H2S-Modified Natural Ilmenite: A Recyclable Magnetic Sorbent for Recovering Gaseous Elemental Mercury from Flue Gas

H2S-modified natural ilmenite (i.e., ilmenite-C-S) was developed as a recyclable magnetic sorbent to recover Hg-0 in the flue gas as a cobenefit of the wet electrostatic precipitators (WESPs). Ilmenite-C-S showed an excellent Hg-0 capture performance at 40-100 C, and the chemical adsorption of Hg-0 on ilmenite-C-S was hardly inhibited by H2O and SO2. The chemical adsorption of Hg-0 on ilmenite-C-S mainly followed the Mars-Maessen mechanism (i.e., gaseous Hg-0 was first adsorbed, and it was then oxidized to HgS by S-2(2-) on ilmenite-C-S). As the formed Hg species was HgS, the leaching of Hg species during the wet dust collection of the WESP was negligible. Ilmenite-C-S after the five cycles of Hg-0 capture, Hg-0 recovery, and sorbent regeneration still had an excellent superparamagnetism with a saturation magnetization of 14.1 emu g(-1) and a superior performance for Hg-0 capture with Hg-0 removal efficiency of approximately 100%. Meanwhile, the ultralow concentration of Hg-0 in the flue gas was recovered as a high concentration of gaseous Hg-0 (>10 mg m(-3)), which can be condensed to liquid Hg-0. Therefore, Hg-0 recovery by ilmenite-C-S as a cobenefit of the WESP was a cost-effective technology for the centralized control of Hg-0 emission from coal-fired plants.