Effects of Properties of Activated Carbon on Its Activity for Mercury Removal and Mercury Desorption from Used Activated Carbons

Abstract

Activated carbon (AC) is a promising adsorbent for removing mercury from combustion flue gases. Knowing the effects of the physicochemical properties of AC on its mercury removal rate would help select appropriate AC for mercury removal. We thus evaluated the effect of the physicochemical properties of various ACs on their mercury removal capabilities and the thermal stabilities of mercury compounds generated on used ACs in the present study. The Brunauer–Emmett–Teller (BET) surface area and pore structure of AC had no significant effect on its mercury removal rate, although the ACs used in the present study had a BET surface area of 700–1200 m2/g, large enough for mercury removal. The AC with a high concentration of Fe showed a high mercury removal rate. The surface functional groups had no relationship to the mercury compounds desorbed from the used ACs. More mercury compound species were generated on used fruit shell and coconut ACs (five species) than those generated on bamboo AC (four species) or coal AC (three species). The mercury compounds generated on used coal AC showed relatively lower thermal stabilities than those generated from other ACs, indicating that coal AC was easier to regenerate and that the mercury compounds generated on used coal AC could be recycled at lower temperatures.