A candidate material for mercury control in energy production processes: Carbon foams loaded with gold

Tighter control of pollutant emissions in energy generation from coal combustion is essential for the maintenance of coal as a member of the energy panel in coming years. Coal-fired power plants are the primary source of mercury emission in Europe and the second in the world. This study focuses on the development of regenerable sorbents to mercury capture avoiding the generation of new toxic wastes. The sorbents based on carbon foams impregnated with gold have been optimized to achieve the maximum mercury retention efficiency using the minimum amount of gold. Moreover, the sorbent has been designed to facilitate the recovery of the gold once the sorbent has been exhausted. Although this technology requires a higher initial investment than other alternatives, such as the injection of activated carbons, the apparent high cost of the sorbent is offset by the possibility of using the same material over several cycles. A mercury retention mechanism is proposed based on mercury amalgamation and mercury oxidation/adsorption through the double function of gold and support. The results confirm that the reactions between the mercury and gold depend on the size of the gold nanoparticles and the presence of oxygenated groups on the surface of the carbon support.