Outstanding performance of reproducible sulfureted Fe-Ti spinel for the centralized control of Hg (both gaseous Hg0 and aqueous Hg2+) emitted from coal-fired power plants with seawater flue gas desulfurization

Abstract

The emission of aqueous Hg2+ into the sea during seawater flue gas desulfurization (SFGD) is of great concern. In this study, a novel technology for the centralized control of Hg discharged from coal-fired power plants (CFPPs) with SFGD was developed using sulfureted Fe-Ti spinel as a magnetic and regenerable sorbent to sequentially adsorb unoxidized gaseous Hg0 from flue gas and aqueous Hg2+ from desulfurized seawater. The sulfureted Fe-Ti spinel exhibited an excellent ability to adsorb gaseous Hg0 and aqueous Hg2+. Although SO2 in the flue gas and Fe2+ released from sulfureted Fe-Ti spinel both promoted Hg2+ reduction to Hg0, the sulfureted Fe-Ti spinel displayed a moderate ability to adsorb Hg0 in seawater. Hence, there was a critical Hg2+ concentration for Hg0 re-emission (19.6 μg/L). Hg0 re-emission was completely suppressed by sulfureted Fe-Ti spinel addition, as aqueous Hg2+ concentration consistently remained below the critical concentration due to its excellent Hg2+ adsorption rate. Therefore, the alternate capture of gaseous Hg0 in flue gas and aqueous Hg2+ in desulfurized seawater by sulfureted Fe-Ti spinel may be a promising technology for the centralized control of Hg discharged from CFPPs equipped with SFGD to both atmosphere and sea.