Search

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]

• Applying rGO-assisted catalysts to remove Hg and/or NO is systematically reviewed. • Advantages and characterization analysis of rGO-assisted catalysts are summarized. • Catalytic mechanisms of removing Hg0 and/or NO are reported and discussed. • Future perspective of rGO-assisted catalysts on Hg0 and/or NO removal is proposed. The escalating levels of electric power demand have created a lot of air pollution, especially from coal-fired power plants. Due to coal burning, this makes an urgent need for elemental mercury (Hg0) and nitric oxide (NO) treatment technologies. Among different approaches, heterogeneously oxidize Hg0 to HgO by using modified metal oxides-based selective catalytic reduction (SCR) catalysts and absorbing with wet flue gas desulfurization (WFGD) has emerged as a promising solution due to its remarkable economic value and high Hg0 removal efficiency. Although several modification researches have been reported, there are still technical gaps to improve the performance of the catalysts, including their activity and resistance in complex reaction conditions. We believe that graphene as a novel material has the potential to enhance the properties of traditional catalysts. However, there is still a lack of article focus on the removal of Hg0 and/or NO with graphene-based catalysts. This article thus summarizes the preparation method, characterization analysis, catalytic activity, and reaction mechanisms to reduce the knowledge barrier for developing novel graphene-modified catalysts. By conducting this study, we look forward to explaining the research progress of graphene-based catalysts and offering valuable suggestions to guide future modification. [ABSTRACT FROM AUTHOR]

[Display omitted] • rGO modified CeO 2 /TiO 2 was synthesized and explored the removal efficiency of Hg0. • The photothermal catalytic oxidation of Hg0 was dominated by physical adsorption. • S-scheme heterojunction rGO/CeO 2 /TiO 2 performed high redox ability. • The Hg0 oxidation efficiency of 5GCT was 1.5 times higher than CeO 2 /TiO 2 at 200 °C. This study explored the photothermal catalytic oxidation of Hg0 by using S-scheme heterojunction CeO 2 /TiO 2 modified by reduced graphene oxide (rGO) at 100-200 °C. The surface properties of self-prepared photothermal catalysts were characterized by BET, SEM, TEM, EDS, XRD, Raman, UV–Vis, XPS, EPR, and UPS. The crystal structure of TiO 2 was mainly anatase and the nano-sized CeO 2 /TiO 2 was uniformly distributed on the surface of the rGO sheet. The oxidation efficiency of Hg0 decreased with reaction temperature in the order of Ƞ 100 °C = Ƞ 150 °C > Ƞ 200 °C , implying that the oxidation of Hg0 was controlled by mass transfer governed by adsorption instead of photothermal catalytic reaction. Both photo- and thermos-catalytic reaction mechanisms were involved in the oxidation of Hg0 at 100–200 °C. Moreover, rGO-modified CeO 2 /TiO 2 could tolerate multi-pollutants (SO 2 and NO) except for 100 ppm NO, which slightly reduced the oxidation efficiency of Hg0. [ABSTRACT FROM AUTHOR]