Morphology-controlled synthesis and sulfur modification of 3D hierarchical layered double hydroxides for gaseous elemental mercury removal

[Display omitted] Porous structure and effective active site are beneficial for gaseous elemental mercury (Hg0) capture. Two kinds of hierarchical porous layered double hydroxides (LDHs) were synthesized through an in-situ growth method. Sulfur was used for the modification of these LDHs to enhance Hg0 removal performance. Two as-prepared NiAl-S4@SiO2 microspheres displayed three-dimensional morphologies, accordingly exhibited as core-shell and urchin-like morphologies. XRD, BET, FTIR, TEM and SEM were employed to investigate the structure effect on Hg0 uptake. The results indicated that after S-modification, the Hg0 removal efficiencies as well as SO2 resistance were enhanced. The Hg0 removal performances follow the order of: NiAl-S4@SiO2-urchin > NiAl-S4@SiO2-core at 100 °C. The mechanism for Hg0 removal was discussed based on the results of TPD, EDX and XPS. The porous structure of NiAl-S4@SiO2 composite was beneficial for gas transformation and intercalated [S4]2− ions were favorable for mercury uptake. The polysulfide combined with adsorbed mercury and formed HgS. Such materials exhibit promising potential for mercury uptake from SHg mixed flue gas.