Effect of the properties of MnOx/activated carbon and flue gas components on Hg0 removal at low temperature

Abstract

Manganese oxide loaded on activated carbon (Mn/AC) was synthesized using an impregnation method, and its capacity for Hg⁰ removal in simulated flue gas was investigated at 120 °C. The Hg⁰ removal performance was significantly enhanced by manganese oxide. The effects of the Mn loading on Hg⁰ removal were evaluated. X-ray diffraction (XRD) and Brunauer–Emmett–Teller (BET) were employed to characterize the samples. In addition, the effects of individual flue gas components, including SO₂, NO and HCl, on the Hg⁰ removal performance over the Mn/AC sorbent were investigated. The results indicated that 10% Mn/AC was the optimal sorbent under the simulated flue gas conditions. The XRD and BET analyses indicated that the Mn₃O₄ crystal particles and surface area were the primary factors that contributed to Hg⁰ removal. The competitive adsorption and formation of Mn(SO₄)_x were the primary reasons that SO₂ inhibits Hg⁰ removal. In a pure N₂ atmosphere, a low concentration of NO decreased the Hg⁰ removal due to consumption of active oxygen species. However, a high concentration of NO promoted Hg⁰ removal due to the formation of N-containing active species that were generated on the sample surface. The Mn/AC sample remained highly active toward Hg⁰ removal in the presence of HCl due to reaction with active chlorine species.