Remove elemental mercury from simulated flue gas by CeO₂-modified MnO_x/HZSM-5 adsorbent

In this study, we synthesized a Ce-modified Mn/HZSM-5 adsorbent via the ultrasound-assisted impregnation for Hg⁰ capture. Given the addition of 15% CeO₂, ~ 100% Hg⁰ efficiency was reached at 200 °C, suggesting its promotional effect on Hg⁰ removal. The doped Ce introduced additional chemisorbed oxygen species onto the adsorbent surfaces, which facilitated the oxidation of Hg⁰ to HgO. Even though adding CeO₂ led to a weakened adsorbent acidity, yet it appeared that this negative affect could be completely overcome by the enhanced oxidative ability, which finally endowed Ce-modified Mn/HZSM-5 with a satisfactory Hg⁰ removal performance within the whole investigated temperature range. During the Hg⁰ capture process, chemisorption was predominant with Mn⁴⁺operating as the main active site for oxidizing Hg⁰ to Hg²⁺. Finally, the 15Ce-Mn/HZSM-5 adsorbent exhibited good recyclability and stability. However, its tolerance to H₂O and SO₂ appeared relatively weak, suggesting that some modification should be conducted to improve its practicality.