Enhancing the photothermal catalytic efficiencies of Hg0 and NO with Bi2O3/TiO2 modified by reduced graphene oxide (rGO).

This study aimed to develop novel photothermal catalysts to simultaneously remove Hg⁰ and NO at lower temperatures of 100–200 °C. A new type of photothermal catalysts incorporating reduced graphene oxide (rGO) and bismuth (Bi) modified TiO 2 (rGO/Bi 2 O 3 /TiO 2) was developed and further investigated the optimal mass ratio of rGO to Bi-modified TiO 2. The surface characterizations of Bi 2 O 3 /TiO 2 and rGO/Bi 2 O 3 /TiO 2 were further performed by using various physical and chemical analytical instruments. A continuous-flow photothermal catalytic reaction system was established to explore the simultaneous catalytic efficiencies of Hg⁰ and NO and to ascertain the optimal operating parameters in this study. Experimental results indicated that the catalytic oxidation efficiency of Hg⁰ decreased with reaction temperature, following the order of η (100 ℃) > η (150 ℃) > η (200 ℃). Among them, 3%Bi 2 O 3 /TiO 2 exhibited better thermal stability and higher catalytic oxidation efficiency of Hg⁰. Therefore, the photothermal catalysts were further modified with rGO to form 4%rGO/3%Bi 2 O 3 /TiO 2 (4G3BT), which made the catalytic oxidation efficiency of Hg⁰ went up to 80%. The ratio of the intensities of D band to G band (I D /I G) in rGO was about 1.25, indicating significant adsorption effects of rGO. Further simulating with Langmuir-Hinshelwood (L-H) kinetic model, it was determined that, with the increase of reaction temperature, the reaction rate constant (k) tended to increase, while the reaction equilibrium constant (K Hg0) decreased. It suggested that the photocatalytic reaction of Hg⁰ was primarily dominated by physical adsorption. [Display omitted] • The optimal modification proportion of rGO and Bi 2 O 3 was 3%Bi 2 O 3 /TiO 2 doped by rGO. • rGO/Bi 2 O 3 /TiO 2 was proven to simultaneously remove Hg⁰ and NO emitted from CFPPs. • The 4G3BT can achieve 80% Hg⁰ oxidation efficiency and 84% NO reduction efficiency. • Low-temperature SCR catalysts can be applied for simultaneous Hg⁰ and NO removal. [ABSTRACT FROM AUTHOR]