CO2 capture from ambient air by β-NaFeO2 in the presence of water vapor at 25–100 °C

Abstract

Sodium ferrite (β-NaFeO2) was synthesized by heating raw mixtures of α-Fe2O3 and NaNO3 at 800 °C. The CO2 absorption properties of the synthesized β-NaFeO2 powders were then examined at temperatures of 25–100 °C under an air flow in the presence of water vapor by X-ray diffractometry (XRD), thermogravimetry (TG), and scanning electron microscopy (SEM). XRD results clarified that β-NaFeO2 reacted with CO2 and H2O to produce α-Fe2O3 and Na2CO3⸱H2O. TG results clarified that the absorption rates of CO2 from the air by β-NaFeO2 at 25 and 50 °C were greater than those at 75 and 100 °C and that CO2 absorption was promoted at a higher relative humidity. Thus, adsorption of water vapor onto the surface of β-NaFeO2 promoted CO2 absorption from air. A basic water solution formed at the surface of β-NaFeO2 in the presence of water vapor and this solution rapidly reacted with CO2 at temperatures as low as 25 °C. We also confirmed that β-NaFeO2 could be regenerated and used repeatedly for CO2 absorption in the presence of water vapor at 25 °C.