A Molten-Salt Pyrolysis Synthesis Strategy toward Sulfur-Functionalized Carbon for Elemental Mercury Removal from Coal-Combustion Flue Gas

The emission of mercury from coal combustion has caused consequential hazards to the ecosystem. The key challenge to abating the mercury emission is to explore highly efficient adsorbents. Herein, sulfur-functionalized carbon (S-C) was synthesized by using a molten-salt pyrolysis strategy and employed for the removal of elemental mercury from coal-combustion flue gas. An ideal pore structure, which was favorable for the internal diffusion of the Hg-0 molecule in carbon, was obtained by using a SiO2 hard template and adjusting the HF etching time. The as-prepared S-C with an HF etching time of 10 h possessed a saturation Hg-0 adsorption capacity of 89.90 mg center dot g(-1), far exceeding that of the commercial sulfur-loaded activated carbons (S/C). The S-C can be applied at a wide temperature range of 25-125 degrees C, far exceeding that of commercial S/C. The influence of flue gas components, such as SO2, NO, and H2O, on the Hg-0 adsorption performance of S-C was insignificant, indicating a good applicability in real-world applications. The mechanism of the Hg-0 removal by S-C was proposed, i.e., the reduced components, including sulfur thiophene, sulfoxide, and C-S, displayed a high affinity toward Hg-0, which could guarantee the stable immobilization of Hg-0 as HgS in the adsorbent. Thus, the molten-salt pyrolysis strategy has a broad prospect in the application of one-pot carbonization and functionalization sulfur-containing organic precursors as efficient adsorbents for Hg-0.

Automated summary

The emission of mercury from coal combustion has caused significant hazards to the ecosystem. This study focuses on exploring highly efficient adsorbents for reducing mercury emissions. Sulfur-functionalized carbon (S-C) was synthesized and used to remove elemental mercury from coal-combustion flue gas. S-C exhibited an ideal pore structure, high Hg-0 adsorption capacity, and broad applicability. The proposed mechanism for mercury removal by S-C and the potential of molten-salt pyrolysis strategy in adsorbent development were also discussed.