Rational design of amine-functionalized Al2O3 sorbents for direct air capture: Mechanistic insights and performance evaluation
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Author list: Nokpho P.; Sawatrot D.; Wongphaisal N.; Phianchana K.; Korkerd K.; Wang X.; Piumsomboon P.; Chalermsinsuwan B.
Publisher: Elsevier
Publication year: 2025
Volume number: 26
ISSN: 2590-1230
eISSN: 2590-1230
Languages: English-Great Britain (EN-GB)
Abstract
Amine-functionalized alumina adsorbents offer a promising solution for direct air capture (DAC) of CO2, 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 CO2 capture efficiency, kinetics, and cyclic stability. The MEA-modified sorbent with 50 wt% loading achieved the highest CO2 adsorption capacity of 23.33 mg/g at 30 °C and 400 ppm CO2, which was significantly higher than unmodified Al2O3 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 R2 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. © 2025 The Authors
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