Enhancing the oxidation efficiency of elemental mercury in the presence of NO and SO2 by using Cu(II)O doped TiO2 photothermal catalysts: Kinetics and mechanisms

• Cu(II)O/TiO 2 as photothermal catalysts with were explored to remove Hg. • 5%Cu(II)O/TiO 2 has the greatest Hg 0 oxidation performance. • NO and SO 2 could chemisorb on the surface of catalysts. • The influence of SO 2 and NO in the Hg 0 oxidation reaction was clarified by DFT. This study aimed to apply sol–gel synthesized Cu(II)O doped TiO 2 to enhance the oxidation of gaseous elemental mercury (Hg 0 ) in the flue gases containing NO and SO 2 at the temperatures of 120-180℃ under the irradiation of near-ultraviolet (near-UV). The influences of SO 2 and NO on the oxidation efficiency of Hg 0 were investigated by in-situ diffuse reflection infrared spectroscopy (DRIFT) and density functional theory (DFT). Experimental results showed that an optimal 5 %Cu(II)O/TiO 2 had the oxidation efficiencies of Hg 0 from 40 to 100 % at 120-180℃. The oxidation efficiencies of Hg 0 were 85 and 70 % at 120℃, and 40 and 5 % at 180 °C, in the presence of solely SO 2 and NO, respectively. Surface characterization showed that Cu(II)O was evenly dispersed over the surface of TiO 2 catalysts. NO could inhibit the oxidation of Hg 0 since it consumed the chemisorbed oxygen (O α ) and compete with Hg 0 at the surface active sites. In contrast, SO 2 could promote the oxidation efficiency of Hg 0 due to the formation of HgSO 4 on the surface of Cu(II)O/TiO 2 catalysts. In the exposure of NO/SO 2 , NO and SO 2 can be adsorbed on the catalyst surface reacting with ̇ OH. The photothermal oxidation reactivity of Hg 0 was inhibited due to the competitive adsorption between NO/SO 2 and Hg 0 . The Langmuir-Hinshelwood (L-H) kinetic model successfully simulated the oxidation rate of Hg 0 . Moreover, DFT was further applied to estimate the binding energies of different gas molecules confirming the competence for active sites on the surface of Cu(II)O/TiO 2 between NO/SO 2 and Hg 0 .