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 α-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 α-Fe2O3(001) surface, and the Hg(0) adsorption on HCl-adsorbed α-Fe2O3(001) surface is subsequently researched, demonstrating that HCl dissociates on the surface of α-Fe2O3, improving the Hg(0) adsorption reactivity. With further chlorination of the α-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 α-Fe2O3 as well as the coadsorption of both gaseous components, are respectively performed to explore the pathways of Hg(0) 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.