Adsorption and catalytic oxidation of elemental mercury over regenerable magnetic Fe-Ce mixed oxides modified by non-thermal plasma treatment

This study proposes the novel application of non-thermal plasma treatment to improve the oxidation capacity of regenerable magnetic Fe-Ce mixed oxides (FCs) for the efficient removal of elemental mercury (Hg-0) from coal combustion flue gas. Sample characterization shows that the textural property, crystalline phases, and magnetic property of FCs undergo no obvious changes after plasma treatment. But greater Ce4+ concentration and richer lattice oxygen are generated on the treated FCs. The treated FCs exhibit far better Hg-0 removal performance compared to raw FC. The effects of treatment time (0-20 min), reaction temperature (100-250 degrees C), and flue gas components (SO2, NO, O-2, HCl and H2O) on Hg-0 removal performance are also discussed. Both Hg-0 adsorption capacity and adsorption rate evaluated at 150 degrees C for the treated FCs are extremely close to those obtained with a commercial activated carbon manufactured specifically for mercury removal from flue gas. Furthermore, the Hg-0 removal mechanism is proposed for the treated FCs. The treated FCs include separate active sites for Hg-0 adsorption and catalytic oxidation. Ce4+ species with greater oxidation state and lattice oxygen are largely consumed during the Hg-0 removal process. However, these components are replenished by subsequent non-thermal plasma treatment. Finally, the spent FCs can be effectively recycled through magnetic separation, thermal desorption, and non-thermal plasma treatment.