Removal of elemental mercury from flue gas using the magnetic attapulgite by Mn-Cu oxides modification

Mercury pollution has become one of the most concerned environmental issues in the world because of its high toxicity, non-degradability, and bioaccumulation. Attapulgite adsorbents modified by magnetic manganese-copper (Mn_xCu_y-MATP) were fabricated by co-precipitation and ultrasonic impregnation method, aiming at removing Hg⁰ from coal-fired flue gas. BET, SEM, XRD, VSM, and XPS were used to systematically explore the physical and chemical properties of the adsorbents, the effects of manganese and copper additions, reaction temperature, and various components in the flue gas on the efficiency of Hg⁰ removal were investigated. Mn₈Cu₅-MATP exhibited the optimal properties, and excessive copper loadings led to the aggregation of the active components. The efficiency of mercury removal can be effectively improved by NO and HCl regardless of the absence and presence of O₂, because the NO⁺, NO₃, NO₂, and Cl* produced during the reaction can promote the adsorption and oxidation of Hg⁰. SO₂ and H₂O inhibited the oxidation of Hg⁰ because of the competitive adsorption at the active sites, while a large amount of sulfite and sulfate were formed to block the pores. However, the introduction of copper caused the sample to obtain SO₂ resistance, which resulted in a mercury removal efficiency of 84.3% even under 1500 ppm SO₂. In addition, after 5 cycles of adsorption and regeneration, Mn₈Cu₅-MATP can still maintain excellent Hg⁰ removal ability. The fabricated adsorbent can save the actual production cost and effectively improve the mercury removal efficiency in sulfur-containing flue gas.