Abstract
In this study, the photo-oxidation and kinetics of elemental mercury (Hg0) with self-prepared TiO2 and CeO2/TiO2 at 100–200 ℃ were explored. The surface properties of the photocatalysts were characterized before conducting the Hg0 photo-oxidation experiments. Both field emission scanning electron microscopy and high-resolution transmission electron microscopy showed that the grain size of TiO2 {101} was smaller than TiO2 {001}. XPS spectral showed that cerium (Ce) valence shifting between CeO2 and Ce2O3 generated strong oxidant O2-. Chemisorbed oxygen (Oα) was found to be more active than lattice oxygen (Oβ). Doping CeO2 to anatase-TiO2 effectively enhanced the photo-oxidation of Hg0. Higher Hg0 photo-oxidation efficiency and better thermal stability were observed in CeO2/TiO2{001} than CeO2/TiO2{101}. The photo-oxidation efficiency of Hg0 decreased with reaction temperature. In N2+Hg0+NO, low NO concentration (< 100 ppm) suppressed and high NO concentration (>300 ppm) enhanced the oxidation of Hg0. In N2+Hg0+SO2, SO2 competed with Hg0 for active sites on the surface of photocatalysts and suppressed the photo-oxidation of Hg0 since sulfate and sulfite as reaction products were observed on the surface of photocatalysts. Both facets could not prevent from being poisoned, however, CeO2/TiO2{001} could decelerate sulfur poisoning. On simulation by LH kinetic model, the reaction rate constant increased and the equilibrium constant decreased with reaction temperature, indicating that the photo-oxidation of Hg0 was dominated by physical adsorption.
Published Version
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