Abstract: Elemental mercury capture on heat-treated activated carbon (TAC) was studied using a laboratory-scale fixed bed reactor. The capability of TAC to perform Hg⁰ capture under both N₂ and baseline gas atmospheres was studied and the effects of common acid gas constituents were evaluated individually to avoid complications resulting from the coexistence of multiple components. The results suggest that surface functional groups (SFGs) on activated carbon (AC) are vital to Hg⁰ capture in the absence of acid gases. Meanwhile, the presence of acid gas components coupled with defective graphitic lattices on TAC plays an important role in effective Hg⁰ capture. The presence of HCl, NO₂, and NO individually in basic gases markedly enhances Hg⁰ capture on TAC due to the heterogeneous oxidation of Hg⁰ on acidic sites created on the carbon surface and catalysis by the defective graphitic lattices on TAC. Similarly, the presence of SO₂ improves Hg⁰ capture by about 20%. This improvement likely results from the deposition of sulfur groups on the AC surface and oxidation of the elemental mercury by SO₂ due to catalysis on the carbon surface. Furthermore, O₂ exhibits a synergistic effect on Hg⁰ oxidation and capture when acid gases are present in the flue gases.

Key words: Flue gases, Mercury, Activated carbon (AC)

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