SO 2 -Driven In Situ Formation of Superstable Hg 3 Se 2 Cl 2 for Effective Flue Gas Mercury Removal.

Flue gas mercury removal is mandatory for decreasing global mercury background concentration and ecosystem protection, but it severely suffers from the instability of traditional demercury products ( e.g. , HgCl 2 , HgO, HgS, and HgSe). Herein, we demonstrate a superstable Hg 3 Se 2 Cl 2 compound, which offers a promising next-generation flue gas mercury removal strategy. Theoretical calculations revealed a superstable Hg bonding structure in Hg 3 Se 2 Cl 2 , with the highest mercury dissociation energy (4.71 eV) among all known mercury compounds. Experiments demonstrate its unprecedentedly high thermal stability (>400 °C) and strong acid resistance (5% H 2 SO 4 ). The Hg 3 Se 2 Cl 2 compound could be produced via the reduction of SeO 3 2- to nascent active Se 0 by the flue gas component SO 2 and the subsequent combination of Se 0 with Hg 0 and Cl - ions or HgCl 2 . During a laboratory-simulated experiment, this Hg 3 Se 2 Cl 2 -based strategy achieves >96% removal efficiencies of both Hg 0 and HgCl 2 enabling nearly zero Hg 0 re-emission. As expected, real mercury removal efficiency under Se-rich industrial flue gas conditions is much more efficient than Se-poor counterparts, confirming the feasibility of this Hg 3 Se 2 Cl 2 -based strategy for practical applications. This study sheds light on the importance of stable demercury products in flue gas mercury treatment and also provides a highly efficient and safe flue gas demercury strategy.