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

Abstract

Porous carbons derived from one-pot carbonization and activation of wood sawdust in a molten salt (LiCl-KCl) medium were employed for Hg0 removal. The carbons derived from molten salt carbonization (MSC) displayed much superior Hg0 removal performance comparing with the carbons derived from N2 pyrolysis method (NC). The best molar ratio of LiCl-KCl was 59:41, the optimal molten salt temperature was 700 °C, and the best mass ratio of wood sawdust to molten salt was 1:10. The MSC displayed good applicability at 50–125 °C. The saturation Hg0 adsorption capacity of MSC was about 7828.39 μg·g−1, far exceeding those for carbonaceous adsorbents reported in literatures. A Hg0 removal mechanism over MSC was proposed, i.e., the hierarchical porous structure accelerated mass transfer of Hg0, and the CO groups served as electron acceptors from Hg0 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 Hg0.