Amine-Functionalized and KOH-Activated Metakaolin for CO₂ Capture: Surface Engineering, Kinetics, and Regeneration

Authors: Udochukwu, E.C.

DOI Info: http://doi.org/10.5281/zenodo.18061379

ABSTRACT

This work presents a systematic evaluation of metakaolin-based sorbents modified via KOH activation and amine functionalization for low-concentration CO₂ capture. The materials were engineered to enhance surface area, pore architecture, and functional group density, enabling effective adsorption under realistic post-combustion and ambient conditions. Adsorption kinetics showed that KOH-activated metakaolin followed pseudo-first-order behaviour, indicating physisorption, whereas amine-functionalized samples aligned with pseudo-second-order kinetics, reflective of chemisorptive interactions. Under 1000 ppm CO₂, the KOH-activated variant exhibited a maximum uptake of 1.42 mmol·g^-1, outperforming raw and amine-grafted counterparts. In humid environments of 65 % RH, the amine-functionalized sample improved uptake by 22 %, reaching 1.06 mmol·g^-1, demonstrating strong affinity in moisture-rich conditions. Both sorbents displayed over 88% capacity retention after five regeneration cycles at 100 ^oC, confirming low-energy desorption and structural resilience. These findings position metakaolin as a scalable, cost-effective, and dual-mode sorbent platform for carbon capture applications, particularly in decentralized or humid operational settings.

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