BACKGROUND: This paper reports an analysis of the mass transfer behaviour of CO2 absorption in hollow fibre membrane modules in parallel and cross-flow dispositions. The ionic liquid EMISE, 1-ethyl-3-methylimidazolium ethylsulfate, is used to achieve a zero solvent emission process and the experimental results are compared with CO2 permeation through the membrane, without solvent in the lumenside. RESULTS: Overall mass transfer coefficients Koverall, CF = (0.74 +/- 0.02) x 10-6 m s-1 and Koverall, PF = (0.37 +/- 0.018) x 10-6 m s-1 were obtained for cross-flow and parallel flow, respectively. These values are one order of magnitude lower than the coefficient obtained in permeability experiments, Koverall, PERM = (6.16 +/- 0.1) x 10-6 m s-1, indicating the influence of the absorption in the process. Including the specific surface and gas volume of each contactor in the analysis, a similar value of a first-order kinetic rate constant, KR = 2.7 x 10-3 s-1 is obtained, showing that the interfacial chemical reaction CO2-ionic liquid is the slow step in the absorption process. CONCLUSION: An interfacial chemical reaction rate constant KR = 2.7 x 10-3 s-1, describes the behaviour of the CO2 absorption in the ionic liquid EMISE using membrane contactors in parallel and cross-flow dispositions. Copyright (c) 2012 Society of Chemical Industry