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

Abstract

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 HS-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 HS-modified Fe-Ti spinel exhibited excellent Hg capture performance with an average adsorption rate of 1.92 μg g min at 60 °C and a capacity of 0.69 mg g (5% of the breakthrough threshold) due to the presence of S 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 did not degrade remarkably. Meanwhile, the ultralow concentration of Hg in flue gas was increased to a high concentration of Hg, which facilitated the centralized control of Hg pollution.

Biomass Carbon Magnetic Adsorbent Constructed by One-Step Activation Method for the Removal of Hg0 in Flue Gas

“…Wang et al 57 reported that the saturation magnetization value of magnetic carbon composite derived from pinewood sawdust was 15.6 emu g –1 , indicating that the separation of magnetic carbon composite was facile, and almost all adsorbent could be completely recollected using a magnet. Zou et al 58 reported that the improved Fe–Ti spinel remained as a great superparamagnetic structure. The saturation magnetization of it has decreased from 24.6 to 11.8 emu g –1 after the four cycles of Hg 0 capture/recovery.…”

Study on the Preparation of Magnetic Mn–Co–Fe Spinel and Its Mercury Removal Performance

“…However, from 175 • C to 200 • C, the increase in mercury removal efficiency weakened again. This is because the mercury adsorption process is the result of the combined effect of physical adsorption and chemical adsorption [10,37]. When the temperature was low (100-125 • C), the chemical adsorption was not obvious, and the physical adsorption was dominant.…”

Theoretical insight into mercury species adsorption on graphene-based Pt single-atom catalysts

“…7,8 Hg 2+ and Hg p can be effectively removed from flue gas using wet flue gas desulfurization and electrostatic precipitators. 9,10 Due to its high vapor pressure and low water solubility, Hg 0 is the most tedious to remove by these techniques. 11,12 However, adsorption has sufficed as the most effective approach for Hg 0 removal, along with HgCl and HgCl 2 .…”