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AN ELECTROCHEMICAL SYSTEM FOR REMOVING AND RECOVERING ELEMENTAL MERCURY FROM FLUE-STACK GASES
Bolger**, P. T. AND D C. Szlag*. AN ELECTROCHEMICAL SYSTEM FOR REMOVING AND RECOVERING ELEMENTAL MERCURY FROM FLUE-STACK GASES. 10.1021/es015838g, ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 36(20):4430-4435, (2002).
the impending EPA regulations on the control of mercury emissions from the flue stacks of coal-burning electric utilities has resulted in heightened interest in the development of advanced mercury control technologies such as sorbent injection and in-situ mercury oxidation. Although these technologies can effectively remove mercury from a flue stack, they share, along with many other control technologies, the common shortcoming of inter-media pollution transfer, i.e., the traffic of mercury from the air phase to the solid phase and the subsequent generation of hazardous waste. This work addresses the need for a total system of mercury removal and recovery from coal-utility flue stacks and from the environment. The research explores the capture of elemental mercury from the gas phase on an electrically conductive porous sorbent. The sorbent is then transferred to, and made the anode in, an electrochemical cell and the adsorbed elemental mercury is oxidized to mercury(II) which can be recaptured at the cathode as solid elemental mercury: in this manner the sorbent is regenerated and the mercury recovered. Activated carbon cloth was selected as the most suitable sorbent as it had the highest mercury adsorption capacity of the sorbents tested and is electrically conductive. It is shown that it is possible to remove >95% of the elemental mercury from a carbon cloth by direct electro-oxidation and all of the mercury from a cloth by indirect electro-oxidation. This preliminary research demonstrates that activated carbon cloth has the potential to be a simple, cost-effectiv "drop-in" technology for the control of mercury emissions in coal-fired utility plants.