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

Abstract

This study proposes the novel application of non-thermal plasma treatment to improve the oxidation capacity of regenerable magnetic FeCe mixed oxides (FCs) for the efficient removal of elemental mercury (Hg0) 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 Hg0 removal performance compared to raw FC. The effects of treatment time (0–20 min), reaction temperature (100–250 °C), and flue gas components (SO2, NO, O2, HCl and H2O) on Hg0 removal performance are also discussed. Both Hg0 adsorption capacity and adsorption rate evaluated at 150 °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 Hg0 removal mechanism is proposed for the treated FCs. The treated FCs include separate active sites for Hg0 adsorption and catalytic oxidation. Ce4+ species with greater oxidation state and lattice oxygen are largely consumed during the Hg0 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.