Lower desorption temperature in CO ₂ capture using various magnesium oxide loading on iron(III) oxide by ultrasonic-assisted synthesis: the adsorption-desorption and isotherm studies

This study introduces a novel approach to CO₂ capture using the ultrasonic-assisted wet impregnation technique with various MgO loadings on Fe₂O₃. This method allows for enhanced dispersion of MgO particles, leading to improved adsorption and desorption characteristics. The characterization was conducted using XRD, N₂ adsorption-desorption isotherms and FESEM. CO₂ adsorption isotherm at 25 °C and TPD-CO₂ were applied to obtain the CO₂ capture activities. The linearized form of adsorption isotherm model was fitted to the experimental data from the CO₂ adsorption isotherm at 25 °C. The most effective adsorbent is 20MgO/Fe₂O₃ with 20 wt% dopant loading which has an adsorption capacity of 3.83 and 56.99 mg/g for physisorption and chemisorption, respectively. It has the highest pore size distribution at 80–150 nm among MgO/Fe₂O₃ series adsorbents. This discrepancy is ascribed to a good distribution of the MgO particle on the Fe₂O₃ surfaces and the pores generated on the MgO surfaces. XRD revealed a greater peak shift to a higher angle of 2θ for the (104) plane starting from 20MgO/Fe₂O₃. This shows that the Fe³⁺ ion in the Fe₂O₃ structure has been successfully replaced by a smaller ion radius of Mg²⁺ and the ion was successfully incorporated into the Fe₂O₃ as a substitutional atom. The Freundlich isotherm model fit the best with the experimental data suggesting that the heterogeneity surface facilitated a successful multilayer adsorption process. The novelty of this work lies in the ability to enhance CO₂ adsorption efficiency while lowering the desorption temperature, offering a practical CO₂ capture applications.