Recyclable Naturally Derived Magnetic Pyrrhotite for Elemental Mercury Recovery from Flue Gas

Abstract

Magnetic pyrrhotite, derived from the thermal treatment of natural pyrite, was developed as a recyclable sorbent to recover elemental mercury (Hg) from the flue gas as a cobenefit of wet electrostatic precipitators (WESP). The performance of naturally derived pyrrhotite for Hg capture from the flue gas was much better than those of other reported magnetic sorbents, for example Mn-Fe spinel and Mn-Fe-Ti spinel. The rate of pyrrhotite for gaseous Hg capture at 60 °C was 0.28 μg g min and its capacity was 0.22 mg g with the breakthrough threshold of 4%. After the magnetic separation from the mixture collected by the WESP, the spent pyrrhotite can be thermally regenerated for recycle. The experiment of 5 cycles of Hg capture and regeneration demonstrated that both the adsorption efficiency and the magnetization were not notably degraded. Meanwhile, the ultralow concentration of gaseous Hg in the flue gas was concentrated to high concentrations of gaseous Hg and Hg during the regeneration process, which facilitated the centralized control of mercury pollution. Therefore, the control of Hg emission from coal-fired plants by the recyclable pyrrhotite was cost-effective and did not have secondary pollution.

Green Preparation of Nanoporous Pyrrhotite by Thermal Treatment of Pyrite as an Effective Hg(Ⅱ) Adsorbent: Performance and Mechanism

“…As observed in Figure 9c, [20]. Figure 9g exhibits the Hg 4f spectrum of MPy-600 after Hg(II) removal.…”

“…MPy-600 does not show superparamagnetism, and the permanent magnetization is as low as 4.278 emu/g. The saturation magnetization of MPy-600 after adsorption decreases to 12 emu/g [20,34]. Thus, the magnetic property of MPy-600 guarantees the convenient magnetic separation from the aqueous solution in adsorption applications.…”

“…In addition, the binding energy of the O 1s spectrum at 533.4 eV is attributed to the O in the SiO2. The higher spectral peaks are ascribed to iron diffusion, and when combined with minute amounts of oxygen, hydroxide, and water, ferric-hydroxides are formed [20]. Figure 9g exhibits the Hg 4f spectrum of MPy-600 after Hg(II) removal.…”

“…Therefore, in order to gain highly reactive products, our group developed a cost-effective method by thermally activating pyrite [15]. Thermally activated pyrrhotite as a promising adsorbent has been studied for the removal of various contaminants, such as Cu(II) [16], Pb(II) [17,18], U(VI) [19], and Hg 0 [20]. They all exhibit excellent adsorption characteristics.…”

Nanosized Copper Selenide Functionalized Zeolitic Imidazolate Framework‐8 (CuSe/ZIF‐8) for Efficient Immobilization of Gas‐Phase Elemental Mercury

“…When taking these two points into consideration, the mineral sulfides (MSs) were recognized as the most promising alternatives to ACs since their surfaces were “fully” covered by highly reactive sulfide sites. [7b] However, the research on Hg 0 adsorption over MSs seemed to reach its upper limit recently with the highest equilibrium adsorption capacity reaching around 0.1 g Hg 0 g −1 MSs . This is far less than the theoretical molar 1:1 ratio of Hg 0 /S 2− value since inevitable agglomeration occurred on the unsupported mineral sulfides, which thus hinders the contacts between the active sites and Hg 0 .…”