• DEA-based nanofluids enhance CO 2 absorption over conventional solvents. • Optimal Fe 3 O 4 loading of 0.05 wt% achieved 94% CO 2 separation efficiency. • Mass transfer coefficients increased by up to 27% with Fe 3 O 4 /DEA nanofluids. • Methanol co-solvent improved absorption by up to 15%, formulation-dependent. • Nanoscale mechanisms reduced diffusion resistance and enhanced contact area. The urgent need to mitigate carbon dioxide (CO 2 ) emissions from fossil fuel utilization has driven the development of more efficient post-combustion capture methods. This study investigates the enhancement of CO 2 absorption in fixed-bed columns using diethanolamine (DEA) and methyldiethanolamine (MDEA) solutions containing Fe 3 O 4 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 Fe 3 O 4 nanofluids consistently outperformed NiO formulations. An optimal Fe 3 O 4 loading of 0.05 wt% in DEA increased CO 2 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 Fe 3 O 4 nanoparticles and methanol produced the most effective formulation for CO 2 absorption. These findings confirm the potential of amine nanofluid systems as scalable, energy efficient candidates for next generation carbon capture technologies.
Esmaeili et al. (Fri,) studied this question.