Enhanced CO₂ Capture Using TiO₂ Nanoparticle-Functionalized Solvent: A Study on Absorption Experiments

The growing amount of carbon dioxide (CO₂) in the atmosphere significantly contributes to global warming and climate change. This study focuses on the use of aqueous potassium carbonate (K₂CO₃) solutions as a solvent for CO₂ absorption, emphasizing the role of titanium dioxide (TiO₂) nanoparticles in enhancing performance. A detailed understanding of reaction kinetics and the dynamic behavior of the absorber is crucial for optimizing the process. However, critical parameters such as the rate constant k_OH of the reaction between CO₂ and OH^- in K₂CO₃ solutions are rarely found in existing studies. This work investigates the kinetics of CO₂ absorption in 25 wt% K₂CO₃ solutions at three temperatures (40, 55, and 70 °C), varying concentrations of TiO₂ nanoparticles to identify optimal conditions. Reaction rates were measured in a stirred cell reactor, and the data were interpreted using Danckwerts theory. The results revealed a notable improvement in absorption efficiency with the addition of nanoparticles, and the study also pinpointed optimal operational parameters to prevent sedimentation issues. The presence of TiO₂ nanoparticles was found to enhance the solution's physical properties, such as diffusivity and surface tension, which facilitated an improved mass transfer. The best performance was achieved with a TiO₂ concentration of 0.06 wt% at 70 °C, leading to an increase of diffusivity value equal to 1.5 times and, as a consequence, the same increase has been observed for the overall reaction rate. In contrast, higher or lower concentrations negatively impacted efficiency due to poor dispersion or nanoparticle agglomeration. These results provide practical insights for developing more efficient and sustainable CO₂ capture methods, contributing to solutions for the climate crisis.