H2S-Modified Fe-Ti Spinel: A Recyclable Magnetic Sorbent for Recovering Gaseous Elemental Mercury from Flue Gas as a Co-Benefit of Wet Electrostatic Precipitators

The nonrecyclability of the sorbents used to capture Hg from flue gas causes a high operation cost and the potential risk of exposure to Hg. The installation of wet electrostatic precipitators (WESPs) in coal-fired plants makes possible the recovery of spent sorbents for recycling and the centralized control of Hg pollution. In this work, a H2S-modified Fe-Ti spinel was developed as a recyclable magnetic sorbent to recover Hg from flue gas as a co-benefit of the WESP. Although the Fe-Ti spinel exhibited poor Hg capture activity in the temperature range of flue gas downstream of flue gas desulfurization, the H2S-modified Fe-Ti spinel exhibited excellent Hg capture performance with an average adsorption rate of 1.92 mu g(-1) min(-1) at 60 degrees C and a capacity of 0.69 mg g(-1) (5% of the breakthrough threshold) due to the presence of S-2(2-) on its surface. The five cycles of Hg capture, Hg recovery, and sorbent regeneration demonstrated that the ability of the modified Fe-Ti spinel to capture Hg-0 did not degrade remarkably. Meanwhile, the ultralow concentration of Hg in flue gas was increased to a high concentration of Hg-0, which facilitated the centralized control of Hg pollution.