Development of selenized magnetite (Fe3O4−xSey) as an efficient and recyclable trap for elemental mercury sequestration from coal combustion flue gas

Abstract

Abatement of elemental mercury (Hg0) pollution in coal combustion flue gas remains a challenging task especially for the optimal trade-off among effectiveness, environmental-friendliness and cost. In this work, magnetite (Fe3O4) was simply selenized (Fe3O4−xSey) as an efficient and recyclable sorbent for Hg0 sequestration from coal combustion flue gas. The Fe3O4−xSey as obtained exhibited an advantageous core-shell like spherical structure, in which the interior Fe3O4 core kept unchanged during the selenization process and warranted the recyclability of Fe3O4−xSey, while the exterior part exposed to Hg0 was selenized into iron diselenide (FeSe2) that has high affinity towards Hg0. Moreover, the selenization process introduced more mesopores that were favorable for Hg0 migration and accommodation. Co-benefitted from these perspectives, the Fe3O4−xSey exhibited a Hg0 adsorption capacity and uptake rate as high as 8.8 mg g−1 and 3.7 μg g−1 min−1, respectively, far exceeding the capacity and rate of bare Fe3O4 and traditional Hg0 remediators. The Hg0 stably immobilized by Fe3O4−xSey primarily as mercury selenide (HgSe) indicates the Hg-laden Fe3O4−xSey has negligible mercury re-emission concerns when it is dumped and landfilled. The spent Fe3O4−xSey can also be effectively retrieved and regenerated for reusing purpose with mercury recovery simultaneously, which could dramatically save the operation costs. Thus, the Fe3O4−xSey can be expected to be a promising alternative to traditional sorbents for Hg0 sequestration from coal combustion flue gas considering its high efficiency, negligible environmental risk and decent recyclability and reusability.