In recent years, CO 2 removal from outlet gas stream of industrial plants has become a significant issue due to various reasons, especially global warming. In this study, an exclusive experimental and theoretical investigation was carried out on using ?-Al 2 O 3 /water and ?-Al 2 O 3 /water nanofluids for CO 2 removal N 2 /CO 2 gas mixture by using a membrane contactor. For this purpose, the gas mixture and absorbent passed through fibers and shell side of a commercial polysulfone hollow fiber type membrane contactor, respectively. In experimental study, the performance of applied system was firstly compared with wetted wall column as a conventional process, and it was found that the former had better capability to separate CO 2 . Then, the variation of objective parameters of CO 2 removal efficiency; overall mass transfer coefficient, and flux of absorbed CO 2 into solvent, with different operating parameters including the type of nanofluid, nanoparticle content of nanofluid, absorbing nanofluids and feed gas flow rates, and initial CO 2 concentration in the feed mixed gas were investigated. Results showed that applying nanofluids (especially ?-Al 2 O 3 ) caused improvement in CO 2 removal efficiency; overall mass transfer coefficient, and flux of absorbed CO 2 into solvent. By adding only 0.02 vol. % ?-Al 2 O 3 nanoparticle to pure water, CO 2 removal efficiency reached to about 92% at low gas flow rates, overall mass transfer coefficient grew about 4 times at low feed CO 2 concentration; and flux of CO 2 absorption into solvent enhanced about 50% at high absorbent flow rates. In numerical part of the work, after defining the geometry and the conservation equations of the system, some simplifying assumptions were made. Momentum conservation equations and continuity equations for component appeared in the form of ordinary differential equations and partially differential equations, respectively. Momentum conservation equations were solved through analytical methods. The finite element method was considered as numerical method that was performed by COMSOL Multiphysics version 4.3, and continuity equations for different components were solved by this means. In order to validate the results obtained from simulation, they were compared with the experimental ones. It was observed that there was a relatively good agreement between them with average error of 9.37%. Afterward, by using the simulation results, some other parameters including velocity distribution, CO 2 concentration, and flux of absorbed CO 2 into solvent along the membrane contactor were determined. Also, effects of some other parameters, which had not been investigated experimentally, were studied numerically. These included of the effects of solvent temperature, gas flow in shell side, flow direction, and membrane wetting. It was found that working at lower temperatures with gas flow inside the fibers and counter current flow direction, and applying non-wetted membrane enhanced CO 2 removal efficiency. Also, simulation results revealed that among these parameters using of non-wetted membrane had greater influence on CO 2 removal efficiency. Key Words: CO 2 separation, hollow fiber membrane contactor, ?-Al 2 O 3 ?-Al 2 O 3 nanoparticle, nanofluid, simulation