Effect of CO_2 in Flue Gas on Arsenic Adsorption over a Carbonaceous Surface

摘要

The density functional theory was employed to study the effect mechanism of CO2 on arsenic adsorption by a carbonaceous surface. Geometry optimization and frequency calculation of each structure were calculated by B3LYP-D3/631G(d), and the single-point energy of each structure was obtained by B3LYP-D3/6-311+G(d,p). Results show that, when As and As2O3 were absorbed on the carbonaceous surface, the adsorption energies were in the range from -526.96 to -463.17 kJ/mol for As and from -24.19 to -11.09 kJ/mol for As2O3. It shows that the carbonaceous surface has a chemical adsorption for As and physical absorption for As2O3. In the presence of CO2, the absorption energies decrease, which shows that CO2 plays a positive impact on As and As2O3 adsorption by the carbonaceous surface. By electrostatic potential analysis, it can be concluded that CO2 absorbed on the carbonaceous surface enhances active sites and, thus, improves the adsorption capacity of the carbonaceous surface for As and As2O3. Results show that electrostatic potential is a reliable tool to analyze the strength and orientation of the adsorption reaction, which can be well-predicted and explained by analyzing the magnitude and positions of extrema on the surface. The calculation results clarify the effect of CO2 on arsenic adsorption by the carbonaceous surface and provide theoretical foundation for the emission and control of arsenic.