Simultaneous aqueous Hg(II) adsorption and gaseous Hg0 re-emission inhibition from SFGD wastewater by using Cu and S co-impregnated activated carbon

Seawater flue gas desulfurization (SFGD) has shown great effectiveness in the controlling of sulfur dioxide (SO2) emission and the removing of mercury (Hg) from flue gases of coal-fired power plants. Some problems pertaining to SFGD for Hg control, however, remain to be solved: (1) environmental impact from the discharge of Hg-containing seawater to the ocean, and (2) re-emission of gaseous Hg from the aeration tank to the atmosphere. This study synthesizes the copper/sulfur co-impregnated activated carbon (Cu-S-AC) to simultaneously capture aqueous Hg(II) and inhibit gaseous Hg-0 re-emission from actual SFGD wastewater. Cu-S-AC exhibited greater Hg(II) adsorption than both raw activated carbon (AC) and sulfur-impregnated activated carbon (S-AC) at an initial Hg(II) concentration of higher than 8000 ng/L. The Hg(II) adsorption of Cu-S-AC was slightly greater at pH 7 and 8 than that under acidic conditions. The Hg(II) adsorption was well-fitted with both linear and Freundlich isotherms. The results of thermodynamic analyses veiled the endothermic and spontaneous adsorption of Hg(II) on Cu-S-AC. In addition, the pseudo-second-order equation provided the best correlation coefficient for the Hg(II) adsorption on Cu-S-AC. Notably, the increases of pH and temperature increased the Hg-0 re-emission. Nevertheless, Cu-S-AC addition significantly inhibited the Hg-0 re-emission (92%) from SFGD wastewater. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

Seawater flue gas desulfurization is effective in controlling sulfur dioxide emissions and removing mercury from coal-fired power plant flue gases. However, issues such as environmental impact and re-emission of gaseous mercury need to be addressed. The study found that copper/sulfur co-impregnated activated carbon can capture aqueous mercury and inhibit gaseous mercury re-emission effectively.