The amine-functionalized alumina captures CO2 directly from the ambient air in the rotating adsorption bed

Global warming presents formidable challenges, prompting the exploration of Direct Air Capture (DAC) as a promising solution. This study employed the ultrasonic impregnation method to load polyethyleneimine (PEI) onto cost-effective millimeter-sized spherical gamma-Al2O3 microspheres, thereby preparing an efficient aminemodified adsorbent. Characterization reveals a uniform dispersion of PEI, resulting in an adsorbent with an effective pore structure, enhancing CO2 diffusion. The adsorption experiment combines DAC with high gravity technology, best conditions at a PEI load of 16.37%, high gravity factor of 2.67, and gas flow rate of 30 L/min. Under these conditions, an impressive adsorption capacity of 41.75 mg/g was achieved, marking an increase of 12.11 mg/g compared to the traditional fixed-bed method. The amine efficiency also reaches 0.25. The Freundlich model outperforms the Langmuir model in fitting isotherm curves, suggesting that the experimental data align with the characteristics of a heterogeneous surface and multilayer adsorption. The fitting results of kinetic models further show that RAB's adsorption rate constant has a significantly better fitting value compared to traditional fixed bed methods. The research provides valuable insights for the application and development of DAC technology, enabling new possibilities for future carbon capture and emission reduction efforts.