Abstract
ABSTRACTThis research investigated the effects of transition metal oxide impregnation on the physical/chemical properties and on the multipollutant (i.e., Hg0/SO2/NO) control of a commercial coconut shell-based activated carbon. V, Mn, and Cu oxides of 5 wt% as their precursor metal hydroxides were impregnated onto the activated carbon surface. After the transition metal oxide impregnation, the surface area and pore volume of activated carbon decreased. The surface morphology of activated carbons was similar prior to and after impregnation. Mn3+/Mn4+ and Cu+/Cu2+ were shown to be the major valence states presenting in the MnOx and CuOx/CAC samples, respectively. CuOx/CAC possessed the greatest Hg0 removal efficiency of approximately 54.5% under N2 condition and 98.9% under flue gas condition, respectively at 150°C. When the gas temperature increased to 350°C, the metal oxide-impregnated activated carbon still possessed appreciable Hg0 removal, especially for CuOx/CAC. The VOx/CAC had the largest SO2 removal enhancement of approximately 28.3% at 350°C. The NO removal of raw and impregnated activated carbon was very small under flue gas condition, indicating that adsorption of NO using metal oxide-impregnated activated carbon may not be a suitable route for NO control.
Highlights
Mercury (Hg) is a global pollutant, highly harmful to human, animals, and plants
The NO removal enhancement of metal oxide-impregnated activated carbons is still very small under flue gas condition, indicating that adsorption of NO may not be a suitable route for NO control; NO reduction on the activated carbon at 350°C unlikely occurred to enhance NO removal
This study provided understandings on the effects of transition metal oxide (V/Mn/Cu) impregnation on the physicochemical properties and multipollutant Hg0/SO2/ NO control of a highly microporous activated carbon
Summary
Mercury (Hg) is a global pollutant, highly harmful to human, animals, and plants. Hg emission from coal-fired power plants (CFPPs) has aroused the greatest concern to the public due to its unique physicochemical properties, high toxicity, long retention time in the environment, and potentially adverse effects on the ecosystem. The three stable forms of Hg in the coal-fired flue gas: elemental (Hg0), oxidized (Hg2+) and particulate-bound (Hgp) govern the fate of this species (Yan et al, 2005; Granite et al, 2006; Li et al, 2012). The Hg2+ and Hgp can be successfully removed with the existing air pollution control devices (APCD) in CFPPs. Hg2+ can be removed by wet flue gas desulfurization because Hg2+ is highly soluble in water. Low-level Hg0 in CFPP flue gases is very difficult to remove
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