Effect of amorphous ordered mesoporous carrier on adsorption and desorption of Hg0 over CeOx-amTiO2

Abstract

Improper disposal of deactivated mercury (Hg) adsorbents will cause secondary contamination which is still hazardous to human beings. Wet desorption is a green and environmentally friendly method, but there is a lack of sufficient study. In this work, a cerium oxide loaded ordered mesoporous amorphous titanium dioxide (CeOx-amTiO2) composite is obtained based on the evaporation-induced self-assembly (EISA) process. It possesses a high specific surface area (∼198 m2/g), uniform pore diameters (∼14.7 nm), and large pore volume (∼0.49 cm3/g). The CeOx-amTiO2 demonstrates high adsorption capacity in various atmospheres (63.3 % in pure N2, 95.0 % in N2 + 400 ppm H2S), and achieves a desorption efficiency of 93.2 % in 0.2 mol/L sodium thiosulfate (Na2S2O3) solution. The large specific surface area and ordered mesostructure significantly facilitate the mass transfer process, reasonably explaining the strong adsorption capacity and fast desorption kinetics. X-ray photoelectron spectroscopy (XPS) characterization and thermodynamic calculations reveal that the reduction of Ce3+ plays a key role in the desorption of Hg. In addition, the amorphous carrier structure reduces the binding strength between the adsorption product and the adsorbent, further accelerating the desorption process. This study provides a pathway for the efficient desorption of Hg0 removal adsorbents.