions of carbonated N-methyldiethanolamine (MDEA)-piperazine (PZ) aqueous solutions were measured at the temperatures ranging from 293.15 to 323.15K. A theoretical model was proposed to correlate the surface tensions and the calculated results agreed well with the experiments. The residual MDEA and PZ in the carbonated aqueous solutions were determined on the basic of 'shuttle' mechanism. The temperature, amine concentration and CO2 loading (alpha, mole number of CO2/mole number of MDEA + PZ) dependences of the surface tensions were demonstrated. (c) 2011 Elsevier B.V. All rights reserved.