Mercury removal by biomass-derived porous carbon: Experimental and theoretical insights into the effect of H2S

To develop more effective alternative sorbent for gaseous elemental mercury (Hg0) removal, a porous carbon was synthesized from sustainable biomass (starch) by the combination of freeze-drying and CO2 activation. The biomass-derived porous carbon has high surface area, large pore volume and developed pore structure. The Hg0 adsorption ability of porous carbon was tested and compared with a commercial coconut shell activated carbon. The effect of Hydrogen sulfide (H2S) on Hg0 adsorption was investigated. H2S can significantly improve the Hg0 removal ability of porous carbon and activated carbon. Porous carbon shows greater Hg0 removal ability than activated carbon with and without H2S, which confirms the feasibility of effectively removing Hg0 by using porous carbon. The excellent textual properties of porous carbon facilitates the formation of more active sulfur sites on surface in the presence of H2S. Porous carbon is very available to be modified for realizing a high Hg0 removal ability. Density functional calculations were performed to clarify the mechanism of Hg0 adsorption on porous carbon. HgS is the most possible product for Hg0 adsorption on porous carbon with H2S. HgS can be formed by the direct reaction of Hg0 with C-S species via the Eley-Rideal mechanism.