High capacity co-precipitated manganese oxides sorbents for oxidative mercury capture

Removal of flue gas mercury (Hg) from coal-fired power plants continues to be a challenge and the search for improved sorbents is far from over. Manganese oxides supported on zirconium dioxide (MnOx/ZrO2) prepared by a co-precipitation method, were characterised and evaluated for Hg capture. Relationships between surface area, total pore volume, particle size distribution and mercury capture have been investigated. Material with a particle size range of 75-250 μm achieved the greatest Hg breakthrough. Overall, these are greater than those achieved for impregnated activated carbons with higher surface areas (585, 968 and 1014 m2/g). Scanning electron microscopy and energy dispersive X-ray detection (SEM/EDAX) indicates that there is uneven dispersion of MnOx and ZrO2 in the sorbent materials, and two distinctive particle types can be identified - the more porous type, which is 'manganese-rich' (Mn-rich) and the more smooth with cracks type which is 'zirconium-rich' (Zr-rich). Agglomerations of mercury clusters were observed only on the surface of 'Mn-rich' particles, so the conclusion can be drawn that the rate of Hg capture on the particle surface area is dependent on manganese content and distribution.