Nickel and iron impregnated alkali-modified fly ash nanoparticle for improved CO2 capture performance in MDEA aqueous solutions

The use of amine-based absorbers, such as N -methyldiethanolamine (MDEA), for CO 2 capture presents a promising strategy for emission reduction as global warming intensifies. However, high energy consumption and limited absorption/desorption efficiencies constrain its application. To address these challenges, this study developed a composite catalyst derived from fly ash (FA), which is alkali-modified and incorporates nickel (Ni) and iron (Fe) elements, with the aim of enhancing CO 2 absorption and desorption performance while reducing energy consumption. Experimental results indicated that the Ni/FA-AM catalyst significantly improved adsorption and absorption efficiencies, achieving an 8% increase in capacity, a 63% increase in peak adsorption rate, and a reduction of 6000 seconds in saturation time. Studies conducted in a wetted-wall column revealed that the absorption process predominantly occurs in the liquid phase. Additionally, the catalyst demonstrated a 19% improvement in desorption performance, a 10% increase in peak desorption rate, and a 24% reduction in energy consumption, while maintaining stability over five consecutive cycles. The alkali-modified and Ni/Fe-enriched fly ash was confirmed to form active acid-base sites, facilitating the formation and disappearance of bicarbonate, thereby enhancing CO 2 capture efficiency. This was validated through XRD, BET, TPD, PY-IR, TEM, and FT-IR with 13 C NMR characterization. This study highlights the potential of modified fly ash as a low-cost and efficient catalyst for CO 2 capture.