Adsorption mechanism of As2O3 on metal oxides (CaO, γ-Al2O3, α-Fe2O3): A density functional theory study

Arsenic (mainly As2O3) removal is one of the key concerns in the ultra-clean emissions of coal-fired flue gas. Facing the no consensus on the adsorption mechanism of As2O3 on typical metal oxides (CaO, gamma-Al2O3 and alpha-Fe2O3) and the influence mechanism of SO2 on that, this work adopted the DFT calculation to conduct the systematic study from multiple perspectives, including adsorption energy, EDD, PDOS, Gibbs free energy and FMO. The results show As2O3 adsorption on CaO (0 0 1), gamma-Al2O3 (0 0 1) and alpha-Fe2O3 (0 0 1) surface are mainly chemisorption, where that on CaO (0 0 1) surface is strongest. The adsorption ability of the metal oxides to As2O3 under 0-1173.15 K satisfies CaO (0 0 1) > gamma-Al2O3 (0 0 1) > alpha-Fe2O3 (0 0 1). SO2 competes with As2O3 for adsorption active sites, and that on CaO is greater than alpha-Fe2O3 (0 0 1) and gamma-Al2O3 (0 0 1). The newly formed adsorption sites are less active for As2O3 adsorption after SO2 adsorbed on the three metal oxides surfaces. The gamma-Al2O3 (0 0 1) and alpha-Fe2O3 (0 0 1) surface with pre-adsorbed SO2 decreases the stability of hexahedral As2O3, which benefits for the adsorption occurrence.