Mn3‐xCrx‐LDO, a new sorbent, for efficient elemental mercury removal from coal‐fired flue gas

A series of Mn 3‐x Cr x ‐LDHs (layered double hydroxides) precursors were synthesized through the co‐precipitation method and subsequently calcined at varying temperatures to yield Mn 3‐x Cr x ‐LDO (layered double oxide) mercury removal sorbents. An exhaustive examination was conducted to determine how different calcination temperatures, molar ratios of Mn to Cr, and reaction temperatures influenced the removal efficiency of elemental mercury. Notably, when the molar ratio of Mn to Cr was held constant at 1:2, and the calcination temperature was set at 350°C, the sorbent achieved a remarkable Hg 0 removal efficiency exceeding 94.4% across a broad reaction temperature range of 100–250°C. In particular, it demonstrated an impressive efficiency of 99.82% at 150°C. A suite of characterization techniques was employed to systematically characterize the physicochemical properties, including scanning electron microscopy (SEM), N 2 adsorption–desorption, X‐ray diffraction (XRD), H 2 ‐temperature‐programmed reduction (H 2 ‐TPR), X‐ray photoelectron spectroscopy (XPS), and Hg 0 temperature‐programmed desorption (Hg 0 ‐TPD). The results revealed that Mn 1 Cr 2 ‐LDO retains some of the layered structure of LDHs, with a larger specific surface area and exhibiting superior redox properties. Additionally, the study explored the impact of O 2 , SO 2 , and NO on Hg 0 adsorption. It was found that SO 2 had an inhibitory effect due to competitive adsorption, while NO can counteract the inhibitory effect of SO 2 to a certain extent. The Hg 0 adsorption process on the Mn 1 Cr 2 ‐LDO sorbent follows the Mars–Maessen mechanism, where lattice oxygen oxidizes Hg 0 . This research underscores the potential of the LDHs precursor system in developing LDO sorbents for mercury removal, highlighting its promising applications in this field.