Enhancing CO2 absorption using nanofluids a combined experimental and machine learning approach

Abstract

Carbon dioxide (CO2) is a major greenhouse gas contributing to global warming. In response to international climate goals, including net-zero emission targets by 2035, efficient CO2 capture technologies are critical. This research investigates the use of nanofluids to enhance CO2 absorption and develops a machine learning model for accurate prediction of absorption capacity. Nanoparticles were characterized using Scanning Electron Microscopy (SEM) to determine their size and morphology. Nanofluids were prepared using deionized (DI) water as the basefluid and nanoparticles of ZnO, TiO2, SiO2, Fe2O3, Al2O3, and MWCNT. Experiments were conducted using a custom-fabricated stainless steel 316L absorption cell, based on the direct contact absorption method. Nanofluid concentrations of 0.03, 0.06, 0.09, and 0.12 wt% were tested under initial CO2 pressures of 5, 7.5 and 10 bar. The effects of nanoparticle type, concentration, and pressure on CO2 absorption were evaluated. Results showed a clear enhancement in absorption with the use of nanofluids. An increase in the concentration of nanofluid, enhances the CO2 absorption capacity. However, there exists optimum concentration, any increase further, decreases the absorption capacity. The optimum concentrations were found to be: 0.09 wt% for TiO2 and SiO2, 0.06 wt% for ZnO and Fe2O3. The best CO2 absorption performance was found at 0.12 wt% for Al2O3 nanofluid and 0.03 wt% for MWCNT nanofluid among the tested concentrations. From the results, it was found that there was an increase of 8.07%, 14.23% and 17.21 % at 5, 7.5 and 10 bar initial pressure, respectively for Al2O3 nanofluid at 0.12 wt%, an increase of 10.3%, 18.67% and 13.61% at 5, 7.5 and 10 bar initial pressure respectively for SiO2 nanofluid at 0.09 wt%, an increase of 17.84%, 23.9% and 25.85% at 5, 7.5 and 10 bar initial pressure respectively for TiO2 nanofluid 0.09 wt%, an increase of 17.9%, 20.98% and 25.4% at 5, 7.5 and 10 bar initial pressure respectively for ZnO nanofluid at 0.06 wt%, an increase of 21.03%...