Experimental and Density Functional Theory Study of the Adsorption Characteristics of CaO for SeO2 in Simulated Flue Gas and the Effect of CO2

Coal-fired power plants have been identified as a major source of selenium emissions that can be controlled by mineral adsorption. The adsorption capacity of CaO for SeO2 adsorption was studied in a simulated flue gas atmosphere, and the amounts of SeO2 absorbed by CaO before and after high-temperature roasting were experimentally evaluated and compared. To explain the effect of CO2 on the adsorption of SeO2, the effect of preadsorbed CO2 on SeO2 adsorption by CaO was investigated by density functional theory calculations. The experimental results showed that the adsorption capacity reached the maximum at 700 degrees C, while the adsorption capacity decreased gradually for temperatures higher than 700 degrees C. CO2 in the simulated flue gas caused the carbonation reaction on the surface of CaO, leading to the inhibition of SeO2 adsorption by CaO. The computational results indicated that SeO2 and CO2 adsorb on the CaO surface by chemisorption, with the O atoms on the CaO(001) surface as the adsorption active sites. Not only did CO2 occupy the active sites on the surface but also the interaction between the Se atom and the O atom of CO2 was found to be weaker than that between the Se atom and the O atom on a clean CaO surface.