Catalytically enhanced adsorption of flue gas mercury by CuS modified iron or manganese oxides

Abstract

This work systematically studies Hg⁰ removal performance of CuS modified Fe₂O₃ or MnO₂ (S_aMe_bO_z). It shows Fe₂O₃ has a stronger catalytic enhancement than MnO₂ on Hg⁰ removal of S_aMe_bO_z. Increasing Fe₂O₃ amount leads to a volcanic change in Hg⁰ removal performance of S_aFe_bO_x. At the optimal molar ratio of Fe₂O₃ to CuS with 3:2, Hg⁰ removal efficiency and Hg⁰ adsorption rate are 93.2% and 99.3%, respectively, where 92.5% of Hg⁰ is removed by adsorption. S^2-, adsorbed oxygen (O_ads), lattice oxygen (O_lat), and hollow site of MnO₂ are the main active sites to adsorb or catalyze Hg⁰, and O_ads has a stronger Hg⁰ adsorption capacity than O_lat. Hg⁰ removal by S_aMe_bO_z involves the catalytic oxidation of Hg⁰ to HgO by active sites, followed by the stable HgS formation through the reaction of HgO with active sulfur (S^2-). The findings provide important guidance for flue gas Hg⁰ removal in complete adsorption way.