Research on the removal of As₂O₃ by γ-Al₂O₃ adsorption based on density functional theory

In order to protect selective catalytic reduction (SCR) catalysts for flue gas denitration in coal-fired power plants, the adsorption of As₂O₃ on γ-Al₂O₃(0 0 1) surface is investigated theoretically through density functional theory (DFT) in this study. The adsorption sites, adsorption structures, adsorption energies, electronic clouds, transition processes, and intermediate and transition structures are investigated. The theoretical results indicate that the adsorption of As₂O₃ molecule on the surface of γ-Al₂O₃(0 0 1) could be either physical or chemical, depending on the sites the molecule hangs over. Compared with the experimental results from other researchers, this study unveils that, although the apparent adsorption of As₂O₃ molecule on γ-Al₂O₃(0 0 1) surface is physical, some of the sites on γ-Al₂O₃(0 0 1) surface presents strong chemical affinity towards As₂O₃ adsorption. Further, this study depicts the adsorption process to clarify the reason of the net effect of As₂O₃ adsorption on γ-Al₂O₃ being physical. Meanwhile, the study also reveals that apparent physical adsorption of As₂O₃ on γ-Al₂O₃(0 0 1) surface is due to the high energy barrier that prohibits the transformation of physical adsorption to chemical adsorption. The research results provide useful information for exploiting γ-Al₂O₃ as a potential metal oxides sorbent.