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Abstract
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The urgent need to mitigate carbon dioxide (CO2) emissions from fossil fuel utilization has driven the development of more efficient post-combustion capture methods. This study investigates the enhancement of CO2 absorption in fixed-bed columns using diethanolamine (DEA) and methyldiethanolamine (MDEA) solutions containing Fe3O4 and NiO nanoparticles, with and without methanol as a co-solvent. Experiments were conducted under varying nanoparticle concentrations, gas and liquid flow rates, and operating pressures to evaluate separation efficiency, overall volumetric mass transfer coefficients, and operational stability. Results showed that DEA-based solutions exhibited higher removal efficiencies than MDEA due to faster reaction kinetics, while Fe3O4 nanofluids consistently outperformed NiO formulations. An optimal Fe3O4 loading of 0.05 wt% in DEA increased CO2 separation efficiency to 94% and enhanced the overall volumetric mass transfer coefficient by up to 27% compared with the base solvent. Methanol addition yielded absorption improvements of up to 15%, although its effect was strongly dependent on the nanoparticle amine combination.
Enhanced performance was attributed to several nanoscale mechanisms, including Brownian microconvection, the shuttle effect, and improved gas liquid boundary layer disruption, which together reduced diffusion resistance and increased interfacial contact area. The experimental setup demonstrated that increasing liquid flow rate amplified mass transfer by enlarging wetted surfaces and promoting turbulence within the packed column. Overall, the combined use of Fe3O4 nanoparticles and methanol produced the most effective formulation for CO2 absorption. These findings confirm the potential of amine nanofluid systems as scalable, energy efficient candidates for next generation carbon capture technologies.
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