Mechanism of selenium sorption by activated carbon

Selenium, along with mercury and halides, represents one of the most volatile trace metallic emissions from coal-fired combustors and utility boilers. This study investigates the potential of activated carbon in capturing gas phase selenium species in the low temperature range (125 degrees C to 250 degrees C) and elucidates the mechanism of interaction between selenium species and activated carbon, Selenium dioxide is chosen as the representative selenium species and experimental investigations are carried out in a differential bed reactor to illustrate the mechanism of SeO2 and carbon interaction. Activated carbons with different structural properties are studied as adsorbents for selenium dioxide capture at law temperature. The capture mechanism Is found to involve both physical and chemical adsorption in the low temperature range, At 125 degrees C, about 1.5 wt% of selenium is captured at equilibrium. Carbon surface analyses and XPS studies confirm the presence of both elemental and oxide forms of selenium on the surface suggesting partial reduction of selenium dioxide to elemental selenium at carbon surface.