Oxidation efficiency and reaction mechanisms of gaseous elemental mercury by using CeO2/TiO2 and CuO/TiO2 photo-oxidation catalysts at low temperatures in multi-pollutant environments

Abstract

• The catalytic oxidation efficiency of Hg 0 at low temperatures in multi-pollutant environments was investigated. • The oxidation efficiency of Hg 0 over 5%CuO/TiO 2 was obviously higher than that over 7%CeO 2 /TiO 2 . • In the atmosphere of N 2 +Hg 0 +SO 2 , SO 2 competed with Hg° for the active sites and thus inhibited the oxidation efficiency of Hg 0 . • 5%CuO/TiO 2 had better sulfur resistance than 7%CeO 2 /TiO 2 mainly due to strong interaction of Cu and Ti. Background :This study aimed to establish novel photothermal catalysts suitable for the reaction at temperatures of 100-200 ℃ to develop an innovative Hg0 and NO simultaneous removal technology in a lower temperature environment. To further explore the stability and sulfur resistance of 7%CeO 2 /TiO 2 and 5%CuO/TiO 2 , the oxidation efficiency and reaction mechanisms of Hg 0 were investigated in multi-pollutant environments at low temperatures. Methods: TiO 2 , CeO 2 /TiO 2 , and CuO/TiO 2 used to oxidize Hg 0 at low temperatures were prepared by the sol-gel method, which were localized to glass beads for each test. A self-designed photothermal catalytic reaction system consisted of a mercury generator, a mixing chamber, a catalytical reactor, and an m on-line mercury measuring instrument. Significant Findings: The oxidation efficiencies of Hg 0 for different reaction temperatures were ordered as η 100℃ >η 150℃ >η 200℃ in the atmosphere of N 2 +Hg 0 . In the atmosphere of N 2 +Hg 0 +NO, low concentration of NO (<300 ppm) exhibited inhibitive effect to Hg 0 oxidation, while high concentration of NO (>300 ppm) enhanced Hg 0 oxidation. In the atmosphere of N 2 +Hg 0 +SO 2 , SO 2 could occupy the active sites for Hg 0 oxidation and inhibited the oxidation of Hg 0 .