Density functional theory study on the heterogeneous reaction between Hg0 and HCl over spinel-type MnFe2O4

- Hg0 oxidation by HCl on MnFe2O4 sorbent was investigated using DFT method.
- HgCl and HgCl2 are adsorbed on MnFe2O4 surface in the chemisorption manner.
- Hg0 oxidation by HCl over MnFe2O4 follows the Langmuir-Hinshelwood mechanism.
- The first step (Hg0 → HgCl) is the rate-determining step of mercury oxidation.

Magnetic manganese ferrite (MnFe2O4) with spinel structure has received considerable attention for its potential application in gaseous pollutants removal because of its surface redox reactivity properties. Density functional theory (DFT) calculations were performed to investigate heterogeneous mercury oxidation by HCl over MnFe2O4 surface. The results indicate that Hg0 is chemically adsorbed on MnFe2O4 (1 0 0) surface with an adsorption energy of −60.82 kJ/mol. HCl can decompose on MnFe2O4 surface to form active surface chlorine species for mercury oxidation. Both intermediate (HgCl) and final (HgCl2) products are adsorbed on MnFe2O4 (1 0 0) surface in a dissociative adsorption manner. Hg0 oxidation by HCl over MnFe2O4 surface follows the Langmuir-Hinshelwood mechanism in which a bimolecular reaction occurs between adsorbed Hg0 and active surface chlorine species. The mercury oxidation process over MnFe2O4 surface was investigated by examining the energy profile of reaction pathway. Heterogeneous Hg0 oxidation by HCl occurs through a two-step reaction pathway (Hg0 → HgCl → HgCl2) in which the first step (Hg0 → HgCl) is the rate-determining step.