Simultaneous control of elemental mercury/sulfur dioxide/nitrogen monoxide from coal-fired flue gases with metal oxide-impregnated activated carbon

This 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 MnO_x and CuO_x/CAC samples, respectively. CuO_x/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 CuO_x/CAC. The VO_x/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.