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 Hg-0 and NO at lower temperatures of 100-200 degrees C. A new type of photothermal catalysts incorporating reduced graphene oxide (rGO) and bismuth (Bi) modified TiO2 (rGO/Bi2O3/TiO2) was developed and further investigated the optimal mass ratio of rGO to Bi-modified TiO2. The surface characterizations of Bi2O3/TiO2 and rGO/Bi2O3/TiO2 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 Hg-0 and NO and to ascertain the optimal operating parameters in this study. Experimental results indicated that the catalytic oxidation efficiency of Hg-0 decreased with reaction temperature, following the order of eta((100 degree celsius))> eta((150 degree celsius))> eta((200 degree celsius)). Among them, 3%Bi2O3/TiO2 exhibited better thermal stability and higher catalytic oxidation efficiency of Hg-0. Therefore, the photothermal catalysts were further modified with rGO to form 4%rGO/3%Bi2O3/TiO2 (4G3BT), which made the catalytic oxidation efficiency of Hg-0 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 Hg-0 was primarily dominated by physical adsorption.