Effect of NaNO3 on MgO–CaCO3 Absorbent for CO2 Capture at Warm Temperature

The effect of NaNO 3 on the activation of MgCO 3 –CaCO 3 double salts to form a MgO–CaCO 3 absorbent and the cyclic CO 2 absorption ability of the obtained absorbent have been investigated to analyze the affecting mechanism of NaNO 3 . The MgCO 3 –CaCO 3 double salts were prepared by two methods: coprecipitation of Mg(NO 3 ) 2, Ca(NO 3 ) 2, and Na 2 CO 3 and modification of dolomite by NaNO 3 . The results indicate that NaNO 3 has an obvious effect on lowering the activation temperature of the MgCO 3 –CaCO 3 double salts, and NaNO 3 is the key component in facilitating the CO 2 absorption by the MgO–CaCO 3 absorbent. The affecting mechanism has also been analyzed using X-ray diffraction characterization, particle diameter distribution analysis, Brunauer–Emmett–Teller analysis, and the scanning electron microscopy characterization of the absorbents. The results indicate that the molten NaNO 3 facilitates the decomposition of MgCO 3 in MgCO 3 –CaCO 3 double salts, affects the crystal lattice of the activated absorbents, and favors the CO 2 absorption by improving the ion diffusion in the absorbent.