Effect of calcination temperature on the activity and structure of MnOx/TiO2 adsorbent for Hg0 removal

• The effect of calcination temperature on the Hg0 removal of MnOx/TiO2 method is investigated.
• The Hg0 removal activity of MnOx/TiO2 adsorbent is closely related to the calcination temperature.
• Excessively higher calcination temperature would lead to the deactivation of MnOx/TiO2 for Hg0 removal.
• The oxidation state of manganese would convert from Mn4 + to Mn3 + with the calcination temperature increasing.

The influence of calcination temperature (200–800 °C) on the activity and structure of MnOx/TiO2 adsorbent prepared by a deposition–precipitation method is investigated by using an elemental mercury (Hg0) removal setup and a variety of techniques such as N2 adsorption/desorption, SEM, XRD, H2-TPR, FTIR, TG-DSC, and XPS. The results exhibit that the Hg0 removal activity of MnOx/TiO2 adsorbent is closely related to the calcination temperature. The Hg0 removal activity firstly increases below 400 °C and then decreases with the increase of calcination temperature. Calcination at various temperatures may cause several successive structural changes such as the evaporation of water, decomposition of manganese compounds, enhancement of MnOx crystallization, and the crystal phase transformation of MnOx and TiO2. Some agglomerations of MnOx/TiO2 occur at higher calcination temperature, resulting in the drastic decreases of BET surface area and pore volume. Meanwhile, the particle sizes greatly increase. With an increase in calcination temperature, the oxidation state of manganese would convert from Mn4 + to Mn3 +, and the surface chemisorbed oxygen decreases due to the removal of surface chemisorbed oxygen. Excessively higher calcination temperature would lead to the deactivation of MnOx/TiO2.

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