SO 2 -Driven In Situ Formation of Superstable Hg 3 Se 2 Cl 2 for Effective Flue Gas Mercury Removal.
Naiqiang YanQinyuan HongZhao-Yang ZhangXiangling CaiYurui FanZhisong LiuWenjun HuangNaiqiang YanZan QuLizhi ZhangPublished in: Environmental science & technology (2023)
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.