Investigation of the Absorption of CO 2 into Nanofluids in Stirred Tank Majid Ghasemi Falavarjani m.ghasemifalavarjani@ce.iut.ac.ir March 10, 2012 Absorption of gases into liquid is a prevalent way of reducing or separating a gas component from a gas mixture. Extensive research has been carried out to increase the efficiency of absorption process. These include adding chemicals to the liquid phase to reduce the mass transfer resistance of liquid phase by chemical reaction, addition of microparticles, adding nanoparticles to the liquid phase and using external fields like electromagnetic fields Using nanofluid is one of the methods that may increase the mass transfer coefficient in gas absorption process. Nanofluids can be used as an effective method for increasing the mass transfer coefficients.In this study, volumetric mass transfer coefficients (K L a) in absorption of carbon dioxide into ?-Al 2 O 3 /water and Fe 3 O 4 /water nanofluids were investigated. An agitated vessel with two disk flat-blade turbine impellers and 1.4 l volume equipped with variable speed DC electromotor and magnetic fields was constructed.Volumetric mass transfer coefficients for absorption of carbon dioxide in base fluid and different volume concentrations of ?-Al 2 O 3 /water nanofluid were measured at two different gas flow rates. The results showed that the mass transfer coefficient increased by concentration of ?-Al 2 O 3 nanoparticles up to 0.05%V/V in base fluid for 1.0 l/min gas flow rate and constant speed propeller, then remained constant (0.05 to 0.2%V/V).The mass transfer coefficient increased by power per unit volume inserted by the propeller for ?-Al 2 O 3 /water nanofluid. It is suggested that adding nanoparticles to the base fluid may break the bubbles reducing the size of the bubbles and increasing the volumetric mass transfer coefficient. The highest volumetric mass transfer coefficient measured was equal to 0.08 1/s in 0.05 %V/V concentration of nanofluid ?-Al 2 O 3 /water for 1.0 l/min gas flow rate and 1400 rpm propeller speed. At all concentrations of nanofluid (0.01–0.2%V/V), the volumetric mass transfer coefficient enhancement (volumetric mass transfer coefficient of nanofluid to base fluid, E kla ) initially increased and then decreased vs power per unit volume inserted by the propeller. The highest mass transfer coefficient enhancement was measured to be 2.15 in 1150 rpm impeller speed, 0.05%V/V concentration and 1.0 1/min gas flow rate. The effects of addition of Fe 3 O 4 magnetic nanoparticles on absorption of carbon dioxide into water were also investigated. The results showed that the mass transfer coefficient increased by concentration of Fe 3 O 4 nanoparticles up to 0.005%V/V in base fluid for 1.0 l/min gas flow rate and constant speed propeller. Applying a direct magnetic field intensity of 390 gauss (G) did not show significant effect on the volumetric mass transfer coefficient of carbon dioxide absorption in pure water and Fe 3 O 4 /water nanofluid. Keywords: Volumetric mass transfer coefficients, absorption, carbon dioxide, nanofluid, ?-Al 2 O 3 /water, Fe 3 O 4 /water, stirred tank , magnetic field.