Removal of Hg0 from a simulated flue gas by photocatalytic oxidation on Fe and Ce co-doped TiO2 under low temperature

Abstract Fe and Ce co-doped TiO 2 composites were synthesized by a sol-gel method and subsequently employed as a photocatalyst to oxidize elemental mercury (Hg 0 ) from a zinc smelting flue gas. Hg 0 photo-oxidation were conducted under UV irradiation (253.7 nm). A series of influence factors have been investigated: calcination temperature, pH of the sol, amounts of Fe 2 O 3 and CeO 2 , reaction temperature and flue gas components. Hg 0 photo-oxidation efficiency as high as 95% at 30 °C was obtained over Fe 5 Ce 5 Ti synthesized at the sol pH = 6 as a result of the optimum optical absorption properties and maximum specific surface area (109.543 m 2 /g) of this material. Besides, O 2 and SO 2 contributed to favor photo-oxidation of Hg 0 while NO exhibited inhibition. Based on UV–vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) revealed a red-shifted absorption edge for Fe 5 Ce 5 Ti, which prevented the recombination of the photogenerated charge carriers and decreased the band gap width (2.34 eV). In addition, X-ray photoelectron spectroscopy (XPS) indicated that HgO was the main species of the mercury on the used Fe 5 Ce 5 Ti sample. This species was generated by photo-oxidation of Hg 0 with O β , O 2− and h + .