SO₂-Driven In Situ Formation of Superstable Hg₃Se₂Cl₂ for Effective Flue Gas Mercury Removal

Abstract

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., HgCl2, HgO, HgS, and HgSe). Herein, we demonstrate a superstable Hg3Se2Cl2 compound, which offers a promising next-generation flue gas mercury removal strategy. Theoretical calculations revealed a superstable Hg bonding structure in Hg3Se2Cl2, 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% H2SO4). The Hg3Se2Cl2 compound could be produced via the reduction of SeO3 2– to nascent active Se0 by the flue gas component SO2 and the subsequent combination of Se0 with Hg0 and Cl– ions or HgCl2. During a laboratory-simulated experiment, this Hg3Se2Cl2-based strategy achieves >96% removal efficiencies of both Hg0 and HgCl2 enabling nearly zero Hg0 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 Hg3Se2Cl2-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.

Sulfur Dioxide Promoted Mercury Fast Deposition over a Selenite-Chloride-Induced Surface from Wet Flue Gas

“…With the introduction of the Cl element, it can be embedded in HgSe monolayers to further enhance the mercury bonding stability. The theory calculations have demonstrated the thermodynamic stability of the conversion from HgSe to HgSeCl 2 and the high dissociation energy of the Hg–Se–Cl compound …”

“…The theory calculations have demonstrated the thermodynamic stability of the conversion from HgSe to HgSeCl 2 27 and the high dissociation energy of the Hg−Se−Cl compound. 40 3.4. Scale-Up Experiments for Large Mercury Capacity.…”

Unveiling the Halogenation-Induced Formation of Hg3Se2X2 (X = Cl, Br, and I) Compounds for Multiphase Mercury Cycling

“…Elemental selenium (Se 0 ) and metal selenides hold promise for Hg adsorption, resulting in the formation of low-solubility HgSe ( K sp = 10 –58 ) and a mercury–selenium antagonistic relationship. , However, HgSe shows limited thermal stability and releases mercury under strongly acidic conditions. Our recent studies found the interaction between halogens and the Se–Hg layer, leading to the creation of [HgSe]-X compounds . This discovery presents a novel approach for enhancing mercury removal.…”

“…Our recent studies found the interaction between halogens and the Se−Hg layer, leading to the creation of [HgSe]-X compounds. 28 This discovery presents a novel approach for enhancing mercury removal. Halogens play a pivotal role in swiftly capturing and concerting Hg 0 into the more removable Hg 2+ .…”

Adsorption of magnetic manganese ferrites to simulated monomeric mercury in flue gases

“…The increasing concentration of mercury in the environment has attracted the attention of governments and environmental organizations, and has become a worldwide environmental problem. The Minamata Convention on mercury, which entered into force in 2017, emphasizes cost-effective abatement and efficient decontamination of mercury pollution, as well as the sound management and utilization of mercury-rich waste [5]. Coal-fired power plants are reported to be the most significant source of mercury emissions, so in response to this problem, the Emission Standards for Air Pollutants from Power Plants (GB 132232011), published in July 2011, for the first-time limit mercury emission concentrations to no more than 0.03 mg/m 3 of mercury and mercury compounds from coal-fired power plants [6].…”