Enhanced CO2 adsorption on amine-impregnated fly ash modified by Chitosan: Performance and mechanistic insights

Fly ash (FA) has demonstrated cost-effective potential for CO 2 capture, yet its practical application is hindered by inadequate pore structure and complex processing. Chitosan (CS), a polysaccharide rich in amine groups, offers distinct advantages as it enables straightforward synthesis of adsorbents without requiring high temperature/pressure or templates, and provides regular pores, making it an ideal candidate for modifying FA to enhance its pore structure and streamline the preparation process. Therefore, the adsorbent of polyethyleneimine(PEI)-impregnated FA modified by CS was developed to investigate CO 2 adsorption performance at different conditions. The properties and mechanisms were characterized by XRD, SEM, FT-IR etc. Characterization results revealed that the introduction of CS transformed the irregular macropores of FA adsorbents into ordered three-dimensional networks, significantly improving the pore structure and specific surface area, while introducing amine groups from CS into the adsorbents. The FA/CS 1 -50PEI achieved a maximum CO 2 adsorption capacity of 1.96 mmol/g (40 °C, 100 mL/min and 15 % CO 2 ) in experiments. After 10 adsorption–desorption cycles (40 °C, 200 mL/min and 15 % CO 2 ), it retained 93 % of initial adsorption performance, demonstrating exceptional stability and effectioncy for CO 2 adsorption. DRIFTS analysis confirmed the successful introduction of amine groups from CS, and the appearance of carbamate’s specific peak at different wavenumbers further validated the involvement of amine groups in CS and PEI in the adsorption process. Additionally, adsorption kinetic analysis revealed the adsorption mechanism involved both physisorption and chemisorption. It also confirmed that CS not only provided regular pores for PEI impregnation, but also the amine groups in CS exposed to the pore surface participate in adsorption reaction with the that in PEI.