Revealing Insights into the Mechanism of Hg0 Removal over MnO2 Hollow Sphere Adsorbents: Effect of Calcination Temperatures

In this study, MnO2 hollow spherical adsorbents were synthesized using the template approach, and the impacts of calcination temperatures on their physicochemical parameters and Hg-0 removal ability were investigated. The adsorbent calcined at 300 degrees C (labeled as Mn300) demonstrated the highest performance; at 200 degrees C, the Hg-0 removal efficiency reached over 90%. The presence of surface acid sites promoted the physisorption of Hg-0 and compensated for the relatively weak oxidative ability, which made much of the Hg-0 susceptible to capture on the adsorbent surface and consequently explained Mn300's superior Hg-0 capture capacity. The Mars-Maessen mechanism helped to understand the Hg-0 capture pathways over Mn300, with Mn4+ and chemisorbed oxygen serving as the active species to oxidize Hg-0 to HgO. Finally, Mn300 demonstrated reasonable recyclability and a rather weak gas-component adaptability, indicating that additional modification is required to improve the practical use of the adsorbent.

Automated summary

In this study, MnO2 hollow spherical adsorbents were synthesized and their physicochemical parameters and Hg-0 removal ability were investigated at different calcination temperatures. The results showed that the adsorbent calcined at 300 degrees C demonstrated the highest performance, with over 90% Hg-0 removal efficiency achieved at 200 degrees C. The presence of surface acid sites promoted the physisorption of Hg-0 and compensated for the weak oxidative ability, leading to superior Hg-0 capture capacity. The Mars-Maessen mechanism helped to understand the Hg-0 capture pathways over Mn300.