The application of coal liquefaction residue raffinate slag-based sorbents for elemental mercury removal from coal-fired flue gas

Capture of elemental mercury (Hg-0) attracts global attention because of its toxicity and bioaccumulation. Carbon-based sorbents are extensively studied due to the high porosity that can increase Hg-0 adsorption ability. In this study, the RS-based sorbents were prepared from sulfur-containing coal liquefaction residue raffinate slag (CLR-RS), an industrial waste, by CH3COOK activation. The N-2 adsorption, XRD, SEM, XRF, Hg-TPD, and XPS techniques were used to study the physicochemical properties of sorbents. The sorbent that was prepared at 850 degrees C from the blend of CH3COOK/RS at 3:5 (by mass) exhibited excellent Hg-0 removal performance under N-2 + O-2, and an improved performance was observed under N-2 + O-2 + SO2 + NO + H2O. The Hg-TPD and XPS analyses revealed that HgS and HgO were formed on used RS-based sorbents. O-2 in flue gas could improve the ability in capturing Hg-0 by promoting the formation of HgS and HgO. The findings have suggested that the prepared sorbents based on CLR-RS could be potentially applied for industrial Hg-0 capture, and the sustainable utilization could be realized by recycling RS.