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چکیده
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Objective: This study investigates the effect of titanium dioxide (TiO₂) nanoparticles as performance enhancers for CO₂ absorption in an aqueous monoethanolamine (MEA) solution using a microreactor system. Materials and Methods: CO₂ absorption experiments were conducted in a T-shaped microreactor with an inner diameter of 800 μm and a length of 25 cm under atmospheric pressure, using a gas feed containing 10 mol% CO₂. The main operating parameters included temperature, solvent flow rate, gas flow rate, inlet solvent concentration (5 and 10 vol% MEA), and metal-oxide nanoparticle concentrations (0.01, 0.05, and 0.1 wt%). Results: Under the optimal operating conditions (25 °C, solvent flow rate of 200 ml/hr, and gas flow rate of 100 ml/min), the CO₂ absorption efficiencies of aqueous MEA solutions at 5 and 10 vol% were 75.6% and 84.8%, respectively. Under the same conditions, the absorption efficiencies obtained using MEA-based nanofluids (5 vol% MEA) containing 0.01, 0.05, and 0.1 wt% TiO₂ nanoparticles were 80.2%, 92.1%, and 94.2%, respectively. For nanofluids prepared with 10 vol% MEA, the corresponding efficiencies were 73.5%, 87.3%, and 92.1%. The optimal nanofluid consisted of 5 vol% MEA with 0.05 wt% TiO₂, achieving a CO₂ absorption efficiency of 92.1%, corresponding to a 16.5% improvement over the base solvent without nanoparticles. FESEM images and zeta-potential results confirmed a uniform dispersion of TiO₂ nanoparticles with no significant agglomeration. The presence of active hydroxyl groups in the FTIR spectra and a zeta potential of +16.1 mV indicated moderate and sufficient stability of the nanofluid during the experiments. Visual observations over a 12-hour period also confirmed stable and homogeneous dispersion. Conclusion: The findings indicate that adding small amounts of TiO₂ nanoparticles enhances the CO₂ absorption performance of 5 vol% MEA solutions. In contrast, a reduction in absorption efficiency was observed in 10 vol% MEA due to the higher surface tension of the base solvent. This adverse effect was mitigated at higher nanoparticle loadings (0.05 and 0.1 wt%), where TiO₂ nanoparticles improved CO₂ absorption in both 5 vol% and 10 vol% MEA solutions.
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