Using H2S plasma to modify activated carbon for elemental mercury removal

Abstract

Non-thermal plasma was applied to modify activated carbons (ACs) in the presence of H2S for improving the elemental mercury (Hg0) removal performance. The physical and chemical properties of raw and modified ACs were characterized by scanning electron microscopy with energy disperse X-ray spectroscopy, Brunauer-Emmett-Teller and X-ray photoelectron spectroscopy. The Hg0 removal performance of modified AC was tested by a bench-scale fixed bed. The results indicated that H2S plasma treatment enhanced S content of raw AC. Moreover, S content and Hg0 removal efficiency of modified AC increased with the increase of H2S concentration. The reason was that higher concentration H2S resulted in more S active sites on modified AC and S active site played a significant role during the Hg0 removal process. Besides, non-thermal plasma treatment in the presence of H2S had a weak impact on BET surface area. By further analysis, it could be inferred that the improvement of Hg0 removal performance was ascribed to the chemisorption rather than physisorption. Combined the results of temperature programmed desorption and XPS analysis, the mechanism of Hg0 removal was that elemental S on the surface of modified AC reacted with Hg0 to form HgS.