Design of O/SO dual-doped porous carbon as superior sorbent for elemental mercury removal from flue gas.

A porous carbon was synthesized via hydrothermal carbonization and CO activation. O and SO were successfully co-doped onto carbon surface by applying non-thermal plasma technique. Porous carbon possessing excellent textural properties is effective to adsorb the radicals generated by plasma. Plasma promotes the adsorption of O and SO on carbon surface with the formation of abundant CO, C-S and C-SO (x = 1-3) groups. The O/SO dual-doped porous carbon was utilized to adsorb elemental mercury (Hg) from the flue gas of coal combustion. The Hg adsorption ability of the O/SO dual-doped porous carbon is closely related with the concentrations of O and SO for plasma treatment and the treatment time. The optimal O/SO dual-doped porous carbon exhibited far greater Hg adsorption capacity than a commercial brominated activated carbon. Density functional theory was employed to understand the Hg adsorption mechanism at the molecular level. CO, C-S and C-SO (x = 1-3) groups enhanced the interaction of Hg with surface carbon atom. The activity of them for enhancing Hg adsorption is in the order of C-SO >  CO > C-S > C-SO > C-SO. Porous carbon can be activated by plasma in flue gas containing O and SO, and used as superior sorbent for Hg removal.