Microporous membrane absorbers were used for the separation of carbon dioxide-nitrogen mixtures. The membranes applied were made of polytetrafluoroethylene (PTFE) and the absorbents included aqueous solutions of different kinds of amines. We determined the separation efficiency and the overall mass transfer coefficient of carbon dioxide of the membrane modules, and evaluated the separation performance under different absorbent concentrations and temperatures. Absorption rates through the PTFE hollow fiber membranes were measured at temperatures ranging from 2 to 60 degreesC, and the removal rate of carbon dioxide was found to increase with the increase of the volumetric flow rate of an absorbent. We also conducted a theoretical model analysis to predict the separation efficiency. The results showed that the theoretical model agreed well with the experimental observation for the case of aqueous amine solutions.