Detailed study on the regeneration of CoS2 loaded porous carbon for elemental mercury removal from flue gas

•Regeneration of spent CoS2/carbon sorbent has been systematically studied.•Hg0 capture ability of CoS2/carbon can be recovered by elemental sulfur and H2S.•Elemental sulfur can recover the active sulfur sites for Hg0.•H2S can regenerate both cobalt and sulfur sites for Hg0. Metal sulfides are promising sorbents in elemental mercury (Hg0) removal from flue gas, but they need to be regenerated during Hg0 removal cycle. Developing an effective regeneration method and elucidating the associated mechanisms hold significant importance in reducing operating costs for Hg0 removal by metal sulfides. This paper reported a CoS2 loaded porous carbon for Hg0 capture and investigated the regeneration of the deactivated sorbent using elemental sulfur for the first time. The elemental sulfur can fully recover the Hg0 capture ability of the hybrid sorbent, and display the same regeneration stability during five Hg0 removal cycle in comparison with toxic H2S. The regained activity of the sorbent in Hg0 capture depends mainly on the regeneration of S22− sites. The regenerated sorbent contains higher amount of S22− sites than the fresh sample, but less Co3+ and Sn2−(n >2) sites. Particularly, elemental sulfur is more effective in recovering S22− sites than H2S. The particle size of CoS2 on carbon decreases obviously during the Hg0 adsorption and regeneration, but cannot be restored by elemental sulfur and H2S. This work provides a detailed insight into the deactivation of metal sulfides for Hg0 removal, and will help the design of sorbent regeneration method for practical gaseous Hg0 capture.