Abstract: The calcination of kaolinite at 700°C for 2h produced reactive metakaolin, which, upon leaching with 4M H2SO4, followed by precipitation as aluminium hydroxide and calcination, resulted in activated alumina. To enhance the performance of CO2 capture, the alumina was functionalized with monoethanolamine (MEA), triethanolamine (TEA), and a combined MEA-TEA system. X-ray diffraction confirmed the transformation of crystalline kaolinite to amorphous metakaolin and the formation of y-alumina and zeolitic phases after amine modification. TEA-functionalized alumina exhibited the highest crystallinity. SEM/EDX analyses showed increased surface roughness, particle agglomeration, and successful incorporation of amine species. FTIR spectra identified Al-O, N-H, and C-N functional groups and carbonate species after CO2 adsorption. CO2 uptake was volumetrically measured at ambient conditions in a flue gas adsorption setup. Among all the samples, TEA-functionalized alumina exhibited the highest adsorption capacity (135mg g-1), outperforming MEA-functionalized (110mg g-¹) and unmodified alumina (102mg g1-), whereas the combined MEA-TEA system exhibited poor performance. The adsorption data fitted well to Langmuir, Freundlich, and Temkin models, with a maximum Langmuir capacity of 312.5mg g-¹. The kinetics showed a fast rate and attained equilibrium within 8-10min, showing the material's suitability for practical CO2 capture applications.
