Elemental mercury removal over a novel starch-modified MnOx/bentonite composite

Abstract To improve the activity of elemental mercury (Hg 0 ) removal over the bentonite supported MnO x material (MnO x /bentonite), a novel starch-modified MnO x /bentonite composite (MnO x /starch-bentonite) was synthesized for Hg 0 capture. The Hg 0 removal activity tested under the atmosphere of pure N 2 and in the presence of O 2 showed that the MnO x /starch-bentonite exhibited better activity and stability than MnO x /bentonite. It was evident that the Hg 0 removal efficiency over the novel catalytic sorbent (BS10M2) only declined by 16.9%, while that over MnO x /bentonite fell by 68.7% after a 5 h test under the atmosphere of N 2  + 6%O 2 at 120 °C. The starch modification decreased the surface area but enhanced the surface activity of bentonite, and more activate sites were generated on the surface of bentonite after being impregnated with potassium permanganate (KMnO 4 ) solution. The improved Hg 0 removal performance was probably due to the generation of more Mn 4+ and the newly introduced ester groups formed by the partial oxidation reaction between starch and KMnO 4 on the support, which played essential roles in mercury catalytic oxidation and adsorption. The MnO x were generated in two ways: KMnO 4 decomposition in a neutral solution condition and KMnO 4 reduction by the starch with hydroxyl groups.