Magnetic iron–manganese binary oxide supported on carbon nanofiber (Fe3−xMnxO4/CNF) for efficient removal of Hg0 from coal combustion flue gas

Abstract

Samples of magnetic iron–manganese binary oxide supported on activated carbon fiber (Fe3−xMnxO4/CNF) were prepared for Hg0 removal from flue gas. The results showed that the Hg0 removal performance of Fe3−xMnxO4/CNF was significantly promoted with the increase of Mn incorporating content into Fe3O4 spinel structure. The optimal sample of Fe2MnO4/CNF, at the optimal reaction temperature of 150–200 °C, attained above 90% of Hg0 removal efficiency (Ea). CNF played an important role in Hg0 removal by Fe3−xMnxO4/CNF due to the disperation of Fe3−xMnxO4 particles and the enhancement for electron transfer process. O2 enhanced the Hg0 removal via the Mars-Maessen mechanism, and NO improved the Hg0 removal performance slightly because of the formation of NO2. SO2 and H2O played an inhibitive role in Hg0 removal due to the competition of active sites for Hg0 adsorption. A mechanism of Hg0 removal over Fe3−xMnxO4/CNF is proposed, in which both Mn cations and lattice/chemisorbed oxygen were thought to the active sites for Hg0 adsorption/oxidation. Further, the spent Fe3−xMnxO4/CNF could be regenerated with no obvious decrease of Hg0 removal performance by water washing followed by thermal treatment at 450 °C in N2 and calcination at 200 °C in air.