Elemental Mercury Removal from Flue Gas over Silver-Loaded CuS-Wrapped Fe₃O₄ Sorbent

Abstract

In this study, CuS-wrapped Fe3O4 was selected as the support for Ag loading to prepare a recyclable magnetic Ag-based sorbent for zero-valent mercury (Hg0) removal. The synthesized Ag/CuS@Fe3O4 sorbent showed outstanding Hg0 removal activity and SO2 resistance at 50 °C. The Hg0 capture capacity of Ag/CuS@Fe3O4 was 18.72 μg g–1 for 5 min, which was about 3.40 and 1.11 times higher than those of bare Fe3O4 and CuS@Fe3O4. Exposure of Ag/CuS@Fe3O4 to the simulated gas containing SO2 (0.05 v/v%) at 50 °C achieved the Hg0 removal efficiency of >84% during 3 h activity test. Characterization results indicated that both Cu and S sites of CuS were active sites in the reaction process, providing high Hg0 capture capacity. Meanwhile, the Ag species not only provided new activity sites but also improved the reactive activity of Cu sites due to the formation of ternary amalgam. In addition, the S sites were supplemented by SO2, which prevented the Ag active sites from being destructed by the formation of Ag2S.