Removal of flue gas mercury by porous carbons derived from one-pot carbonization and activation of wood sawdust in a molten salt medium

Porous carbons derived from one-pot carbonization and activation of wood sawdust in a molten salt (LiCl-KCl) medium were employed for Hg-0 removal. The carbons derived from molten salt carbonization (MSC) displayed much superior Hg-0 removal performance comparing with the carbons derived from N-2 pyrolysis method (NC). The best molar ratio of LiCl-KCl was 59:41, the optimal molten salt temperature was 700 degrees C, and the best mass ratio of wood sawdust to molten salt was 1:10. The MSC displayed good applicability at 50-125 degrees C. The saturation Hg-0 adsorption capacity of MSC was about 7828.39 mu g.g(-1), far exceeding those for carbonaceous adsorbents reported in literatures. A Hg-0 removal mechanism over MSC was proposed, i.e., the hierarchical porous structure accelerated mass transfer of Hg-0, and the C=O groups served as electron acceptors from Hg-0 atoms to form organic matter bonded mercury (Hg-OM). The molten salt could be easily separated from the mixture of MSC for recycling multiple times. Thus, molten salt carbonization method appears to be promising in one-pot carbonization and activation of biomass as efficient adsorbents for gaseous Hg-0.

Automated summary

Porous carbons derived from one-pot carbonization and activation of wood sawdust in a molten salt medium showed superior performance in Hg-0 removal compared to carbons derived from N-2 pyrolysis method. The best molar ratio of LiCl-KCl was found to be 59:41, with an optimal molten salt temperature of 700 degrees C and a mass ratio of wood sawdust to molten salt of 1:10. The carbonization method displayed good applicability at temperatures ranging from 50 to 125 degrees C, with a high saturation Hg-0 adsorption capacity.