Mn-Based catalysts with a Mn loading of 4 wt% were prepared using an impregnation method. Their Hg-0 removal efficiencies were in the following order: 4% Mn/MK10 (montmorillonite K 10) > 4% Mn/SiO2 > 4% Mn/TiO2 > 4% Mn/Al2O3. Results from various characterization techniques, such as BET, XRD, STEM, H-2-TPR, Hg-0-TPD and XPS, suggested that the species, morphologies, and distributions of MnOx led to the different performances in Hg-0 removal. The support effect on Hg-0 adsorption and oxidation was studied. For 4% Mn/Al2O3 and 4% Mn/SiO2, physical adsorption dominates Hg-0 removal at low temperature (150 degrees C), while chemical adsorption is more important at high temperature (350 degrees C). At both low and high temperatures, chemical adsorption and oxidation play leading roles in 4% Mn/TiO2 and 4% Mn/MK10, respectively. The effect of MnOx species and their morphologies on Hg-0 oxidation was investigated. Amorphous MnO2 benefits Hg-0 oxidation at both low and high temperatures, while amorphous Mn2O3 only facilitates Hg-0 oxidation at high temperature. Hg-0 oxidation on Mn-based catalysts follows a Mars-Maessen mechanism where the lattice oxygen of MnOx reacts with the absorbed Hg-0.