Elemental mercury (Hg0) removal over spinel LiMn2O4 from coal-fired flue gas

Spinel LiMn2O4 was prepared using a sol-gel method to investigate gaseous elemental mercury (Hg-0) removal performance from coal-fired power plants. The physical and chemical characterization results indicated that LiMn2O4 had a basic MnO6 unit and Li ions in the spinel lambda-MnO2 structure. LiMn2O4 exhibited better Hg removal performance than that of pure Mn2O3 and mixed oxides of Li2O-Mn2O3. Hg-0 removal efficiency of LiMn2O4 was 93.09% (600 min reaction) at an optimum temperature of 150 degrees C. Higher temperature (>200 degrees C) was not favorable for Hg-0 removal. O-2 enhanced the Hg-0 removal efficiency of LiMn2O4, while SO2 and H2O inhibited the reaction, and the co-existence of them had a poison effect on Hg-0 removal. The primary Hg-0 removal mechanism was chemical-adsorption, Hg-0 was firstly catalytic oxidized to Hg2+ along with the reduction of high valance of Mn (Mn4+/Mn3+) to low valance (Mn3+/Mn2+). Hg2+ was combined with adsorbed oxygen and existed as Hg-O on LiMn2O4 surface. The existence of Li ions constructs a lambda-MnO2 structure and benefits the oxidation process. Furthermore, based on the Hg-TPD results, the desorption activation energy was 58.82 kJ/mol. (C) 2016 Elsevier B.V. All rights reserved.