Design of 3D MnO 2 /Carbon sphere composite for the catalytic oxidation and adsorption of elemental mercury.

Three-dimensional (3D) MnO2 /Carbon Sphere (MnO2 /CS) composite was synthesized from zero-dimensional carbon spheres and one-dimensional α-MnO2 using hydrothermal method. The hierarchical MnO2 /CS composite was applied for the catalytic oxidation and adsorption of elemental mercury (Hg0 ) from coal-fired flue gas. The characterization results indicated that this composite exhibits a 3D urchin morphology. Carbon spheres act as the core and α-MnO2 nano-rods grew on the surface of carbon spheres. This 3D hierarchical structure benefits the enlargement of surface areas and pore volumes. Hg0 removal experimental results indicated that the MnO2 /CS composite has an outstanding Hg0 removal performance due to the higher catalytic oxidation and adsorption performance. MnO2 /CS composite had higher than 99% Hg0 removal efficiency even after 600min reaction. In addition, the nano-sized MnO2 /CS composite exhibited better SO2 resistance than pure α-MnO2 . Moreover, the Hg-TPD results indicated that the adsorbed mercury can release from the surface of MnO2 /CS using a thermal decomposition method.