Removal of mercury from flue gases over iron modified activated carbon made by in situ ion exchange method

ABSTRACT Ion exchange method was applied to synthesize iron modified activated carbon in the present study. The carbon in volatile compounds of cation-exchange resin could be fixed by ferric ion, resulting in the higher carbon yields of iron contained adsorbents. The optimal temperatures for carbonization and activation of ferric ion-exchanged resin were determined to be 800 °C. The iron modified activated carbon with (Fe/AC-800) and without (Fe/C-800) activation at 800 °C showed different mercury removal mechanisms, and they could be employed to remove mercury from flue gases at reaction temperatures of 180 and 150 °C, respectively. HgO, HgS and HgSO4 were the mainly mercury compounds generated over spent Fe/C-800, whereas only HgO and HgS were observed over spent Fe/AC-800. The formation of HgO over spent Fe/C-800 and Fe/AC-800 were mainly due to the oxidation of mercury by chemisorbed oxygen and lattice oxygen, respectively. The HgSO4 was derived from FeS with the aid of oxygen, and the HgS was formed through the reaction between mercury and FeS and/or elemental sulfur.