Removal of elemental mercury by titanium pillared clay impregnated with potassium iodine

•Titanium pillared clay impregnated by potassium iodine showed high Hg0 removal.•Chemisorption occurred and HgI2 was the main product on the surface of KI-Ti-PILC.•The pseudo-second order model can be used to describe the Hg0 removal by KI-Ti-PILC.

A new kind of titanium pillared clay (Ti-PILC) impregnated by potassium iodine (KI) was synthesized to remove the elemental mercury (Hg0) in the simulated flue gas. The effect of KI loading amount, temperature, flue gas components (O2, SO2, H2O and NO) on Hg0 removal efficiency was investigated with a bench-scale bed. The techniques of Brunauer–Emmett–Teller (BET), Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM), X-ray diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS), were used to characterize the clays. Compared with the original clay or the KI-impregnated clay, the KI-impregnated Ti-PILC showed an excellent Hg0 removal ability due to its larger BET surface area and more mesopores of 2–10 nm. O2 was found to be an important factor for Hg0 removal. The Hg0 removal efficiency was enhanced with the rise in temperature. SO2 had a slight promotion effect while H2O greatly inhibited Hg0 removal. In all these flue gas components, NO was the most effective composition on promoting Hg0 removal. During the adsorption process, chemisorption occurred between iodine and Hg0 on the surface of the material in the temperature range of 80–180 °C. The major product was assumed to be HgI2. The experiments and kinetic models analysis manifested that both physisorption and chemisorption of Hg0 occurred on the surface of KI-Ti-PILC, whereas the adsorption process was mainly chemisorption.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slide