Ion exchange resin derived magnetic activated carbon as recyclable and regenerable adsorbent for removal of mercury from flue gases

Abstract Regenerable ion exchange resin derived magnetic activated carbon (Fe/AC) was prepared to remove mercury from flue gases at 120–180 °C under a high space velocity of 240000 h−1, in this study. The Fe/AC showed higher mercury removal efficiency than those of either magnetic activated carbon without activation or commercial coconut-activated carbon. The optimum temperature for removal of mercury from flue gases was determined to be 120 °C and the existence of SO2 in flue gases promoted the mercury removal efficiency of Fe/AC. Mercury compounds of HgS (metacinnabar), HgO, HgS (cinnabar) and HgSO4 were found over spent adsorbents. The HgO was generated through the reaction of mercury with lattice oxygen and chemisorbed oxygen, while the formation of HgS was due to the reaction between mercury, FeS and sulfur over the adsorbent. The lattice oxygen could oxidize SO2 to SO3, which further reacted with mercury to form HgSO4. The Fe/AC presented excellent regeneration and reuse ability, the mercury removal efficiency of which showed a great increase even after 5 runs of regeneration. The crystalline structure of Fe/AC changed remarkably after regeneration and the FeS over Fe/AC was converted to Fe3O4. The above excellent properties suggest that Fe/AC might be a promising adsorbent to remove mercury from flue gases.