LAUSR

Abstract This study investigated selective CO2 adsorption over N2 by metals exchanged nano-zeolite synthesized. The BET specific surface areas of nano zeolite after exchange by Cu (Cu-NZ) and Fe (Fe-NZ) ions were 869.32 and 721.46 m2/g, respectively. The CO2 adsorption capacities and CO2 selectivity over N2 of Cu-NZ and Fe-NZ were decreased with increasing temperature. Based on the Langmuir- Freundlich adsorption isotherms, the CO2 adsorption capacities of Cu-NZ and Fe-NZ were 7.16 and 6.23 mmol/g, respectively, measured at 20 °C and 1 atm. The highest CO2 selectivities by Cu-NZ and Fe-NZ were 50.71 and 46.38 at 20 °C, respectively. The improvement in CO2 adsorption capacity and adsorption selectivity could be explained due to the electron transfer by both σ-donation (electron transfer from bonding π2p orbitals of CO2 molecules to 4s orbital of Cu 2+ and Fe 3+ ions on the Cu-NZ and Fe-NZ, respectively). Also the d-π2∗ back donation by electron transfer from unoccupied 4d of Cu2+ and Fe 3+ ions to occupied π2p∗ of CO2 molecule would be high effective to CO2 adsorption process. Adsorption kinetics showed that the pseudo-second order model was more suitable than the pseudo-first one for predicting the CO2 adsorption process by Cu-NZ and Fe-NZ. In the regeneration study of CO2-loaded adsorbents, even after 10 cycles of adsorption-desorption, the adsorption capacity of CO2 were decreased only 3.46 and 4.12% by using Cu-NZ and Fe-NZ, respectively. These adsorption and desorption characteristics suggest that Cu-NZ and Fe-NZ can be utilized as good adsorbents for the selective removal of CO2.