A deep insight into the role of O2 on As2O3 capture over γ-Al2O3 sorbent: Experimental and DFT study

Adsorption experiments were carried out to investigate the role of O-2 on As2O3 capture by gamma-Al2O3. Results showed that As2O3 retention over gamma-Al2O3 surface was promoted with the O-2 concentration from 0 to 8%. The adsorption process was also enhanced when temperature was increased from 573 K to 1073 K, and As(V) was the primary adsorption products at high temperatures. Furthermore, As2O3 adsorption mechanism was studied through density functional theory (DFT) calculations. Compared to gamma-Al2O3 surface, the O-2/gamma-Al2O3 surface exhibited stronger adsorption ability for As2O3 molecule. In detail, As2O3 adsorption on the ortho-position of adsorbed O-2 involved strong chemical adsorption, indicating that the activities of neighboring atoms were strengthened by adsorbed O-2, which was consistent with the phenomenon from adsorption experiments. Nevertheless, the As2O3 adsorption on the top site of adsorbed O-2 was physical adsorption. Moreover, thermodynamic analysis exhibited that As2O3 adsorption on either gamma-Al2O3 surface or the ortho-position of adsorbed O-2 were chemical adsorption at 573-1073 K. The stability of adsorption system decreased with increasing temperature, and the adsorption geometry would ultimately convert into more stable structures in next reactions. The experimental and simulation results explicate the role of O-2 on As2O3 capture by gamma-Al2O3, and provide a guide for arsenic emission control.