Mercury capture from natural gas by carbon supported ionic liquids: Synthesis, evaluation and molecular mechanism

• Carbon supported ionic liquids were synthesized for Hg removal from gas stream.
• [Bmim]Cl coated carbon was found to be the most effective adsorbent to capture Hg0.
• The imidazolium cation can form a complex with HgCl2 through the C2 hydrogen.
• Molecular simulation reveals that anion part of ILs plays major role in Hg0 removal.

Superiority of silica supported ionic liquids over other adsorbents in capturing elemental mercury (Hg0) from flue gases has been recently reported. In this study, activated carbon, which is more economical than silica, was experimented as a solid support for ionic liquids (ILs) for gaseous Hg0 removal. Four ILs were successfully coated on activated carbon. The carbon supported ionic liquids (CSILs) were characterized by Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller surface area analysis, field emission scanning electron microscopy, energy-dispersive X-ray, X ray-photoelectron spectroscopy and nuclear magnetic resonance. A continuous fixed bed flow reactor was used to examine the performance of CSILs in treating 20–35 ppm Hg0 vapor at a gas flow rate of 60 mL/min. 1-Butyl-3-methylimidazolium chloride [Bmim]Cl coated activated carbon was the most reactive among CSILs studied and a powdered form of [Bmim]Cl coated activated carbon was able to uptake Hg0 up to 23 mg/g and 60 mg/g with N2 and CH4 as carrier gas, respectively. A molecular simulation was performed to investigate the molecular level interaction between the Hg0 and the ILs to understand the effect of structural variations of the ILs on Hg0 adsorption. The simulation reveals that the anion part of IL plays a major role in Hg0 adsorption. Based on experimental results, a possible mechanism of Hg–IL interaction was elucidated; the imidazolium cation can form a complex with HgCl2 through the C2 hydrogen.

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