Effect of CO2 in flue gas on arsenic adsorption over carbonaceous surface

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-D3/6-31G(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.