DFT and Experimental Study on the Mechanism of Elemental Mercury Capture in the Presence of HCl on α-Fe2O3(001)

To investigate the mechanism of Hg-0 adsorption on the alpha-Fe2O3(001) surface in the presence of HCl, which is considered to be beneficial for Hg-0 removal, theoretical calculations based on density functional theory as well as corresponding experiments are carried out. HCl adsorption is first performed on the alpha-Fe2O3(001) surface, and the He adsorption on HCl-adsorbed alpha-Fe2O3(001) surface is subsequently researched, demonstrating that HCl dissociates on the surface of alpha-Fe2O3, improving the Hg-0 adsorption reactivity. With further chlorination of the alpha-Fe2O3(001) surface, FeCl3 can be achieved and the adsorption energy of Hg-0 on the FeCl3 surface reaches -104.2 kJ/mol, representing strong chemisorption. Meanwhile, a group of designed experiments, including Hg-0 adsorption on HCl-preadsorbed alpha-Fe2O3 as well as the coadsorption of both gaseous components, are respectively performed to explore the pathways of Hg transformation. Combining computational and experimental results together, the Eley-Rideal mechanism with HCl preadsorption can be determined. In addition, subsequent X-ray photoelectron spectroscopy analysis verifies the appearance of Cl species and oxidized mercury, exhibiting the consistency with experiments.