Carbon Dioxide Adsorption onto Polyethylenimine-Functionalized Porous Chitosan Beads

Polyethylenimine-functionalized porous chitosan (PEI–CS) beads were prepared and their CO₂ adsorption performance was evaluated. The CO₂ adsorption capacity of PEI–CS was dependent upon both the amine content and surface area of the functionalized beads. PEI–CS showed a CO₂ adsorption capacity of 2.3 mmol/g at 313 K and 15 kPa of CO₂ in the absence of water vapor that considerably increased to 3.6 mmol/g in the presence of water vapor. To rationalize this phenomenon, the CO₂ adsorption mechanisms in the absence and presence of water vapor were investigated by diffuse reflectance infrared Fourier transform spectroscopy. The results indicated that the mechanism of CO₂ adsorption onto PEI–CS, in both the absence and presence of water vapor, involved the formation of carbamate. Therefore, the higher CO₂ adsorption capacity in the presence of water vapor was attributed to the increased accessibility to amino groups of PEI–CS, owing to swelling of the polyethylenimine chain and/or chitosan framework upon adsorption of water. The herein reported chitosan-based material displays high CO₂ adsorption capacity as well as excellent regenerability and, thereby, shows potential as an adsorbent for CO₂ capture