Carbon Dioxide Adsorption onto Polyethylenimine-Functionalized\nPorous Chitosan Beads

Abstract

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