Phenyl bromine-appended metal-organic frameworks (Br-MOFs) were synthesized and applied in elemental mercury (Hg0) removal from simulated flue gas, considering the stability of bromine on the materials at the same time. The techniques of PXRD, nitrogen adsorption, TGA and XPS were used to characterize the materials. Phenyl bromide on the MOFs was the main active site for Hg0 capture. The optimal Br-MOF showed high Hg0 removal efficiency of more than 99% for 48h at 200°C, whereas the efficiency of un-functionalized MOF and conventional bromine impregnated active carbon dropped to 59.8% and 91.2% within 5h, respectively. The crystalline integrity of the Br-MOF was maintained after Hg0 adsorption. Br-MOF exhibited enhanced Hg0 removal efficiency when SO2 was introduced to the flue gas. However, exposure Br-MOF to flue gas with steam resulted in low Hg0 removal efficiency. Bromine leaching experiments proved that Br-MOFs have high bromine stability over the Hg0 adsorption process, avoiding the possible bromine pollution caused by the conventional bromine impregnated adsorbents. All of these results demonstrated the phenyl bromine-appended MOFs to be potential Hg0 adsorbent regarding its high Hg0 capture efficiency and low environmental risk.
Keywords: Bromine stability; Elemental mercury removal; Flue gas; Metal-organic frameworks; Phenyl bromide functionalization.
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