Abstract
• MEA/Al 2 O 3 sorbent achieved 23.33 mgCO 2 /g at 400 ppm under ambient conditions. • 93.1 % adsorption capacity was maintained after 5 cycles with N 2 regeneration. • Avrami model was the best fit kinetics, suggesting a multi-step adsorption mechanism. • Elovich and Weber–Morris revealed chemisorption and diffusion contributions. • Activation energy of 1.74 kJ/mol indicated favorable DAC kinetic performance. Amine-functionalized alumina adsorbents offer a promising solution for direct air capture (DAC) of CO 2 , addressing the need for efficient and low-energy carbon removal technologies. This study investigates the adsorption performance of alumina modified with four different amines MEA, DEA, PZ, and MDEA at varied loadings to optimize CO 2 capture efficiency, kinetics, and cyclic stability. The MEA-modified sorbent with 50 wt% loading achieved the highest CO 2 adsorption capacity of 23.33 mg/g at 30 °C and 400 ppm CO 2 , which was significantly higher than unmodified Al 2 O 3 at 3.55 mg/g. The sorbent retained 93.1 % of its initial capacity after 5 adsorption–desorption cycles using nitrogen regeneration at 100 °C. Kinetic evaluation showed that the Avrami fractional-order model best fit the data with R 2 values exceeding 0.99, suggesting a multi-step adsorption mechanism. The Elovich and Weber–Morris models indicated contributions from surface heterogeneity and intra-particle diffusion. The activation energy of 1.74 kilojoules per mole reflected minimal kinetic resistance. These findings demonstrate that MEA-functionalized Al₂O₃ exhibits high adsorption capacity, good stability, and favorable kinetics under DAC-relevant conditions. The study provides a mechanistic foundation and practical guidance for designing solid sorbents for scalable atmospheric CO₂ capture.
Publication details
- Authors: Nokpho, P., Sawatrot, D., Wongphaisal, N., Phianchana, K., Korkerd, K., Wang, X., Piumsomboon, P., Chalermsinsuwan, B.
- Published in: (2025) Results in Engineering, 26, pp. 105140.
- Year: 2025
- DOI: 10.1016/j.rineng.2025.105140
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