Mineralization of Gaseous Hg0 in Flue Gas to Cinnabar Induced by Pyrite

The application of metal sulfides in capturing gaseous Hg0 from flue gas is restricted due to their limited adsorption capacities, as Hg0 capture occurs mainly on the surface with little involvement of the saturated sulfur (S) coordination beneath. Herein, the surface adsorption of Hg0 on pyrite (FeS2) is innovatively converted into a chemical reaction through intermittent thermal treatment and water washing, enabling approximately 100% of the lattice S in FeS2 to participate in Hg0 capture. Accordingly, the Hg0 capture capacity of pyrite is enhanced by more than 1 order of magnitude to 1671 mg g–1, and gaseous Hg0 in flue gas is ultimately mineralized into high-grade cinnabar. Thermal treatment promotes the cleavage of Fe–S bonds following Hg0 adsorption, generating highly unsaturated Fe coordination sites, whereas water washing induces the dissociation of these highly unsaturated Fe coordination structures to regenerate unsaturated sulfur coordination sites for subsequent Hg0 adsorption. Therefore, the saturated S coordination beneath the surface can gradually participate in Hg0 adsorption due to the denudation of the pyrite surface by the process of Hg0 adsorption, thermal treatment, and water washing. Pyrite with novel operation displays significant potential to recover gaseous Hg0 emitted from flue gas as cinnabar for centralized control.