Natural ferruginous manganese ore for efficient immobilization of elemental mercury from coal combustion flue gas

Mercury emission from industrial activities poses a serious threat to the ecosystem. The development of cost-effective sorbents for mercury removal is a feasible method to alleviate this problem. In this study, natural ferruginous manganese ore (NFM) was adopted as a cost-effective sorbent for elemental mercury (Hg0) removal from flue gas. Samples characterization indicated that the pore stricture of NFM was deteriorated after calcination procedure. The secondary recrystallization of manganese oxides and decomposition of MnO2 into Mn2O3 also happened during calcination process. Raw NFM exhibited high Hg0 removal efficiency (ET > 80%) over a broad temperature range (100 °C–200 °C), whereas calcination procedure had negative effects on Hg0 removal performance. The effects of calcination temperature (450 °C–650 °C) and reaction temperature (100 °C–400 °C) on Hg0 removal performance were also explored. Under the simulated flue gas condition, both equilibrium mercury adsorption capacity and adsorption rate were superior to those of a commercial activated carbon specifically used for mercury emission reduction. The Hg0 removal mechanism was revealed by combining with Hg0 adsorption/oxidization behavior and XPS analysis. It was demonstrated that chemisorption dominated Hg0 removal process, where MnO2 could serve as active components for Hg0 capture. The results were affirmed by the mercury temperature programmed desorption experiments.