Elemental mercury removal by the modified bio-char from medicinal residues

• The bio-char from medicinal residue was used in Hg0 removal from flue gas.
• Physical activation and chemical impregnation were used to modify the bio-chars.
• Hg0 capture mechanism was investigated by the experimental and kinetic methods.
• The modified bio-chars are cheap and efficient in comparison with CACs based sorbents.

The purpose of this paper is to investigate the bio-char from medicinal residue in gas phase elemental mercury removal. The bio-char was derived from pyrolysis char modified by both physical and chemical modification. Physical activation (microwave and steam) improves pore structure and introduces oxygenic functional groups. Chemical activation (chloride-impregnated) significantly promotes elemental mercury capture capacity. Mercury adsorption by NH4Cl-impregnated bio-char was much better than those by ZnCl2-impregnated and HCl-impregnated bio-chars. A combination kinetic model presents a strong correlation with the adsorption data for the chloride-impregnated bio-chars. The model results reveal the importance of mass transfer during the initial stages of element mercury adsorption for these materials. Furthermore the overall element mercury adsorption process is strongly governed by chemisorption for the chloride-impregnated bio-chars. The studies showed that the modified bio-chars derived from medicinal residue might be cost effective sorbents with high activity, which can be used as an alternate to commercial activated carbons (CACs) or modified CACs in the removal of element mercury.

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