Adsorption mechanism of elemental mercury (Hg0)) on the surface of MnCl2 (110) studied by Density Functional Theory

The objective of this research is to reveal the mechanism of effective and inexpensive sorbent MnCl2 for elemental mercury (Hg-0) removal from the flue gas. The adsorption behavior of Hg-0 on MnCl2 (11 0) surface was investigated theoretically using Density Functional Theory. The geometry optimization and adsorption energy of Hg-0 on MnCl2 surface were calculated by generalized gradient approximation with Perdew Burke Emzerh functional (GGA/PBE) and DNP basis. Results showed that He adsorption on MnCl2 (1 1 0) surface is chemisorption with adsorption energy of -156.620 kJ/mol. According to Hirshfeld charge analysis, Hg-0 has active interaction with Cl atoms (CI-12, CI-32, CI-44) and Mn-40 atom on MnCl2 (110) surface. The partial density of states (PDOS) analysis further reveals that p- and d-orbitals of Cl atoms strongly hybridize with s- and d-orbitals of Hg-0 atom. The d-orbital of Mn-40 also has essential interaction with Hg-0 atom. Both of them contribute to the stable adsorption system of Hg-0 MnCl2. The equilibrium constant decreases with the increase of temperature, which coincides with data for exothermic adsorption system. For the first time, this study investigated the mechanism of Hg-0 adsorption on metal chloride surface using DFT method. It provides a significance theoretical support for metal chloride application in Hg-0 adsorption and removal. The results obtained in this research are in good agreement with previous experiment. This method can be used to reveal Hg-0 capture mechanism in some complex systems. (C) 2015 Elsevier B.V. All rights reserved.